Klebsiella pneumoniae is a common cause of nosocomial and community-acquired infections, and the increasing incidence and prevalence of antibiotic resistant strains is proving to be particularly problematic to clinicians. K. pneumoniae is capable of employing a multitude of mechanisms by which to confer resistance to most available antibiotics. The carbapenem antibiotics are usually reserved for the treatment of complicated or multidrug resistant (MDR) K. pneumoniae infections. The recent emergence of not only MDR but also pan-drug resistant (PDR) K. pneumoniae strains has signified that it is now more important than ever to understand the mechanisms by which these strains confer resistance so that we may find ways to combat or hinder this progression. This project aimed to investigate the regulation of the transcriptional activator RamA, its ability to confer a MDR phenotype, and the mechanisms employed by K. pneumoniae to confer levels of carbapenem resistance sufficient to result in therapy failure. The analysis of a panel of K. pneumoniae strains, containing both RamA expressers and non-expressers, demonstrated that the overexpression of RamA was sufficient to confer an MDR phenotype. Two compounds, chlorpromazine (CPZ) and tigecycline, were shown to act as inducers of ramA, romA and acrA transcription. CPZ exhibited synergy with the antibiotics chloramphenicol, norfloxacin and tetracycline, all of which are known substrates of the AcrAB efflux pump. The current lack of novel classes of antimicrobials in development indicate a potential for a compound, such as CPZ, to be developed and exploited for clinical use. The ability of both CPZ and tigecycline to cause mutations within ramR however, indicate that both compounds may have the ability to select for efflux mutants as a result of their ability to upregulate ramA, which in turn causes the upregulation of the AcrAB efflux pump. The regulation of RamA by the upstream gene ramR, which encodes a TetR family protein was investigated in K. pneumoniae isolates. Sequencing of the ramR genes revealed that strains exhibiting an MDR phenotype commonly contained mutations within their gene sequences. The complementation of a wildtype ramR into a strain containing a 32 amino acid deletion within its ramR, was shown to increase susceptibility to various antibiotics of different classes, and additionally downregulate the expression of ramA, romA and acrA. CPZ, ciprofloxacin and tigecycline K. pneumoniae mutants were shown to exhibit increased MICs to a broad spectrum of antibiotics with respect to their parent strains, and possess mutations within their ramR genes. Complementation of the wildtype ramR resulted in partial reversion to the parental phenotypes, indicating another mechanism must also be involved in conferring the MDR phenotypes. These studies indicated that RamR plays an important role as a negative regulator of RamA, but also that it is not the sole regulator. The development of reduced susceptibility to the carbapenems was investigated in two clinical strains of K. pneumoniae, K1 and K2, isolated from the urine of a single patient at different stages of antibiotic therapy. The strains were shown to exhibit similar resistance phenotypes with the exception of their susceptibilities to the carbapenems. PCR and phenotypic analyses revealed that neither strain contained any carbapenemases or AmpC enzymes, but both contained OXA-1, SHV-1 TEM-1 and CTX-M-15. Analysis of their OMP profiles indicated that both strains lacked OmpK35, and K2 additionally lacked OmpK36. Mutation studies showed that the phenotype and OMP profile exhibited by K2 could be achieved in K1 via single step mutations using ertapenem, imipenem or meropenem. Susceptibility testing of CTXM- 15 clinical strains showed that strains containing CTX-M-15 showed reduced activity against ertapenem in the presence of clavulanic acid. These studies indicated a potential role for CTX-M-15 in conferring reduced susceptibility to the carbapenems when found in conjunction with altered permeability and active efflux. The mechanisms of antibiotic resistance employed by K. pneumoniae are numerous and complex. This work highlights several of these mechanisms and, more importantly, how they can work in synergy with one another to devastating consequences.

