Extended-Spectrum β-Lactamase Genes and Multidrug-Resistant Klebsiella pneumoniae among Hospitalized Patients in a Nigerian Tertiary Hospital

A bstract Background: Antimicrobial resistance poses a growing threat to modern medicine because it is projected to cause up to 10 million deaths annually by 2050 if not checked, thus emphasizing the need for urgent action. Objectives: To identify multidrug-resistant Klebsiella pneumoniae , characterize the extended-spectrum beta-lactamase (ESBL) genes, and identify the risk factors among hospitalized patients at the University of Nigeria Teaching Hospital (UNTH), Enugu, Nigeria. Materials and Methods: K. pneumoniae was isolated from clinical samples of hospitalized patients. ESBL production was screened using chromogenic agar. Antimicrobial susceptibility testing was performed using the modified Kirby-Bauer disc diffusion method and interpreted according to Clinical and Laboratory Standards Institute guidelines. Multiplex polymerase chain reaction was conducted to detect the presence of bla SHV , bla TEM , and bla CTX-M genes. Thirteen isolates harboring bla CTX-M were further characterized by the Sanger sequencing method. Results: Among the 200 K. pneumoniae isolates, 40.0% were ESBL producers. The distribution of ESBL genes was as follows: bla CTX-M only (38.8%), bla TEM only (5.0%), bla SHV only (12.5%), bla CTX-M + bla TEM (3.6%), and bla CTX-M + bla TEM + bla SHV (32.5%). Of the 13 sequenced isolates, 84.6% carried bla CTX-M-15 and 15.4% carried bla CTX-M-22 . High levels of resistance were observed across most antibiotics tested, with carbapenems showing the greatest sensitivity. Identified risk factors included prior antibiotic use ( P < 0.001), urinary catheterization ( P < 0.001), recent surgery ( P = 0.008), and age ≥60 years ( P < 0.001). Conclusion: This study highlights the high burden of multidrug resistance among K. pneumoniae isolates at UNTH Enugu, Nigeria, with 40% harboring ESBL genes—predominantly bla CTX-M . The findings underscore the urgent need for strengthened infection prevention and control, robust antimicrobial stewardship, and ongoing surveillance in the facility.