Efflux mediated adaptive and cross resistance to ciprofloxacin and benzalkonium chloride in Pseudomonas aeruginosa of dairy origin.

The present study was undertaken to investigate the role of efflux pump activity (EPA) in conferring adaptive and cross resistances against ciprofloxacin (CF) and benzalkonium chloride (BC) in dairy isolates of Pseudomonas aeruginosa. Biofilm formation potential was correlated with development of adaptive resistance in originally resistant strains. Irrespective of parent strains's susceptibility, isolates developed substantial adaptive resistance against CF and BC. Significant difference was observed in ability of non resistant isolates to develop adaptive resistance against CF and BC (P < 0.02) and subsequent cross resistance. EPA was quantified using EtBr (Ethidium Bromide) model and its role was more prominent [confirmed by its inhibition using efflux pump inhibitor (EPI) 2,4-dinitrophenol (DNP)], in conferring adaptive resistance (P = 0.147) than cross resistance (P = 0.343). Reduction in adaptive resistances due to EPI was more evident in originally non resistant strains, which reaffirms EPA as probable mechanism of adaptive resistance. The present study perhaps first of its kind, suggests an active role of EPA in conferring adaptive and cross resistances in food related P. aeruginosa isolates and supports reverse hypothesis that antibiotic-resistant organisms eventually become tolerant to other antibacterial agents as well.