Insights into molecular characterisation and post-vaccination dynamics of Haemophilus influenza

Hemophilus influenza is a gram-negative bacterium exhibiting the characteristics of facultative anaerobe. The bacterium requires capnophilic conditions for its growth. They are grouped in the category of fastidious organisms as the require X and V factors for their growth. They are present as commensals on the mucosa of the upper respiratory tract of humans. H. influenzae has no veterinary importance, it is exclusively adapted to its human host. The nontypable strain (non-encapsulated) is mostly present in the normal flora of humans but typable strain (encapsulated) can also exists as a commensal. In order to make precise determination about the infectious agents, methods of molecular characterization are helpful to ascertain distinction among closely related isolates. Molecular characterization of Haemophilus influenza is done on the basis of biochemical characteristics, capsular types, biotypes, lipopolysaccharide and lipoologisaccharide, providing valuable insights into pathogenicity, resistance mechanisms and epidemiology of this exclusive human pathogen. Laboratory diagnosis is done for the precise understanding of vaccine efficacy, disease outbreak monitoring, clinical management and for the surveillance purposed. Protein conjugated vaccine is used for its prevention. This has significantly reduced the incidence of Hib diseases but simultaneously, the emergence NTHi infections has also been reported, keeping in mind that NTHi is a prominent cause of otitis media, sinusitis, chronic obstructive pulmonary disease (COPD) and other invasive conditions in susceptible populations. However, utilizing surface proteins as a vaccine antigen can pave way towards protective immunization against NTHi strains. Additionally, the interdisciplinary relationship of molecular analysis with other areas of genomic research in determining pathogenicity, antibiotic resistance, vaccine efficacy of pre and post vaccinal disease epidemiology is the main subject of this review, therefore, an effective approach towards molecular characterization can pave way for developing protein-based vaccines for the control of NTHi infections in the post-Hib vaccine era.