EFFECT OF EFFLUX PUMP EXPRESSION ON ANTIBIOTIC SENSITIVITY PATTERNS IN PSEUDOMONAS AERUGINOSA: PHENOTYPIC AND GENOTYPIC PROFILING OF CLINICAL ISOLATES



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Abstract

Pseudomonas aeruginosa is an opportunistic pathogen of significant global health concern, largely due to its escalating resistance to multiple antibiotics. A major mechanism contributing to its multidrug resistance (MDR) phenotype is the overexpression of efflux pump systems, particularly the mexAB-OprM complex. This study aimed to assess the prevalence, antibiotic susceptibility patterns, and phenotypic and genotypic profiles of efflux pump-mediated resistance in P. aeruginosa clinical isolates.

One hundred clinical specimens were collected from Al-Khidmat Hospital. Antibiotic susceptibility was tested against ten antibiotics using the Kirby-Bauer method, while efflux pump activity was assessed via the ethidium bromide–agar cartwheel method. Genotypic detection of mexA and mexB genes was performed by PCR.

Forty percent of clinical samples yielded bacterial growth, with P. aeruginosa isolates more prevalent in males (54%). High resistance rates were observed against several commonly used antibiotics, particularly cephalosporins, fluoroquinolones, ceftazidime (82%), ciprofloxacin (70%), cefepime (61%) and levofloxacin (66%). In contrast, imipenem (76%), amikacin (73%) and gentamicin (70%) colistin showing (100%) susceptibility demonstrated comparatively higher susceptibility. Among the isolates, 62.5% were classified as MDR strains. Notably, 68% of MDR isolates exhibited phenotypic efflux pump activity. Genotypic analysis confirmed the widespread presence of efflux pump genes, with 71% and 82% of MDR isolates positive for mexA and mexB, respectively. Efflux pump overexpression, particularly involving mexA and mexB is a major driver of MDR in P. aeruginosa. The widespread detection of these genes provides strong genetic evidence that the mexAB-OprM efflux system is the dominant resistance mechanism in this population. These findings underscore the need for routine molecular surveillance of efflux activity in clinical diagnostics and highlight the therapeutic potential of efflux pump inhibitors (EPIs). Combining otherwise resistance antibiotics, such as ciprofloxacin or ceftazidime, with EPIs may restore their efficacy and expand treatment options for MDR infections. Overall, the results emphasize the importance of antibiotic stewardship, targeted resistance monitoring and the development of EPI–antibiotic combinations as future strategies to manage P. aeruginosa resistance.

About the authors

Abd Abdullah

Abasyn University, Khyber Pakhtunkhwa, Peshawar, Pakistan

Email: abdulshinwari4@gmail.com

M.Phil student

Pakistan, 25000,Peshawar, Khyber Pakhtunkhwa, Pakistan

Kashif Bashir

Abasyn University, Khyber Pakhtunkhwa, Peshawar, Pakistan

Email: kashif.bashir@abasyn.edu.pk

PhD

Lecturer 

Pakistan, 25000, Peshawar, Khyber Pakhtunkhwa, Pakistan

Abdul Waheed Khan

Institute of Biotechnology & Microbiology, Bacha Khan University, Charsadda, Pakistan

Email: awk780@gmail.com

PhD, Student

Pakistan, Charsadda, Pakistan

Moheb Khan

Center for Circadian Clocks, Soochow University, Suzhou, Jiangsu, China

Email: moheb.khan24@gmail.com

PhD Student

China, Suzhou 215123, Jiangsu, China

Zarkish Tariq

University of Science and Technology, Bannu, Khyber Pakhtunkhwa, Pakistan

Email: zarkishtariq8090@gmail.com

BS Zoology

Mphil Scholar

Pakistan, Bannu, Khyber Pakhtunkhwa, Pakistan

Falak Niaz

Riphah International University, Malakand Campus Chakdara, Khyber Pakhtunkhwa, Pakistan

Email: falaknaz@riphah.ede.pk
ORCID iD: 0009-0004-3872-4167

Mphil 

student

Pakistan, Chakdara 18800, Khyber Pakhtunkhwa, Pakistan

Faiz Ur Rehman

Government Superior Science College Peshawar, Khyber Pakhtunkhwa, Pakistan

Author for correspondence.
Email: faiz02140@gmail.com

M.Phil, Lecturer

Pakistan

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