First Report of High-Risk Rare blaSIM, blaSPM, and blaGIM Metallo-β-Lactamase Genes in Clinical Pseudomonas aeruginosa Isolates from Nigeria
1 Department of Microbiology, Ebonyi State University, Abakaliki, Ebonyi State.
2 Department of Pharmacy, Institute of Emerging and Re-emerging Infectious Diseases Research, Alex Ekwueme Federal University Teaching Hospital, Abakaliki, Ebonyi State.
3 Department of Microbiology, Federal University of Allied Health Sciences, Enugu State.
4 Department of Public Health, Federal University of Allied Health Sciences, Enugu State.
5 Department of Biotechnology, Federal University of Allied Health Sciences, Enugu State.
Review
World Journal of Advanced Pharmaceutical and Medical Research, 2026, 10(02), 011-024.
Article DOI: 10.53346/wjapmr.2026.10.2.0013
Publication history:
Received on 28 February 2026; revised on 05 April 2026; accepted on 08 April 2026
Abstract:
Background: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) mediated by metallo-β-lactamases (MBLs) represents a critical public health threat worldwide. While common MBL genes have been documented in Nigeria, the occurrence of rare MBL variants including blaSIM, blaSPM, and blaGIM remains unexplored. This study aimed to detect these high-risk MBL genes in clinical P. aeruginosa isolates from Enugu State University Teaching hospital Enugu, Nigeria.
Methods: A total of 200 mid-stream urine samples were collected from patients at Enugu State University Teaching Hospital, Enugu State Nigeria. P. aeruginosa isolates were identified using standard microbiological techniques. MBL production was phenotypically screened using the Imipenem-EDTA combined disc test. All 39 phenotypically confirmed MBL-producing isolates were subjected to molecular detection of blaSIM, blaSPM, and blaGIM genes using polymerase chain reaction method (PCR) with specific primers. Antimicrobial susceptibility testing was performed against 16 antibiotics. Statistical analysis was performed using SPSS version 26.0, with chi-square test used to compare resistance rates and Fisher's exact test applied where appropriate. A p-value < 0.05 was considered statistically significant.
Results: Out of 200 urine samples, 95 (47.5 %) yielded P. aeruginosa, with 39 (41.1 %) confirmed as MBL producers phenotypically. These isolates exhibited high resistance to carbapenems (imipenem, meropenem, doripenem: 100 %), cephalosporins (cefotaxime, cefepime: 100 %), amoxicillin-clavulanic acid (100 %), and fluoroquinolones (ofloxacin, levofloxacin: 100 %). Statistical analysis revealed significantly higher resistance to these antibiotics compared to colistin (p < 0.001). All isolates remained susceptible to colistin (100 %) and showed variable susceptibility to gentamicin (43.6 % susceptible) and amikacin (61.5 % susceptible). The difference in susceptibility between gentamicin and amikacin was statistically significant (p = 0.041). PCR analysis of all 39 MBL-producing isolates revealed that 39 (100 %) harbored blaSIM and blaSPM genes, while blaGIM was detected in 32 isolates (82.1 %). Co-carriage of all three genes (blaSIM + blaSPM + blaGIM) was observed in 32 isolates (82.1 %), while 7 isolates (17.9 %) carried blaSIM and blaSPM only. This study represents the first documentation of blaSIM, blaSPM, and blaGIM genes in clinical P. aeruginosa isolates from Enugu State University Teaching Hospital Enugu Nigeria.
Conclusion: The emergence of these rare, high-risk MBL genes in Nigerian clinical isolates signals a dangerous expansion of the carbapenem resistance landscape. The high prevalence and co-carriage of multiple MBL genes among urinary isolates from a single tertiary hospital suggests possible clonal dissemination and underscores the urgent need for enhanced antimicrobial stewardship and infection control measures.
Keywords:
Pseudomonas aeruginosa; Metallo-β-lactamase; blaSIM; blaSPM; blaGIM; Carbapenem resistance; Nigeria
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