Antibiotic Susceptibility and Arsenic Tolerance of Urinary Bacteria Isolated from Arsenic-Exposed People in Nepal

Abstract

Community-based information on antibiotic susceptibility of urinary bacteria is useful in clinical practice, including empiric therapy. Owing to evidence of coselection of metal and antibiotic resistance, there is growing concern on testing of such selective pressure in clinical as well as environmental bacterial isolates. We examined arsenic tolerance and antibiotic resistance in urinary isolates and their possible coselection among arsenic-exposed subjects. Urinary arsenic levels were assessed by atomic absorption spectrophotometer. Antibiotic resistance and arsenic tolerance of urinary bacteria were observed by modified Kirby-Bauer and minimum inhibitory concentration methods, respectively. The percentage of one, two, and multidrug-resistant urinary isolates were 30.4%, 37%, and 30.4%, respectively. Isolates showed variable tolerance to arsenic species. Gram-negative isolates were more tolerant to arsenic species than Gram positive. Although statistically insignificant, arsenic tolerance tended to increase from total susceptible to two-drug resistance. However, multiple drug resistance was not induced by the urinary arsenic (p>0.05). We observed moderately positive correlation between urinary arsenic level to arsenic tolerance of isolates (p<0.05). Although tolerance significantly correlated to urinary arsenic level, coselection/coresistance of arsenic to the antibiotic resistance in urinary isolates is inconclusive and remains to be further elucidated.