Antibiotic resistance profiling of marine halophilic bacteria and haloarchaea

Drug resistance in microorganisms is an emerging phenomenon that poses challenges to public health and treatment. The reservoir of drug resistance genes found in the resistome of environmental isolates in aquatic saline systems has been augmenting continuously. The spread of drug resistance is attributed to the dissemination of drug resistant pathogens occurring in sewage and wastewater released in the marine environments like seas. Halophiles are salt loving organisms that are found naturally in these marine environments, sea water, salterns and lakes. The present study aimed at investigation of the antibiotic resistance profile of halophiles isolated from marine ecosystems of the coastal Maharashtra, India using disk diffusion method. The plausible mechanism of drug resistance in the marine halophiles was investigated by detecting plasmids and antibiotic efflux pumps using EtBr-Cart wheel assay. The haloarchaea, Haloarcula sp. RR14 and Halovivax sp. RT5 showed multidrug resistance and presence of efflux pumps (MICEtBr= 0.5 µg/ml). The resistance of gram positive halophiles was in following order: Salimicrobium salexigens RR5 > Salimicrobium flavidum RR2 > Alkalibacillus almallahensis RR3. Amongst gram negative halophiles, their resistance was in following order: Halomonas smyrnensis RR7 > Halomonas koreensis RR1 > Marinobacter oulmenensis RR6. Plasmids were detected in Haloarcula sp., Halomonassp. and Marinobacter sp. The present study related to antibiotic resistance of halophiles from marine environment is significant as some of the marine halophilic isolates like Halomonas sp. have been reported as potential pathogens in recent times.