Role of heavy metals on antibiotic resistance properties in lactose fermenting isolates collected from textile industry effluents

It is crucial to monitor the microbial ambience in heavy metal enriched industrial effluents that generally discharge into the environment. Therefore, the present study aimed to understand the load of heavy metals in multidrug-resistant lactose fermenting microorganisms isolating from textile industry effluents. Samples were collected from five different textile industrial canals. In most of the cases, the colony forming units (CFUs) per plate were uncountable at 10-6 dilution but countable at 10-10 dilution. A total of 100 lactose fermenting (LF) isolates were selected using 4 differential media and tested for the determination of minimum inhibitory concentrations (MICs) of heavy metals and antibiotic susceptibility. For nickel (Ni), the MIC was 0.3 mM for almost 98% isolates. The MIC was 0.5 mM for chromium (Cr) in almost 99% isolates. For lead (Pb), 100% isolates had a MIC of 0.4 mM. The most prevalent (36%) resistance pattern was found for sulfamethoxazole-trimethoprim (SXT) and only 10% isolates showed resistance to cefotaxime (CTX). The combined effect of heavy metals and antibiotics revealed that in most cases, the antibiotic zone of inhibition was increased. Plasmid profiling showed that among 14 selective isolates, high sized (21kb) plasmid was found in 6 isolates.   Key words: Antibiotics, effluents, heavy metals, minimum inhibitory concentration (MIC), antimicrobial resistance.