Extended spectrum β-lactamases or ESBLs, which are derived from non-ESBL precursors by point mutation of β-lactamase genes (bla), are spreading rapidly all over the world and have caused considerable problems in the treatment of infections caused by bacteria which harbour them. The mechanism of this resistance is not fully understood and a better understanding of these mechanisms might significantly impact on choosing proper diagnostic and treatment strategies. Previous work on SHV β-lactamase gene, blaSHV, has shown that only Klebsiella pneumoniae strains which contain plasmid-borne blaSHV are able to mutate to phenotypically ESBL-positive strains and there was also evidence of an increase in blaSHV copy number. Therefore, it was hypothesised that although specific point mutation is essential for acquisition of ESBL activity, it is not yet enough, and blaSHV copy number amplification is also essential for an ESBL-positive phenotype, with homologous recombination being the likely mechanism of blaSHV copy number expansion. In this study, we investigated the mutation rate of non-ESBL expressing K. pneumoniae isolates to an ESBL-positive status by using the MSS-maximum likelihood method. Our data showed that blaSHV mutation rate of a non-ESBL expressing isolate is lower than the mutation rate of the other single base changes on the chromosome, even with a plasmid-borne blaSHV gene. On the other hand, mutation rate from a low MIC ESBL-positive (≤ 8 µg/mL for cefotaxime) to high MIC ESBL-positive (≥16 µg/mL for cefotaxime) is very high. This is because only gene copy number increase is needed which is probably mediated by homologous recombination that typically takes place at a much higher frequencies than point mutations. Using a subinhibitory concentration of novobiocin, as a homologous recombination inhibitor, revealed that this is the case.

As infecções associadas aos cuidados de saúde constituem um problema grave nas unidades hospitalares bem como nos serviços de atendimento extra-hospitalares. Diferentemente de outros países, no Brasil, existe uma incidência alta dessas infecções causadas por microorganismos Gram-negativos produtores de β-lactamase de espectroestendido (ESBL). Estas enzimas hidrolisam compostos β-lactâmicos e são consideradas mundialmente como de importância clínica, pois a localização de seus genes emelementos móveis facilitam a transmissão cruzada. Este estudo foi realizado com amostras bacterianas isoladas de material clínico e de fezes de pacientes internados em um hospital da rede pública no Rio de Janeiro, Brasil. Estes pacientes estavam internados em duas unidades de terapia intensiva cardiológica, no período de janeiro a dezembro de 2007. O estudo teve por objetivo realizar a caracterização fenotípica e genotípica desses isolados associados à colonização ou infecção dos pacientes. Os testes fenotípicos e genotípicos foram realizados na Universidade do Estado do Rio de Janeiro e incluíram provas bioquímicas, teste de susceptibilidade, teste confirmatório para a expressão da produção da enzima ESBL e Reação de Polimerase em Cadeia (PCR) com iniciadores específicos para cinco genes: blaTEM, blaSHV, CTX-M1, Toho1 e AmpC. As espécies bactérianas mais frequentemente isoladas foram Escherichia coli (25%) e Klebsiella pneumoniae (30,56%), e os genes mais prevalentes foram blaTEM (41,6%), AMPC (41,6%) blaSHV (33,3%), CTX-M1 (25%), e Toho1 (19,44%). Identificamos em 25% das amostras enterobactérias que não eram E. coli, K. pneumoniae ou Proteus sp, com fenótipo para ESBL e a expressão dos mesmos genes, confirmando a necessidade de investigação nestes grupos microbianos. O substrato mais sensível para a expressão da área de sinergismo no Teste de Aproximação foi o ceftriaxone (80%). Identificamos também que 17% das amostras positivas para ESBL apresentaram co-produção para AmpC e 50% apresentaram mais de um gene para os iniciadores testados. A presença da carbapenemase foi avaliada em amostras bacterianas com susceptibilidade intermediária para ertapenem, através do Teste de Hodge modificado. Os achados do presente estudo caracterizaram a co-produção de AmpC e ESBL, bem como sugerem a necessidade da revisão e a ampliação dos métodos para a detecção de