Molecular Characterization of Extended-Spectrum Beta-Lactamase-Producing Enterobacterales Among Cancer Patients at the Mbarara Regional Referral Hospital, Southwestern Uganda

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Background and objective Extended-spectrum β-lactamase-producing Enterobacterales (ESBL-PE) are an important cause of antimicrobial-resistant infections among immunocompromised patients. Cancer patients are vulnerable because of frequent hospital exposure, invasive procedures, chemotherapy-associated immunosuppression, and antibiotic use. This study aimed to determine the molecular characteristics of ESBL-PE among cancer patients at Mbarara Regional Referral Hospital (MRRH), Southwestern Uganda. Methods A laboratory-based cross-sectional study was conducted at the Microbiology and Molecular Laboratory of Mbarara University of Science and Technology (MUST). The study used archived clinical Enterobacterales isolates recovered from clinical specimens collected from inpatient and outpatient cancer patients receiving care at MRRH between June and November 2025. The isolates had been identified using standard microbiological methods, and ESBL-PE were confirmed using the double-disk synergy test (DDST). Molecular detection of ESBL and other antimicrobial resistance-associated genes was performed using conventional polymerase chain reaction (PCR) with gene-specific primers. Target genes included blaCTX-M, blaTEM, blaSHV, blaOXA-1, AmpC-blaCITM, blaKPC, blaNDM, blaVIM, blaIMP, blaOXA-48, AAC(6’)-Ib, mcr-1, qnr, FosA, and blaPER. PCR products were separated by agarose gel electrophoresis and visualized under ultraviolet illumination. Data were entered into a database and analyzed using frequencies and percentages to summarize the distribution of resistance genes among isolates. Results A total of 281 isolates were analyzed. Escherichia coli (E. coli) was predominant (155/281, 55.2%), followed by Klebsiella pneumoniae (K. pneumoniae) (85/281, 30.2%). CTX-M was the most frequently detected resistance gene (106/281, 37.7%), followed by TEM (81/281, 28.8%), SHV (26/281, 9.3%), and AAC (24/281, 8.5%). At least one target resistance gene was detected in 170/281 (60.5%) isolates, while 111/281 (39.5%) had no target genes detected within the PCR panel. Multi-gene carriage occurred in 76/281 (27.0%), with TEM + CTX-M as the most common co-carriage pattern (25/281, 8.9%). Carbapenemase-associated genes remained uncommon. Conclusions The findings of this study describe the distribution of ESBL-PE in this population and highlight the importance of continued surveillance of resistant Enterobacterales among patients receiving cancer care.

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