1 Department of Applied Microbiology, Faculty of Science, Ebonyi State University, Abakaliki, P.M.B. 53, Nigeria.
2 Department of Microbiology and Parasitology, David Umahi Federal University of Health Science, Uburu, Ebonyi State, P. M. B 211, Nigeria
3 Department of Biochemistry, Faculty of Basic Medical Sciences, Federal University of Allied Health Science, Trans-Ekulu, P. M. B 01473, Enugu, Nigeria.
4 Department of Biochemistry, College of Natural and Applied Sciences, Gregory University Uturu, Abia State, Nigeria.
5 Department of Medical Laboratory Science, David Umahi Federal University of Health Science, Uburu, Ebonyi State, P. M. B 211, Nigeria.
6 International Institute of for Infectious Disease, Biosafety and Biosecurity Research, Uburu, Ebonyi State, Nigeria.
7 Department of Public Health, Faculty of Healthcare Services, Federal University of Allied Health Sciences, Trans-Ekulu, P. M. B 01473, Enugu, Nigeria.
8 Department of Pharmaceutical Microbiology and Biotechnology, College of Pharmacy, Gregory University Uturu, P. M. B 1012, Abia State, Nigeria.
9 Department of Biotechnology, Faculty of Science, Ebonyi State University, Abakaliki, P.M.B. 53, Nigeria.
10 Department of Microbiology, Faculty of Basic Medical Science, Federal University of Allied Health Science, Trans-Ekulu, P. M. B 01473, Enugu, Nigeria.
Research Article
GSC Biological and Pharmaceutical Sciences, 2025, 31(02), 113-122.
Article DOI: 10.30574/gscbps.2025.31.2.0181
Received on 03 April 2025; revised on 11 May 2025; accepted on 13 May 2025
Background: Multidrug-resistant (MDR) Gram-negative bacteria (GNB) harboring AmpC β-lactamase determinants represent a significant global public health threat, contributing to life-threatening infections in humans. Despite their growing prevalence, the detection of AmpC β-lactamase remains underreported in low- and middle-income countries (LMICs), where clinical microbiology laboratories often lack the resources for accurate identification. This study aimed to investigate the presence of AmpC resistance genes (blaEBC, blaFOX, and blaDHA) in MDR Gram-negative bacteria to address this critical gap.
Materials and methods: Over a six-month period, 290 non-replicated urine samples were collected from hospitalized patients, yielding clinical isolates of E. coli (n=95), K. pneumoniae (n=34), and Pseudomonas species (n=17). Antibiotic susceptibility testing was performed using the Kirby–Bauer disk diffusion method, and multidrug resistance (MDR) was determined. Isolates resistant to cefoxitin were preliminarily identified as potential AmpC β-lactamase producers and further confirmed using the Cefoxitin-Cloxacillin Double Disk Synergy Test (CC-DDST). AmpC β-lactamase phenotypes were subsequently analyzed using polymerase chain reaction (PCR) to detect the presence of blaFOX-M, blaEBC-M, and blaDHA-M genes.
Results: The study identified 146 MDR Gram-negative bacteria with high resistance rates to multiple antibiotic classes, including β-lactams, cephalosporins, carbapenems, anti pseudomonals, folate inhibitors, and protein synthesis inhibitors. Resistance was notably lower to macrolides (e.g., azithromycin), aminoglycosides (e.g., gentamicin), and fluoroquinolones (e.g., ciprofloxacin). Among the MDR isolates, 23 (7.9%) were confirmed as AmpC producers, with prevalence rates of 1.0% in P. aeruginosa, 1.7% in K. pneumoniae, and 5.2% in E. coli. Genetic analysis revealed the presence of FOXM (100%), EBC (95.7%), and DHAM (13.0%) genes among the MDR isolates.
Conclusion: This study highlights the alarming prevalence of MDR Gram-negative bacteria with high resistance to critical antibiotic classes, particularly β-lactams, carbapenems, and cephalosporins. The widespread detection of AmpC β-lactamase genes (FOXM, EBC, and DHAM) underscores the complexity of managing MDR infections. Our findings suggest that combination therapy involving azithromycin, gentamicin, and ciprofloxacin may offer a viable treatment strategy for MDR infections. Regional variations in resistance patterns emphasize the urgent need for enhanced surveillance, routine detection of resistance mechanisms, and stricter antibiotic stewardship to combat the global threat of antimicrobial resistance.
Gram-negative bacteria; Ampc β-lactamase; Multidrug-resistant bacteria; MDR infections
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Esther Chigbaziru Nwojiji, Ijeoma Onyinye Okolo, Chigoziri Akudo Osuji, Ugonna Cassandra Aniokete, Sikiru Oladimeji Akomolafe, Uchechukwu Okekeaji, Christiana Inuaesiet Edemekong, Ikemesit Udeme Peter and Ifeanyichukwu Romanus. Molecular Detection of Ampicillinase blaEBCM, blaFOX and blaDHAM resistant genes in multi-drug resistant Gram-negative bacteria. GSC Biological and Pharmaceutical Sciences, 2025, 31(2), 113-122. Article DOI: https://doi.org/10.30574/gscbps.2025.31.2.0181