Made available in DSpace on 2014-06-11T19:29:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-02-19Bitstream added on 2014-06-13T19:18:23Z : No. of bitstreams: 1 redondo_nc_me_arafcf.pdf: 1795708 bytes, checksum: 2cebfc96cd2f986b6bad66834d77de3d (MD5) / Universidade Estadual Paulista (UNESP) / Tendo em vista verificar algumas características essenciais aos microrganismos para serem considerados como probióticos, o objetivo deste trabalho foi avaliar *in vitro* de características probióticas do *Enterococcus faecium *CRL183 e do* Lactobacillus helveticus *ssp* jugurti* 416. Primeiramente foi testada a capacidade destes microrganismos em resistir aos pH 1.5, 2.0, 3,0 e 4,0 em meio de cultivo específico para cada espécie. Em seguida foi realizado o teste de sobrevivência ao trânsito gastrintestinal, onde, foram simuladas as condições do estômago e do intestino delgado, determinando-se a viabilidade dessas bactérias frente à pepsina em pH 2.0 e a pancreatina em pH 8.0. A resistência aos sais biliares foi avaliada inoculando o *Enterococcus faecium *CRL183 e do* Lactobacillus helveticus * ssp* jugurti* 416 em meio de cultivo suplementado com 0,1; 0,2; 0,3 e 0,5% de Oxgall. Já para teste de produção da hidrolase de sais biliares, foi vericada a ocorrência da mudança de cor das colônias ou precipitação dos sais biliares taurodeoxicolico e glicodeoxicolico (TDCA e GDCA). No estudo de auto-agregação e coagregação essas cepas foram colocadas separadamente (auto-agregação) e associados (coagregação) e verificada a densidade óptica (*DO*560). Foi testada a produção de substâncias antagônicas pelos dois microrganismos estudado frente a *Escherichia coli* 0157: H7, *Listeria monocytogenes* V2 e *Salmonella Enteritidis *por meio do teste *spot-on-the lawn*.* *Os resultados demonstraram que os microrganismos resistiram a todos os pH. Essas bactérias mostraram também ser tolerantes ao teste de sobrevivência ao trânsito gastrintestinal e também no teste de sobrevivência a sais biliares, porém neste teste, o *Enterococcus faecium *CRL 183 obteve um tempo de retardo menor em relação ao *Lactobacillus helveticus ssp. jugurti* 416. Já os resultados obtidos... / The purpose of this work was to assess in vitro the probiotic characteristics of Enterococcus faecium CRL183 and Lactobacillus helveticus ssp jugurti 416, having as an aim to verify some characteristics which are essential to the microorganisms, in order to be considered as probiotic. Firstly, the capacity of these microorganisms to resist to pH 1.5, 2.0, 3.0and 4.0 was tested in a specific culture medium for each species. Then the survival test to the gastrointestinal passage was done, and the conditions of the stomach and small intestine were simulated, so determining the viability of these bacteria comparing with pepsin at pH 2.0 and pancreatin at pH 8.0. The resistance to bile salts was assessed by inoculating Enterococcus faecium CRL183 and Lactobacillus helveticus ssp jugurti 416 in a culture medium supplemented with 0,1; 0,2; 0,3 and 0,5 % of Oxgall. However, for the production test of the hydrolase of bile salts, it was verified the occurrence of change in color of the colonies, or the precipitation of the bile salts taurodeoxycholic and glycodeoxycholic (TDCA and GDCA). In the auto-aggregation and co-aggregation studies, these strains were placed separately (auto-aggregation) and associated (co-aggregation), and then the optical density was verified (DO560), for completion and adhesion intestinal epithelium was tested Enterococcus faecium CRL183 and Lactobacillus helveticus ssp jugurti 416 with the Escherishia coli 0157: H7. The production of antagonist substances by both studied microorganisms was tested in comparison with Escherishia coli 0157: H7, Listeria monocytogenes V2 and Salmonella enteriotidis, by using the spot-on-the-lawn test. The results demonstrated that the microorganisms resisted to all pH. These bacteria also showed to be tolerant to the survival test to the gastrointestinal passage and also to the survival test to bile salts, though in this test,...(Complete abstract click electronic access below)

Orientador: Arnaldo Yoshiteru Kuaye / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-12T19:50:34Z (GMT). No. of bitstreams: 1 Rosado_MarciliaSantos_M.pdf: 15617760 bytes, checksum: 0a6732c38e48cb504e3b62de52b13c78 (MD5) Previous issue date: 2009 / Resumo: Dentre os microrganismos que apresentam capacidade de aderir e formar biofilmes em superfícies de processamento de alimentos, como equipamentos e utensílios, estão às bactérias do gênero Enterococcus, presentes em alimentos como leite e derivados. Sua presença em queijos tem sido muito estudada por sua capacidade de conferir características tecnológicas desejáveis ao produto. Este trabalho objetivou avaliar as características tecnológicas de Enterococcus faecium 946Ec, isolado de queijo de coalho, a possível formação de biofilme em superfície de aço inoxidável e seu controle por agentes sanitizantes. A cultura de E. faecium 946Ec foi caracterizada tecnologicamente, apresentando lenta produção de ácido, baixa atividade proteolítica e produção de diacetil; a curva de crescimento no caldo MRS apresentou contagem de 1,48 x 109 UFC.mL-1 após 24 horas. A avaliação da formação de biofilme foi realizada em cupons de aço inoxidável AISI 304, com rugosidade média de 0,366 mm, nos tempos de 0, 1,2, 4, 6,8 e 8 dias e temperaturas de 4,5, 10,5, 25, 39,5 e 45,5 °C, segu ndo delineamento composto central rotacional. O inóculo inicial utilizado foi de aproximadamente 1x104 UFC.cm-2. A análise de variância mostrou ajuste significativo (p<0,05) do modelo, permitindo a construção de um modelo matemático capaz de predizer a adesão em função do tempo e temperatura. A faixa ótima para a formação do biofilme foi observada nas combinações de 3 a 7,5 dias e 22 a 43 °C. A microscopia eletrônica de varredura (MEV) permitiu a visualização das topografias, das bactérias aderidas e produção e exopolissacarídeos. A contagem média a 25 °C por 4 dias foi de 4,08 x 105 UFC.cm-2 pela MEV, bem próxima a obtida por contagem padrão em placas de 8,93 x 105 UFC.cm-2. A ação de hipoclorito de sódio 100 mg.L-1 