[Efficacy of gentamycin combined with beta-lactam antibiotics against penicillin-resistant and non-resistant Streptococcus agalactiae].

BACKGROUND

Evaluation of the incidence, tolerance and the bactericidal activity against penicillin, ampicillin, cefotaxime, gentamicin and the combination of penicillin plus gentamicin, ampicillin plus gentamicin, cefotaxime plus gentamicin and cefotaxime plus ampicillin in 22 clinical isolates of Streptococcus agalactiae.

METHODS

Killing curves were performed. The concentrations of antibiotics was selected taking into account its level in cerebrospinal fluid.

RESULTS

We detected 5 (22.7%) tolerant strains to penicillin and ampicillin and 2 of them (9.0%) were also tolerant to cefotaxime. Bactericidal activity was seen in a 100% of the strains against the association penicillin plus gentamicin, ampicillin plus gentamicin and cefotaxime plus gentamicin, being greater than the bactericidal activity against cefotaxime (77.3%), penicillin, ampicillin and cefotaxime plus ampicillin (54.5% respectively).

CONCLUSIONS

Considering the high incidence of tolerance and the deficient bactericidal activity of the beta-lactam antibiotics against tolerant and no tolerant strains, it seems necessary to include gentamicin in the treatment of Streptococcus agalactiae severe infections. Several studies of experimental models must be performed to verify in vivo, the in vitro results.