Antibiotic resistance is a growing threat to human health and is defined by the World Health Organization as a crisis that must be managed with the utmost urgency. Antibiotic resistant bacteria increase both mortality and morbidity and have a great impact on the global economy. Resistance is not confined to human health care, but is present also among animals and in our environment at large. Indeed, resistant bacterial strains have now been found in virtually all parts of the world, even in locations without direct human contact. The human gastrointestinal tract is populated by a complex, dynamic, diverse and highly interactive collection of microorganisms, including bacteria, archaea, fungi, yeasts and viruses, which constitutes our gastrointestinal microbiota. This microbiota is an important reservoir of resistance genes (our gastrointestinal resistome) and a “melting pot” for transfer of resistance genes between microbes, including potential pathogens. In this thesis I investigated the prevalences of two clinically important kinds of antibiotic resistance: extended-spectrum β-lactamases (ESBL) and vancomycin-resistant enterococci (VRE), as well as asymptomatic carriage of potential enteropathogens among healthy preschool children in Uppsala. Fecal samples from unidentified, individual diapers were collected in 2010 (125+313 samples) and in 2016 (334 samples). In addition, 204 environmental samples from the children’s preschools were collected in autumn 2016. A prevalence of 2.9% ESBL-producing Enterobactericeae was demonstrated in the first samples from 2010. No VRE were found and the occurrence of enteropathogens were reassuringly low. Results on ESBL prevalence in 2016 and transmission of resistance between children will be presented when the manuscript is published and at the dissertation.

The genus Enterococcus has an exceptional ability to acquire and transmit antibiotic resistance genes and is considered to be a major vector in their dissemination. Enterococci are part of the normal gut microbiota of humans and animals and are frequently encountered in food products including dry fermented sausage. Since fermented sausages are not heat-treated before consumption they might be a vehicle for transmitting resistance and virulence traits of enterococci by conjugation with commensal bacteria present in the human gut and pathogenic bacteria that might be present, such as Listeria species. A PCR-based assay was developed to detect enterococci in dry fermented sausage meat at the generic level by targeting a 16S rRNA sequence and a total of 29 Enterococccus strains (15 E. faecalis, 13 E. faecium, and one E. gallinarum) were identified. The susceptibility of these enterococci to antibiotics was tested and it was found that 27/29 were resistant to more than one antibiotic and possessed antibiotic resistance determinants. All strains were positive for at least one virulence gene. Strong biofilm formation occurred at lower than optimum temperature in all three species of enterococci and probably contributed to their survival in the harsh conditions experienced during dry sausage fermentation and drying. SmaI pulsed-field gel electrophoresis (PFGE) patterns exhibited genomic heterogeneity within and between the two larger groups of isolates. In spite of this heterogeneity, the phenotypic similarities observed suggested that food could still be a vehicle for distribution of antibiotic resistant bacteria among humans. In vitro conjugation experiments demonstrated transfer of the tetracycline resistant determinant, tet(M), from E. faecium S27 isolated from fermented sausage to clinical isolates of both E. faecium and E. faecalis. The streptomycin resistance of E. faecium S27 was also transferred to a clinical strain, E. faecalis 82916, which was confirmed by the presence of the streptomycin resistance gene, aadA, in the donor and transconjugant strains. E. faecium S27 also transferred tet(M) and streptomycin resistance to Listeria monocytogenes GLM-2 by in vitro mating. Evidence suggests that enterococci in fermented meats may contribute to the spread of resistance determinants. / October 2015

MSc (Med), Epidemiology and Biostatistics, Faculty of Health Sciences, University of the Witwatersrand / Introduction Given the increasing prevalence of non-typhoidal salmonella in humans, especially as an opportunistic illness associated with HIV, enhanced surveillance for non-typhoidal salmonella (NTS), including screening for antibiotic resistance, is conducted annually in South Africa. We aimed to determine whether there is an association between trimethoprim-sulfamethoxazole (TMP-SMX) prophylaxis and multi-drug resistant NTS infection, to establish whether various factors modify the relationship between TMP-SMX resistance and invasive NTS infection, to examine whether these associations vary by province, and to quantify the resistance rates of NTS to a range of antibiotics. Methods This study was a secondary analysis of enhanced surveillance data on NTS collected between 2003 and 2005. We used descriptive methods to assess the prevalence of NTS by year, province and serotype, and to determine the prevalence of four MDR patterns. Univariate and multivariate regression models were used to investigate the relationships between TMP-SMX prophylaxis and MDR NTS. Univariate logistic regression was used to assess the relationship between invasive NTS and TMP-SMX resistance. Results TMP-SMX prophylaxis is associated with the ACKSSuT pattern (OR 1.91, 95% CI 1.14 – 3.19, p=0.0080) and the AKSSuT MDR pattern (OR 2.00, 95% CI 1.26 – 3.15, p=0.0015). Being on TMP-SMX prophylaxis is associated with an increased odds of having at least one of the four MDR patterns investigated (OR 1.43, 95% CI 1.00 – 2.04, p=0.0388). We also found high rates of resistance to all antibiotics tested except for ciprofloxacin and imipenem. The highest resistance rate was observed for sulfamethoxazole (>75.85%). S. enterica Isangi isolates showed the highest levels of resistance, with 94.43% having at least one MDR pattern. Other factors significantly associated with MDR NTS were ESBL production, prior treatment with antibiotics, HIV status and resistance to TMP-SMX. Discussion and conclusions Isolates from patients on TMP-SMX prophylaxis were associated with an increased odds of having the ACKSSuT and AKSSuT MDR patterns, not taking into account other explanatory factors. These associations did not remain significant when possible confounders were taken into account. Despite the threat of increased multi-drug resistance, TMP-SMX prophylaxis remains important in certain clinical settings.

