Determination of Antibiotic and Metal Resistance Patterns in Bacteria Isolated from Potable Water from Karachi, Pakistan

Water bodies with bacteria having antibiotic and metal resistance genes constitute a significant public concern. Excessive use of antibiotics in medicine, agriculture and industrial effluent contamination are suspected to be one of the major causes of increase antibiotic and metal resistance. This study was carried out to determine the antibiotic resistance and metal tolerance in bacteria isolated from potable water from different areas of the city of Karachi. Out of total 3721 bacterial isolates, 4.48% showed the resistance against all the eight antibiotics tested similarly 20.50% showed the resistance against all the four metals tested. More than 50% of the bacterial isolates showed resistance against the antibiotics, ampicillin, streptomycin, erythromycin, rifampicin and metranidazole. The percentage of metal tolerant organisms was also found to be variable ranging from 57.99% showing tolerance to 0.5mM copper to 31.98% showing tolerance to 0.5 mM cobalt. The plasmid profiles of various representative organisms although showed no correlation between the number and size of the plasmid to the level of antibiotic resistance or heavy metal tolerance, however the presence of similar size plasmids among different bacteria isolated from different locations of the city was observed. The finding suggests that potable water is an important source for the spread of antibiotic resistant and metal tolerant bacteria in Karachi. Research also indicates that there is probably a significant amount of antibiotics and metal in the environment of Karachi that exerts high selection pressure on the organisms to maintain antibiotic resistance and heavy metal tolerant genes in their genome.