outros padrões de resistência na nossa Instituição. / Healthcare-associated infections are a major problem in hospital units as well as in units outside hospital, where procedures are performed. In Brazil, differently from other countries, a large proportion of these infections are caused by extended spectrum beta-lactamase (ESBL) producing Gram-negative microorganisms. These enzymes, which hydrolyse β-lactams, are considered of clinical importance worldwide. Their localization in genes that are located in móbile structures facilitate cross infection. This study was performed with bacterial isolates found in clinical specimens and faeces of patients hospitalized in a public hospital in the city of Rio de Janeiro, Brazil. These patients were in two different cardiological intensive care units from January till December 2007. The goal of the study was the phenotypic and genotypic characterization of the bacterial isolates which were associated with colonization or infection. Phenotypic and genotypic tests were performed in Universidade do Estado do Rio de Janeiro (Rio de Janeiro State University) and included biochemical tests, susceptibility tests, a comfirmatory test for the expression of ESBL, and polymerase chain reaction (PCR) with specific primers for five gentes : blaTEM, blaSHV, CTX-M1, Toho1 and AmpC. The most frequently isolated bactéria were Escherichia coli (25%) and Klebsiella pneumoniae (30,56%), and the most prevalent genes were blaTEM (41,6%), AMPC (41,6%) blaSHV (33,3%), CTX-M1 (25%), and Toho1 (19,44%). In 25% of samples we identified enterobacteria that were not E. coli, K. pneumoniae oor Proteus spp, but with the ESBL phenotype and the expression of the same genes, suggesting these microbes needed investigating. The most sensitive substrate for expressing synergism in the double-disk diffusion test was ceftriaxone (80%). We also identified that 17% of ESBL positive isolates showed co-production of AmpC and 50% showed more than one gene tested by PCR. The presence of carbapenemase was studied in bacterial isolates with intermediate susceptibility to ertapenem, by a modified Hodge test. The findings in the present study characterize the co-production of AmpC and ESBL, and suggest the need for reviewing detection methods used and possibly using other methods for the detection of other resistance patterns in our Institution.

As infecções associadas aos cuidados de saúde constituem um problema grave nas unidades hospitalares bem como nos serviços de atendimento extra-hospitalares. Diferentemente de outros países, no Brasil, existe uma incidência alta dessas infecções causadas por microorganismos Gram-negativos produtores de β-lactamase de espectroestendido (ESBL). Estas enzimas hidrolisam compostos β-lactâmicos e são consideradas mundialmente como de importância clínica, pois a localização de seus genes emelementos móveis facilitam a transmissão cruzada. Este estudo foi realizado com amostras bacterianas isoladas de material clínico e de fezes de pacientes internados em um hospital da rede pública no Rio de Janeiro, Brasil. Estes pacientes estavam internados em duas unidades de terapia intensiva cardiológica, no período de janeiro a dezembro de 2007. O estudo teve por objetivo realizar a caracterização fenotípica e genotípica desses isolados associados à colonização ou infecção dos pacientes. Os testes fenotípicos e genotípicos foram realizados na Universidade do Estado do Rio de Janeiro e incluíram provas bioquímicas, teste de susceptibilidade, teste confirmatório para a expressão da produção da enzima ESBL e Reação de Polimerase em Cadeia (PCR) com iniciadores específicos para cinco genes: blaTEM, blaSHV, CTX-M1, Toho1 e AmpC. As espécies bactérianas mais frequentemente isoladas foram Escherichia coli (25%) e Klebsiella pneumoniae (30,56%), e os genes mais prevalentes foram blaTEM (41,6%), AMPC (41,6%) blaSHV (33,3%), CTX-M1 (25%), e Toho1 (19,44%). Identificamos em 25% das amostras enterobactérias que não eram E. coli, K. pneumoniae ou Proteus sp, com fenótipo para ESBL e a expressão dos mesmos genes, confirmando a necessidade de investigação nestes grupos microbianos. O substrato mais sensível para a expressão da área de sinergismo no Teste de