Endemic Serratia marcescens infection in a neonatal intensive care nursery associated with gastrointestinal colonization.

Serratia marcescens (SM) produced a prolonged outbreak in a neonatal intensive care unit of high level gastrointestinal colonization (10(9) SM/g feces) which in the early part of the outbreak predisposed to respiratory infection. The early outbreak featured a strain of SM carrying a 54 X 10(6) dalton conjugative plasmid which mediated resistance to gentamicin, tobramycin and beta-lactam agents. The second part of the outbreak involved primarily gastrointestinal colonization with SM strains that were plasmid-free. Acquisition of SM was related to very low birth weight (less than 1500 g). Among very low birth weight neonates, SM colonization was associated with pneumonia, patent ductus arteriosus, congestive heart failure and septicemia. Among neonates greater than 1500 g, SM colonization was associated with bronchopulmonary dysplasia, use of a respirator, patent ductus arteriosus and congestive heart failure. Respirator contamination, respiratory tract colonization and consequent pneumonia were reduced by more frequent changing of respirator tubing. Colonized sinks remained chronically colonized with multiresistant SM.