Microbiological Spectrum and Antibiotic Resistance Patterns of Diabetic Foot Infections Among Adults in some Tertiary Health Care Facilities in Adamawa State, Nigeria

Abstract

Diabetic foot infections are major complications of diabetes mellitus and are associated with prolonged morbidity, antimicrobial use, hospitalization, and risk of lower-limb amputation.  Local data on causative organisms and resistance patterns are essential for effective empirical therapy.  This study determined the microbiological spectrum and antibiogram of diabetic foot ulcers among adult patients attending the Surgical Outpatient Department of Modibbo Adama University Teaching Hospital, Yola, Adamawa State, Nigeria.  An observational cross-sectional study was conducted from January to December 2025 among consecutively recruited consenting adult patients with diabetic foot ulcers.  Demographic and clinical data were collected using a semi-structured questionnaire and medical proforma.  A total of 81 diabetic foot wound samples were obtained.  Ulcers were graded using Wagner’s classification.  Bacterial and fungal isolates were identified using conventional microbiological and biochemical methods.  Antibiotic susceptibility testing was performed using the Kirby–Bauer disc diffusion method.  Extended-spectrum beta-lactamase production was detected using the double-disc diffusion synergy test, while methicillin-resistant Staphylococcus aureus was identified using the cefoxitin susceptibility test.  A total of 118 microbial isolates were recovered from 81 diabetic foot ulcer specimens.  Most patients were male, 57/81 (70%), with a mean age of 60.67 ± 11.76 years.  Monomicrobial infections accounted for 45/81 (56%) cases, while 36/81 (44%) were polymicrobial.  Type 2 diabetes mellitus was predominant, 68/81 (84%), and 45/81 (56%) had lived with diabetes for more than 10 years.  Wagner grade 3 ulcers were the most frequent, 26/81 (32%).  Gram-negative bacilli predominated, 89/118 (75.4%), followed by Gram-positive bacteria, 26/118 (22%), and Candida albicans, 3/118 (2.6%).  The leading isolate was Klebsiella pneumoniae, 28/118 (24%).  Gram-negative isolates showed high resistance to Ampicillin and commonly used beta-lactams, while carbapenems retained comparatively better activity.  Among Gram-positive isolates, S. aureus showed 100% susceptibility to linezolid and vancomycin, but 75% were methicillin-resistant.  No vancomycin resistance was detected.  Overall, multidrug resistance was observed in 79/118 (67%) isolates, while 29/118 (24.5%) were extensively drug-resistant.  Among Gram-negative isolates, ESBL production, carbapenem resistance, and colistin resistance were detected in 40/89 (45%), 20/89 (22.5%), and 4/66 (6%) isolates, respectively.  Diabetic foot infections in this setting were predominantly monomicrobial and mainly caused by Gram-negative bacilli, with a high burden of multidrug resistance, ESBL production, carbapenem resistance, and MRSA.  Routine culture, susceptibility testing, and periodic local antibiogram surveillance are recommended to guide empirical therapy and reduce diabetes-related foot complications in Adamawa State.