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EVALUATION OF THE USE OF DIFFERENT ANTIBIOTICS IN THE DIRECT VIABLE COUNT METHOD TO DETECT FECAL ENTEROCOCCI
Citation:
Santo Domingo, J, T Newby, AND S M. Harmon. EVALUATION OF THE USE OF DIFFERENT ANTIBIOTICS IN THE DIRECT VIABLE COUNT METHOD TO DETECT FECAL ENTEROCOCCI. Presented at American Society of Microbiology, Los Angeles, CA, May 21-25, 2000.
Impact/Purpose:
The goal of this research project is to evaluate and compare methods that rapidly (less than 2 hours) measure fecal contamination of water with respect to accuracy, specificity, and ease of use.
Description:
The detection of fecal pollution is performed via culturing methods in spite of the fact that culturable counts can severely underestimate the densities of fecal microorganisms. One approach that has been used to enumerate bacteria is the direct viable count method (DVC). The objective of this study was to evaluate the use of nalidixic acid, priomidic acid, pipemidic acid, ciprofloxacin, and cephalexin in the DVC method to measure viability of fecal enterococci. The effect of the anitbiotics on five environmental isolates was examined using flow cytometry, scanning electron microsocpy, epifluorescence microscoy, and image analysis. Not all of the antibiotics tested induced an increase in the isolates cell size, even after eight hours of incubation with elevated antibiotic concentrations. Although differences in the general response to the antibiotic treatment were observed between starving and nonstarving cells, in general the combination of ciprofloxacin and cephalexin was more effective in promoting increase in cell size than the individual antibiotics. Additionally, cell biovolume was found to be a more sensitive indicator of viability for fecal enterococci than cell length and surface area.