Abstract & Commentary

New nosocomial pathogen makes its debut in NICU

Novel Clostridium species infects neonates

Source: Alfa MJ, et al. An outbreak of necrotizing enterocolitis associated with a novel Clostridium species in a neonatal intensive care unit. Clin Infect Dis 2002; 35(Suppl 1):S101-S105.

Abstract: An outbreak of eight cases of necrotizing enterocolitis occurred over a two-month period in a Canadian neonatal intensive care unit (NICU). All affected infants had bloody stool, and six of eight had typical X-ray findings of gas in the bowel wall (pneumatosis intestinalis). Seven of the infants were receiving parenteral antibiotics at the time of onset. Blood cultures from three infants and stool cultures from two infants grew a bacillus identified as Clostridium clostridioforme by a rapid anaerobe identification panel. Because the facility had never isolated this species of Clostridia previously, and because C. clostridioforme has not been previously associated with necrotizing enterocolitis, the isolate was sent to a national reference laboratory. It appeared to be a previously unidentified species and was given the tentative name "C. neonatale."

The authors performed a point prevalence study in the NICU and adjacent intermediate care nursery. Five of 24 neonates had rectal swabs positive for C. neonatale. Pulsed field gel electrophoresis analysis of bacterial DNA demonstrated clonality among blood, stool, and rectal swab isolates.

Commentary by Robert Muder, MD, hospital epidemiologist at the Pittsburgh VA Medical Center.

Necrotizing enterocolitis is a disorder that primarily affects low birth weight neonates (< 1,500 g). Intestinal perforation, peritonitis, and bacteremia are frequent; the mortality rate is 20% to 40%. The pathogenesis of necrotizing enterocolitis is incompletely understood. Mucosal ischemia due to hypoxemia, hypotension, or endotoxemia is thought to be a major contributing factor. The disease may occur in outbreaks; these have been associated with a variety of bacterial species including staphylococci, several Clostridium species, E. coli, Klebsiella, and Pseudomonas. Some investigators postulate a role for both ischemia and bacterial pathogens.

The outbreak reported by Alfa, et al, is distinctive first for the association with a previously unidentified bacterial species, and the occurrence of disease in relatively mature neonates; six of eight were at least 35 weeks gestation. There was a fairly significant reservoir of asymptomatic intestinal carriage of C. neonatale. Patient-to-patient transmission was highly likely based on the finding of clonal identity among isolates. Clostridia species are spore formers; the spores are highly resistant to a variety of disinfectant and can persist in the environment for prolonged periods of time.

Clostridia spores are not killed by the waterless alcohol-based hand disinfectants that are being used with increasing frequency. Thus, if C. neonatale is indeed a causative agent of necrotizing enterocolitis, it has characteristics favoring its persistence and spread in the hospital environment.