Antimicrobial resistance profiles and detection of mecA, blaCTX-M-1, and blaSHV genes in bacteria among diabetic foot ulcer patients from selected referral hospitals in Uganda

Abstract

Effective management of Diabetic foot ulcers (DFU) requires timely treatment of infections with appropriate antibiotics based on culture and susceptibility results. However, challenges in diagnostic testing persist and consequently, data on prevalent bacteria, their antimicrobial resistance profiles and genes remains scanty. This study profiled the prevalent bacteria in Diabetic foot infection (DFI), their antimicrobial susceptibility patterns, and associated resistance genes. A multi-center cross sectional study was conducted from November 2021-January 2022, involving 117 patients with DFU, attending selected referral hospitals (Kiruddu, Jinja, Kampala International Teaching Hospital, Kitagata, Mbarara, Fort Portal and Hoima). Wound swabs were aseptically collected and placed in Stuart transport medium, then pre-enriched prior to inoculation onto Blood, MacConkey and Chocolate Agar to isolate aerobic microorganisms. Bacteria identification was based on colony morphology, Gram stain, conventional biochemical tests and Antibiotic susceptibility testing using Kirby-Bauer disk diffusion method were performed. Methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum beta-lactamase-producing Enterobacterales (ESBL-PE) were identified phenotypically. mecA gene in selected MRSA, and blaCTX-M-1 and blaSHV-1 in ESBL-PE were detected using Uniplex PCR and electrophoresed using 1.5% agarose gel. Data was analyzed using MS Excel version 15 and Stata version 15 (Stata Corp®). Microbiologically confirmed infection was observed in 89.7% (105/117) of DFU cases, yielding 144 bacterial isolates. Poly-microbial infections were detected in 23.8% of patients. Gram-positive bacteria accounted for 55.6% (80/144) of isolates. Staphylococcus aureus (36.1% (52/144)) and Proteus spp (13.9% (20/144)) were the most prevalent Gram-positive and Gram-negative bacteria, respectively. Notably, 98.6% (142/144) of the isolates were multidrug resistant organisms (MDR). Staphylococcus aureus sensitivity was highest for Gentamycin and Ciprofloxacin (48% each) and lowest for Cefoxitin (2%). Proteus spp sensitivity was highest for Imipenem (87%) and lowest for Tetracycline, Ampicillin and Amoxiclav (0%). mecA gene was identified in 56% (5/9) of MRSA. Among the selected MDR Gram negative isolates, 60% had blaCTX-M-1, 20% had blaSHV and both blaCTX-M-1 and blaSHV in one Klebsiella pneumoniae. The high prevalence of MDR bacteria in DFI underscores the need for culture and sensitivity testing guided treatment. Detection of resistance genes calls for sustained surveillance efforts, stringent infection prevention and control, and alternative therapy exploration.