Cloro Residual Total (CRT) e ácido peracético 300 mg.L-1 Ácido Peracético (APA) sobre os biofilmes de E. faecium formados na superfície de 60 cupons de aço inoxidável, por 10 minutos, foram avaliados e os microrganismos foram detectados em 60 e 57 cupons, com reduções decimais de 3,00 e 4,02 ciclos log UFC.cm-2 respectivamente. Embora o ácido peracético tenha sido o mais eficiente, o microrganismo não foi eliminado nos tratamentos, o que demonstra a dificuldade de sanitização das superfícies após a formação do biofilme / Abstract: Among the microorganisms that exhibit ability to adhere and form biofilms on surfaces of food processing, such as equipment and utensils, are the bacteria of the genus Enterococcus, present as contaminants in foods such as milk and dairy products. Its presence in cheese has been widely studied for its capacity to provide the technological characteristics desirable product. The objective of this work was to evaluate the technological characteristics of Enterococcus faecium 946Ec, isolated from the artesanal Coalho cheeses, the possible formation of biofilms in surface of stainless steel and its control by sanitizers. The culture was characterized technologically, as a low acid producer, with low proteolytic activity and a diacetyl producer. The curve of growth of Enterococcus faecium 946Ec in MRS broth presented counts of 1,48x109 CFU.mL-1 after 24 hours. The evaluation of the biofilm formation was realized in coupons from stainless steel AISI 304, with roughness average of 0,366 mm, in times of 0, 1.2, 4, 6,8 and 8 days and in temperatures of 4,5; 10,5; 25; 39,5 and 45,5 °C, ac cording to a central composite design. The analysis of variance indicated the significant (p<0,05) adjust of the model, allowing the construction of a mathematical model capable of predicting the adhesion in function of time and temperature. The optimum interval for the formation of biofilms was observed in combinations of 3 to 7,5 days and 22 to 43 °C. The scanning electron microscopy allowed the vi sualization of the topography, the biofilm formation and exopolysaccharides production. The average counting at 25 °C for 4 days was 4,08 x 10 5 CFU.cm-2 using the SEM method, compared with results of the standard plate count of 8,93 x 105 CFU.cm-2. The action of sodium hypochlorite sanitizers 100 mg.L-1 Total Residual Chlorine (TRC) and peracetic acid 300 mg.L-1 Peracetic Ácid (PAA), during 10 minutes, was evaluated in 60 coupons with biofilm formation. The microorganism was detected in 57 and 60 coupons submitted to peracetic acid and sodium hypochlorite respectively, with decimal reductions of 3,00 and 4,02 cycles log CFU.cm-2 respectively. Although peracetic acid has been the most efficient, the microorganism has not been eliminated in the treatments, which demonstrates the difficulty of sanitization of the surfaces after the biofilm formation / Mestrado / Mestre em Tecnologia de Alimentos

A l’instar des D,D-transpeptidases de la famille des protéines de liaison à la pénicilline (PLP), les L,D-transpeptidases catalysent la formation des ponts interpeptidiques du peptidoglycane. Chez un mutant de Enterococcus faecium, la totalité du peptidoglycane est synthétisée par les L,D-transpeptidases entrainant une résistance à toutes les β-lactamines à l’exception des carbapénèmes. Le peptidoglycane de Mycobacterium tuberculosis étant majoritairement synthétisé par des L,D-transpeptidases, ces enzymes sont une cible potentielle pour le développement de nouveaux traitements de la tuberculose. Les objectifs de cette thèse sont de comprendre la spécificité des L,D­transpeptidases pour les carbapénèmes et d’identifier les sites de fixation des précurseurs du peptidoglycane à ces enzymes. Les résultats montrent que l’oxyanion formé lors de l’attaque du cycle β-lactame des carbapénèmes par la cystéine active est stabilisé dans le site actif des L,D­transpeptidases. Cette stabilisation combinée à l’absence d’hydrolyse de l’acylenzyme conduisent à l’inactivation rapide, totale et irréversible des L,D­transpeptidases par les carbapénèmes. La structure de l’acylenzyme indique que ces propriétés sont indépendantes de la nature de la chaine latérale des antibiotiques qui pourrait être optimisée. La localisation de l’accepteur d’acyle dans la Poche II de Ldtfm ainsi que des interactions supplémentaires avec les chaines glycanes du peptidoglycane montrent que d’autres sites que celui ciblé par les β­lactamines, mimes du donneur d’acyle, sont des cibles pour le développement de nouveaux antibiotiques qui pourraient agir en synergie avec les β­lactamines. / L,D-transpeptidases, as D,D-transpeptidases belonging to the penicillin-binding protein (PBP) family, catalyse the last cross-links step of peptidoglycan biosynthesis. The peptidoglycan of an Enterococcus faecium mutant is exclusively cross-linked by L,D-transpeptidases leading to resistance to all β-lactams except the carbapenems. Since peptidoglycan cross-links are predominantly synthesized by L,D-transpeptidases in Mycobacterium tuberculosis these enzymes are potential targets for chemotherapy of tuberculosis. The aims of the thesis are to identify the kinetic features that account for the specificity of L,D-transpeptidases for carbapenems and to characterise the binding sites for the peptidoglycan precursors in these enzymes. Our results show that the oxyanion resulting from nucleophilic attack of carbapebems by the catalytic cysteine is stabilized into the active site of L,D-transpeptidases. This stabilisation, combined to the absence of hydrolysis of the acylenzyme, leads to the rapid, total and irreversible inactivation of L,D-transpeptidases by carbapenems. Resolution of the acylenzyme structure shows that these kinetic features are independent from the carbapenem side chain that could be modified to optimize the antibiotics. The binding of the acyle acceptor has been identified in Pocket II of Ldtfm that is distinct from the binding site for β-lactams (Pocket I), which mimic the acyle donor. This site and additional peptidoglycan binding sites reveal additional targets for development of new antibiotics that might act in synergy with β-lactams.

