Capsulation loci of non-serotype b encapsulated Haemophilus influenzae.
Invasive infections caused by non-type b encapsulated Haemophilus influenzae have increased recently. Because capsule is a major virulence factor, capsulation of 62 recently isolated non-serotype b encapsulated strains was examined. Repeated serotyping confirmed only 69.0% of isolates. The combination of slide agglutination and cap genotyping confirmed 78.9% of type a, 100% of type e, and 86.4% of type f strains. Seven nonencapsulated strains may have lost capsulation through homologous recombination. Three strains that could not be serotyped or genotyped failed to hybridize with any cap probe and are probably nontypeable H. influenzae. Of isolates that retained an intact cap locus, 62.2% had evidence of cap amplification. The epidemiology of non-type b encapsulated H. influenzae infections is complicated by the poor specificity of available serologic reagents and by spontaneous capsule loss. Recently isolated invasive non-type b encapsulated H. influenzae frequently have cap amplification, which may contribute to their virulence.
Ogilvie
C
C
Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
Omikunle
A
A
Wang
Y
Y
St  Geme III
J W
JW
Rodriguez
C A
CA
Adderson
E E
EE
D016667:Bacterial Capsules / Q000235:genetics*; D015139:Blotting, Southern; D004269:DNA, Bacterial / Q000235:genetics*; D017353:Gene Deletion; D005838:Genotype; D018073:Haemophilus Vaccines / Q000235:genetics; D006193:Haemophilus influenzae / Q000145:classification / Q000235:genetics*; D006801:Humans; D016133:Polymerase Chain Reaction; D011135:Polysaccharides, Bacterial / Q000235:genetics
D004269:DNA, Bacterial; D018073:Haemophilus Vaccines; C044237:Haemophilus influenzae type b polysaccharide vaccine; D011135:Polysaccharides, Bacterial