Non-typeable Haemophilus influenzae (isolate 164) (NTHi (isolate 164))

Non-typeable Haemophilus influenzae (NTHi) are unencapsulated, gram-negative coccobacilli found exclusively in humans, which lack the gene locus for a polysaccharide capsule that is present in typeable (encapsulated) strains[3][13]. Isolate 164 (ST164) refers to a particular multilocus sequence type identified by whole-genome sequencing as genetically distinct but closely related to other clusters[1]. NTHi are major colonizers of the human respiratory tract and are opportunistic pathogens capable of causing both acute and chronic infections, especially otitis media, sinusitis, bronchitis, and pneumonia in children and adults[5][12]. Their high genetic diversity and adaptability is facilitated by phase-variable genes and antigenic variation of surface-exposed proteins and lipooligosaccharides[4][3]. NTHi possess several adhesive and invasive factors, including HMW1/HMW2 proteins, Hia and Hap autotransporter proteins, and phase-variable pili, which mediate adherence and immune evasion[2][5][3]. Standard molecular targets for antimicrobials are bacterial enzymes or cell wall components, which are targeted by antibiotics. No specific receptor, enzyme, or transporter from isolate 164 is recognized as a canonical drug target. The bacterium’s resistance patterns and lack of effective vaccines present notable clinical challenges[13][5][7].

Other names

NTHi 164Non-typeable H. influenzae ST164Haemophilus influenzae, non-typeable isolate 164

Inhibition of cell wall synthesis (β-lactam antibiotics such as ampicillin, amoxicillin, cefuroxime, ceftriaxone) - Inhibition of bacterial protein synthesis (macrolides: azithromycin) - Inhibition of DNA gyrase (quinolones: ciprofloxacin)