Association of IS 1016 with the hia Adhesin Gene and Biotypes V and I in Invasive Nontypeable Haemophilus influenzae

A subset of invasive nontypeableHaemophilus influenzae (NTHI) strains has evidence of IS1016 , an insertion element associated with division IH. influenzae capsule serotypes. We examined IS1016 -positive invasive NTHI isolates collected as part of Active Bacterial Core Surveillance within the Georgia Emerging Infections Program for the presence or absence ofhmw1 andhmw2 (two related adhesin genes that are common in NTHI but absent in encapsulatedH. influenzae ) andhia (homologue ofhsf , an encapsulatedH. influenzae adhesin gene). Isolates were serotyped using slide agglutination, confirmed as NTHI strains using PCR capsule typing, and biotyped. Two hundred twenty-nine invasive NTHI isolates collected between August 1998 and December 2006 were screened for IS1016 ; 22/229 (9.6%) were positive. Nineteen of 201 previously identified IS1016 -positive invasive NTHI isolates collected between January 1989 and July 1998 were also examined. Forty-one IS1016 -positive and 56 randomly selected IS1016 -negative invasive NTHI strains were examined. Thehia adhesin was present in 39 of 41 (95%) IS1016 -positive NTHI strains and 1 of 56 (1.8%) IS1016 -negative NTHI strains tested;hmw (hmw1 ,hmw2 , or both) was present in 50 of 56 (89%) IS1016 -negative NTHI isolates but in only 5 of 41 (12%; allhmw2 ) IS1016 -positive NTHI isolates. IS1016 -positive NTHI strains were more often biotype V (P < 0.001) or biotype I (P = 0.04) than IS1016 -negative NTHI strains, which were most often biotype II. Pulsed-field gel electrophoresis revealed the expected genetic diversity of NTHI with some clustering based on IS1016 ,hmw orhia , and biotypes. A significant association of IS1016 with biotypes V and I and the presence ofhia adhesins was found among invasive NTHI. IS1016 -positive NTHI strains may represent a unique subset of NTHI strains, with characteristics more closely resembling those of encapsulatedH. influenzae .