The affect of pH and bacterial phenotypic state on antibiotic efficacy

Antibiotics are routinely used in woundcare for the treatment of local and systemic infections. Our goals in this paper were to (i) evaluate the antibiotic sensitivity of bacteria isolated from burn and chronic wounds and (ii) evaluate the effect of pH and bacterial phenotype on the efficacy of antibiotics. Chronic and burn wound isolates, which had been routinely isolated from patients at West Virginia University Hospital, USA, were evaluated for their sensitivity to antibiotics. Antimicrobial susceptibility testing was performed using a standardised disk diffusion assay on agar (quasi/non biofilm) and poloxamer (biofilm). Many of the Gram-positive and -negative isolates demonstrated changes in susceptibility to antibiotics when grown at different pH values and phenotypic states. Findings of this study highlight the clinical relevance that both pH and the phenotypic state of bacteria have on antibiotic performance. The study in particular has shown that bacteria exhibit an enhanced tolerance to antibiotics when grown in the biofilm phenotypic state. Such a finding suggests that more appropriate antibiotic sensitivity testing for woundcare and medicine is warranted to help assist in the enhancement of positive clinical outcomes.