Detection of Anaerobic Infection in Diabetic Foot Ulcer Using PCR Technique and the Status of Metronidazole Therapy on Treatment Outcome
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Index: WOUNDS. 2012;24(10):283–288.
Abstract: Metronidazole is the drug of choice for anaerobic infection in diabetic foot ulcers (DFU) for a majority of clinicians. The present study was conducted to determine if Metronidazole is really making a difference in the healing of DFU. Methods. Deep tissue samples from the wound area of 61 diabetic foot patients were tested for anaerobic bacterial infection (Peptostreptococcus productus, Bacteroides, and Clostridium) by polymerase chain reaction (PCR). PCR-positive patients were randomized into 2 groups: Metronidazole and non-Metronidazole. Antibiotics for the control of infection were given in both groups as per clinical condition of patients. Treatment outcome was assessed by complete healing of the wound. Results. Out of 61 patients, PCR detected evidence of anaerobic infection in 32 (52%), while culture methods detected only 5 (8%) (Clostridium spp.), hence emphasizing the significance of the PCR technique over culture methods in detection of microbes. In this study, Clostridium was found with maximum prevalence of n (75%), followed by Bacteroides with n (53.1%), and Peptostreptococcus productus with n (40.6 %). Across all Wagner Ulcer Classification grades, Clostridium was the most prevalent anaerobe, and significantly associated with wound age and total leukocyte count. No difference was noted in wound healing in both groups at the end of 16 weeks. Conclusions. The authors propose that it is not mandatory to supplement Metronidazole in antibiotic regime for treatment of DFU.
Diabetic foot ulcers (DFU) are estimated to effect 15% of all individuals with diabetes during their lifetime and precede almost 85% of all foot amputations.1,2 They are the most common, disabling, and costly complications of diabetes. Diabetic foot wounds become easily infected due to several factors including suppressed immunity, inadequate blood supply, and neuropathy. Infection of a diabetic foot is one of the key contributing factors to morbidity and to a majority of lower limb amputations. It is further complicated by anaerobic pathogens resulting in delayed wound healing. The increase in resistance among anaerobic pathogens poses a problem in the choice of empiric antibiotic regimens.3 Metronidazole has become a choice among clinicians for eradication of anaerobic infection. The decision regarding management of anaerobic infection in a diabetic foot with specific therapy like Metronidazole is still a matter of debate.4
To the author’s knowledge, there are no published studies mentioning the use of PCR technique in detection of anaerobic infection in DFU, and determining efficacy of Metronidazole in treatment outcome of such foot ulcers. This study was designed primarily to detect prevalence of anaerobic infection by using PCR technique and to evaluate if Metronidazole is really making a difference in healing of DFU that detect positive for anaerobes.
The protocol was approved by the Ethics Committee of the Department of Endocrinology and Metabolism, Banaras Hindu University (Varanasi, Uttar Pradesh, India) and informed consent was obtained from all subjects. The study enrolled diabetic foot patients visiting Sir Sundarlal Hospital, Banaras Hindu University, Varanasi, U.P, India, during the period of May 2010 to April 2011.
Deep tissue biopsy specimens were obtained from 61 patients with DFU who had an ankle brachial pressure index (ABPI) < 0.9 and a Wagner Ulcer Classification ≥ Grade 3. The specimens were collected in sterile phosphate buffered saline (PBS) from the wound sites and subsequently tested for the presence of anaerobes by PCR technique.