Tesis por compendio / [ES] La obesidad representa un importante reto para la salud pública debido a su elevada prevalencia y a las comorbilidades asociadas. Las dietas hipercalóricas activan el sistema inmunitario intestinal y alteran la microbiota intestinal causando daños metabólicos en el organismo. De hecho, la pérdida de homeostasis inmunológica intestinal se considera un evento que precede a la aparición de la inflamación sistémica de bajo grado asociada a la obesidad. Dado que la microbiota intestinal es un factor modificable, su modulación puede convertirse en una oportunidad para reducir el impacto de la obesidad. Por ello la identificación de los factores que participan en la respuesta inflamatoria a las dietas obesogénicas y la búsqueda de alternativas terapéuticas basadas en la microbiota constituyen una vía de investigación prometedora para combatir la obesidad. Esta Tesis Doctoral evalúa el potencial de nuevos probióticos y estrategias dietéticas para combatir la obesidad basadas en sus propiedades inmunomoduladoras. En el Primer Capítulo investigamos el potencial anti-obesogénico del propil propano tiosulfinato (PTS), un compuesto organosulfurado derivado de la especie Allium, en dos dosis diferentes (0,1 o 1 mg/kg/día) utilizando un modelo murino de obesidad inducida por la dieta (DIO). Nuestros hallazgos demostraron los efectos protectores de PTS frente a la obesidad, ya que su administración redujo el peso corporal y mejoró la homeostasis de glucosa. En el tejido adiposo y el hígado, PTS redujo la inflamación y el metabolismo lipídico aberrante causado por la dieta obesogénica. Además, PTS incrementó la actividad termogénica en el tejido adiposo marrón y reforzó la función barrera intestinal. En vista de los modestos cambios en el ecosistema microbiano intestinal, concluimos que estos efectos no eran mediados por la microbiota. En el Segundo Capítulo evaluamos el potencial anti-obesogénico y el mecanismo de acción de una nueva bacteria llamada Phascolarctobacterium faecium DSM 32890. Para ello, realizamos diferentes experimentos in vitro e in vivo usando diferentes cultivos celulares (macrófagos derivados de médula ósea y células linfoides innatas intestinales del grupo 1 (LC1s)) y modelos murinos DIO (ratones C57BL/6J y Rag1-/-). El tratamiento de ratones alimentados con una dieta hipercalórica con P. faecium incrementó la proporción de los macrófagos M2 en el intestino, lo que contrarrestó el aumento de ILC1s y, en última instancia, mitigó la intolerancia a la glucosa y el aumento de peso corporal, independientemente de la viabilidad de la bacteria. Además, P. faecium reforzó la función barrera intestinal y evitó la inflamación sistémica causada por la dieta hipercalórica. Estos beneficios metabólicos se mantuvieron en ausencia de inmunidad adaptativa, pero se perdieron cuando la bacteria se coadministró con un inhibidor (GW2580) de la polarización de macrófagos M2. Por último, realizamos un amplio estudio con datos metagenómicos de 6.361 personas que mostró una relación inversa entre P. faecium y la obesidad, independientemente de la nacionalidad, el sexo o la edad, lo que sugiere la asociación de esta bacteria con la salud metabólica. En el Tercer Capítulo, investigamos la implicación de las ILC1s intestinales en la progresión de la obesidad y las alteraciones metabólicas asociadas. Para ello, evaluamos longitudinalmente la respuesta de las ILC1s y las consecuencias su depleción de ILC1s en un modelo murino DIO. En el intestino, el bloqueo de ILC1s evitó el aumento de macrófagos M1 e ILC2s y promovió la activación de la vía ILC3-IL22, aumentando la producción de mucina, la expresión de péptidos antimicrobianos y el número de células neuroendocrinas. Además, el bloqueo de ILC1s restableció el perfil microbiano y el metaboloma, acercándose al perfil asociado con la salud metabólica. En última instancia, estas mejoras se asociaron con una mayor secreción de hormonas intestinales, y una reducción de la insulinemia y la adiposidad. / [CA] L'obesitat és un repte per a la salut pública degut a la elevada prevalença i les comorbiditats. Les dietes hipercalòriques activen el sistema immunitari intestinal i alteren la microbiota intestinal causant danys metabòlics en l'organisme. De fet, la pèrdua d'homeòstasi immunològica a escala intestinal es considera un esdeveniment primerenc que precedeix l'aparició de la inflamació sistèmica de baix grau associada a l'obesitat. Atés que la microbiota intestinal és un factor modificable, la seua modulació pot convertir-se en una oportunitat per a reduir l'impacte de l'obesitat. Per això, la identificació dels factors que participen en la resposta inflamatòria a les dietes obesogèniques i la recerca d'alternatives terapèutiques basades en la microbiota son una via d'investigació prometedora per a combatre l'obesitat. Aquesta Tesi Doctoral avalua el potencial de nous probiòtics i estratègies dietètiques per a combatre l'obesitat basada en propietats immunomoduladores. En el Primer Capítol investiguem el potencial anti-obesogènic del propil propà tiosulfat (PTS), un compost organosulfurat derivat de l'espècie Allium, en dues dosis diferents (0,1 o 1 mg/kg/dia) utilitzant un model murí d'obesitat induïda per la dieta. Els resultats demostren els efectes protectors de PTS enfront a l'obesitat, ja que la seua administració va reduir el pes corporal i va millorar l'homeòstasi de glucosa. En el teixit adipós i el fetge, PTS va prevenir l'augment de la resposta inflamatòria i les alteracions del metabolisme lipídic causades per la dieta hipercalòrica. A més, PTS va incrementar l'activitat termogènica en el teixit adipós marró i millorà la funció barrera intestinal alterats per la dieta. Observàrem canvis modestos en la microbiota intestinal, concloent que els efectes no estan mediats de manera significativa per la microbiota. En el Segon Capítol avaluem el potencial anti-obesogènic i el mecanisme d'acció d'un nou bacteri Phascolarctobacterium faecium DSM 32890. Hem realitzat experiments in vitro i in vivo utilitzant diferents cultius cel·lulars (macròfags derivats de medul·la òssia i de cèl·lules limfoides innates intestinals del grup 1 (LC1s) i models murins d'obesitat induïda per la dieta (ratolins C57BL/6J, i Rag1-/- ). El tractament de ratolins alimentats amb una dieta hipercalòrica amb P. faecium incrementà la proporció dels macròfags M2 a l'intestí, contrarestant l'augment d'ILC1s i en última instància, mitigà la intolerància a la glucosa i l'augment del pes corporal, independentment de la viabilitat del bacteri. A més, P. faecium reforçà la funció bacterial intestinal i evità la inflamació sistèmica causada per la dieta hipercalòrica. Aquests beneficis metabòlics es mantenien en absència d'immunitat adaptativa, però es perderen quan el bacteri es coadministrà amb un inhibidor (GW2580) de la polarització de macròfags M2. Finalment, realitzàrem un ampli estudi amb dades metagenòmiques de 6.361 persones que mostrà una relació inversa entre P. faecium i l'obesitat, independentment de la nacionalitat, el sexe o l'edat, suggerint l'associació d'aquest bacteri amb la salut metabòlica. En el Tercer Capítol, investiguem la implicació de les ILC1s residents en l'intestí en la progressió de l'obesitat i les alteracions metabòliques associades. Evaluàrem longitudinalment la resposta de les ILC1s i les conseqüències de la depleció de ILC1s en un model murí d'obesitat. A l'intestí, el bloqueig de ILC1s va evitar l'augment de macròfags M1 i ILC2s, i va promoure l'activació de la via ILC3-IL22, augmentant la producció de mucina, l'expressió de pèptids antimicrobians i el nombre de cèl·lules neuroendocrines. El bloqueig de ILC1s va restablir la microbiota i el seu metaboloma, similar a l'estat saludable. Aquestes millores es van associar amb una major secreció d'hormones intestinals, i una reducció de la insulinèmia i l'adipositat. / [EN] Obesity is a major public health challenge due to its high prevalence, and association with metabolic comorbidities. Hypercaloric diets are known to overactivate the intestinal immune system and disrupt