Blood stream infections with Pseudomonas aeruginosa or Serratia subspecies in preterm infants are associated with a markedly elevated risk of same-pathogen bloodstream infections in other infants in the NICU, based on results from a large database in Germany.

Blood stream infections involving P. aeruginosa or Serratia subspecies, while rare, are “exceptional in their potential to spread in the NICU and attack very low birth weight infants. Because they are also those pathogens with the highest reported BSI (blood stream infection)-related mortality rates, vigorous attempts should be made to intensify infection control measures whenever P. aeruginosa or Serratia have been isolated from a patient in the NICU,” researchers led by Dr. Felix Reichert reported online March 8 in Pediatrics.

Dr. Reichert of the department of neonatology at Charité University Medical Center, Berlin, and his associates used data from the German National Neonatal Infection Surveillance System to estimate the probability of a hospitalized very-low-birth-weight infant to develop a bloodstream infection with a particular pathogen when another infant previously diagnosed with a bloodstream infection from the same pathogen was being cared for in the same unit (Pediatrics 2016 Mar 8. doi: 10.1542/peds.2015-2860). They limited their search to 44,818 very-low-birth-weight infants (defined as less than 1,500 g) who were born between Jan. 1, 2000, and Dec. 31, 2011.

The researchers found 2004 culture-positive bloodstream infections; 407 were from methicillin-sensitive Staphylococcus aureus; 246 to Enterobacter spp; 243 to vancomycin-sensitive Enterococcus spp; 210 to cefotaxime-sensitive Escherichia coli; 190 to cefotaxime-sensitive Klebsiella spp; 138 to Candida albicans; 58 to Serratia; and 38 to P. aeruginosa. Pathogens with 30 or fewer bloodstream infections were not analyzed further analyzed.

Rates of bloodstream infections acquired while another infant with a same-pathogen infection was being cared for in the unit varied between 2.2 (Enterococcus) and 8.2 (Serratia) per 100 exposed infants. The relative risk for acquiring a bloodstream infection in the presence or absence of an infant with a preceding same-pathogen bloodstream infection varied between 4.3 (Enterococcus) and 77.5 (Serratia).

When a same-pathogen bloodstream infection was observed in the same unit during the preceding 30 days, rates of blood stream infection per 100 exposed infants varied between 1.4 (C. albicans) and 6.5 (Serratia). The relative risk for acquiring a bloodstream infection while a same-pathogen infection had been diagnosed in the preceding 30 days in the same department varied between 2.3 (Enterococcus) and 59.5 (Serratia)

The authors acknowledged certain limitations of the study, including the fact that the reporting system used “made no distinction between various strains of Enterococcus, Enterobacter, or Serratia, and there was no genotyping of the pathogens involved. Thus, two temporally related BSIs [blood stream infections] in the same department might well be a coincidence.”

The German National Neonatal Infection Surveillance System is supported by the Federal Department of Health and funds from the Charité University Medical Center. The authors reported having no financial disclosures.