Aproximação foi o ceftriaxone (80%). Identificamos também que 17% das amostras positivas para ESBL apresentaram co-produção para AmpC e 50% apresentaram mais de um gene para os iniciadores testados. A presença da carbapenemase foi avaliada em amostras bacterianas com susceptibilidade intermediária para ertapenem, através do Teste de Hodge modificado. Os achados do presente estudo caracterizaram a co-produção de AmpC e ESBL, bem como sugerem a necessidade da revisão e a ampliação dos métodos para a detecção de outros padrões de resistência na nossa Instituição. / Healthcare-associated infections are a major problem in hospital units as well as in units outside hospital, where procedures are performed. In Brazil, differently from other countries, a large proportion of these infections are caused by extended spectrum beta-lactamase (ESBL) producing Gram-negative microorganisms. These enzymes, which hydrolyse β-lactams, are considered of clinical importance worldwide. Their localization in genes that are located in móbile structures facilitate cross infection. This study was performed with bacterial isolates found in clinical specimens and faeces of patients hospitalized in a public hospital in the city of Rio de Janeiro, Brazil. These patients were in two different cardiological intensive care units from January till December 2007. The goal of the study was the phenotypic and genotypic characterization of the bacterial isolates which were associated with colonization or infection. Phenotypic and genotypic tests were performed in Universidade do Estado do Rio de Janeiro (Rio de Janeiro State University) and included biochemical tests, susceptibility tests, a comfirmatory test for the expression of ESBL, and polymerase chain reaction (PCR) with specific primers for five gentes : blaTEM, blaSHV, CTX-M1, Toho1 and AmpC. The most frequently isolated bactéria were Escherichia coli (25%) and Klebsiella pneumoniae (30,56%), and the most prevalent genes were blaTEM (41,6%), AMPC (41,6%) blaSHV (33,3%), CTX-M1 (25%), and Toho1 (19,44%). In 25% of samples we identified enterobacteria that were not E. coli, K. pneumoniae oor Proteus spp, but with the ESBL phenotype and the expression of the same genes, suggesting these microbes needed investigating. The most sensitive substrate for expressing synergism in the double-disk diffusion test was ceftriaxone (80%). We also identified that 17% of ESBL positive isolates showed co-production of AmpC and 50% showed more than one gene tested by PCR. The presence of carbapenemase was studied in bacterial isolates with intermediate susceptibility to ertapenem, by a modified Hodge test. The findings in the present study characterize the co-production of AmpC and ESBL, and suggest the need for reviewing detection methods used and possibly using other methods for the detection of other resistance patterns in our Institution.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-09-27T14:21:32Z No. of bitstreams: 1 osmarnascimentosilva.pdf: 5346948 bytes, checksum: c6c4bb9eae4172e04c4553f57d4e27d0 (MD5) / Approved for entry into archive by Diamantino Mayra (mayra.diamantino@ufjf.edu.br) on 2016-09-27T15:15:36Z (GMT) No. of bitstreams: 1 osmarnascimentosilva.pdf: 5346948 bytes, checksum: c6c4bb9eae4172e04c4553f57d4e27d0 (MD5) / Made available in DSpace on 2016-09-27T15:15:36Z (GMT). No. of bitstreams: 1 osmarnascimentosilva.pdf: 5346948 bytes, checksum: c6c4bb9eae4172e04c4553f57d4e27d0 (MD5) Previous issue date: 2015-04-28 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Com o aumento na incidência de infecções resistentes a múltiplos antibióticos, existe hoje um grande interesse pelos peptídeos antimicrobianos (PAMs) como modelos para a produção de novos antibióticos. Os PAMs são mediadores multifuncionais da resposta imune inata, com atividade antibacteriana direta. O uso de PAMs como agentes terapêuticos tem algumas limitações, como a estabilidade, a toxicidade e alta massa molecular. Apesar dessas limitações, eles apresentam propriedades compensatórias, como imunomodulatória e antitumoral bem como a capacidade de inibir β-lactamases. O desenho racional de PAMs tem sido usado para gerar análogos com atividade melhorada. No presente trabalho avaliamos