Deep tissue biopsy vs. superficial swab culture, including microbial loading determination, in the microbiological assessment of Skin and Soft Tissue Infections (SSTIs)

Abstract

Thirty-two patients affected by SSTIs including DFIs were enrolled between 2013 and 2014. Superficial swab was obtained before and after cleansing with sterile saline, and after ultrasonic debridement; deep tissue biopsy was obtained from ulcer base. Samples were diluted with 1 mL of saline, serial 10-fold dilutions to 10 were made and 50 μL of each dilution was plated onto appropriate media. Bacteria were identified by Vitek II system. Microbial load was expressed as CFU/mL. Statistical analysis was performed by χ2. Incidence of Gram positives was higher than Gram negatives (S. aureus and P. aeruginosa being the most frequent); concordance (same bacteria isolated before and after debridement) never exceeded 60%. Ultrasonic debridement significantly reduced bacterial load or even suppressed bacterial growth. While reliability of superficial swab is poor for microbiological diagnosis of SSTIs, swabbing after ultrasonic debridement and biopsy of the ulcer base may be equally reliable.

Epidemiology and Microbiology of Skin and Soft Tissue Infections: Preliminary Results of a National Registry

“…As expected, in our registry, the superficial swab is the most commonly adopted method for the collection of clinical samples (74 of the 187 microbiological tests; 39.6%) while the culture of deep tissue biopsy was performed only in 55 cases (55/187, 29.4%). Though many authors still debate about the rate of concordance between these two methods, [26][27][28] most of the guidelines indicate that the culture of deep tissue sampling (collected by curettage and biopsy or aspiration of infected secretions) provides the most useful information on the causative organisms often lying in deeper layers, while the cultures of superficial swabs are easily contaminated by harmless bacteria belonging to indigenous microbial flora. 26,29 Of the overall 187 microbiological exams performed in our study, 45 (24.1%) failed to detect any microorganisms; blood culture reporting the highest negative rate (no bacterial growth in 25 out of 52 blood cultures, 49%): indeed bacteraemia is uncommon in mild SSTI and guidelines recommend blood cultures only for severe SSTIs requiring hospitaliszation.…”

“…Though many authors still debate about the rate of concordance between these two methods, [26][27][28] most of the guidelines indicate that the culture of deep tissue sampling (collected by curettage and biopsy or aspiration of infected secretions) provides the most useful information on the causative organisms often lying in deeper layers, while the cultures of superficial swabs are easily contaminated by harmless bacteria belonging to indigenous microbial flora. 26,29 Of the overall 187 microbiological exams performed in our study, 45 (24.1%) failed to detect any microorganisms; blood culture reporting the highest negative rate (no bacterial growth in 25 out of 52 blood cultures, 49%): indeed bacteraemia is uncommon in mild SSTI and guidelines recommend blood cultures only for severe SSTIs requiring hospitaliszation. 22,30 Upon analysing the 142 positive cultures, we noted that multiple pathogens were isolated in 50 cases (35.2%), especially from surgical wound and diabetic foot infections; while a single microorganism had been detected in the remaining 92 cultures (64.8%).…”

Effectiveness of ultrasonic debridement on reduction of bacteria and biofilm in patients with chronic wounds: A scoping review

“…27 A small RCT and an observational study on DFUs, VLUs, and pressure ulcers reported on the Misonix lowfrequency ultrasound (SonicOne OR, Ultrasonic Debridement System, Misonix Inc., Farmingdale, NY) device. 23,24 Findings from these studies demonstrated that this device significantly reduced bacterial load or suppressed bacterial growth. Furthermore, findings from our previous study demonstrated that another device (Qoustic Wound Therapy System [Arobella Medical, LLC, Minnetonka, MN]) contributed to the removal of biofilms and promoted wound healing in patients with DFUs, VLUs, arterial ulcers, and pressure ulcers.…”

“…A total of nine articles were included in this scoping review. [20][21][22][23][24][25][26][27][28] A PRISMA flowchart of the current review is shown in Figure 1…”

The role of dalbavancin in the multi-disciplinary management of wound infections in orthopaedic surgery

“…16 The choice of the sample type to be collected for laboratory diagnosis is of paramount importance. 17 Samples should be collected carefully to avoid touching non-involved surfaces of mucosae, colonized by contaminating bacteria.…”