Elimination Of Type B Disease May Heighten Virulence Of Other Serotypes.(Brief Article)

2001 AUG 8 - (NewsRx.com & NewsRx.net) --

by N.R. Saltmarsh, staff medical writer - As Haemophilus influenzae type B infections recede in the vaccine era, other serotypes may be emerging to take their place, say researchers in Utah.

Although H. influenzae type B causes severe disease, other serotypes were thought to have low virulence, wrote E.E. Adderson and colleagues in Pediatrics.

"Some have hypothesized that with the virtual elimination of H. influenzae type B, other serotypes might acquire virulence traits and emerge as important pathogens of children," they said.

Now an unusual cluster of five cases of severe type A disease in young children would seem to lend credence to that idea.

After observing four cases of invasive disease caused by H. influenzae type A, the epidemiologists reviewed microbiology records at three reference laboratories that perform all serotyping in Utah. Southern blot analysis with the cap probe pUO38 and with pulsed-field gel electrophoresis was used to analyze strains of H. influenzae type A and control strains, and polymerase chain reaction was used to detect the putative virulence mutation, the IS1016-bexA deletion.

Over the course of 10 months, Adderson and coworkers observed five children with severe invasive disease caused by H. influenzae type A, even though no type A isolates had been submitted to the reference laboratories from 1992 to 1998. The age range of patients was six to 48 months. Four of them had meningitis and bacteremia and one had purpura fulminans.