[Susceptibility to betalactam antibiotics, glycopeptides and aminoglycosides in commensal strains of erythromycin-resistant alpha-hemolytic streptococci and Gemella spp].
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.


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.
Cerdá-Zolezzi
Paula
P
Departamento de Microbiología, Medicina Preventiva y Salud Pública, Facultad de Medicina, Universidad de Zaragoza, Zaragoza, España.
Goñi-Cepero
Pilar
P
Millán-Laplana
Leticia
L
Rubio-Calvo
Carmen
C
Durán
Estrella
E
Oca
Mercedes
M
Gómez-Lus
Rafael
R
D000617:Aminoglycosides / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D006020:Glycopeptides / Q000494:pharmacology*; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology; D006460:Hemolysin Proteins / Q000378:metabolism; D006801:Humans; D008169:Lung Abscess / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D010612:Pharyngitis / Q000382:microbiology; D012141:Respiratory Tract Infections / Q000382:microbiology; D040141:Staphylococcaceae / Q000187:drug effects*; D013290:Streptococcal Infections / Q000382:microbiology; D013291:Streptococcus / Q000187:drug effects*; D047090:beta-Lactams / Q000494:pharmacology*
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D006020:Glycopeptides; D006460:Hemolysin Proteins; D047090:beta-Lactams