Diversity of Nontypeable Haemophilus influenzae Strains Colonizing Australian Aboriginal and Non-Aboriginal Children

Abstract

e Nontypeable Haemophilus influenzae (NTHI) strains are responsible for respiratory-related infections which cause a significant burden of disease in Australian children. We previously identified a disparity in NTHI culture-defined carriage rates between Aboriginal and non-Aboriginal children (42% versus 11%). The aim of this study was to use molecular techniques to accurately determine the true NTHI carriage rates (excluding other culture-identical Haemophilus spp.) and assess whether the NTHI strain diversity correlates with the disparity in NTHI carriage rates. NTHI isolates were cultured from 595 nasopharyngeal aspirates collected longitudinally from asymptomatic Aboriginal (n ‫؍‬ 81) and non-Aboriginal (n ‫؍‬ 76) children aged 0 to 2 years living in the Kalgoorlie-Boulder region, Western Australia. NTHI-specific 16S rRNA gene PCR and PCR ribotyping were conducted on these isolates. Confirmation of NTHI by 16S rRNA gene PCR corrected the NTHI carriage rates from 42% to 36% in Aboriginal children and from 11% to 9% in non-Aboriginal children. A total of 75 different NTHI ribotypes were identified, with 51% unique to Aboriginal children and 13% unique to non-Aboriginal children (P < 0.0001). The strain richness (proportion of different NTHI ribotypes) was similar for Aboriginal (19%, 65/346) and non-Aboriginal children (19%, 37/192) (P ‫؍‬ 0.909). Persistent carriage of the same ribotype was rare in the two groups, but colonization with multiple NTHI strains was more common in Aboriginal children than in non-Aboriginal children. True NTHI carriage was less than that estimated by culture. The Aboriginal children were more likely to carry unique and multiple NTHI strains, which may contribute to the chronicity of NTHI colonization and subsequent disease.

Complete Deletion of the Fucose Operon in Haemophilus influenzae Is Associated with a Cluster in Multilocus Sequence Analysis-Based Phylogenetic Group II Related to Haemophilus haemolyticus: Implications for Identification and Typing

“…Although H. haemolyticus has, on rare occasion, been isolated from invasive infections (6), several lines of evidence indicate that the pathogenicity of H. haemolyticus is much reduced compared with H. influenzae. While up to 20% of presumptive H. influenzae nasopharyngeal isolates can be identified as H. haemolyticus by molecular characterization (7)(8)(9), H. haemolyticus is rarely cultured from middle ear fluid (10,11), supporting the view that H. haemolyticus, in contrast to NTHi, is a respiratory commensal infrequently associated with otitis media. Reinvestigation of presumptive H. influenzae isolates, cultured from lower respiratory tract samples from cystic fibrosis patients (12) or from unselected clinical samples submitted to the laboratory on suspicion of lower respiratory tract infection (13), detected that Ͻ1% were misidentified strains, further supporting a minor pathogenic role for H. haemolyticus.…”

Haemophilus influenzae: a potent perinatal pathogen disproportionately isolated from Indigenous women and their neonates

“…Indigenous women are known to have higher rates of preterm delivery than nonindigenous women (13.7 vs 7.9%), but the number of preterm births in the NTHi group (83%) exceeded predictions based on indigenous origin. Indigenous Australian children are known to have high respiratory carriage rates with NTHi related to overcrowded living conditions . A predisposition to obstetric NTHi infection among indigenous mothers has not to our knowledge been previously reported.…”

Geographic consistency in dominant, non-typeable Haemophilus influenzae genotypes colonising four distinct Australian paediatric groups: a cohort study

“…In the Kalgoorlie studies, NTHi carriage rates among the Aboriginal (Study 3) and non-Aboriginal (Study 4) children were 36.3 % (183/504) and 9.4 % (98/1045), respectively [14]. In Study 1, 84 different PRTs were identified among 2179 NTHi isolates.…”

“…Additionally, Day 12–21 if perforation.(469)551(569)73(13)3Kalgoorlie (WA) Otitis Media Research Project. Prospective Aboriginal cohort [12, 14]1999–2005100(36.3 %)1 wk to 24 mAges 1–3, 6–8 wks, then months 4, 6, 12, 18, 24.(193)231(346)65(28)4Kalgoorlie (WA) Otitis Media Research Project. Prospective non-Aboriginal cohort [12, 14]1999–2005180(9.4 %)1 wk to 24 mAges 1–3, 6–8 wks, then months 4, 6, 12, 18, 24.(102)109(192)37(34)

RCT randomised-controlled trial, AOM acute otitis media, NP nasopharyngeal, PRT PCR-ribotype, NT Northern Territory, WA Western Australia

a A single isolate of each PRT from each swab

b All families provided written informed consent for their child’s participation

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