A Comparison of Tissue versus Swab Culturing of Infected Diabetic Foot Wounds. (30th March 2016) - Huang, Ying
Abstract : Objective . To compare the efficacy of swabbing versus tissue biopsy for microbiological diagnosis of diabetic foot infection. Methods . This was a prospective trial. Fifty-six patients with diabetic foot infection were divided into the following 3 groups according to the PEDIS grading system: grade 2 (n = 10 ), grade 3 (n = 29 ), and grade 4 (n = 17 ). Two specimens were collected from each wound for microbial culturing after debridement, including a superficial swab and a deep tissue punch biopsy specimen. Results . Swab culturing identified all of the microorganisms isolated from the corresponding deep tissue specimens in 9/10 of grade 2 wounds (90.0%), and this proportion decreased to 12/29 (41.4%) and 7/17 (41.2%) for grades 3 and 4 wounds, respectively (p = 0.0 2 ). Moreover, the sensitivity for identifying Gram-negative bacteria, such as E. coli and Citrobacter, by swabbing was low (33.3%). In addition, some Gram-negative bacteria, such as Serratia and Ralstonia pickettii, were isolated from deep tissues but not from swabs. Conclusions . Swab culturing may be reliable for identification of pathogens in diabetic foot wounds classified as grade 2. However, it is advisable to culture deep tissue specimens for wounds of grade ≥3 because swab culturing is associated with a high risk of missing pathogens, especially Gram-negative bacteria.