Les bactéries de l'environnement et du sol en particulier sont des producteurs actifs de molécules antibiotiques et les composés antibiotiques utilisés en médecine ont pour la plupart été isolés de bactéries saprophytes du sol qui ont elle mêmes développé une variété de mécanismes pour contrer les effets des antibiotiques conduisant à un arsenal de gènes de résistance à des antibiotiques dans l'environnement (ARGD). Une évaluation de l'abondance et de la diversité en terme de gènes de résistance à des antibiotiques a donc été conduite. Pour cette analyse, nous avons compilé 71 jeux de données de séquences d'ADN métagénomique environnementale variées: océans, et identifié des gènes de résistance pour chacun d'eux. Le sol est confirmé par cette étude comme un environnement extrêmement divers en terme de résistance à des antibiotiques. Cet étude in silico a été complété d'abord par une approche en microcosmes visant à étudier les effets soit de pollution soit par des molécules antibiotiques pures, soit par des effluents de ferme utilisés pour la fertilisation des sols. Les microcosmes de sols ont été incubés pendant 6 mois au laboratoire en conditions contrôlées. L'abondance de gènes de résistance à des antibiotiques a été évaluée au cours du temps par PCR quantitative. Une seconde étude visant à évaluer l'impact de la consommation de molécules antibiotiques par une population humaine sur son environnement immédiat, dont le sol, a été entreprise. Le village de Trois-Sauts est situé sur les berges du haut-Oyapock en Guyane Française. Les prescriptions antibiotiques sont très récentes dans cette région et les molécules distribuées ont été précisément répertoriées. Un transect de sol de 3km a été échantillonné chaque 600m afin de vérifier l'existence d'un gradient d'anthropisation entre le village (0m) et les échantillons de forêt les plus distants (3000m). Tous nos résultats confirment la présence à une forte abondance de gènes de résistance à des antibiotiques dans l'environnement, et en particulier dans le sol. Les facteurs à l'origine de la sélection et de la dissémination des gènes de résistance restent cependant difficiles à appréhender dans des environnements aussi complexes. C'est cependant avec une meilleure compréhension des phénomènes conduisant à l'émergence et à la dissémination des gènes de résistance à des antibiotiques au sein des flores pathogènes, depuis leur réservoir environnemental, que nous pourrons agir en vue de préserver les antibiotiques encore actifs aujourd'hui et ceux encore à développer. / Environmental bacteria and especially soil bacteria are active producers of antibiotic molecules and most drugs used nowadays are isolated from saprophytic soil bacteria and these microorganisms have also evolved numerous resistance pathways leading to an arsenal of Antibiotic Resistance Genes Determinants (ARGD) known as the environmental resistome. A survey of ARGD prevalence is required in order to characterize this natural phenomenon with critical implications in our current infectious diseases management. In order to perform such analysis we compiled a set of 71 metagenomic datasets from various environmental origins: soils, oceans, lakes, human feces, indoor air, etc., and compared their sequences with a database of known antibiotic resistance gene determinants (ARGD). ARGD-annotated reads are found in every environment analyzed confirming their ubiquity. Soil is found to be the richest and shares a large part of ARGD with the human gut microbiome, indicating ARGD transfers between these environments. Experiments using qPCR and metagenomic DNA sequencing on soil samples from two sites with known and distinct antibiotic pollution history were conducted to understand how ARGD abundance and diversity in soil are affected when impacted by antibiotic molecules. The first site is a reference soil from a long-term experiment without history of antibiotic pollution (Rothamsted Park Grass, UK). Soil microcosms are setup with addition of either antibiotic-containg animal manure