Clinical presentation and bacteriology of Diabetic Foot Ulcers at Mulago Hospital

Abstract

Background Diabetic foot ulcer is common cause of morbidity and mortality in Mulago hospital. Peripheral neuropathy and peripheral arterial disease are the major risk factors for diabetic foot ulceration and the severity of these two conditions may determine treatment options and ulcer outcome. Foot ulcers are often complicated by infection that may lead to prolonged hospital admission, amputations, sepsis and death. Multidrug resistant organisms that are emerging in diabetic foot infections may threaten the available and affordable antimicrobials used to treat diabetic foot infections in our setting. The study was done to fill the knowledge gap on the current clinical status of diabetic foot ulcers and identify the common bacterial isolates and their susceptibility patterns.

General objective To describe the clinical presentation of foot ulcers in diabetic patients and identify the common bacterial isolates from diabetic foot ulcers and their susceptibility patterns.

Methods This was a descriptive case series involving 60 consecutive patients with diabetic foot ulcers admitted to the endocrinology unit at Mulago hospital between July and December 2010. Patients were recruited after provision of written informed consent. The socio-demographics of the patients and relevant clinical history on diabetes and diabetic foot ulcer were noted. Both feet were examined for peripheral neuropathy and peripheral arterial disease using standard clinical methods. Deep tissue swabs from the ulcers were then taken at debridement for both aerobic and anaerobic cultures and susceptibility tests using standard microbiological methods.

Result: Of the 60 patients, thirty four (56.7%) had neuroischemic foot ulcers, eleven (18%) had neuropathic ulcers, eleven (18%) had ischemic ulcers and only four (7.3%) had unclassified ulcers. Fifty nine (98.3%) of the samples grew 93 aerobic bacteria in total and no anaerobe was isolated. Polymicrobial infection occurred in twenty five (41.7%) samples of which only three (12%) had mixed growth. Seventy five (80.6%) of the isolates were Gram negative aerobes, mainly E.coli Klebsiella, Pseudomonas and Proteus while eighteen (19.4%) were Gram positive, mainly Staphylococcus aureus and Enterococcus faecalis. Seventy eight (83.9%) of the isolates were Multidrug resistant organisms (MDRO). Of the ten staphylococcus aureus isolated, six (60%) were Methicillin resistant staphylococcus aureus (MRSA) while twenty of the forty six (43.5%) extended spectrum beta lactamases producing isolates were ESBL. However, most isolates were susceptible to vancomycin, imipenem and ciprofloxacin.

Conclusion: Diabetic foot ulcers in this study were mostly neuroischemic and infection was mostly due to aerobic Gram negative organisms with high prevalence of MDRO, ESBL and MRSA. Vancomycin and imipenem were the only drugs with 100% sensitivity.

Recommendation: The results of this study may be used to start empiric antibiotic therapy in patients with diabetic foot ulcers and to emphasize the need for continuous surveillance on bacterial sensitivity to inform antimicrobial choices.