a atividade antibacteriana in vitro e in vivo da clavanina A e através da modificação incremental criamos dois análogos dos peptídeos mostoparano-L e clavanina A (clavanina-MO e mastoparanoMO),além disso, utilizamos o desenho racional de peptídeos para a criação de dois inibidores de β-lactamase (dBLIPs 1 e 2). A clavanina A mostrou se eficiente na eliminação de S. aureus em um modelo de infecção de ferida e impediu o início da sepse e, assim, reduziu a mortalidade de camundongos infectados em um modelo de infecção bacteriana sistêmica. A clavanina-MO e mastoparano-MO impediram o crescimento de bactérias planctônicas e levaram à erradicação de biofilmes bacterianos maduros. Os peptídeos modificados mostram-se promissores como agentes terapêuticos contra infecções bacterianas sistêmicas e biofilmes causadas por uma variedade de bactérias. dBLIP-1 e dBLIP-2 em combinação com antibióticos convencionais foram eficazes na eliminação de Escherichia coli e Staphylococcus aureus que expressam β-lactamases em um modelo murino de infecção sistêmica. dBLIPs 1 e 2 fornecem pistas para superar a resistência à base de β-lactamase. / With the increased incidence of multiple antibiotic resistant infections, there is huge interesting in antimicrobial peptides (AMPs) as templates to produce novel antibiotics. The AMPs are multifunctional mediators of innate immune response with direct antibacterial activities. Nevertheless, the use of AMPs as therapeutic agents has certain limitations such as stability, toxicity and high molecular mass. Despite such limitations, they show additional properties such as antitumor and immunomodulatory as well as the ability to inhibit β-lactamases. Furthermore, the rational AMPs design has been used to produce analogues with improved activity. In the present study, we utilized the rational AMPs design for generation of two β-lactamase inhibitors (dBLIPs 1 and 2) and through two incremental modification created analogues of clavanin A and mostoparan-L (clavanin-MO and mastoparan-MO respectively) peptides. Both inhibitors in combination with conventional antibiotics were effective for control of Staphylococcus aureus and Escherichia coli expressing β-lactamase in a murine model of systemic infection. dBLIPs 1 and 2 provide clues to overcome resistance to β-lactamase base. The clavanin-MO and mastoparan-MO prevented the growth of planktonic bacteria, leading to the mature biofilm eradication of pathogenic Gram-negative and -positive. The clavanina-MO and mastoparan-MO are promising therapeutic agents against systemic infections and bacterial biofilms caused by a wide bacterial variety.

The use of reporter gene fusions to assess cellular processes such as protein targeting and regulation of transcription or translation is established technology in archaeal, bacterial, and eukaryal genetics. Fluorescent proteins or enzymes resulting in chromogenic substrate turnover, like β-galactosidase, have been particularly useful for microscopic and screening purposes. However, application of such methodology is of limited use for strictly anaerobic organisms due to the requirement of molecular oxygen for chromophore formation or color development. We have developed β-lactamase from Escherichia coli (encoded by bla) in conjunction with the chromogenic substrate nitrocefin into a reporter system usable under anaerobic conditions for the methanogenic archaeon Methanosarcina acetivorans. By using a signal peptide of a putative flagellin from M. acetivorans and different catabolic promoters, we could demonstrate growth substrate-dependent secretion of β-lactamase, facilitating its use in colony screening on agar plates. Furthermore, a series of fusions comprised of a constitutive promoter and sequences encoding variants of the synthetic tetracycline-responsive riboswitch (tc-RS) was created to characterize its influence on translation initiation in M. acetivorans. One tc-RS variant resulted in more than 11-fold tetracycline-dependent regulation of bla expression, which is in the range of regulation by naturally occurring riboswitches. Thus, tc-RS fusions represent the first solely cis-active, that is, factor-independent system for controlled gene expression in Archaea.

