Risk Factors and Antibiotic Resistance Patterns of MBL-Producing Pseudomonas aeruginosa in Outpatients and Inpatients in Southeast Nigeria

Background: Metallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa represents a critical public health threat due to limited treatment options. Understanding differences between outpatient and inpatient isolates is essential for implementing targeted infection control strategies. Methods: A total of 400 clinical samples (urine, wound swabs, and high vaginal swabs) were collected from patients at Enugu State University Teaching Hospital, Enugu Nigeria. P. aeruginosa was identified using standard microbiological techniques. MBL production was phenotypically screened using the Imipenem-EDTA combined disc test. Antibiotic susceptibility was determined by Kirby-Bauer disc diffusion method. Multiple Antibiotic Resistance (MAR) index was calculated using standard formular and demographic and clinical risk factors were analyzed. Results: Of 400 samples, 131 (32.75 %) yielded P. aeruginosa, with 53 (13.25 %) confirmed as MBL-producers. Outpatients showed higher MBL prevalence (14.23 %) compared to inpatients (11.56 %). The highest MBL-positive rate of (23.26 %) occurred in patient’s ≥ 46 years. Female gender was associated with higher MBL carriage (17.65 % versus 7.82 % in males; p < 0.05). All MBL-producers exhibited 100 % resistance to carbapenems (imipenem, meropenem, and ertapenem), amoxicillin-clavulanic acid, and cefoxitin. Inpatient isolates showed significantly lower resistance to piperacillin-tazobactam (0 % versus 69.44 %; p <0.001) and ciprofloxacin (23.53 % versus 72.22 %; p < 0.01) compared to outpatient isolates. Gentamicin remained highly effective (88.24-94.44 % susceptibility). MAR indices ranged from 0.47-0.83, exceeding the 0.2 threshold for high-risk sources. Conclusion: This study reveals alarming community dissemination of MBL-producing P. aeruginosa in ESUTH Enugu in Southeast Nigeria, with outpatients demonstrating higher prevalence and broader resistance profiles than inpatients. Advanced age and female gender were significant risk factors. These findings necessitate urgent community-based antimicrobial stewardship and enhanced surveillance beyond hospital settings.