Invasive Haemophilus influenzae in British Columbia: non-Hib and non-typeable strains causing disease in children and adults

Objectives: To characterize invasive Haemophilus influenzae and to examine the population at risk for invasive H. influenzae disease in British Columbia, Canada, 2008-2009. Methods: H. influenzae recovered from individual patients were characterized by serotyping, biotyping, multilocus sequence typing (MLST), and antibiotic susceptibility testing. Age information was recorded from specimen requisition forms. Results: Of the 98 cases, 66% were caused by non-typeable strains, followed by serotypes b (12%), a (10%), f (10%), and e (1%). Cases caused by serotypes b and f and non-typeable strains were mainly in adults over 18 years of age, while cases due to serotype a were mainly in children under the age of 2 years. Different sequence types were found in encapsulated strains according to their serotypes, and non-typeable strains had their own unique sequence types. No capsule switching was documented. Antibiotic resistance was common among non-typeable strains, with 31% identified as genotypic beta-lactamase-negative ampicillin-resistant (BLNAR) strains. Conclusion: Invasive H. influenzae disease in a population vaccinated against Hib was age-dependent and involved both non-typeable and encapsulated strains. Adults were susceptible to invasive diseases due to non-typeable and serotype b and f strains, while in children, most diseases were due to serotype a bacteria. Crown Copyright (C) 2010 Published by Elsevier Ltd on behalf of International Society for Infectious Diseases. All rights reserved.