Abstract
The antibiotic resistance and heavy metal tolerance pattern of 201 water borne thermotolerant coliforms isolated from rural areas were studied. Most of the isolates exhibited resistance to one or more antibiotics under study, and expressed tolerance to multiple metals. Twenty four strains representing different resistance combinations were tested for plasmid transfer to Escherichia coli K-12 recipient strain. Plasmid transfer was detected in all 24 strains studied for conjugation. Among antimicrobials bacitracin, ampicillin, and among metals nickel, copper, cadmium, cobalt, chromium and arsenic resistances were transferred most frequently. Linked transfer of antibiotics and metals was demonstrated in 12 strains. Thirty two cultures of thermotolerant coliforms were studied for R-plasmid curing using acridine orange. Among antibiotics, curing of resistance was observed for streptomycin, cephaloridine and kanamycin. Curing of resistance to nickel, copper, mercury, chromium, copper and arsenic were also observed. The potential health risk of plasmid mediated resistances to antibiotics and metal ions in coliforms isolated from rural drinking water sources is discussed. Key words: Thermo-tolerant coliforms, R-plasmids, conjugation transfer, resistance transfer
Highlights
Thermo-tolerant coliforms is an indicator group of fecal coliforms, which has all the properties of total coliforms, and capable to ferment lactose with the production of acid and gas in 24 h at 44.5°C (APHA, 1992)
Thermotolerant isolates (201) from various drinking water sources were studied for antibiotic susceptibility test (Figure 1)
The results indicated widespread occurrence of antibiotic resistance among thermotolerant isolates in drinking water sources
Summary
Thermo-tolerant coliforms is an indicator group of fecal coliforms, which has all the properties of total coliforms, and capable to ferment lactose with the production of acid and gas in 24 h at 44.5°C (APHA, 1992). Fecal coliforms are natural inhabitants of the gut of humans and other warm-blooded animals. They are present in water bodies contaminated with human and animal fecal waste. The contaminated water bodies serve as natural habitats of pathogenic coliforms, thereby playing a role in the disease process (Ademola et al, 2009). Water-borne potential pathogens such as E. coli 0157, Salmonella spp., Shigella spp. and Vibrio cholerae can lead to diarrhoeal outbreaks that may have serious medical implications (WHO, 2000). Considerable concern has been expressed over the prevalence of multiple antibiotic resistant (MAR) bacteria in drinking water sources. The indiscriminate use and subsequent release of residual antibiotics in wastewater is considered an important factor for the emergence, selection and dissemination of antimicrobial resistant bacteria.
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