Klebsiella type 33 septicemia in an infant intensive care unit

Between January 25 and March 30, 1971, septicemia with kanamycin-resistant Klebsiella pneumoniae type 33 occurred in 10 of 94 infants in an intensive care unit. All 10 infants also had evidence of localized infection (pneumonia in 5, infected aortic thrombi in 2, meningitis in 1, necrotizing enterocolitis in 1, and abdominal abscess in 1). There was widespread environmental contamination in the unit, but no common source of Klebsiella type 33 other than infected infants could be identified. Spread appeared to occur primarily via the hands of personnel. Control measures resulted in a decrease in cross contamination and dramatic slowing of the outbreak. The strains of Klebsiella type 33 isolated during this epidemic were more virulent than three other Klebsiella serotypes tested in virulence studies in mice.