Effect of pH and Human Serum on the Susceptibility of Group D Streptococci (Enterococci) to Ampicillin In Vitro
AUTOR(ES)
Gilbert, D. N.
RESUMO
The in vitro susceptibility of group D streptococci (enterococci) to ampicillin was studied comparing the results obtained in Mueller-Hinton broth (MHB) with those obtained in normal human serum (NHS). The rate of enterococcal killing was consistently faster in NHS than in MHB at equivalent ampicillin concentrations. Whereas an increasing media pH appeared to decrease the susceptibility of enterococci to ampicillin by determinations of the minimum bactericidal concentration (MBC) of ampicillin, an opposite increase in susceptibility was observed when the rate of bactericidal activity was studied. This difference may be explainable by the instability of ampicillin at higher pH values. In both MHB and NHS a paradoxical decrease in the rate and extent of enterococcal killing occurred as the ampicillin concentration was increased above the minimally effective concentration. These results demonstrate the inadequacies of the MBC test system and the need for standardizing test media used for determining the susceptibility of enterococci to ampicillin.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=429150Documentos Relacionados
- Effect of pH on in vitro antimicrobial susceptibility of the Bacteroides fragilis group.
- Effect of Carbon Dioxide and pH on Susceptibility of Bacteroides fragilis Group to Erythromycin
- Effect of Culture Medium Composition and pH on the Production of M Protein and Proteinase by Group A Streptococci
- Impact of pH and cationic supplementation on in vitro postantibiotic effect.
- Effect of pH on In Vitro Phagocytosis of Streptococcus pyogenes