or pure molecules and incubated for 6 months to monitor changes in ARGD concentration following these perturbations. Our second study-site is a very remote settlement in French Guiana where antibiotics are available since recently and may have impacted the local soil microbial community. Soil samples are taken following a line-transect going from the village (antibiotic source) to 3km deep in the forest in a gradient of human-impact. Our results all confirm prevalence of ARGD in soil at significant abundance but also that ARGD distribution is more correlated to environmental factors such as soil type, microbial taxonomy composition or microcosms incubation conditions than antibiotic molecules exposure in both sites. Pathogens ARGD diversity is far lower than ARGD diversity found in the environment and not all the soil resistome is readily accessible for transfer. In order to characterize the soil mobile gene pool, a strategy is proposed to isolate specifically mobile DNA directly from the environment for sequencing purposes. Better knowledge on the microbial ecology factors limiting ARGD transfers to pathogens may greatly help us reduce the current threat on our limited medical antibiotic molecules resource.

Étude de la Sous-Classe B3 et des Inhibiteurs des Métallo β-Lactamases En raison de l'introduction dagents antibactériens, les bactéries ont développé divers moyens de résistance. Le plus commun, déjà fortement développé, est la production denzymes qui hydrolysent la forme la plus largement répandue d'agent antibactérien, les antibiotiques à noyau β-lactame (Frère 1995). Ces enzymes, appelées β-lactamases, ont deux origines. Les β-lactamases à sérine correspondant aux classe A, C et D auraient évolué à partir dune DD-transpeptidase ancestrale, alors que les métallo β-lactamases (MBLs), nont pour linstant aucun ancêtre connu (Ambler 1980) (Matagne et al. 1999). Les MBLs sont importantes médicalement, puisqu'elles peuvent hydrolyser la plupart des β-lactames, y compris les carbapénèmes, qui échappent à l'activité des enzymes à sérine les plus actives (Rasmussen et al. 1997). Un transfert des MBLs entre espèce est également envisageable, du fait que certains gènes codant pour ces enzymes sont présents sur des plasmides (Osano et al. 1994) (Laraki et al. 1999). Les inhibiteurs classiques des β-lactamases à sérine active ont peu ou pas d'effet sur les MBLs et dans certains cas ils peuvent même être hydrolysés par les MBLs. Les MBLs sont produites, comme les β-lactamases à sérine, dans le périplasme des bactéries Gram-négatives ou sont sécrétées par les bactéries Gram-positives, cependant elles ont un mode d'action différent. À la différence des β-lactamases à sérine qui emploient une sérine dans leur site actif pour hydrolyser le noyau β-lactame, les MBLs utilisent lion zinc (Bush et al. 1995). Puisque ces enzymes ne présentent pas le même besoin en ions zinc pour faire preuve dune activité maximale, un débat continuel est mené afin de savoir si les MBLs utilisent un ou deux ions zinc dans leur site actif in vivo. Les MBLs forment un groupe hétérogène qui a été divisé en sous-groupes B1, B2 et B3 par similitude de séquence et spécificité de substrat (Galleni et al. 2001) (Garau et al. 2004). C'est l'hétérogénéité de cette classe qui a rendu la recherche d'un inhibiteur générique difficile. Divers inhibiteurs de MBLs ont été décrits; ceux-ci incluent le captopril, un inhibiteur compétitif des MBLs qui sest avéré efficace contre les enzymes mono-zinc BcII et CphA (Heinz et al. 2003). L'acide thiomandelique s'est avéré un inhibiteur à large spectre pour le composé racémique, avec des valeurs de Ki en-dessous de 1 µM, pour toutes les enzymes testées des sous-classes B1 et B3; bien qu'il ait été inefficace sur CphA du sous-groupe B2 (Mollard et al. 2001). Les hydrazones de sulfonyle inhibent IMP-1, le plus bas Ki étant de 0.7 µM, mais ont un effet limité sur d'autres enzymes B1 telles que BcII (Siemann et al. 2002). Les acides succiniques substitués inhibent également IMP-1 montrant des