[Susceptibility to betalactam antibiotics, glycopeptides and aminoglycosides in commensal strains of erythromycin-resistant alpha-hemolytic streptococci and Gemella spp]. / Sensibilidad a antibióticos betalactámicos, glucopéptidos y aminoglucósidos en cepas comensales de estreptococos alfahemolíticos y Gemella spp. resistentes a eritromicina.

OBJECTIVE: Susceptibility to seven betalactam antibiotics, glycopeptides and aminoglycosides was investigated in 190 erythromycin-resistant alpha-hemolytic streptococci and 30 Gemella spp, mainly from normal flora. MATERIAL AND METHODS: Antimicrobial susceptibility testing was performed by a standard agar diffusion test and a standard agar dilution method according to NCCLS/CLSI criteria. RESULTS: 62.6% of alfahemolytic streptococci and 53.3% of Gemella spp. were not susceptible to penicillin (MIC50: 0,5 microg/mL). Cefuroxime was the least active cephalosporin (MIC50: 1 microg/mL and 0.5 microg/mL, in streptococci and Gemella spp., respectively), whereas cefotaxime, ceftriaxone (MIC50: 0.25 microg/mL) and cefepime (MIC50: 0.5 microg/mL) were more active than penicillin. All isolates were susceptible to vancomycin, teicoplanin and gentamicin. Four alfahemolytic streptococcal strains showed high-level resistance to streptomycin, and three strains to kanamycin. There were no significant differences in resistance rates to the antibiotics studied between strains with different macrolide resistance phenotypes. Resistance to penicillin and other betalactam antibiotics (73.8%) was prevalent in M phenotype strains and resistance to penicillin and other classes of antibiotics predominated in constitutive (cMLS(B)) strains (71.4%). CONCLUSIONS: Resistance to penicillin in erythromycin-resistant strains was notably high in this study. This fact has important clinical implications because of the endogenous character of alpha-hemolytic streptococcal and Gemella spp. infections. The lower cefuroxime activity suggests that use of this agent against other pathogens would be effective in preserving the oropharyngeal microflora analyzed.

Sensibilidad a antibióticos betalactámicos, glucopéptidos y aminoglucósidos en cepas comensales de estreptococos alfahemolíticos y Gemella spp. resistentes a eritromicina / Susceptibility to betalactam antibiotics, glycopeptides and aminoglycosides in commensal strains of erythromycin resistant alfahemolytic streptococci and Gemella spp

Objetivo. Se investigó la sensibilidad de 190 estreptococos alfahemolíticos y 30 Gemella spp., en su mayoría comensales y resistentes a eritromicina, frente a 7 antibióticos betalactámicos, glucopépticos y aminoglucósidos. Material y métodos. Para determinar la sensibilidad a los antimicrobianos se utilizaron las técnicas de dilución y difusión en agar, según las normas del National Committee for Clinical Laboratory Standards/Clinical and Laboratory Standards Institute (NCCLS/CLSI). Resultados. El 62,6% de los estreptococos alfahemolíticos y el 53,3% de Gemella spp. no fueron sensibles a penicilina (concentración inhibitoria mínima al 50% [CIM50]: 0,5 mg/ml). Cefuroxima fue la cefalosporina que presentó menor actividad (CIM50: 1 mg/ml y 0,5 mg/ml, en estreptococos y Gemella spp.), mientras que cefotaxima, ceftriaxona (CIM50: 0,25 mg/ml) y cefepima (CIM50: 0,5 mg/ml) presentaron una actividad superior a penicilina. El 100% de los aislamientos fueron sensibles a vancomicina, teicoplanina y gentamicina. Cuatro cepas de estreptococos alfahemolíticos presentaron resistencia de alto nivel a estreptomicina y tres a kanamicina. No hubo diferencia significativa en el comportamiento de los antibióticos estudiados frente a las cepas con diferente fenotipo de resistencia a macrólidos. Tanto en los aislamientos con fenotipo M como en aquéllos con fenotipo constitutivo (MLSBc) predominó la resistencia a penicilina y a otros antibióticos betalactámicos frente al patrón de resistencia, que incluye sólo penicilina o bien penicilina, otros antibióticos betalactámicos y aminoglucósidos. Conclusiones. Las tasas de resistencia a penicilina en las cepas comensales resistentes a eritromicina son particularmente elevadas, hecho que tiene una importante implicación clínica por el carácter endógeno de las infecciones causadas por estas bacterias. La menor actividad de cefuroxima podría sugerir que su utilización frente a otros patógenos preservaría en mayor grado a la microbiota orofaríngea estudiada (AU)

Objective. Susceptibility to seven betalactam antibiotics, glycopeptides and aminoglycosides was investigated in 190 erythromycin-resistant alfahemolytic streptococci and 30 Gemella spp, mainly from normal flora. Material and methods. Antimicrobial susceptibility testing was performed by a standard agar diffusion test and a standard agar dilution method according to NCCLS/CLSI criteria. Results. 62.6% of alfahemolytic streptococci and 53.3% of Gemella spp. were not susceptible to penicillin (MIC50: 0,5 mg/mL). Cefuroxime was the least active cephalosporin (MIC50: 1 mg/mL and 0.5 mg/mL, in streptococci and Gemella spp., respectively), whereas cefotaxime, ceftriaxone (MIC50: 0.25 mg/mL) and cefepime (MIC50: 0.5 mg/mL) were more active than penicillin. All isolates were susceptible to vancomycin, teicoplanin and gentamicin. Four alfahemolytic streptococcal strains showed high-level resistance to streptomycin, and three strains to kanamycin. There were no significant differences in resistance rates to the antibiotics studied between strains with different macrolide resistance phenotypes. Resistance to penicillin and other betalactam antibiotics (73.8%) was prevalent in M phenotype strains and resistance to penicillin and other classes of antibiotics predominated in constitutive (cMLSB) strains (71.4%). Conclusions. Resistance to penicillin in erythromycin-resistant strains was notably high in this study. This fact has important clinical implications because of the endogenous character of alfahemolytic streptococcal and Gemella spp. infections. The lower cefuroxime activity suggests that use of this agent against other pathogens would be effective in preserving the oropharyngeal microflora analyzed (AU)