2. Saskatchewan Disease Control Laboratory, University of Regina, Regina, SK, Canada.
3. Prince Albert Parkland Health Region, Prince Albert, SK, Canada.
Background: Before introduction of conjugated Haemophilus influenzae serotype b (Hib) vaccines into the routine childhood immunization programs, Hib was a major cause of meningitis in infants and children under the age of 5. In the post-Hib vaccine era, the epidemiology of invasive H. influenzae has changed substantially with most invasive diseases now caused by non-Hib strains, including H. influenzae serotype a (Hia) and serotype f, as well as non-encapsulated or non-typeable strains. This case report describes the microbiology of Hia in a recurrent invasive infection in an infant. The Hia strain involved is described together with current knowledge of Hia infection including methods of protection.
Methods: Isolates were characterised by Gram stain, growth factor requirements, biotype, serotype, detection of IS1016-bexA deletion, multilocus sequence typing, pulsed-field gel electrophoresis and antimicrobial susceptibility testing.
Results: All three isolates appeared to be identical, belonged to biotype II, serotype a, sequence type 23, lacked the IS1016-bexA partial deletion, and were susceptible to commonly prescribed antibiotics tested.
Conclusion: Hia has emerged as a significant invasive pathogen in the post Hib vaccine era. MLST and PFGE serve as useful techniques for typing of Hia. Many attributes of Hia and the disease it causes bear resemblance to Hib and Hib disease, including the ability to cause recurrent infections. This raises the potential for protection by vaccination and chemoprophylaxis.
Keywords: Haemophilus influenzae, serotype a, recurrent infection, Hib