valeurs dIC50 impressionnantes mais aucune valeur de Ki nest donnée (Toney et al. 2001). L'incubation de CphA avec les β-lactames, moxalactame et céfoxitine, cause l'inactivation de l'enzyme par les produits de la réaction, mais ces inactivateurs sont des substrats pour les enzymes des sous-classes B1 et B3 (Zervosen et al. 2001). La recherche dinhibiteurs s'est tout naturellement concentrée sur les variants IMP et VIM, qui sont des MBLs portées par un plasmide; pour linstant, aucun inhibiteur identifié nest efficace sur tous les sous-groupes (Jin et al. 2004) (Kurosaki et al. 2005) (Siemann et al. 2002). La première partie de cette étude s'est concentrée sur lidentification de molécules modèles potentiellement inhibitrices de MBLs pouvant être développées en inhibiteurs à large spectre des MBLs. Par le criblage nous avons identifié trois modèles différents susceptibles de donner des inhibiteurs efficaces; lun deux est capable de chélater l'espèce mono-zinc, lacide 2,4 pyridine dicarboxylique; un autre est spécifique de FEZ-1, le N,3-Dihydroxy-5-(4-hydroxybenzoyl) benzamide et le dernier est efficace contre toutes les MBLs testées, lacide [(3-Mercaptopropanoyl)amino](phenyl) propanoic. Les résultats obtenus montrent des constantes dinhibition allant du micromolaire au nanaomolaire. La sous-classe B3 contient la MBL L1, dont le spectre daction est le plus large. Cette enzyme peut hydrolyser un éventail de substrats tel que les pénicillines, les céphalosporines et les carbapénèmes (Crowder et al. 1998). Elle partage le repliement αβ/βα et le site di-zinc des autres MBLs mais cest un tétramère, une caractéristique unique parmi les β-lactamases (Saino et al. 1982) (Bicknell et al. 1985). La forme tétramerique de L1 la rend plus difficile à étudier par des techniques telles que la spectroscopie de résonance magnétique nucléaire ou la spectrométrie de masse. Par conséquent, pour la deuxième partie de cette étude, nous avons décidé d'étudier L1, visant à trouver les conditions dans lesquelles l'enzyme était présente comme monomère, sans besoin de mutation. Les résultats que nous avons obtenus étaient imprévus et nous ont menés à examiner une méthode de production d'apo-enzyme pour les MBLs. L'enzyme a pu facilement être dénaturée et le zinc être enlevé. L'activité a été trouvée après renaturation suite à l'addition de zinc. Cette étude pourrait être poursuivie à l'avenir, les résultats préliminaires obtenus ici sont peu concluants, mais présentent un intérêt cinétique ainsi quun bénéfice à l'étude des MBLs commencée dans ce travail. Le nombre de MBLs connues augmente constamment et la caractérisation de chaque enzyme doit être accomplie pour gagner une pleine compréhension des β-lactamases, afin quil reste un espoir d'empêcher la diffusion supplémentaire de la résistance bactérienne. Pour cette raison le but de la troisième partie de cette étude était de caractériser plus profondément la MBL, GOB-1 de Chryseobacterium meningosepticum. L'analyse de sa séquence en acides aminés, par Bellais et al. 2000 place GOB-1 dans la sous-classe B3 en dépit de son unique résidu liant le zinc Gln116. Nous avons produit GOB-1 en utilisant un vecteur d'expression basé sur le système dexpression du phage T7 et avons purifié l'enzyme. Des mutants de GOB-1 ont été créés par mutagénèse dirigée du résidu liant le zinc Gln116. Une étude cinétique détaillée a alors été réalisée en présence et absence de zinc additionnel montrant que GOB-1 est une enzyme très efficace, capable dhydrolyser efficacement tous les β-lactames testés. Les mutants du résidu Gln116 de GOB-1, produits par mutagénèse dirigée ont montré une perte d'activité qui ne peut pas être corrigée par addition de zinc, démontrant ainsi que GOB-1 n'est pas une enzyme hybride des sous-classes B2 et B3, comme cela avait été précédemment suggéré (Garau et al. 2004), mais plutôt une enzyme nouvelle et améliorée de la sous-classe B3, utilisant les dispositifs structuraux précédemment utilisés par les enzymes de la sous-classe B2 mais en améliorant l'effet.

