Antimicrobial resistance and plasmid profiles of Aeromonas hydrophila isolated from River Njoro, Kenya

The purpose of this study was to investigate the presence of Aeromonas hydrophila at commonly used water collection points on the River Njoro and to determine the in-vitro antimicrobial susceptibility and plasmid profiles of isolates. In total, 126 samples were collected and 36.5% of them were positive for A. hydrophila. The A. hydrophila were recovered on membrane filters, cultured on Trypticase Soy agar, Bile aesculin agar and Aeromonas Medium agar. They were further characterized using cytochrome oxidase and API 20E tests. Detection of drug susceptibility was determined using modified disc diffusion method to ampicillin (25 ìg), cefaclor (30 ìg), ceftizoxime (30 ìg), cefixime (5 ìg), cefazidime (30 ìg), gentamicin (200 ìg), streptomycin (25 ìg), chloramphenicol (50 ìg), nalidixic acid (30 ìg) and ciprofloxacin (1 ìg). Most of the isolates showed multi-drug resistance to two or more antibiotics. Chloramphenicol, nalidixic acid, ciprofloxacin, cefazidime and cefixime were the most sensitive drugs with 100% efficacy whereas ampicillin, cefaclor and streptomycin were the most resistant drugs having 100, 67 and 50 resistance, respectively. There was low resistance against ceftizoxime (16.7%) and gentamicin (23.3%). These results indicates that all A. hydrophila isolated from River Njoro had complete resistance to ampicillin and showed variable resistance to cefaclor, streptomycin, gentamycin and ceftizoxime. R-plasmids were extracted from multi-drug resistance strains and separated by agarose gel (0.8%) electrophoresis for profiling. Plasmid profiling revealed that most of the multi-drug resistant isolates contained one plasmid of 21.0 kb. Although some strains exhibited different antimicrobial resistance patterns, all of their plasmids were of the same size (21.0 kb). However, there were no plasmids in the antimicrobial sensitive isolates. This study also indicates that plasmid 21.0 kb is common in A. hydrophila and is important for antimicrobial resistance and virulence. Further studies are required to ascertain the role of this plasmid as a virulence marker.Key words: Aeromonas hydrophila, antimicrobial resistance, plasmid profile

Antimicrobial resistance and plasmid profiles of Aeromonas hydrophila isolated from River Njoro, Kenya

The purpose of this study was to investigate the presence of Aeromonas hydrophila at commonly used water collection points on the River Njoro and to determine the in-vitro antimicrobial susceptibility and plasmid profiles of isolates. In total, 126 samples were collected and 36.5% of them were positive for A. hydrophila. The A. hydrophila were recovered on membrane filters, cultured on Trypticase Soy agar, Bile aesculin agar and Aeromonas Medium agar. They were further characterized using cytochrome oxidase and API 20E tests. Detection of drug susceptibility was determined using modified disc diffusion method to ampicillin (25 μg), cefaclor (30 μg), ceftizoxime (30 μg), cefixime (5 μg), cefazidime (30 μg), gentamicin (200 μg), streptomycin (25 μg), chloramphenicol (50 μg), nalidixic acid (30 μg) and ciprofloxacin (1 μg). Most of the isolates showed multi-drug resistance to two or more antibiotics. Chloramphenicol, nalidixic acid, ciprofloxacin, cefazidime and cefixime were the most sensitive drugs with 100% efficacy whereas ampicillin, cefaclor and streptomycin were the most resistant drugs having 100, 67 and 50 resistance, respectively. There was low resistance against ceftizoxime (16.7%) and gentamicin (23.3%). These results indicates that all A. hydrophila isolated from River Njoro had complete resistance to ampicillin and showed variable resistance to cefaclor, streptomycin, gentamycin and ceftizoxime. R-plasmids were extracted from multi-drug resistance strains and separated by agarose gel (0.8%) electrophoresis for profiling. Plasmid profiling revealed that most of the multi-drug resistant isolates contained one plasmid of 21.0 kb. Although some strains exhibited different antimicrobial resistance patterns, all of their plasmids were of the same size (21.0 kb). However, there were no plasmids in the antimicrobial sensitive isolates. This study also indicates that plasmid 21.0 kb is common in A. hydrophila and is important for antimicrobial resistance and virulence. Further studies are required to ascertain the role of this plasmid as a virulence marker

Prevalence of multidrug resistant enteropathogenic bacteria causing diarrhea in Kibera community in Nairobi, Kenya

Diarrhea cases are on the increase in Kibera slum resulting in use of enormous amounts of antimicrobial agents and as a result, some pathogens develop resistance. This study was conducted in order to characterize some of the Gram-negative bacteria incriminated in the cause of diarrhea and their antimicrobial sensitivity. A total of 150 stools from children and adults collected from Kibera Community Health Centre were cultured in selective media and biochemical tests were done on suspected colonies. Serotyping using specific antisera was used to confirm species identity. Direct antimicrobial sensitivity tests using the Kirby-Bauer method were performed on ampicillin, tetracycline, kanamycin, chloramphenicol, streptomycin, gentamicin, ciprofloxacin and norfloxacin. The enteropathogenic bacteria identified in Kibera were pathogenic Escherichia coli with prevalence rate of 14%, while Shigella had a rate of 12%, Salmonella 8%, Yersinia enterocolitica 4% and no Vibrio cholerae. Most of the isolates showed multidrug resistance to two or more antibiotics. Norfloxacin and ciprofloxacin were the most sensitive drugs with 100% efficacy whereas ampicillin and gentamicin were the most resistant drugs having 84.2%and 68.4% resistance respectively. These results shows that even the antibiotics considered to be potent in treating diarrhoea are gradually becoming ineffective and should be closely monitored. Keywords: multi-drug resistance, diarrhea and enterics Journal of Tropical Microbiology and Biotechnology Vol. 2(1) 2006: 24-3