Biofilm prevalence and microbial characterisation in chronic wounds in a Sri Lankan cohort

Abstract

Biofilms have been associated with chronic wound infections in diabetic patients. The study assessed the occurrence of biofilms in chronic diabetic wounds (CDWs) in a Sri Lankan cohort. Tissue specimens collected during surgical debridement were analysed by quantitative differential viable counting, scanning electron microscopy (SEM), fluorescence insitu hybridization (FISH) and light microscopy with Gram and Haematoxylin‐Eosin staining. All specimens harboured >5·0 log10 CFU per g bacteria and 2–9 distinct species per specimen were recovered from twenty wounds by culture. The most frequently isolated bacterium was Pseudomonas spp. (12/20;60%). Strict anaerobes were isolated from 10/20 specimens. Gram and Haematoxylin‐Eosin staining showed aggregated micro‐colonies, embedded in the wound tissue bed (20/20) but the exopolymer matrix was not visible in all samples (13/20). Fluorescence microscopy using a eubacteria‐specific FISH probe indicated the presence of bacterial aggregates within the deep layers of the wound tissues (20/20). SEM revealed the presumptive architecture of matrix‐embedded microbial clusters (20/20). The approximate diameter of bacterial aggregates in tissues ranged between 12 and 400 µm. Bacterial infiltration into the internal portions of the tissues was apparent using FISH, Gram, and Haematoxylin‐Eosin staining. All CDWs carried biofilm‐specific morphological features. FISH was more specific than SEM and indicated the presence of microcolonies within deeper tissues.

Distinct microbiome profiles and biofilms in Leishmania donovani-driven cutaneous leishmaniasis wounds

“…Cutaneous leishmaniasis lesions are chronic in nature. It has been reported that the prevalence of biofilms in non-cutaneous leishmaniasis chronic wounds is more than 78.2% 11,12 . We detected biofilms in 61.5% (24/39) of the cutaneous leishmaniasis lesions using fluorescence in situ hybridization in formalin-fixed paraffin-embedded tissue (FFPE-FISH).…”

Possible clinical implications and future directions of managing bacterial biofilms in cutaneous leishmaniasis wounds

“…A Sri Lankan study on biofilms in diabetic wounds reported that most chronic diabetic foot wounds are colonized with Pseudomonas spp. [9]. Under similar settings, we found that the biofilms of ulcerated local CL wounds were mainly composed by class bacilli, family Enterobacteriaceae, and genus Pseudomonas [6].…”

“…The size of the CL wound biofilms (7-140 µm) [6] was lower than what has been reported with diabetic foot wounds (12-400 µm) [9]. This could probably be due to early sampling of the reported CL wounds [6] or the patchy distribution of biofilms.…”

“…Laboratory confirmation of biofilms by FISH/SEM needs invasive sampling and sophisticated infrastructure. In contrast to a pilot study conducted on diabetic wounds [18], local experience has proven that Gram staining is less accurate in biofilm detection [6,9]. FISH, SEM and Gram staining, all use biopsy tissues to confirm biofilms.…”