In vitro susceptibility of pathogenic Vibrio species to norfloxacin and six other antimicrobial agents

Abstract

The in vitro activity of norfloxacin and six other antimicrobial agents was tested against 93 vibrio strains representing the currently described pathogenic Vibrio species. Norfloxacin had excellent activity against all species, with the following MICs for 90% of the strains: 0.016 ,ug/ml for Vibrio cholerae (including tetracycline-resistant V. cholerae 01 strains), 0.25 ,ug/ml for V. parahaemolyticus, and 0.063 ,ig/ml for V.vulnificus.Tetracycline is currently the drug of choice for serious vibrio infections (10,14). Since 1978, however, an increasing number of Vibrio cholerae 01 strains have been identified that have plasmid-mediated resistance to multiple antibiotics, including tetracycline. These strains have been responsible for major epidemics in Tanzania (9) and Bangladesh (7) and are currently endemic in parts of Africa (J. G. Morris 503, 1984). Appearance of these strains has prompted a search for alternative antimicrobial agents with activity against vibrios. Norfloxacin is a new carboxyquinoline derivative that has in vitro activity against a number of enteric pathogens, including campylobacter, salmonella, shigella, toxigenic Escherichia coli, yersinia, and, in testing involving a limited number of strains, V. parahaemolyticus and V. cholerae (4,8,11,13). In vitro activity against V. cholerae 01 would make norfloxacin an attractive drug for further study in areas with tetracycline-resistant cholera. Demonstration of activity against the other known pathogenic Vibrio species would also enhance the potential usefulness of norfloxacin as a broad-spectrum agent for treatment of bacterial gastroenteritis. In this study we compared the in vitro activity of norfloxacin to that of nalidixic acid, tetracycline, chloramphenicol, ampicillin, trimethoprim-sulfamethoxazole, and gentamicin against 93 vibrio strains representing all known pathogenic Vibrio species (10).( Results of the microtiter MIC assays are given in Tables 1 and 2. All vibrio strains tested were susceptible to norfloxacin, with MICs of .0.5 pLg/ml. V. cholerae strains were very susceptible to the drug, with MICs of 0.016 ,ug/ml for 90% of the strains tested. The presence of an R factor did not influence the norfloxacin MICs. Only one V. cholerae strain had a norfloxacin MIC of >0.016 ,ug/ml: the MIC for this strain was 0.25 ,ug/ml, with a corresponding MIC of nalidixic acid of 32 jLg/ml. A significant inoculum effect was observed for one of the four V. cholerae 01 strains tested, with MICs of <0.008 ,ug/ml at 103 and 105 organisms per ml and 1.0 ,ug/ml at 107 organisms per ml. For one of the two V. parahaemolyticus strains tested, the MIC increased from 0.25 to 1.0 ,ug/ml with an increase in the inoculum from 105 to 107 organisms per ml. The MIC for the V. vulnificus strain increased from 0.031 ,ug/ml at 103 organisms per ml to 0.125 ,ug/ml at 105 organisms per ml and 1 ,ug/ml at 107 organisms per ml.Our data indicate that norfloxacin may be a useful agent for treatment of cholera. Peak stool concentrations of the drug after a single 400-mg o...

Clinical Characteristics and Molecular Subtyping ofVibrio vulnificusIllnesses, Israel

“…These results concur with those of similar studies of clinical and environmental V. vulnifi cus biotype 1 isolates from the United States (32,33) and Taiwan (22). Only a few isolates from Taiwan showed resistance to ceftazidime and moxalactam.…”

Construction of a tetracycline inducible expression vector and characterization of its use in Vibrio cholerae

“…The results showed that the MIC for aTc for V. cholerae was 300 ng/ml while aTc MIC for E. coli was 3 ug/ml which is in agreement with previous findings (Oliva et al, 1992). The 10-fold difference in the aTc MIC between V. cholerae and E. coli is similar to the respective tetracycline MICs reported for each organism (Morris et al, 1985; Oliva et al, 1992). …”

Occurrence of Vibrio cholerae non-O1 in three wastewater treatment plants in Agadir (Morocco)

“…In this study, all environmental isolates were non-O1 serotype, strains resistant to SXT (19%) also showed resistance to NAL, and the majority of AMX resistant strains showed resistance to other antibiotics such as NAL, TIC, and FOS. However, ampicillin's resistance has been reported and increases for V. cholerae non-O1 strains (Morris et al 1985;Sciortino et al 1996). The presence of plasmids has not been examined, but they might explain differences in the frequency of resistant strains.…”