the microbiome, ultimately causing detrimental metabolic effects. The loss of intestinal immune homeostasis is considered an early step preceding the development of systemic low-grade inflammation associated with obesity and metabolic complications. In this regard, extensive evidence supports that the gut microbiome may be modified favorable and, thus, help to ameliorate these conditions. Hence, identifying factors triggering the low-grade inflammation and microbiome-base solutions to reduce the obesity burden represent promising avenues of research. This Doctoral Thesis aims to advance the knowledge and provide novel probiotics and dietary strategies to combat the burden of obesity based on their immunomodulatory properties to shape the metabolic response to the diet. In the First Chapter, we have investigated the anti-obesogenic potential of propyl propane thiosulfinate (PTS), an organo-sulfur compound derived from Allium species, at two different doses (0.1 or 1 mg/kg/day) using a murine model of diet-induced obesity (DIO). Our preclinical findings showed the protective effects of PTS against obesity, reducing body weight gain and maintaining glucose homeostasis, thus suggesting its potential to ameliorate the impact of the HFHSD. In the adipose tissue and the liver, PTS reduced inflammation and the aberrant lipid metabolism caused by the obesogenic diet. Additionally, PTS promoted thermogenic activity in the brown adipose tissue and enhance intestinal gut barrier defense. In view of the modest changes in the microbial ecosystem, we concluded that the effects of PTS were not mediated by the gut microbiota. In the Second Chapter, we have evaluated the anti-obesogenic potential and the mechanism of action of the new intestinal strain, Phascolarctobacterium faecium DSM 32890, isolated in our laboratory from a healthy volunteer. To that aim, we have performed different in vitro and in vivo experiments, including the use of different types of cell cultures (bone marrow-derived macrophages and group 1 of innate lymphoid cells (ILC1s)) and DIO murine models (wild-type C57BL/6J and Rag1-/- mice). Treatment of HFHSD-fed mice with P. faecium, regardless of its viability, shifted the macrophage phenotype towards an M2-type, which counteracted the obesity-induced increase in gut-resident ILC1s and ultimately mitigated glucose intolerance and body weight gain. Moreover, P. faecium treatment prevented systemic inflammation, boosted secretory immunoglobulin A production and induced antimicrobial peptide and interleukin 22 expression. These metabolic benefits were maintained in the absence of an adaptive immune system but were lost when the bacterium was co-administered with an inhibitor (GW2580) of M2 macrophage polarization. We confirmed that P. faecium was more prevalent in the gut metagenomes of non-obese adults regardless of nationality, sex or age, suggesting that it might contribute to safeguard metabolic health in humans. In the Third Chapter, we have investigated the involvement of gut-resident ILC1s in obesity progression and metabolic disruption. To address this goal, we evaluated longitudinally, in a DIO murine model, the ILC1s response to an obesogenic diet and the consequences of the ILC1s depletion. In the intestine, ILC1s depletion blunted the increases in M1 macrophages and ILC2s. Additionally, ILC1s depletion promoted the ILC3-IL22 pathway, increasing mucin production, the expression of antimicrobial gut peptides, and the number of neuroendocrine cells. Moreover, ILC1s depletion restored microbial and metabolomic profiles, resembling those associated with a healthy symbiotic state. The improvements in gut homeostasis were linked to a higher gut hormone secretion, and reduced insulinemia and adiposity. / Rebeca Liébana García has been beneficiary of an FPU contract (FPU 18/02026) and a mobility grant (EST22/00430) from Spanish Ministry of Universities. The experimental work conduced in this Doctoral Thesis has been funded by the Spanish Ministry of Science and Innovation (MICINN AGL2017-88801-P, PID2020-119536RB-I00), the Centre for the Development of Industrial Technology (CDTI, Ref 20170847), and the EU H2020 Marie Sklodowska Curie Actions (MSCA-IF “MicroILCs, GA: 8905454). / Liébana García, R. (2023). Effect and Mechanisms of Action of Intestinal Bacteria and Bioactive Compounds on the Immune System and Metabolism in Obesity Models [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/201910 / Compendio

Lower respiratory tract infectious diseases are a world-wide healthcare burden with bacterial pathogens accounting for a large portion of primary and secondary infections. The human respiratory tract is home to hundreds of species of microbes that comprise the human airway microbiome. These commensals play a crucial role in human health in part by providing colonization resistance against pathogens. In a previous study from the Surette lab it was shown that specific bacterial isolates from the respiratory microbiome inhibits the growth of pathogens aerobically. This included an isolate of Staphylococcus aureus which inhibited the growth of Enterococcus faecium. This activity was further characterized in this thesis and the underlying mechanism was explored through comparative genomics. As well, this observation provided proof-of-concept for a large-scale screen for additional isolates which inhibit pathogen growth. I hypothesized that the respiratory tract microbiota included many other bacteria capable of inhibiting the growth of respiratory tract pathogens in both aerobic and anaerobic environments, and that anaerobic conditions will identify new activities not detected aerobically. To examine and identify potential beneficial bacteria, I have screened ~5000 respiratory tract bacteria from the Surette lab’s airway isolate collection against four pathogens: Streptococcus pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumoniae. The respiratory tract commensals were pinned onto the pathogen-lawn and their interaction was expressed as zones of clearing or altered growth phenotypes of the pathogen. The results of the screen showed that anti-pathogen activity was a common feature of respiratory tract commensals. In particular, S. pneumoniae was inhibited by taxonomically diverse members of the microbiota representing three phyla (Proteobacteria, Firmicutes and Actinobacteria). Many of the facultative anaerobes that inhibited S. pneumoniae expressed their activity in anerobic conditions. / Thesis / Master of Science (MSc) / The human respiratory tract harbours commensal and pathogenic bacteria, and the latter cause most of the lower respiratory tract infections. The commensal bacteria help to train the immune system and impede the growth of pathogens through colonization resistance. A previous study by the Surette lab identified bacterial isolates from the respiratory tract that inhibit the growth of select pathogens, among them, a particular strain of Staphylococcus aureus. Based on the results of the earlier study, I hypothesized that the respiratory tract bacteria is a good source of commensals that can inhibit the growth of S. aureus and other respiratory pathogens, such as Streptococcus pneumoniae, Pseudomonas aeruginosa and Klebsiella pneumoniae. To find potential therapeutic bacteria, I screened ~5000 respiratory tract isolates from the Surette lab’s strain collection for the ability to impair growth of target pathogens. Additionally, I further characterized the activity of the previously identified S. aureus strain against various Lactobacillalles strains and used comparative genomics to identify potential biosynthetic genes required for biosynthesis of molecules with antibacterial activity within the genome of S. aureus. The research reported in this thesis demonstrates that many commensal bacteria that live within our airways have the ability to inhibit the growth of bacterial pathogens. This work may provide a new source of antibiotics against respiratory infections and new strategies to reduce susceptibility to infections in vulnerable populations.

