Comparison of microbiological results of deep tissue biopsy and superficial swab in diabetic foot infections

Objectives: In this study, we aimed to compare superficial swab cultures with deep tissue biopsy cultures and also to evaluate the reliability of superficial swap cultures in diabetic foot infected patients. Materials and methods: To compare two culture methods, the hospitalized patients with diabetic foot infections were retrospectively evaluated at Dicle University and Diyarbakir Education and Research Hospital, between October 2009 and November 2010. The patients were divided two groups as with osteomyelitis (osteomyelitis group, Wagner ≥3) and with soft tissue infections (soft tissue infection (STI) group, Wagner <3). The cultures of deep tissue biopsy specimens and swab samples were collected from all patients. Results: In 75 patients with osteomyelitis, the compatibility rate in deep tissue biopsy culture with superficial swab culture was 58.7% whereas in STI group this rate was 89.1% (p<0.001). Of 41 superficial swap cultures, 33 of them (81%) had the same microorganisms with the identified microorganisms in deep tissue cultures. Staphylococcus aureus was the predominant pathogen isolated from deep tissue biopsy cultures and also from superficial swap cultures. The distributions of microorganisms in deep tissue culture and swap cultures were similar. Conclusions: This study indicates that superficial swab culture could be valuable to identify the pathogens in infected diabetic wounds without osteomyelitis. The accuracy of swab specimens diminishes when osteomyelitis develops. Deep tissue culture seems more sensitive and reliable in osteomyelitis group. J Microbiol Infect Dis 2011;1(3):122-127