Desde a primeira enzima ?-lactamase de espectro estendido (ESBL) detectada, na década de 1980, o número de diferentes enzimas ESBL têm aumentado exponencialmente. Houve também aumento no número de relatos de isolamento de bactérias resistentes presentes em alimentos de origem animal. O objetivo deste estudo foi avaliar enterobactérias de microbiota de frangos comerciais saudáveis, de granjas localizadas no interior do Estado de São Paulo (Brasil), quanto à resistência a antimicrobianos e ao potencial de virulência. Foram avaliadas todas as enterobactérias que apresentaram resistência à cefotaxima e/ou ceftazidima de 200 frangos comerciais para consumo humano. O teste de sensibilidade aos antimicrobianos foi realizado por disco de difusão para diferentes classes de antimicrobianos incluindo ?- lactâmicos e não ?-lactâmicos. Reação em cadeia da polimerase e sequenciamento foram utilizados para a pesquisa de genes codificadores de ESBL, ?-lactamases AmpC e determinantes de resistência às quinolonas mediada por plasmídeos (PMQR). A similaridade genética dos isolados foi caracterizada por eletroforese em campo pulsado (PFGE) e a localização cromossômica ou plasmideal de genes de resistência foi avaliada por I-Ceu IPFGE ou S1-PFGE. Além disso, experimentos de conjugação, tipagem de plasmídeos, investigação de filogenia e de virulência foram realizados. Em todas as amostras de cloaca coletadas foram identificados Enterobacteriaceae, incluindo Escherichia coli, Escherichia fergusonii, Klebsiella oxytoca e Klebsiella pneumoniae resistentes à cefotaxima e/ou ceftazidima. Salmonella sp não foi detectada. Foi encontrada ampla diversidade genômica entre todos os isolados classificados entre diferentes tipos de PFGE. Foram detectados diferentes genes codificadores de ?-lactamases, a maioria em diferentes plasmídeos, de diversos tamanhos, sendo alguns conjugativos, presentes em diferentes populações bacterianas. Foram identificados isolados de E. coli produtores de CTX-M-2, com inserção do gene blaCTX-M-2 no cromossomo bacteriano. Plasmídeo IncI (ST113/ST114) foi identificado carreando o gene blaCTX-M-8. Foram também encontrados os genes codificadores de ?- ii lactamase, blaCTX-M-2 e blaCTX-M-15, sendo carreados por plasmídeos. Foi identificado gene blaCMY-2 disseminado por plasmídeos de diferentes grupos de incompatibilidade, na população comensal de E. coli. Nos isolados que abrigavam gene PMQR, além das resistências às quinolonas, foi observado também resistência a outras importantes classes de antimicrobianos. Genes determinantes de PMQR abrigados em plasmídeos tipo ColE foram encontrados em E. coli, E. fergusonii, K. oxytoca e K. pneumoniae. Todas as aves comerciais de granjas localizadas no interior do Estado de São Paulo, incluídas nesse estudo, apresentaram isolados considerados multirresistentes a antimicrobianos e o trato intestinal destes frangos é reservatório dos genes de resistência em enterobactérias da microbiota normal. Além disso, alguns isolados demonstraram alto potencial de virulência, incluindo a capacidade de adesão e invasão em células epiteliais in vitro. / of commercial poultry in farms located at the countryside of São Paulo State (Brazil). All enterobacteria presenting cefotaxime and/or ceftazidime resistance from 200 commercial broiler chickens for human consumption were evaluated. Antimicrobial susceptibility testing was performed by disc diffusion for different classes of antimicrobials, including ?-lactams and non-?-lactams. The genes encoding ESBL, ampC ?-lactamases and determinants of plasmid mediated quinolone resistance (PMQR) were screened by polymerase chain reaction and sequencing. Genetic similarity of bacterial isolates was characterized by pulsed field gel electrophoresis (PFGE) and the location of the resistance genes in the chromosome or plasmids was evaluated by I-CeuI-PFGE or S1-PFGE. Additionally, experiments of conjugation, plasmid typing, phylogeny and virulence characterization were performed. Enterobacteriaceae were identified in all cloacal swab samples, including Escherichia coli, Escherichia fergusonii, Klebsiella oxytoca and Klebsiella pneumoniae resistant to cefotaxime and/or ceftazidime. Salmonella sp. was not detected. High genetic diversity was detected among all isolates, classified into diferent types of PFGE. Different genes coding for ?