EPIDEMIOLOGY AND ATTACK INDEX OF GRAM-NEGATIVE BACTERIA CAUSING INVASIVE INFECTION IN 3 SPECIAL-CARE NEONATAL UNITS AND RISK-FACTORS FOR INFECTION

Of 13 consecutive episodes of gram-negative septicemia (Escherichia co li eight, Klebsiella oxytoca four, Klebsiella pneumoniae one) among 11 3 infants in three special-care neonatal units studied, five episodes were epidemiologically related according to a novel fingerprinting met hod for enterobacteria, In ten episodes the invasive phenotype was fou nd in the fecal nora of up to 54% of the fellow infants in the same wa rd and for periods of up to 70 days, Two units exchanged patients, whi ch further promoted the transmission of invasive strains, The attack i ndex was highest for certain E. coli strains, generally low for K. oxy toca strains, but lowest for other E. coli strains, The infants contra cting septicemia had lower birth weight (p=0.04) or were more often cl assified as high-risk infants than matched non-infected fecal carriers of the invasive strains (p=0.04). In summary, gram-negative neonatal septicemia was either due to an apparently high-virulent strain capabl e of attacking the single full-term infant carrier or a high-colonizin g phenotype of lower apparent virulence, which occasionally attacked a high-risk infant among a large number of infants colonized.