A Novel Method for the Examination of Infected Wound Specimens: Percutaneous Wound Sampling With Analysis in Blood Culture (PERKA-B) Method

Wound infections represent a major global public health problem from clinical, epidemiological, and economic perspectives. Although the incidence of surgical site infections varies by region, the global rate is estimated to be approximately 2-3% . Chronic wounds, such as diabetic foot ulcers, venous ulcers, and pressure ulcers, constitute a similarly significant burden, with their prevalence increasing steadily worldwide. Recent estimates indicate that global expenditures related to wounds and wound infections have reached 148 billion US dollars. A substantial proportion of these costs is attributable to prolonged hospitalizations and antibiotic therapy.

Rational antibiotic use in wound infections relies primarily on the identification of the causative pathogen and determination of its antimicrobial susceptibility profile through microbiological examination of appropriate clinical specimens. Because superficially collected samples carry a high risk of contamination, deep tissue biopsy or aspirate specimens are generally considered more reliable than swab samples. In routine clinical microbiology practice, standard examination of wound specimens involves inoculation onto 5% sheep blood agar in combination with MacConkey or eosin methylene blue (EMB) agar. These media are incubated at 35°C for 24 hours and subsequently evaluated. If no growth is observed, incubation is extended for an additional 24 hours, and cultures without growth after 48 hours are reported as negative. When growth is detected, further identification of the isolates is performed.

Despite meticulous specimen collection, a substantial proportion of wound samples continue to yield negative culture results. Previous investigations have documented culture-negative rates of approximately 12% in diabetic foot infections, 19% in chronic wound infections, and 10-15% in surgical site infections. In such circumstances, clinicians are often obliged to initiate empirical antimicrobial therapy when microbiological analyses fail to identify a causative pathogen, despite strong clinical evidence of infection. This approach may lead to unwarranted antibiotic administration or reliance on broad-spectrum agents, thereby increasing the risk of adverse patient outcomes and contributing to elevated healthcare expenditures. Consequently, refinement of microbiological diagnostic techniques is imperative to ensure accurate pathogen identification and to facilitate the rational selection of antimicrobial therapy.

Media used in automated blood culture systems are enriched compared with conventional solid media, such as 5% sheep blood agar, MacConkey agar, and EMB agar, and are specifically designed to enhance microbial recovery. In addition, the longer incubation periods used in these systems may further improve pathogen detection. Although blood culture systems are routinely used to detect microorganisms in blood samples obtained from peripheral veins of patients with suspected bloodstream infections, there is currently no standardized protocol for the inoculation of non-blood clinical specimens into blood culture bottles.