Saturated steam (SS) and propylene oxide (PPO) fumigation are two common methods to improve microbiological quality and safety of tree nuts. Validation of these processes is needed to ensure adequate control of bacterial pathogens. Since pathogens cannot be studied in food processing environments, surrogates with resistance comparable to the pathogens needed to be identified. The objective was to investigate the suitability of Enterococcus faecium, Pediococcus acidilactici, and Staphylococcus carnosus as surrogate bacteria for Salmonella spp. on whole cashews and macadamia nuts, processed with SS or PPO. Whole cashews and macadamia nuts were co-inoculated with a cocktail of Salmonella enterica and one of the three potential surrogates. Nuts were dried to original aw, packaged in poly-woven bags (2.3 kg) and commercially processed using vacuum assisted steam at 80 ͦ C or PPO fumigation. Salmonella and the potential surrogates were enumerated by serial dilution, and plated onto TSA with overlay of XLT-4 (Salmonella) or media selective for the potential surrogates. Mean log reductions (CFU/g) of Salmonella and each potential surrogate were compared using a paired T-test. SS results: reduction of Salmonella (6.0 ± 0.14) was significantly larger than E. faecium (4.3± 0.12), or P. acidilactici (3.7± 0.14) on whole cashews. Salmonella (5.9 ± 0.18) was significantly larger than P. acidilactici (4.4± 0.18) on whole macadamia nuts. PPO results: reduction of Salmonella (7.3 ± 0.19) was significantly greater than E. faecium (6.4± 0.31), or P. acidilactici (6.3± 0.33) on whole macadamia nuts. Reduction of Salmonella was significantly greater than E. faecium and P. acidilactici reduction on cashews. P. acidilactici may be considered a surrogate for Salmonella reduction on whole macadamia nuts and whole cashews processed using SS at 80 ͦ C. E. faecium and P. acidilactici may be considered surrogates for Salmonella reduction on whole macadamia nuts and whole cashews processed using PPO. Reduction of St. carnosus exceeded that of Salmonella indicating it is not a suitable surrogate for Salmonella using either processing intervention. / Master of Science in Life Sciences

Les entérocoques font partie de la flore normale intestinale des animaux et des humains. Plusieurs études ont démontré que les entérocoques d’origine animale pouvaient représenter un réservoir de gènes de résistance aux antibiotiques pour la communauté humaine et animale. Les espèces Enterococcus faecalis et Enterococcus faecium sont importantes en santé publique; elles sont responsables d’environ 12% de toutes les infections nosocomiales aux États-Unis. Au Canada, les cas de colonisation et/ou d’infections à entérocoques résistants à la vancomycine ont plus que triplé de 2005 à 2009. Un total de 387 isolats E. faecalis et E. faecium aviaires, et 124 isolats E. faecalis porcins ont été identifiés et analysés pour leur susceptibilité aux antibiotiques. De hauts pourcentages de résistance envers les macrolides et les tétracyclines ont été observés tant chez les isolats aviaires que porcins. Deux profils phénotypiques prédominants ont été déterminés et analysés par PCR et séquençage pour la présence de gènes de résistance aux antibiotiques. Différentes combinaisons de gènes de résistance ont été identifiées dont erm(B) et tet(M) étant les plus prévalents. Des extractions plasmidiques et des analyses par hybridation ont permis de déterminer, pour la première fois, la colocalisation des gènes erm(B) et tet(M) sur un plasmide d’environ 9 kb chez des isolats E. faecalis porcins, et des gènes erm(B) et tet(O) sur un plasmide de faible poids moléculaire d’environ 11 kb chez des isolats E. faecalis aviaires. De plus, nous avons démontré, grâce à des essais conjugatifs, que ces plasmides pouvaient être transférés. Les résultats ont révélé que les entérocoques intestinaux aviaires et porcins, lesquels peuvent contaminer la viande à l’abattoir, pouvaient représenter un réservoir de gènes de résistance envers la quinupristine-dalfopristine, la bacitracine, la tétracycline et les macrolides. Afin d’évaluer l’utilisation d’un antisérum polyclonal SA dans l’interférence de la résistance à de fortes concentrations de bacitracine (gènes bcrRAB), lors d’un transfert conjugatif répondant aux phéromones, un isolat multirésistant E. faecalis aviaire a été sélectionné. Après induction avec des phéromones produites par la souche réceptrice E. faecalis JH2-2, l’agrégation de la souche donatrice E. faecalis 543 a été observée ainsi que des fréquences de transfert élevées en bouillon lors d’une courte période de conjugaison. Le transfert conjugatif des gènes asa1, traB et bcrRAB ainsi que leur colocalisation a été démontré chez le donneur et un transconjugant T543-1 sur un plasmide de 115 kb par électrophorèse à champs pulsé (PFGE) et hybridation. Une CMI de > 2 048 µg/ml envers la bacitracine a été obtenue tant chez le donneur que le transconjuguant tandis que la souche réceptrice JH2-2 démontrait une CMI de 32 µg/ml. Le séquençage des gènes asa1, codant pour la substance agrégative, et traB, une protéine régulant négativement la réponse aux phéromones, a révélé une association de cet élément génétique avec le plasmide pJM01. De plus, cette étude présente qu’un antisérum polyclonal SA peut interférer significativement dans le transfert horizontal d’un plasmide répondant aux phéromones codant pour de la résistance à de fortes doses de bacitracine d’une souche E. faecalis aviaire multirésistante. Des isolats cliniques E. faecium d’origine humaine et canine ont été analysés et comparés. Cette étude rapporte, pour la première fois, la caractérisation d’isolats cliniques E. faecium résistants à l’ampicilline (EFRA) d’origine canine associés à CC17 (ST17) au Canada. Ces isolats étaient résistants à la ciprofloxacine et à la lincomycine. Leur résistance envers la ciprofloxacine a été confirmée par la présence de substitutions dans la séquence en acides aminés des gènes de l’ADN gyrase (gyrA/gyrB) et de la topoisomérase IV (parC/parE). Des résistances élevées envers la gentamicine, la