Bacteriology of diabetic foot ulcers in Benin City, Nigeria

This study aimed to determine the bacteriological pattern and antimicrobial susceptibility of diabetic foot ulcer (DFU) infections seen in our practice, with a view to suggesting optimal therapy for these patients. Forty-seven persons with DFU were seen. The mean age was 56 years. Of these, 30 (64%) had wound swabs sent for bacteriological assessment and antibiotic sensitivity patterns. There were 20 non-gangrenous ulcers and 10 gangrenous ulcers. Proteus spp and coliform organisms were the most predominantly isolated organisms in gangrenous ulcers, while Staphylococcus aureus, coliforms, and Pseudomonas aeruginosa were commonly isolated in non-gangrenous ulcers. Grampositive organisms were sensitive to ciprofloxacin (100%), gentamicin (100%), and perfloxacin (88%). Gram-negative organisms were sensitive to ciprofloxacin (74%), gentamicin (43%), and perfloxacin (39%). We conclude that ciprofloxacin and gentamicin are the most effective antibiotics against gram-positive and gram-negative organisms, and thus recommend the combination of ciprofloxacin and/or gentamicin and metronidazole as initial therapy for patients with infected DFU while awaiting culture results. Introduction Diabetic foot ulcers (DFUs) are an important cause of morbidity and mortality among persons with diabetes mellitus.1–4. The reported prevalence rates in Nigeria range from 0.9–8.3%.1 Diabetes foot lesions are the leading cause of non-traumatic amputations worldwide.2–4 They are also responsible for long-stay hospital admissions with the attendant high cost of management among persons with diabetes.3 Infected foot ulcers may be complicated by septicaemia and can result in the death of the patient. Treatment should therefore be aggressive. Treatment options include wound debridement and dressing, and treatment of infection. Antibiotic therapy should be Andrew E Edo, Consultant Endocrinologist, Department of Medicine, College of Health Sciences, Delta State University, Abraka, Nigeria; and A Eregie, Consultant Endocrinologist, Department of Medicine, University of Benin, Benin City, Edo State, Nigeria. Correspondence to: Dr A E Edo, Department of Medicine, College of Health Sciences, Delta State University, Abraka, Delta State, Nigeria. Email:[email protected] commenced after reliable culture specimens are obtained from the infected ulcers while awaiting results of culture and sensitivity. Most studies on diabetic foot lesions in Nigeria focus on the pattern of presentation and treatment outcomes with little emphasis on the bacteriology of DFUs.1,3,5,6 It is, therefore, beneficial to determine the bacteriological pattern of diabetic foot lesions in our environment with a view to providing a practical approach to empirical antibiotic therapy while awaiting the results of wound swab microscopy, culture, and sensivity. Materials and methods All in-patients seen on the medical and surgical wards of the University of Benin Teaching Hospital, Benin City, Nigeria, with a diagnosis of DFUs were consecutively recruited over a 3-year period (January 2002–December 2004). Diabetes was diagnosed and classified on the WHO 1999 criteria.7 Data obtained include age, sex, and ulcer grade using the Wagner’s classification8 (see Table 1). Wound swab samples were obtained by rubbing the swab stick in the deepest accessible area of the lesion while ensuring aseptic techniques. Thirty (64%) patients had a total of 37 wound swab specimens obtained: 20 initial and 2 repeat samples were obtained from the non-gangrenous ulcers while 10 initial and 5 repeat specimens were obtained from the gangrenous ulcers. The samples were then sent for bacteriological assessment to determine the presence of infective organisms, and the antibiotic sensitivity patterns. The data were analysed using appropriate statistical methods and the level of significance was set at p<0.05. Results A total of 47 persons (21 males, 26 females) with DFUs seen during the period were recruited for the study. Type 2 diabetes was diagnosed in 38 (76%) of cases. The mean (±SD) age was 56±13 years. Twenty-four (51%) ulcers were on the right lower limb while 18 (38%) were on the left. Five (11%) persons had ulcers on both feet. Multiple ulcers were seen on one foot in 4 (8%) patients. Using Wagner’s grading system,8 the frequency of occurrence of the various grades of ulcers was: grade 1, 5(10.6%); grade 2, 15 (32%); grade 3, 8 (17%); grade 4, 15 (32%); and grade 5, 4 (8%) respectively. The pattern of organisms is shown in Table 2. In 10 gangrenous foot ulcers, single organisms were isolated in 13 wound swabs and mixed organisms in only 2 swabs in the initial specimen analysed.The single organisms were Proteus spp (6), coliform organisms (4), Pseudomonas aeruginosa (2),