Identification of bacterial invasion in necrotizing enterocolitis specimens using fluorescent in situ hybridization

Objective: Investigation of bacterial invasion into the intestinal wall in necrotizing enterocolitis (NEC) specimens. Study Design: We compared 43 surgical NEC specimens with 43 age-matched controls. We used fluorescent in situ hybridization (FISH), a universal bacterial probe together with species-specific probes for Clostridium spp., Enterobacteriaceae , bacteroides and enterococci/lactobacilli. We used a FISH scoring system to reveal invasion of the intestinal wall, in which 1 represented no colonies and 4 invasion of the intestinal wall. Results: We observed invasion of the intestinal wall in 22/43 of the most affected NEC tissue samples as compared with 16/43 in the least affected NEC tissue samples ( P =0.03). A FISH score of 4 was reached in 7/43 control cases. Enterobacteriaceae dominated the NEC specimens. Clostridium spp. were detected occasionally in NEC samples. Conclusion: Bacterial invasion of the intestinal wall is more present in most affected NEC tissue samples compared with least affected NEC tissue samples or controls. Enterobacteriaceae are prevalent in advanced NEC.