-lactamases were detected, harbored in diverse plasmids, of different sizes, some were conjugative and were present in different bacterial populations. E. coli isolates producing CTX-M-2 were identified, harbouring the blaCTX-M-2 gene inserted into the chromosome. IncI (ST113/ST114) plasmid was identified carrying the blaCTX-M-8 gene. The ?-lactamase coding genes, blaCTX-M-2 and blaCTX-M-15 were also found in plamids. The gene blaCMY-2 was found disseminated in different types of plasmid replicons in the commensal E. coli population. In isolates harbouring PMQR genes, in addition to the quinolones resistance, was observed resistance to other important antimicrobials classes was observed. PMQR determinant genes harbored in ColE-like plasmids were found in E. coli, E. fergusonii, K. oxytoca and K. pneumoniae. All commercial poultry from farms located at São Paulo State, evaluated in this study, carried isolates considered multidrug resistant and the intestinal tract of these chickens is reservoir of resistant genes blaCTX-M-2, blaCTX-M-8 and blaCTX-M-15 in enterobacteria from the normal microbiota. Moreover, some have demonstrated a high virulence potential, with adhesion and invasion capacity in epithelial cells cultured in vitro.

Entre as ß-lactamases, as enzimas CTX-M têm despertado atenção especial pela alta incidência e grande capacidade de propagação. Eventos como recombinação gênica, transferência plasmideal e multirresistência podem ser a razão da manutenção e da ampla disseminação dos genes blaCTX-M. Este é um trabalho retrospectivo que teve como objetivo caracterizar genes blaCTX-M presentes em Klebsiella spp. Foram estudadas 27 linhagens de Klebsiella pneumoniae e 8 linhagens de Klebsiella oxytoca, produtoras de ?-lactamase de espectro estendido, isoladas de pacientes hospitalizados no período de janeiro a junho de 2000. A detecção e identificação dos genes blaCTX-M, assim como dos elementos relacionados com a mobilização destes genes, foi realizada por PCR e seqüenciamento. A localização genética e a mobilidade dos genes blaCTX-M foram pesquisadas por análise plasmideal e hibridação e por conjugação. Os perfis de sensibilidade das linhagens estudadas e das linhagens transconjugantes foram comparados pela determinação da concentração inibitória mínima de antibióticos das classes das cefalosporinas, cefamicinas, aminoglicosídeos e quinolonas. Foram encontrados genes blaCTX-M em plasmídeos conjugativos em 13 (37%) linhagens estudadas: blaCTX-M-9 em 4 K. oxytoca, e blaCTX-M-2 em 9 K. pneumoniae. Os genes blaCTX-M-9 estavam associados ao elemento de inserção ISEcp1, enquanto os genes blaCTX-M-2 estavam associados a integrons de classe I contendo ISCR1. O genes blaCTX-M-2, carreado por plasmídeo, pode estar relacionado com disseminação horizontal entre vários clones de K. pneumoniae, enquanto o gene blaCTX-M-9 foi encontrado sendo carreado por um único clone de K. oxytoca. Este estudo determinou a incidência e a diversidade de enzimas CTX-M no período estudado, além de fornecer dados epidemiológicos que podem explicar a sua prevalência no mundo e contribuir para o entendimento e controle da disseminação deste tipo de resistência. / CTX-M enzymes, the world\'s most prevalent ß-lactamases disseminate very easily. Genetic recombination, plasmid transference and multiresistance could be responsible for the wide spread of blaCTM-X genes. This retrospective study aims to characterize blaCTX-M genes found in Klebsiella spp. The strains were isolated in hospital patients from January to June 2000 and consisted of 27 ESBL-producing Klebsiella pneumoniae and 8 ESBL-producing Klebsiella oxytoca. PCR and sequencing were used in the detection and identification of blaCTX-M genes and genetic elements associated with their mobilization. Determination of genetic localization and mobility of blaCTX-M genes was by plasmid analyses, hybridization and transfer