Nosocomial spread of Haemophilus influenzae type b infection documented by outer membrane protein subtype analysis.

This report provides evidence of nosocomial transmission of Haemophilus influenzae type b infection between two children in an acute care hospital. In the past, transmission of infection between these children would have gone unrecognized, because the isolates from the respective cases differed in susceptibility to ampicillin. However, the outer membrane protein profile of the two isolates was identical and has previously been observed in less than 2% of type b Haemophilus isolates from patients with invasive disease in the St. Louis area. Thus the likelihood is very low that these two children were both infected with this strain by chance alone (P less than 0.0004). From previous experience, the risk of transmission of Haemophilus in an acute care setting would appear to be very low. However, nosocomial transmission may occasionally occur.