RESUMO
Nasal colonization by the pathogen Staphylococcus aureus is a risk factor for subsequent infection. Loss of function mutations in the gene encoding the virulence regulator Rsp are associated with the transition of S. aureus from a colonizing isolate to one that causes bacteraemia. Here, we report the identification of several novel activity-altering mutations in rsp detected in clinical isolates, including for the first time, mutations that enhance agr operon activity. We assessed how these mutations affected infection-relevant phenotypes and found loss and enhancement of function mutations to have contrasting effects on S. aureus survival in blood and antibiotic susceptibility. These findings add to the growing body of evidence that suggests S. aureus 'trades off' virulence for the acquisition of traits that benefit survival in the host, and indicates that infection severity and treatment options can be significantly affected by mutations in the virulence regulator rsp.
Assuntos
Antibacterianos/farmacologia , Atividade Bactericida do Sangue , Farmacorresistência Bacteriana , Genes Reguladores , Polimorfismo Genético , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/fisiologia , Humanos , Viabilidade Microbiana , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/genética , Staphylococcus aureus/isolamento & purificação , Fatores de Virulência/biossínteseRESUMO
Emerging resistance to current antibiotics raises the need for new microbial drug targets. We show that targeting branched-chain amino acid (BCAA) biosynthesis using sulfonylurea herbicides, which inhibit the BCAA biosynthetic enzyme acetohydroxyacid synthase (AHAS), can exert bacteriostatic effects on several pathogenic bacteria, including Burkholderia pseudomallei, Pseudomonas aeruginosa, and Acinetobacter baumannii. Our results suggest that targeting biosynthetic enzymes like AHAS, which are lacking in humans, could represent a promising antimicrobial drug strategy.
Assuntos
Acetolactato Sintase/antagonistas & inibidores , Acinetobacter baumannii/efeitos dos fármacos , Proteínas de Bactérias/antagonistas & inibidores , Burkholderia pseudomallei/efeitos dos fármacos , Herbicidas/farmacologia , Pseudomonas aeruginosa/efeitos dos fármacos , Compostos de Sulfonilureia/farmacologia , Acetolactato Sintase/metabolismo , Acinetobacter baumannii/enzimologia , Acinetobacter baumannii/crescimento & desenvolvimento , Aminoácidos de Cadeia Ramificada/antagonistas & inibidores , Aminoácidos de Cadeia Ramificada/biossíntese , Animais , Proteínas de Bactérias/metabolismo , Burkholderia pseudomallei/enzimologia , Burkholderia pseudomallei/crescimento & desenvolvimento , Feminino , Melioidose/tratamento farmacológico , Melioidose/microbiologia , Melioidose/mortalidade , Camundongos , Camundongos Endogâmicos BALB C , Testes de Sensibilidade Microbiana , Infecções por Pseudomonas/tratamento farmacológico , Infecções por Pseudomonas/microbiologia , Infecções por Pseudomonas/mortalidade , Pseudomonas aeruginosa/enzimologia , Pseudomonas aeruginosa/crescimento & desenvolvimento , Análise de SobrevidaRESUMO
OBJECTIVES: The multidrug-resistant bacteria Acinetobacter baumannii is a major cause of hospital-associated infection; a vaccine could significantly reduce this burden. The aim was to develop a clinically relevant model of A. baumannii respiratory tract infection and to test the impact of different immunization routes on protective immunity provided by an outer membrane vesicle (OMV) vaccine. METHODS: BALB/c mice were intranasally challenged with isolates of oxa23-positive global clone GC2 A. baumannii from the lungs of patients with ventilator-associated pneumonia. Mice were immunized with OMVs by the intramuscular, subcutaneous or intranasal routes; protection was determined by measuring local and systemic bacterial load. RESULTS: Infection with A. baumannii clinical isolates led to a more disseminated infection than the prototype A. baumannii strain ATCC17978; with bacteria detectable in upper and lower airways and the spleen. Intramuscular immunization induced an antibody response but did not protect against bacterial infection. However, intranasal immunization significantly reduced airway colonization and prevented systemic bacterial dissemination. CONCLUSIONS: Use of clinically relevant isolates of A. baumannii provides stringent model for vaccine development. Intranasal immunization with OMVs was an effective route for providing protection, demonstrating that local immunity is important in preventing A. baumannii infection.
