BACTERICIDAL STUDIES OF PENICILLIN-GENTAMICIN COMBINATIONS AGAINST GROUP B STREPTOCOCCI

• Published in: Journal of antibiotics 1977, Vol.30(6), pp.513-518
• Main Authors: OVERTURF, GARY D., HOROWITZ, MARC, WILKINS, JEANETTE, LEEDOM, JOHN, STEINBERG, EVAN
• Format: Article
• Language: English
• Subjects: Ampicillin - pharmacology; Drug Interactions; Gentamicins - pharmacology; Kanamycin - pharmacology; Microbial Sensitivity Tests; Penicillin G - pharmacology; Penicillins - pharmacology; Streptococcus agalactiae - drug effects; Time Factors
• ISSN: 0021-8820; 1881-1469
• DOI: 10.7164/antibiotics.30.513

The bactericidal activity of penicillin-aminoglycoside combinations was studied in 16 strains of Group B streptococci. Minimal inhibitory concentrations (MIC) against kanamycin or gentamicin were greater than 50μg/ml, whereas ampicillin or penicillin inhibitory concentrations were uniformly less than 0.1μg/ml. Although all strains had bactericidal concentrations (MBC) less than 0.1μg penicillin/ml, penicillin at a concentration equal to each strains respective MBC reduced inoculum colony forming units (CFU) 2 logs in only 6 of 16 strains in bactericidal kinetic studies. However, the addition of gentamicin in concentrations of 5.0 or 10.0μg/ml to penicillin markedly enhanced bactericidal activity in all strains tested. The addition of lower concentrations of gentamicin (1.0μg/ml) had minimal advantage over penicillin alone. No distinct advantage was noted for combinations including either ampicillin or kanamycin. The theoretical advantage of penicillin-aminoglycoside combinations in experimental conditions, suggests that the use of antibiotic combinations in clinical infections due to Group B streptococci, may result in a more rapid eradication of these organisms.