Insights into the Intersection of Biocide Resistance, Efflux Pumps, and Sequence Types in Carbapenem-Resistant : A Multicenter Study.

, a pathogenic bacterium acquired in hospitals, causes diverse infections in humans. Previous studies have reported resistance among strains, potentially selecting multi-drug-resistant variants. In Pakistan, research has primarily focused on carbapenem-resistant (CRAB) strains, overlooking the investigation of efflux pumps (EPs) and biocide resistance. This study aims to assess strains from five hospitals in Pakistan, focusing on antibiotic and biocide susceptibility, the impact of EP inhibitors on antimicrobial susceptibility, and the distribution of ARGs and STs. A total of 130 non-repeated isolates were collected from five tertiary care hospitals in Pakistan and identified using API 20NE and multiplex PCR. Antimicrobial susceptibility testing utilized disc diffusion and broth microdilution assays, while biocide susceptibility was assessed with various agents. The impact of an efflux pump inhibitor (NMP) on antibiotic susceptibility was evaluated. PCR screening for ARGs and EPGs was followed by DNA sequencing validation. MLST was performed using the Pasteur scheme. Most isolates demonstrated resistance to tested antibiotics, with varying levels of susceptibility to biocides. All isolates exhibited the intrinsic class D β-lactamase , while acquired was present in all CRAB isolates. Among EPs, , , , and were prevalent in almost all isolates, with found in 93% of isolates and , , , and displaying lower prevalence ranging from 65% to 79%. The most common STs were ST589 and ST2, accounting for 28.46% and 25.38% of isolates, respectively, followed by ST642 at 12.6%. These findings indicate that strains in Pakistan are resistant to antibiotics (excluding colistin and tigecycline) and may be developing biocide resistance, which could contribute to the selection and dissemination of multi-drug-resistant strains.