RESUMEN
Streptococcus pyogenes (group A Streptococcus-GAS) is an important pathogen for humans. GAS has been associated with severe and invasive diseases. Despite the fact that these bacteria remain universally susceptible to penicillin, therapeutic failures have been reported in some GAS infections. Many hypotheses have been proposed to explain these antibiotic-unresponsive infections; however, none of them have fully elucidated this phenomenon. In this study, we show that GAS strains have the ability to form antimicrobial persisters when inoculated on abiotic surfaces to form a film of bacterial agglomerates (biofilm-like environment). Our data suggest that efflux pumps were possibly involved in this phenomenon. In fact, gene expression assays by real-time qRT-PCR showed upregulation of some genes associated with efflux pumps in persisters arising in the presence of penicillin. Phenotypic reversion assay and whole-genome sequencing indicated that this event was due to non-inherited resistance mechanisms. The persister cells showed downregulation of genes associated with protein biosynthesis and cell growth, as demonstrated by gene expression assays. Moreover, the proteomic analysis revealed that susceptible cells express higher levels of ribosome proteins. It is remarkable that previous studies have reported the recovery of S. pyogenes viable cells from tissue biopsies of patients presented with GAS invasive infections and submitted to therapy with antibiotics. The persistence phenomenon described herein brings new insights into the origin of therapeutic failures in S. pyogenes infections. Multifactorial mechanisms involving protein synthesis inhibition, cell growth impairment and efflux pumps seem to play roles in the formation of antimicrobial persisters in S. pyogenes.
RESUMEN
Community-acquired infections by methicillin-resistant Staphylococcus aureus (CA-MRSA) in the absence of classic risk factors for MRSA diseases have been reported in different continents. In the article presented here, using molecular typing methods as pulsed-field gel electrophoresis, staphylococcal cassette chromosome mec typing, and multilocus sequence typing, we characterized CA-MRSA isolates from Rio Janeiro and Porto Alegre. The results indicated the presence of international CA-MRSA clones in these 2 Brazilian cities. In addition, Panton-Valentine leukocidin and a number of staphylococcal enterotoxin encoding genes were accessed in these MRSA isolates by polymerase chain reaction detection.
Asunto(s)
Resistencia a la Meticilina/genética , Infecciones Estafilocócicas/epidemiología , Staphylococcus aureus/aislamiento & purificación , Toxinas Bacterianas/genética , Brasil/epidemiología , Infecciones Comunitarias Adquiridas/epidemiología , Infecciones Comunitarias Adquiridas/genética , Infecciones Comunitarias Adquiridas/microbiología , Farmacorresistencia Bacteriana Múltiple/genética , Electroforesis en Gel de Campo Pulsado , Exotoxinas/genética , Genotipo , Humanos , Leucocidinas/genética , Reacción en Cadena de la Polimerasa , Infecciones Estafilocócicas/clasificación , Infecciones Estafilocócicas/genética , Staphylococcus aureus/efectos de los fármacos , Staphylococcus aureus/genéticaRESUMEN
OBJECTIVES: To study biofilm production and to detect icaAD, atlE and aap genes in 137 isolates of methicillin-resistant Staphylococcus epidermidis (MRSE) obtained from healthy individuals from the community (35 isolates), from hospitalized patients at the Antônio Pedro University Hospital (25 isolates) and from individuals from a home-care system (HCS; 77 isolates). METHODS: Biofilm production was determined in vitro using polystyrene inert surfaces. icaAD, atlE and aap genes were detected using PCR. Hybridization experiments were also carried out to confirm some PCR results. Antimicrobial susceptibility testing was carried out using the NCCLS methods. RESULTS: Although many of the commensal MRSE isolates produced biofilms, the percentage of biofilm producers was significantly higher (P = 0.0107) among hospital isolates (76%) than among isolates from the community (60%) and from the HCS (57%). An association was observed between multiresistance and biofilm production for isolates obtained from healthy individuals from the community and from household contacts from the HCS (P < 0.0001). The concomitant presence of the ica operon and atlE and aap genes was associated with the strong biofilm-producer phenotype (P < 0.0001). CONCLUSION: Because many of the commensal MRSE isolates obtained from nares produced biofilms and carried icaAD, aap and atlE genes, biofilms or such genetic elements should not be used as markers for clinical significance. The biofilm environment seems to increase genetic exchanges and hence may contribute to multiresistance phenotypes.
