Efflux-mediated ciprofloxacin and cefixime resistance in Pseudomonas aeruginosa

Pseudomonas aeruginosa is a gram-negative, motile and clinically relevant bacterium. It is a significant pathogen associated with immunosuppression, cystic fibrosis and malignancy. Infections due to multidrug-resistant P. aeruginosa cause greater morbidity, death rate, and increased healthcare expenses. Drug efflux is a prevalent mechanism of antibiotic resistance in P. aeruginosa. The objective of the study was to analyze the antibiotic susceptibility profile of a clinical strain of P. aeruginosa (GC14) and to identify the mechanism of antibiotic resistance. The antibiotic resistance of GC14 was tested against 19 antibiotics using an antibiotic susceptibility test. A polymerase chain reaction-based strategy was employed to detect the presence of mexB, mexD and mexY efflux pump genes. The efflux pump inhibition assay was conducted to analyze the effect of efflux pumps on antibiotic resistance in GC14, using carbonyl cyanide m‑chlorophenyl hydrazone (CCCP) as an efflux pump inhibitor. The antibiotic susceptibility test confirmed that GC14 is multidrug-resistant and showed resistance to tetracycline, cefixime, ciprofloxacin, erythromycin, meropenem, azithromycin, doxycycline, aztreonam, co-trimoxazole and gentamycin. The genes encoding transporter protein viz. mexB, mexD and mexY were amplified successfully from P. aeruginosa, revealing the presence of efflux pump genes. The data obtained from the efflux inhibition assay using CCCP showed that efflux pumps play a significant role in ciprofloxacin and cefixime resistance. The study emphasizes the importance of efflux pumps in antibiotic resistance and also confers the necessity of continuous surveillance and regular monitoring of the emergence of multidrug-resistant isolates of P. aeruginosa.