assays. The minimal inhibitory concentrations (MICs) of cephalosporins, cefamicins, aminoglycosides and quinolone antimicrobials evaluated the antibiotic susceptibility profile of transconjugants and strains in the study. The blaCTX-M genes were found in 13 strains (37%): blaCTX-M-9 in 4 K. oxytoca and blaCTX-M-2 in 9 K. pneumoniae. The insertion sequence ISEcp1 was associated with blaCTX-M-9 and blaCTX-M-2 was found in a class I integron bearing ISCR1. Plasmid blaCTX-M-2 genes dissemination was due to horizontal transfer among many K. pneumoniae clones, while blaCTX-M-9 dissemination was associated with a particular clone of K. oxytoca. The study characterized incidence and diversity of CTX-M enzymes during the period studied. Moreover it showed epidemiological data, which may explain CTX-M prevalence worldwide and contribute for the understanding and control of the resistance spread.

No description available.

ß-hemolytic streptococci persist in 10-25% of patients with acute streptococal tonsillitis (about 10.000-25.000 per year in Sweden) in spite of treatment with a recommended dosage and schedule of Phenoxymethylpenicillin. The aim of the study was to investigate different bacteriological factors involved in treatment failures of streptococcal tonsillitis. Patients included in the study were 33 patients who underwent tonsillectomy, 62 persons included in a tonsillitis epidemic outbreak, 267 tonsillitis patients contacting the ENT-clinic, Sahlgrenska Hospital, Göteborg, and 20 healthy volunteers taking Phenoxymethylpenicillin. It was found that the Steer's steel pin replicator was a useful tool to study interference between a- and ß-hemolytic streptococci and a guantitative differen ce in. the inhibitory capacity of the different a-strains was noted, a-streptococci with a strong inhibitory capacity on ß-streptococci were isolated mainly from individuals seemingly resistant to ß-streptococcal tonsillitis, while from patients with repeated tonsillitis no or low numbers of inhibiting a-streptococci were demonstrated. Patients with clinical treatment failure had less a-streptococci with inhibiting capacity on their own ß-streptococcal strain compared with the healthy carriers. These treatment failures also showed beta-lactamase activity in their saliva pellet significantly more often than patients in the control groups. In volunteers penicillin was released from ordinary sugar coated tablets already in the mouth resulting in a decrease of the a-strep- tococcal flora. A synergistic effect on ß-hemolytic killing by low concentration of penicillin and inhibition of a-streptococci was noted in vitro and in vivo. Penicillin tolerance was registered in most strains from the treatment failure group, but in none of the strains from the group of successfully treated patients. A co-operation between different bacteriological factors (bacterial interference, beta-lactamase production, penicillin tolerance) seems to be important in treatment failures of streptococcal tonsillitis. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1986, härtill 6 uppsatser</p> / digitalisering@umu

Bacterial resistance to antibiotics is an emerging epidemic throughout the world and there is a desperate need for new antibiotics and new strategies to maintain the effectiveness of current agents. ??-Lactams, such as the penicillins and cephalosporins, have been the most important class of antibiotic for several decades and represent half of the global antibacterial market, but the continued use of ??-lactams is threatened by ??-lactamases, enzymes that efficiently inactivate ??-lactams through hydrolysis. Class A, C, and D ??-lactamases use an active-site serine residue for hydrolysis and achieve turnover through an acylenzyme intermediate while the class B metallo-??-lactamases (MBLs) use a zinc-bound hydroxide as the active-site nucleophile. Two successful approaches to combat ??-lactamase-mediated resistance have involved the development of ??-lactam antibiotics which bind poorly to ??-lactamases and the combination of ??-lactams with ??-lactamase inhibitors. These strategies have been effective for overcoming resistance due to class A ??