Specific plasmid profiles of Clostridium butyricum associated with grouped cases of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is an unpredictable condition that is commonly encountered in neonatal intensive care units. NEC considered one of the most severe gastrointestinal diseases affecting preterm infants and is often fatal. In this study, we performed a genomic analysis in which 32 Clostridium butyricum strains were compared; 25 strains were isolated from patients with asymptomatic stool carriage and seven were isolated from patients diagnosed with NEC. Phylogenetic analysis revealed two clusters. Cluster 1 was associated with asymptomatic carriers, whereas cluster 2 was associated mainly with NEC patients and was composed of three genetically distinct subclusters. Through genomic analyses, we identified six plasmids, each of which varied in size and gene number. The 21 strains belonging to cluster 1 harboured two specific plasmids, one small conserved plasmid and one large megaplasmid. The strains in subcluster 2.1 harboured two specific plasmids, and the strains in subclusters 2.2 and 2.3 harboured one of two specific plasmids. Interestingly, plasmid profiling revealed specific patterns and the largest C. butyricum plasmid reported to date. The observed differences in plasmids between the two clusters were associated with NEC status and may contribute to the virulence potential that leads to the occurrence of this disease.