kanamycine et la streptomycine, et de la résistance envers les macrolides et les lincosamides a également été observées. La fréquence de résistance envers la tétracycline était élevée tandis que celle envers la vancomycine n’a pas été détectée. De plus, aucune résistance n’a été observée envers le linézolide et la quinupristine-dalfopristine. Les données ont démontré une absence complète des gènes esp (protéine de surface des entérocoques) et hyl (hyaluronidase) chez les isolats canins EFRA testés tandis qu’ils possédaient tous le gène acm (adhésine de liaison au collagène d’E. faecium). Aucune activité reliée à la formation de biofilm ou la présence d’éléments CRISPR (loci de courtes répétitions palindromiques à interespaces réguliers) n’a été identifiée chez les isolats canins EFRA. Les familles de plasmide rep6 and rep11 ont significativement été associées aux isolats d’origine canine. Les profils PFGE des isolats d’origine humaine et canine n'ont révélé aucune relation (≤ 80%). Ces résultats illustrent l'importance d'une utilisation judicieuse des antibiotiques en médecine vétérinaire afin d’éviter la dissémination zoonotique des isolats EFRA canins. Nous pensons que ces résultats contribueront à une meilleure compréhension des mécanismes de résistance aux antibiotiques et de leurs éléments mobiles ainsi qu’à de nouvelles stratégies afin de réduire le transfert horizontal de la résistance aux antibiotiques et des facteurs de virulence. / Enterococci are part of normal intestinal gut flora of animals and humans. Many studies have shown that enterococci from animal origin could represent an antimicrobial resistance genes reservoir for the human community. The two species Enterococcus faecalis and Enterococcus faecium are important in public health; they are responsible for approximately 12% of all nosocomial infections in the United States. In Canada, cases of colonization and/or infections to vancomycin resistant enterococci have more than tripled from 2005 to 2009. A total of 387 poultry E. faecalis and E. faecium isolates, and 124 porcine E. faecalis isolates were identified and analyzed for their antibiotic susceptibilities. High percentages of resistance to macrolides and tetracyclines were found in both avian and porcine isolates. Two predominant phenotypic profiles were determined and analyzed by PCR and sequencing for the presence of antimicrobial resistance genes. Various combinations of antibiotic resistance genes were detected; erm(B) and tet(M) were the most common genes. For the first time, plasmid extraction and hybridization revealed colocalization of erm(B) and tet(M) on a plasmid of ~9 kb in porcine E. faecalis isolates, and of erm(B) and tet(O) on a low-molecular-weight plasmid of ~11 kb in poultry E. faecalis isolates. Furthermore, we demonstrated, through mating experiments, these plasmids could be transferred. Results indicate that the intestinal enterococci of healthy pigs and poultry, which can contaminate meat at slaughter, could be a reservoir for quinupristin-dalfopristin, bacitracin, tetracycline, and macrolide resistance genes. To assess the use of a polyclonal antiserum AS on the contact interference of a high level bacitracin resistant (bcrRAB genes) pheromone-responsive plasmid, a multiresistant E. faecalis isolate of poultry origin was selected. After induction with pheromones produced by the recipient strain E. faecalis JH2-2, clumping of the donor E. faecalis strain 543 was demonstrated as well as high transfer frequencies in short time broth mating. Conjugative transfer of asa1, traB and bcrRAB genes and their co-localization were also demonstrated in the donor strain and a transconjugant T543-1 on a plasmid band of 115 kb by PFGE and Southern blotting. A MIC to bacitracin of > 2 048 µg/ml was obtained for both strains 543 and T543-1 whereas the recipient strain JH2-2 demonstrated a MIC of 32 µg/ml. Sequencing of the asa1 gene encoding for an AS, and traB for a pheromone shutdown protein, confirmed the association of this genetic element to the pheromone-responsive plasmid related to pJM01. More significantly, this study presents the evidence that a polyclonal antiserum AS can significantly interfere with the horizontal transfer of a pheromone-responsive plasmid encoding high-level bacitracin resistance of a poultry multidrug resistant E. faecalis strain. Clinical isolates of E. faecium of human and canine origin were analyzed and compared. This report describes for the first time the characterization of canine clinical ampicillin-resistant E. faecium (AREF) isolates related to CC17 (ST17) in Canada. These isolates were resistant to ciprofloxacin and lincomycin. Resistance to ciprofloxacin was confirmed by amino acid substitutions in DNA gyrase (gyrA/gyrB) and topoisomerase IV (parC/parE) genes. High-level gentamicin, -kanamycin and -streptomycin resistances and macrolides resistance were also observed. The frequency of tetracycline resistance was high whereas vancomycin resistance was not detected. Also, no resistance was observed to linezolid and quinupristin-dalfopristin antibiotics. Data demonstrated the complete absence of enterococcal surface protein (esp) and hyaluronidase (hyl) genes among the canine AREF isolates tested while all were acm (collagen adhesin from E. faecium) positive. However, most of them were shown to harbor efaAfm gene, encoding for a cell wall adhesin. No biofilm formation or clustered regularly interspaced short palindromic repeats (CRISPR) elements were identified in these canine AREF isolates. rep6 and rep11 families of plasmids were significantly associated with isolates from dogs. The PFGE patterns of human and dog isolates were considered unrelated (≤ 80%). These findings also support the importance of prudent use of antibiotics in veterinary medicine to avoid zoonotic spread of canine AREF isolates. We are confident that our results may help to better understand the mechanisms of antibiotic resistance and mobile element carrying them as well as new strategies to reduce the horizontal transfer of antibiotic resistance and virulence traits.