Streptococcus pneumoniae is a major pathogen that causes Otitis Media infections and bacterial meningitis in children as well as community acquired pneumonia in adults. Clinical isolates of S. pneumoniae exhibiting resistance to Beta-lactam antibiotics are being isolated with increased frequency in many countries. Streptococcus pneumoniae strains resistant to Beta-lactam drugs have modified forms of penicillin-binding proteins that exhibit reduced affinity for binding to chemotherapeutic Beta-lactams. Penicillin binding proteins are membrane-bound enzymes that catalyze the terminal step in cell wall synthesis, and are targets for Beta-lactam drugs. Seventeen clinical isolates and six vaccine strains of Streptococcus pneumoniae were characterized using conventional phenotypic methods, susceptibility to antimicrobial agents, capsular serotyping, and by different biochemical and genotyping methods. One strain, Sp D2, was resistant to penicillin and other Beta-lactams used in the study, to erythromycin, and to Trimethoprim/Sulfamethoxazole. Sp D2 exhibited a unique protein profile in 1D SDS-PAGE gels of whole-cell proteins. Cells of Sp D2 were fractionated, and the cytoplasmic membrane fraction was obtained by ultracentrifugation and analyzed using a 1D SDS-PAGE gel. A protein band with a mass of ~50 kDa was excised and subjected to Trypsin In-Gel Digestion, followed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) and database searching. The resulting MALDI-TOF-MS data (peptide mass fingerprints) did not produce any significant matches with proteins in any of the published S. pneumoniae genome databases. The 50 kDa protein was further subjected to N-terminal and internal sequence analysis and database searching, and the protein could not be identified by significant matches. Sp D2 did not react with any anti-pneumococcal polysaccharide capsular antibodies, and is designated as a non-typeable strain. Sp D2 exhibited a positive reaction in the Bile Solubility Test, the Optochin Test, and also positive reactions in PCR assays for the presence of the pneumococcal surface protein gene (PsaA), the autolysin gene (LytA), and the pneumolysin gene (Ply); which confirms that Sp D2 is a strain of S. pneumoniae.

Salmonella continues to threaten public health as well as negatively impact dairy producers on multiple levels. Efficacious solutions to control Salmonella among dairy cattle have long been sought to alleviate these problems. A novel vaccine technology has been developed based on purified siderophore receptors and porin proteins (SRP®) derived from Salmonella Newport. When vaccinated with these SRP® cattle are stimulated to produce antibodies which act in concert with host defenses to disrupt iron acquisition of pathogenic bacteria. To evaluate the effectiveness of this technology, a prospective cohort study was designed utilizing herds (n = 11) that practiced whole herd vaccination with the SRP® vaccine (vaccinated cohort) and herds (n = 11) that had not used the SRP® vaccine. Samples were collected during four rounds at approximately six week intervals from June through October 2009. Samples were transported to the laboratory at West Texas A&M University and cultured for the prevalence of Salmonella using selective enrichment methods. Salmonella isolates were evaluated for antimicrobial susceptibility and serotype. Data was analyzed using commercially available software to evaluate the herd-level effects of vaccination. Salmonella was ubiquitous throughout the Texas Panhandle and Eastern New Mexico, within-herd animal level estimates of prevalence ranged from 0.0 – 92%, over the length of the study period. Overall all rounds vaccinated herds had decreased (P = 0.012) Salmonella prevalence (15.3 vs. 27.5%). Vaccinated herds had numerically fewer Salmonella isolates belonging to the Newport serotype. Salmonella Typhimurium isolates were recovered approximately equally from vaccinated and non-vaccinated herds. Isolates from vaccinated herds were resistant to fewer antimicrobials throughout the study period. The ACSSuT(resistant to ampicillin, chloramphenicol, streptomycin, sulphisoxazole, and tetracycline) and MDR-AmpC (ACSSuT resistance plus resistance to ceftiofur and amoxicillin/clavulanate) resistant phenotypes were more frequently observed among non-vaccinated herds and none of the isolates from vaccinated or non-vaccinated herds were resistant to nalidixic acid, gentamicin, ciprofloxacin, or amikacin. These findings indicate vaccine efficacy for the reduction of Salmonella prevalence. Dairy operators along with herd veterinarians are encouraged to utilize this data with other herd specific factors in determining whether to use this specific vaccine.

