Changes in Haemophilus influenzae capsule locus: possible emergence of novel variants in Brazil

A total of 28 strains of Haemophilus influenzae (Hi) a and b isolated from clinical samples before and after the introduction of the Hib conjugate vaccine in Brazil were analyzed to determine variants of the capsular gene. Our results suggest the occurrence of new variants closely related to types I and II previously described elsewhere. Eleven Hib strains belonged to type I, 8 were type II, and 3 Hia strains were type II. Six strains showed negative results after polymerase chain reaction targeting capsule locus; the variable regions were sequenced and compared with types I and II. Phylogenetic analysis showed that 5 Hib strains were actually subtypes of type I (type I-A), whereas 1 Hia strain was a subtype of type II (type II-A). Types I and II strains were present in both periods of vaccination. This study suggests that a gradual change in the capsule genes of H. influenzae is probably occurring, and novel variants might be emerging among Brazilian isolates.