Fluorescence in situ Hybridization (FISH) in the Microbiological Diagnostic of Deep Sternal Wound Infection (DSWI)

Abstract

Purpose Postoperative mediastinitis after cardiac surgery is still a devastating complication. Insufficient microbiological specimens obtained by superficial swabbing may only detect bacteria on the surface, but pathogens that are localized in the deep tissue may be missed. The aim of this study was to analyze deep sternal wound infection (DSWI) samples by conventional microbiological procedures and fluorescence in situ hybridization (FISH) in order to discuss a diagnostic benefit of the culture-independent methods and to map spatial organization of pathogens and microbial biofilms in the wounds. Methods Samples from 12 patients were collected and analyzed using classic microbiological culture and FISH in combination with molecular nucleic acid amplification techniques (FISHseq). Frequency of and the time to occurrence of a DSWI was recorded, previous operative interventions, complications, as well as individual risk factors and the microbiologic results were documented. Results Tissue samples were taken from 12 patients suffering from DSWI. Classical microbiological culture resulted in the growth of microorganisms in the specimens of five patients (42%), including bacteria and in one case Candida. FISHseq gave additional diagnostic information in five cases (41%) and confirmed culture results in seven cases (59%). Conclusion Microbial biofilms are not always present in DSWI wounds, but microorganisms are distributed in a “patchy” pattern in the tissue. Therefore, a deep excision of the wound has to be performed to control the infection. We recommend to analyze at least two wound samples from different locations by culture and in difficult to interpret cases, additional molecular biological analysis by FISHseq.

Fluorescence In Situ Hybridization as Diagnostic Tool for Implant-associated Infections: A Pilot Study on Added Value

“…It should be emphasized that FISHseq is unsuitable as a sole diagnostic tool due to the existing false-negative FISHseq results (n = 4) and the necessary determination of the antibiogram as well as the extent of bacterial resistance status, which so far can only be elaborated by cultural evaluation. 49 Another meaningful advantage of FISHSeq is the ability to detect the microorganisms causing the infection in their biofilm environment without destroying the biofilm by manipulation. In the present work, we were able to detect the presence of an intact, mature biofilm in only three cases and nonplanktonic growth with a smaller number of colonies (microcolonies) in two other cases in the tissue samples.…”

“…In another four wounds, FISHseq confirmed the culture result, and it could be excluded (EXC, 8, 15, 44, 52) that the commensal pathogen detected by culture was a noncausative wound contamination. In 12 other wounds (12/53, 22.6%), one or more additional pathogens were detected by FISHseq (ADP, 16,20,22,24,31,37,38,41,48,49,50,59). In five wounds, it was also recognized that the pathogen detected was a nonplanktonic bacterial life form (NPF, 10, 34, 42, 50, 60).…”

Non-invasive biomedical sensors for early detection and monitoring of bacterial biofilm growth at the point of care

“…This process may take more than 48 hours. 72 The biofilm may spread to different areas while waiting for the diagnosis results. Transmission electron microscopy (TEM), another method to visualize bacterial biofilms, could only be used to image ultra-thin samples.…”

Our current clinical understanding of Candida biofilms: where are we two decades on?

“…Given their presence and pathogenic capacity, then it is unsurprising that fungi are important in chronic wound infections. While Candida is unlikely to play a significant role in these complex infections, it is frequently identified (19,79). Indeed, in culture‐based studies it has frequently been identified in diabetic foot ulcers (73,77).…”