D-077. Association of IS1016 with the hia Adhesin Gene and Biotypes V and I in Invasive Nontypeable Haemophilus influenzae
Background: Since introduction of the conjugate Haemophilus influenzae (Hi) serotype b vaccine for use in infants, the majority of invasive Hi disease is caused by nonencapsulated, or nontypeable H. influenzae (NTHi). A subgroup of PCR-confirmed NTHi isolates has evidence of IS1016, an insertion element associated with division I Hi capsule serotypes, suggesting a closer ancestral relationship with encapsulated Hi. We sought to further characterize IS1016-positive (IS1016-pos) NTHi isolates. Methods: Invasive Hi were collected as part of the Active Bacterial Core surveillance in the Georgia Emerging Infections Program between 1/1/89 and 12/31/06. All isolates were biotyped, serotyped by slide agglutination and confirmed with PCR capsule typing. Chromosomal DNA from all NTHi was probed with pUO38 (a Hib cap-gene containing plasmid) and IS1016; all IS1016-pos and 56 randomly selected IS1016 negative (IS1016-neg) NTHi were examined by PFGE; for hmw1, hmw2 (two related adhesin genes common in NTHi; absent in encapsulated Hi), and hia (homologue of hsf, an encapsulated Hi adhesin gene) by PCR and Southern blot. Results: 437 of a total of 704 invasive Hi isolates were PCR-confirmed NTHi. All 430 NTHi further tested lacked capsule-specific genes by Southern blot. 41/ 430 (9.5%) were positive for IS1016. IS1016-pos NTHi were more likely to be biotype V (p <0.001) or biotype I (p=0.04) than IS1016-neg NTHi, which were more likely to be biotype II (p <0.001). 80% (16/20) of the uncommon biotype V NTHi were IS1016-pos. The hia adhesin was found in 39/41 (95%) of IS1016-pos and 1/56 (1.8%) of IS1016-neg NTHi tested (p<0.001); conversely, hmw (hmw1, hmw2 or both) was present in 50/56 (89%) of IS1016-neg NTHi but only 5/41 (12%; all hmw2) of IS1016-pos NTHi (p<0.001). PFGE revealed the expected genetic diversity of NTHi with some clustering based on IS1016, hmw/hia and biotypes. Conclusion: A significant association of IS1016 with biotypes V and I, the presence of hia and the absence of hmw adhesins was found among invasive NTHi. IS1016-positive NTHi may represent a unique subset of NTHi with characteristics more closely resembling those of encapsulated Hi.