Investigation of Antibiotic Resistance Genes (ARGs) in Bacteria Isolated from Environmental Samples

Abstract

Antibiotic resistance is a global health issue and is more daunting in developing countries. Antibiotic resistance genes (ARGs) found in clinical and environmental bacteria are investigated to understand the resistance mechanisms. There is paucity of data about spread of ARGs in environmental bacteria in Pakistan. Therefore, the aim of the study was to assess previously isolated bacteria from environmental samples for prevalence of ARGs encoding resistance to the most frequently used classes of antibi-otics in Pakistan which are penicillins and fluoroquinolones. The study was designed to determine MICs of five antibiotics and to screen and confirm the previously iso-lated 60 bacterial strains for production of class A (ESBL), B (MBL) and C (AmpC) beta-lactamases. PCR was also optimized for detection of two ARGs, blaTEM and qnrS. Results showed that MICs were higher for penicillins than for fluoroquinolones (AMP>AMX>CIP>OFX>LEV). Only five strains (8.3 %) were ESBL producers among which four belonged to the genus Aeromonas and one to Escherichia. Three isolates (5 %) proved to be MBL producers among which two belonged to the genus Citrobacter and one to Stenotrophomonas. Four isolates (6.6 %) were AmpC produc-ers among which three belonged to the genus Pseudomonas and one to Morganella. The optimized PCR was able to detect the ARGs blaTEM-1 and qnrS2 in Aeromonas spp. and Escherichia sp. The obtained sequences shared high homology with the pre-viously identified ARGS. The environmental bacteria in the aquatic environment of Pakistan carry ARGs of clinical relevance which is an indication of anthropogenic antibiotic resistance contamination. Keywords: Antibiotic resistance, Antibiotic resistance genes, ESBLs, MBLs, AmpCs, Environmental bacterial isolates