Assuntos
Acinetobacter baumannii , Sepse , Animais , Camundongos , Imunização , Vacinação , Pulmão/microbiologia , Sepse/microbiologia , Proteínas da Membrana Bacteriana Externa , Vacinas Bacterianas , Camundongos Endogâmicos BALB CRESUMO
Central to the regulation of bacterial gene expression is the multisubunit enzyme RNA polymerase (RNAP), which is responsible for catalyzing transcription. As all adaptive processes are underpinned by changes in gene expression, the RNAP can be considered the major mediator of any adaptive response in the bacterial cell. In bacterial pathogens, theoretically, single nucleotide polymorphisms (SNPs) in genes that encode subunits of the RNAP and associated factors could mediate adaptation and confer a selective advantage to cope with biotic and abiotic stresses. We investigated this possibility by undertaking a systematic survey of SNPs in genes encoding the RNAP and associated factors in a collection of 1,429 methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates. We present evidence for the existence of several, hitherto unreported, nonsynonymous SNPs in genes encoding the RNAP and associated factors of MRSA ST22 clinical isolates and propose that the acquisition of amino acid substitutions in the RNAP could represent an adaptive strategy that contributes to the pathogenic success of MRSA.
Assuntos
Adaptação Fisiológica/genética , RNA Polimerases Dirigidas por DNA/genética , Farmacorresistência Bacteriana/genética , Regulação Bacteriana da Expressão Gênica/genética , Staphylococcus aureus Resistente à Meticilina/genética , Polimorfismo de Nucleotídeo Único/genética , Substituição de Aminoácidos/genética , Antibacterianos/farmacologia , Humanos , Staphylococcus aureus Resistente à Meticilina/isolamento & purificação , Rifampina/farmacologia , Infecções Estafilocócicas/tratamento farmacológicoRESUMO
Expression of ß-lactamase is the single most prevalent determinant of antibiotic resistance, rendering bacteria resistant to ß-lactam antibiotics. In this article, we describe the development of an antibiotic prodrug that combines ciprofloxacin with a ß-lactamase-cleavable motif. The prodrug is only bactericidal after activation by ß-lactamase. Bactericidal activity comparable to ciprofloxacin is demonstrated against clinically relevant E. coli isolates expressing diverse ß-lactamases; bactericidal activity was not observed in strains without ß-lactamase. These findings demonstrate that it is possible to exploit antibiotic resistance to selectively target ß-lactamase-producing bacteria using our prodrug approach, without adversely affecting bacteria that do not produce ß-lactamase. This paves the way for selective targeting of drug-resistant pathogens without disrupting or selecting for resistance within the microbiota, reducing the rate of secondary infections and subsequent antibiotic use.
Assuntos
Antibacterianos/farmacologia , Cefalosporinas/farmacologia , Ciprofloxacina/análogos & derivados , Ciprofloxacina/farmacologia , Pró-Fármacos/farmacologia , beta-Lactamases/metabolismo , Antibacterianos/síntese química , Antibacterianos/metabolismo , Cefalosporinas/síntese química , Cefalosporinas/metabolismo , Ciprofloxacina/metabolismo , Resistência Microbiana a Medicamentos/fisiologia , Escherichia coli/efeitos dos fármacos , Hidrólise , Testes de Sensibilidade Microbiana , Estrutura Molecular , Pró-Fármacos/síntese química , Pró-Fármacos/metabolismo , Relação Estrutura-Atividade , Inibidores da Topoisomerase II/síntese química , Inibidores da Topoisomerase II/metabolismo , Inibidores da Topoisomerase II/farmacologiaRESUMO
Staphylococcus aureus is a major cause of bacteremia, which frequently results in serious secondary infections such as infective endocarditis, osteomyelitis, and septic arthritis. The ability of S. aureus to cause such a wide range of infections has been ascribed to its huge armoury of different virulence factors, many of which are under the control of the quorum-sensing accessory gene regulator (Agr) system. However, a significant fraction of S. aureus bacteremia cases are caused by agr-defective isolates, calling into question the role of Agr in invasive staphylococcal infections. This review draws on recent work to define the role of Agr during bacteremia and explain why the loss of this major virulence regulator is sometimes a price worth paying for S. aureus.