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: Colistin was considered as one the most effective antibiotic against Acinetobacter baumannii, a widely-known opportunistic pathogen. In recent years, a number of colistin resistant strains have also been reported. This work is commenced to investigate the contribution of efflux pumps toward resistance to colistin-like cyclic polypeptide antibiotics, as the efflux pumps serve as the escape routes leading to drug-resistance. RNA was extracted from A. baumannii isolates cultured from samples procured by tracheal aspiration of infected patients. The expression of gene(s) that played major roles in the regulation of efflux pump families and involvement of integron systems were studied using real time PCR. Antimicrobial susceptibility tests were conducted to test antibiotic resistance of the isolate. It was observed that genes coding for sugE, ydhE, ydgE, mdfA, ynfA and tolC significantly contributed to resistance against colistin antibiotics, however, no significant transcriptional change was observed in the efflux pump, MexAB-OprM. Results suggest that A. baumanii readily pumps out colistin via efflux pumps belonging to MATE and SMR family. Integral role of efflux pumps and integron 1 genetic system was elucidated towards evolution of multi-drug resistant strain(s). Therefore, for accurate therapeutics, an early detection of efflux genes is crucial before prescribing against colistin resistant A. baumanii.

Soil-dwelling nematode Caenorhabditis elegans (C. elegans) is widely found in close vicinity with different types of microbes, including bacteria, fungus, viruses, etc. However, sensing environmental stress, they often undergo a dormant state called dauer for better survival. Our current study aims to decipher chemosensory responses of worms under Salmonella Typhimurium (WT-STM) infection and how bacterial gene modulating worms' chemosensory system to mediate dauer larvae development. We initially observed the olfactory preference of C. elegans toward the pathogenic WT-STM. Although prolonged exposure showed enhanced lawn occupancy of worms in fepB mutant Salmonella strain with better associative learning response compared to WT-STM counterpart. We also found strong participation of AWC neuron for sensing ΔfepB strain and mediating worms’ behavioral plasticity. Overall out study implying a relationship between chemosensory neurons and bacteria emitted signals alter worms’ behavioral plasticity which help us to understand complex scenario of host-pathogen interaction.

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