Pathogens on surfaces in child care centers can contribute to illness among attendees and may thereby contribute to medical visits as well. This intervention study was conducted to assess the effect of using specific sanitizing products and cleaning protocols in child care centers on the incidences of lower respiratory infections, diarrheal illness, antibiotic use, and medical visits among children attending the centers and on the levels and antibiotic resistance of indicator bacteria in those centers. During the ten-week study period, children from twelve centers were observed. Six of the centers were randomly assigned to the intervention. The other six were controls. Intervention centers were given cleaning protocols and sanitizing products. Control centers were asked to retain their original procedures and products.Acute illness was determined from records kept by the center directors and telephone calls made to parents of ill children. A call was also made to one randomly selected healthy child's parents for every two ill children recorded. Parents were given a questionnaire requesting information including bedroom sharing status, environmental tobacco smoke exposure, and chronic illnesses.After controlling for within-center clustering and zero-inflation, statistically non-significant trends of reduction were seen in the weeks of lower respiratory infections, diarrheal illness, and medical visits. Multivariable zero-inflated Poisson regression revealed that the number of weeks intervention center children were using antibiotics was 32% lower than among the control center children. This was a statistically significant reduction (95% CI = 0.54-0.86; p = 0.001).Bacterial samples were collected from ten sites within each center at the beginning and the end of the study period to determine the effect of the intervention on the microbial population. The study determined the heterotrophic plate count bacteria numbers and the rates of resistance to ampicillin and cephalothin. Neither heterotrophic bacterial concentrations nor antibiotic resistance rates significantly changed over the course of the study.

Pseudomonas aeruginosa is a ubiquitous environmental Gram-negative bacterium that is also a major opportunistic human pathogen in nosocomial infections and cystic fibrosis chronic lung infections. These P. aeruginosa infections can be extremely difficult to treat due to the high intrinsic antibiotic resistance and broad repertoire of virulence factors, both of which are highly regulated. It was demonstrated here that the psrA gene, encoding a transcriptional regulator, was up-regulated in response to sub-inhibitory concentrations of antimicrobial peptides. Compared to wild-type and the complemented mutant, a P. aeruginosa PAO1 psrA::Tn5 mutant displayed intrinsic super-susceptibility to polymyxin B, a last resort antimicrobial used against multi-drug resistant infections, and indolicidin, a bovine neutrophil antimicrobial peptide; this super-susceptibility phenotype correlated with increased outer membrane permeability. The psrA mutant was also defective in simple biofilm formation, rapid attachment, and normal swarming motility, phenotypes that could be complemented by the cloned psrA gene. The role of PsrA in global gene regulation was studied by comparing the psrA mutant to wild-type by microarray analysis, demonstrating that 178 genes were up or down-regulated by greater than 2-fold (P ≤0.05). Dysregulated genes included those encoding known PsrA targets, the type III secretion apparatus and effectors, adhesion and motility genes and a variety of metabolic, energy metabolism and outer membrane permeability genes. This indicates that PsrA is a central regulator of antimicrobial peptide resistance and virulence. P. aeruginosa containing a mutation in the PhoQ sensor kinase-encoding gene was highly attenuated for persistence in a rat chronic lung infection model. In addition, the polymyxin B hyper-resistant phoQ mutant displayed reduced type IV pili-dependent twitching motility and was less cytotoxic towards human bronchial epithelial cells, indicating that the virulence defect observed could be due at least in part to these phenotypes. Using microarrays it was further demonstrated that PhoQ regulates a large number of genes that are PhoP-independent and that the phoQ mutation leads to up-regulation of PhoP- and PmrA regulated genes as well as other genes consistent with its virulence phenotypes.