Les entérocoques font partie de la flore normale intestinale des animaux et des humains. Plusieurs études ont démontré que les entérocoques d’origine animale pouvaient représenter un réservoir de gènes de résistance aux antibiotiques pour la communauté humaine et animale. Les espèces Enterococcus faecalis et Enterococcus faecium sont importantes en santé publique; elles sont responsables d’environ 12% de toutes les infections nosocomiales aux États-Unis. Au Canada, les cas de colonisation et/ou d’infections à entérocoques résistants à la vancomycine ont plus que triplé de 2005 à 2009. Un total de 387 isolats E. faecalis et E. faecium aviaires, et 124 isolats E. faecalis porcins ont été identifiés et analysés pour leur susceptibilité aux antibiotiques. De hauts pourcentages de résistance envers les macrolides et les tétracyclines ont été observés tant chez les isolats aviaires que porcins. Deux profils phénotypiques prédominants ont été déterminés et analysés par PCR et séquençage pour la présence de gènes de résistance aux antibiotiques. Différentes combinaisons de gènes de résistance ont été identifiées dont erm(B) et tet(M) étant les plus prévalents. Des extractions plasmidiques et des analyses par hybridation ont permis de déterminer, pour la première fois, la colocalisation des gènes erm(B) et tet(M) sur un plasmide d’environ 9 kb chez des isolats E. faecalis porcins, et des gènes erm(B) et tet(O) sur un plasmide de faible poids moléculaire d’environ 11 kb chez des isolats E. faecalis aviaires. De plus, nous avons démontré, grâce à des essais conjugatifs, que ces plasmides pouvaient être transférés. Les résultats ont révélé que les entérocoques intestinaux aviaires et porcins, lesquels peuvent contaminer la viande à l’abattoir, pouvaient représenter un réservoir de gènes de résistance envers la quinupristine-dalfopristine, la bacitracine, la tétracycline et les macrolides. Afin d’évaluer l’utilisation d’un antisérum polyclonal SA dans l’interférence de la résistance à de fortes concentrations de bacitracine (gènes bcrRAB), lors d’un transfert conjugatif répondant aux phéromones, un isolat multirésistant E. faecalis aviaire a été sélectionné. Après induction avec des phéromones produites par la souche réceptrice E. faecalis JH2-2, l’agrégation de la souche donatrice E. faecalis 543 a été observée ainsi que des fréquences de transfert élevées en bouillon lors d’une courte période de conjugaison. Le transfert conjugatif des gènes asa1, traB et bcrRAB ainsi que leur colocalisation a été démontré chez le donneur et un transconjugant T543-1 sur un plasmide de 115 kb par électrophorèse à champs pulsé (PFGE) et hybridation. Une CMI de > 2 048 µg/ml envers la bacitracine a été obtenue tant chez le donneur que le transconjuguant tandis que la souche réceptrice JH2-2 démontrait une CMI de 32 µg/ml. Le séquençage des gènes asa1, codant pour la substance agrégative, et traB, une protéine régulant négativement la réponse aux phéromones, a révélé une association de cet élément génétique avec le plasmide pJM01. De plus, cette étude présente qu’un antisérum polyclonal SA peut interférer significativement dans le transfert horizontal d’un plasmide répondant aux phéromones codant pour de la résistance à de fortes doses de bacitracine d’une souche E. faecalis aviaire multirésistante. Des isolats cliniques E. faecium d’origine humaine et canine ont été analysés et comparés. Cette étude rapporte, pour la première fois, la caractérisation d’isolats cliniques E. faecium résistants à l’ampicilline (EFRA) d’origine canine associés à CC17 (ST17) au Canada. Ces isolats étaient résistants à la ciprofloxacine et à la lincomycine. Leur résistance envers la ciprofloxacine a été confirmée par la présence de substitutions dans la séquence en acides aminés des gènes de l’ADN gyrase (gyrA/gyrB) et de la topoisomérase IV (parC/parE). Des résistances élevées envers la gentamicine, la kanamycine et la streptomycine, et de la résistance envers les macrolides et les lincosamides a également été observées. La fréquence de résistance envers la tétracycline était élevée tandis que celle envers la vancomycine n’a pas été détectée. De plus, aucune résistance n’a été observée envers le linézolide et la quinupristine-dalfopristine. Les données ont démontré une absence complète des gènes esp (protéine de surface des entérocoques) et hyl (hyaluronidase) chez les isolats canins EFRA testés tandis qu’ils possédaient tous le gène acm (adhésine de liaison au collagène d’E. faecium). Aucune activité reliée à la formation de biofilm ou la présence d’éléments CRISPR (loci de courtes répétitions palindromiques à interespaces réguliers) n’a été identifiée chez les isolats canins EFRA. Les familles de plasmide rep6 and rep11 ont significativement été associées aux isolats d’origine canine. Les profils PFGE des isolats d’origine humaine et canine n'ont révélé aucune relation (≤ 80%). Ces résultats illustrent l'importance d'une utilisation judicieuse des antibiotiques en médecine vétérinaire afin d’éviter la dissémination zoonotique des isolats EFRA canins. Nous pensons que ces résultats contribueront à une meilleure compréhension des mécanismes de résistance aux antibiotiques et de leurs éléments mobiles ainsi qu’à de nouvelles stratégies afin de réduire le transfert horizontal de la résistance aux antibiotiques et des facteurs de virulence. / Enterococci are part of normal intestinal gut flora of animals and humans. Many studies have shown that enterococci from animal origin could represent an antimicrobial resistance genes reservoir for the human community. The two species Enterococcus faecalis and Enterococcus faecium are important in public health; they are responsible for approximately 12% of all nosocomial infections in the United States. In Canada, cases of colonization and/or infections to vancomycin resistant enterococci have more than tripled from 2005 to 2009. A total of 387 poultry E. faecalis and E. faecium isolates, and 124 porcine E. faecalis isolates were identified and analyzed for their antibiotic susceptibilities. High percentages of resistance to macrolides and tetracyclines were found in both avian and porcine isolates. Two predominant phenotypic profiles were determined and analyzed by PCR and sequencing for the presence of antimicrobial resistance genes. Various combinations of antibiotic resistance genes were detected; erm(B) and tet(M) were the most common genes. For the first time, plasmid extraction and hybridization revealed colocalization of erm(B) and tet(M) on a plasmid of ~9 kb in porcine E. faecalis isolates, and of erm(B) and tet(O) on a low-molecular-weight plasmid of ~11 kb in poultry E. faecalis isolates. Furthermore, we demonstrated, through mating experiments, these plasmids could be transferred. Results indicate that the intestinal enterococci of healthy pigs and poultry, which can contaminate meat at slaughter, could be a reservoir for quinupristin-dalfopristin, bacitracin, tetracycline, and macrolide resistance genes. To assess the use of a polyclonal antiserum AS on the contact interference of a high level bacitracin resistant (bcrRAB genes) pheromone-responsive plasmid, a multiresistant E. faecalis isolate of poultry origin was selected. After induction with pheromones produced by the recipient strain E. faecalis JH2-2, clumping of the donor E. faecalis strain 543 was demonstrated as well as high transfer frequencies in short time broth mating. Conjugative transfer of asa1, traB and bcrRAB genes and their co-localization were also demonstrated in the donor strain and a transconjugant T543-1 on a plasmid band of 115 kb by PFGE and Southern blotting. A MIC to bacitracin of > 2 048 µg/ml was obtained for both strains 543 and T543-1 whereas the recipient strain JH2-2 demonstrated a MIC of 32 µg/ml. Sequencing of the asa1 gene encoding for an AS, and traB for a pheromone shutdown protein, confirmed the association of this genetic element to the pheromone-responsive plasmid related to pJM01. More significantly, this study presents the evidence that a polyclonal antiserum AS can significantly interfere with the horizontal transfer of a pheromone-responsive plasmid encoding high-level bacitracin resistance of a poultry multidrug resistant E. faecalis strain. Clinical isolates of E. faecium of human and canine origin were analyzed and compared. This report describes for the first time the characterization of canine clinical ampicillin-resistant E. faecium (AREF) isolates related to CC17 (ST17) in Canada. These isolates were resistant to ciprofloxacin and lincomycin. Resistance to ciprofloxacin was confirmed by amino acid substitutions in DNA gyrase (gyrA/gyrB) and topoisomerase IV (parC/parE) genes. High-level gentamicin, -kanamycin and -streptomycin resistances and macrolides resistance were also observed. The frequency of tetracycline resistance was high whereas vancomycin resistance was not detected. Also, no resistance was observed to linezolid and quinupristin-dalfopristin antibiotics. Data demonstrated the complete absence of enterococcal surface protein (esp) and hyaluronidase (hyl) genes among the canine AREF isolates tested while all were acm (collagen adhesin from E. faecium) positive. However, most of them were shown to harbor efaAfm gene, encoding for a cell wall adhesin. No biofilm formation or clustered regularly interspaced short palindromic repeats (CRISPR) elements were identified in these canine AREF isolates. rep6 and rep11 families of plasmids were significantly associated with isolates from dogs. The PFGE patterns of human and dog isolates were considered unrelated (≤ 80%). These findings also support the importance of prudent use of antibiotics in veterinary medicine to avoid zoonotic spread of canine AREF isolates. We are confident that our results may help to better understand the mechanisms of antibiotic resistance and mobile element carrying them as well as new strategies to reduce the horizontal transfer of antibiotic resistance and virulence traits.

