Investigating transmission patterns among preterm neonates during an outbreak of necrotizing enterocolitis related to Clostridium butyricum using whole genome sequencing.

ABSTRACT

BACKGROUND: Necrotizing enterocolitis is the most severe life-threatening acquired gastrointestinal disorder among preterm neonates. We describe here an outbreak of Clostridium butyricum-related necrotizing enterocolitis in preterm neonates that occurred in three different neonatal centres, in southeast France. METHODS: We defined a confirmed case of C. butyricum-related necrotizing enterocolitis in preterm neonates by the presence of clinical signs according to modified Bell criteria and C. butyricum identified from stools sample using real-time polymerase chain reaction or culture. A phylogenetic analysis of the isolated strains by whole genome sequencing was also performed. RESULTS: Between 5 and 27 January 2022, we identified ten confirmed cases of C. butyricum-related necrotizing enterocolitis, including five from neonatal centre 1, four from neonatal centre 2, and one from neonatal centre 3. The attack rate of necrotizing enterocolitis in neonatal centre 1 was 7.1% (5/70). The positivity rate of C. butyricum detected from stool samples was higher during the outbreak period (37/276; 13.4%) than outside this period (7/369; 1.9%), while systematic screening was maintained (P<0.001). Phylogenetic analysis showed a clonality between strains inside four clusters. Two clusters included neonates hospitalised in different neonatal centres, suggesting the transmission of C. butyricum strains during the transfer of neonates between neonatal centres. CONCLUSIONS: This outbreak of C. butyricum-related necrotizing enterocolitis confirms a cross-transmission between preterm neonates, including twin or triplet siblings, and involving necrotizing enterocolitis cases together with asymptomatic carriers. After three months of follow-up, no further cases were identified following the implementation of contact precautions with sporicidal agents.