RESUMO
The constitutive or inducible macrolide-lincosamide-streptogramin (MLS) phenotype of 30 erm(B)-positive Streptococcus pyogenes isolates was determined by different methods and under various growth conditions and correlated to the sequence of the 5'-untranslated regions of erm(B). The MLS phenotype of one-third of the isolates could not be classified. In liquid medium, some of these isolates responded to induction only during the logarithmic phase of growth, while others expressed clindamycin resistance even under noninducing conditions. By increasing the growth rate, we observed a shift from a constitutive towards an inducible pattern of resistance. All data were confirmed by analysis of the 23S rRNA methylation level. The erm(B)-5'-untranslated region was 99% similar in sequence. In erm(B)-positive S. pyogenes, the MLS phenotype is strongly influenced by culture conditions and control of its expression does not depend exclusively on the sequence of the erm(B)-5'-untranslated region.
Assuntos
Antibacterianos/farmacologia , Proteínas de Bactérias/metabolismo , Farmacorresistência Bacteriana , Lincosamidas/farmacologia , Macrolídeos/farmacologia , Streptococcus pyogenes/efeitos dos fármacos , Estreptogramina B/farmacologia , Regiões 5' não Traduzidas , Adolescente , Proteínas de Bactérias/genética , Criança , Pré-Escolar , DNA Bacteriano/química , DNA Bacteriano/genética , Humanos , Lactente , Recém-Nascido , Metilação , Testes de Sensibilidade Microbiana/métodos , RNA Ribossômico 23S/metabolismo , Análise de Sequência de DNA , Homologia de Sequência do Ácido Nucleico , Infecções Estreptocócicas/microbiologia , Streptococcus pyogenes/genética , Streptococcus pyogenes/isolamento & purificaçãoRESUMO
The presence and assortment of 16 known virulence/resistance genetic determinants carried by prophages or prophage-like elements were tested in 212 clinical group A Streptococcus (GAS) strains and related to available data from SmaI macrorestriction/pulsed-field gel electrophoresis analysis and emm typing. A strong correlation existed among the three analyses. This finding supports the substantial contribution to the evolution and diversification of the GAS genome attributed to phages.
Assuntos
Portador Sadio/microbiologia , Genes Virais , Prófagos/genética , Infecções Estreptocócicas/microbiologia , Streptococcus pyogenes/genética , Fatores de Virulência/genética , Adolescente , Técnicas de Tipagem Bacteriana , Criança , Pré-Escolar , Impressões Digitais de DNA , Eletroforese em Gel de Campo Pulsado , Genótipo , Humanos , Itália , Streptococcus pyogenes/classificaçãoRESUMO
Several characteristics were analysed in 37 Staphylococcus aureus isolates from nosocomial catheter infections: the PFGE profile after SmaI digestion of chromosomal DNA, the ability to form a biofilm on a polystyrene surface, antibiotic susceptibility patterns (penicillin, oxacillin, erythromycin, tetracycline, clindamycin, telithromycin, gentamicin, ciprofloxacin, quinupristin/dalfopristin, rifampicin, vancomycin and linezolid), and the presence of genetic determinants of antibiotic resistance and biofilm formation. All strains but three (92 %) were able to grow on a plastic surface as a biofilm. An almost complete association was found between phenotypes and genotypic traits of antibiotic resistance, whilst PFGE profiling showed the highly polyclonal composition of the set of strains under study. Sixteen isolates (43 %) were meticillin-resistant and were subjected to staphylococcal cassette chromosome mec (SCCmec) and cassette chromosome recombinase (ccr) complex type determination by multiplex PCR. Only a subgroup of six strains belonged to the archaic clone PFGE type and bore the SCCmec/ccrAB type I structure. Among the remaining strains some presented small rearrangements of the SCCmec/ccrAB genetic locus, whilst others could barely be traced back to a known structural type. These observations suggest that, at the local level and at a particular site of infection, S. aureus may show great genetic variability and escape the general rule of expansion of the S. aureus pandemic clones.