-lactamases, but the ever-increasing prevalence of extended-spectrum ??-lactamases (ESBLs), metallo-??-lactamases, and carbapenemases compromises the effectiveness of current penicillins, cephalosporins, carbapenems, and mechanism-based ??-lactamase inhibitors. Cyclobutanone analogues of ??-lactam antibiotics were explored in the early 1980s as potential inhibitors of ??-lactamases and D-Ala-D-Ala transpeptidases, but simple analogues showed only weak inhibitory activity and this approach was subsequently abandoned. The increasing threat of multidrug-resistant ??-lactamase-producing organisms in recent years, however, has inspired a re-evaluation of these inhibitors since cyclobutanones have the potential to exhibit broad-spectrum inhibition of both serine- and metallo-??-lactamases through the formation of enzyme-bound hemiketals or hydrates. 7,7-Dichloro-2-thia-bicyclo[3.2.0]heptan-6-one-4-carboxylic acid (65), a dichlorocyclobutanone that had shown modest inhibition of the class B and D ??-lactamases IMP-1 and OXA-10 in earlier work in this laboratory, was prepared in an efficient seven-step sequence from triethyl phosphonoacetate (103) with an overall yield of 28%. Initial efforts to improve upon the potency of the cyclobutanones involved functionalization at C3 and a highly stereoselective chlorination with sulfuryl chloride provided the 3??-chloro derivative 117?? in nearly quantitative yield. Elimination of HCl from 117?? was achieved under a variety of conditions and 3-alkoxy derivatives were prepared from 117?? through diastereoselective substitution reactions with alcohols. Cyclobutanones with 3??-OR substituents were found to favour an endo envelope conformation while the 3??-OR derivatives adopt the exo envelope conformation. Evidence from X-ray crystal structures and ab initio molecular orbital calculations suggests that an anomeric effect contributes to the large conformational preference of the tetrahydrothiophene ring that favours the 3-alkoxy substituent in an axial orientation. In addition, the conformation of the bicyclic system was found to have a dramatic effect on the tendency of the cyclobutanone to undergo hemiketal formation. Cyclobutanone analogues of penicillins, including 3-alkoxy derivatives, and cyclobutanone analogues of penems were evaluated against class A, B, C, and D ??-lactamases and found to be moderate inhibitors of KPC-2, IMP-1, GC1, and OXA-10. The cyclobutanones found to be most potent were those which are hydrated to a larger extent in aqueous solution. Dichlorocyclobutanones were found to be better inhibitors than dechlorinated cyclobutanones and a 3??-methoxy derivative 152??, which favours the exo envelope conformation in which the C4 carboxylate is equatorial, was found to be a better inhibitor than cyclobutanones that favour the endo envelope conformation. A 3,4-unsaturated penem analogue, 153, showed comparable potency to that of 152?? and molecular models of enzyme-inhibitor complexes indicate that an equatorial carboxylate is required for binding to ??-lactamases. An X-ray crystal structure of 152?? bound to the class D ??-lactamase OXA-10 confirms that a serine hemiketal is formed in the active site and that the inhibitor adopts the exo envelope. The biochemical data described above demonstrate that cyclobutanones can indeed act as inhibitors of serine- and metallo-??-lactamases and these cyclobutanones represent the first class of reversible inhibitors to show moderate inhibition of all four classes of ??-lactamase. Although the inhibitory potency of these compounds is modest (low micromolar IC50 values), penem analogue 153 was able to enhance the potency of meropenem against carbapenem-resistant MBL-producing clinical isolates of Chryseobacterium meningosepticum and Stenotrophomonas maltophilia and the synergy demonstrated in these antimicrobial assays is encouraging. Synthetic studies toward other C3-alkyl and C3-thioalkyl-substituted inhibitors are described and the design and synthesis of C7-monochloro- and 7??-hydroxymethyl-7??-chloro cyclobutanone derivatives is presented.