Genetic relatedness of coagulase-negative Staphylococci from gastrointestinal tract and blood of preterm neonates with late-onset sepsis.

BACKGROUND: Coagulase-negative staphylococci (CoNS) are the first colonizers of gastrointestinal tract (GIT) and the commonest cause of late-onset sepsis (LOS) in preterm neonates. Intravascular catheters are considered a major source of CoNS bacteremia. However, several cases of LOS remain without an identified source. To elucidate whether GIT could be a potential source of invasive strains, we aimed to assess the molecular similarity between CoNS from blood and GIT in preterm neonates with LOS.

METHODS: Altogether 22 blood and 53 GIT isolates collected from 22 neonates with LOS caused by CoNS (Staphylococcus haemolyticus in 13, Staphylococcus epidermidis in 7 and Staphylococcus hominis in 2 patients) were included. Rectal swabs were collected twice weekly from birth, but only isolates obtained before LOS were analyzed. S. epidermidis isolates were typed by multilocus variable number of tandem repeats analysis and multilocus sequence typing, S. haemolyticus by pulsed-field gel electrophoresis.

RESULTS: Eighteen of 22 neonates had the same CoNS species in GIT and bloodstream; all these isolates from them (altogether 18 blood and 28 GIT isolates) underwent typing. The genotypic similarity between bloodstream and ≥1 antecedent GIT isolates was observed in 13 of 18 patients-3 of 7 with S. epidermidis and 10 of 11 with S. haemolyticus infection. The concordant GIT isolates were collected 0-7 days before the positive blood culture.

CONCLUSIONS: The similarity between CoNS from GIT and bloodstream indicates that preterm neonates harbour invasive strains in GIT before LOS. Whether there is a causal relationship between GIT colonization and LOS remains to be elucidated in further studies.