Introdução: Enterococcus faecium resistente à vancomicina (EFRV) surgiu como um importante patógeno multirresistente e de etiologia potencialmente letal nas infecções associadas aos cuidados de saúde em todo o mundo. Objetivo: O objetivo deste estudo de coorte retrospectivo foi avaliar os fatores associados à mortalidade em pacientes com bacteremia causadas por EFRV em um grande hospital de referência terciária no sul do Brasil. Métodos: Foram avaliados todos os casos documentados de bacteremia identificados entre maio de 2010 e julho de 2012. Regressão de Cox foi realizada para determinar se as características relacionadas ao hospedeiro ou o tratamento antimicrobiano estavam associadas com a mortalidade por qualquer causa em 30 dias. No total, 35 pacientes documentados com bacteremia por EFRV foram identificados durante o período de estudo. Resultados: A mediana do escore APACHE-II da população do estudo foi 26 (IQR 10). A mortalidade global em 30 dias foi de 65,7%%. Todos isolados de EFRV eram sensíveis à linezolida, daptomicina e quinopristina - dalfopristina. A linezolida foi o único agente antimicrobiano com atividade in vitro contra EFRV que foi administrada à coorte. Após a análise multivariada, o tratamento com linezolida (HR 0,08, 95% CI, 0,02-0,27) e a presença de insuficiência renal aguda no início da bacteremia (HR 4,01, 95% CI, 1,62-9,94) foram associadas de forma independente com o desfecho principal. Conclusão: Apresentação com insuficiência renal aguda e ausência de tratamento com um antibiótico eficaz representa um risco de mortalidade em pacientes com bacteremia por EFRV. / Background: Vancomycin-resistant Enterococcus faecium (VREF) has emerged as a relevant multidrug-resistant pathogen and potentially lethal etiology of health care-associated infections worldwide. Objective: The objective of this retrospective cohort study was to assess factors associated with mortality in patients with VREF bacteremia in a major tertiary referral hospital in southern Brazil. Methods: All documented cases of bacteremia identified between May 2010 and July 2012 were evaluated. Cox regression was performed to determine whether the characteristics related to the host or antimicrobial treatment were associated with the all-cause 30-day mortality. In total, 35 patients with documented VREF bacteremia were identified during the study period. Results: The median APACHE-II score of the study population was 26 (IQR 10). The overall 30-day mortality was 65.7%. All VREF isolates were sensitive to linezolid, daptomycin and quinopristin-dalfopristin. Linezolid was the only antimicrobial agent with in vitro activity against VREF that was administered to the cohort. After multivariate analysis, linezolid treatment (HR, 0.08; 95%CI, 0.02 – 0.27) and presence of acute kidney injury at the onset of bacteremia (HR, 4.01; 95%CI, 1.62 – 9.94) were independently associated with the main outcome. Conclusion: Presentation with acute kidney injury and lack of treatment with an effective antibiotic poses risk for mortality in patients with VREF bacteremia.

Introdução: Enterococcus faecium resistente à vancomicina (EFRV) surgiu como um importante patógeno multirresistente e de etiologia potencialmente letal nas infecções associadas aos cuidados de saúde em todo o mundo. Objetivo: O objetivo deste estudo de coorte retrospectivo foi avaliar os fatores associados à mortalidade em pacientes com bacteremia causadas por EFRV em um grande hospital de referência terciária no sul do Brasil. Métodos: Foram avaliados todos os casos documentados de bacteremia identificados entre maio de 2010 e julho de 2012. Regressão de Cox foi realizada para determinar se as características relacionadas ao hospedeiro ou o tratamento antimicrobiano estavam associadas com a mortalidade por qualquer causa em 30 dias. No total, 35 pacientes documentados com bacteremia por EFRV foram identificados durante o período de estudo. Resultados: A mediana do escore APACHE-II da população do estudo foi 26 (IQR 10). A mortalidade global em 30 dias foi de 65,7%%. Todos isolados de EFRV eram sensíveis à linezolida, daptomicina e quinopristina - dalfopristina. A linezolida foi o único agente antimicrobiano com atividade in vitro contra EFRV que foi administrada à coorte. Após a análise multivariada, o tratamento com linezolida (HR 0,08, 95% CI, 0,02-0,27) e a presença de insuficiência renal aguda no início da bacteremia (HR 4,01, 95% CI, 1,62-9,94) foram associadas de forma independente com o desfecho principal. Conclusão: Apresentação com insuficiência renal aguda e ausência de tratamento com um antibiótico eficaz representa um risco de mortalidade em pacientes com bacteremia por EFRV. / Background: Vancomycin-resistant Enterococcus faecium (VREF) has emerged as a relevant multidrug-resistant pathogen and potentially lethal etiology of health care-associated infections worldwide. Objective: The objective of this retrospective cohort study was to assess factors associated with mortality in patients with VREF bacteremia in a major tertiary referral hospital in southern Brazil. Methods: All documented cases of bacteremia identified between May 2010 and July 2012 were evaluated. Cox regression was performed to determine whether the characteristics related to the host or antimicrobial treatment were associated with the all-cause 30-day mortality. In total, 35 patients with documented VREF bacteremia were identified during the study period. Results: The median APACHE-II score of the study population was 26 (IQR 10). The overall 30-day mortality was 65.7%. All VREF isolates were sensitive to linezolid, daptomycin and quinopristin-dalfopristin. Linezolid was the only antimicrobial agent with in vitro activity against VREF that was administered to the cohort. After multivariate analysis, linezolid treatment (HR, 0.08; 95%CI, 0.02 – 0.27) and presence of acute kidney injury at the onset of bacteremia (HR, 4.01; 95%CI, 1.62 – 9.94) were independently associated with the main outcome. Conclusion: Presentation with acute kidney injury and lack of treatment with an effective antibiotic poses risk for mortality in patients with VREF bacteremia.