Abstract

Background: Among Haemophilus influenzae species, H. influenzae type b commonly causes pneumonia and meningitis in infants, whereas nontypeable H. influenzae commonly causes community-acquired pneumonia in adults.
Methods: We investigated the role of H. influenzae type b as a causative agent of pneumonia among adults; hundred blood and serum samples were collected from adult patients with respiratory tract infection and radiologically confirmed pneumonia but with negative results for routinely suspected organisms causing pneumonia. Complete etiological detection was achieved using enzyme-linked immunosorbent assay for both anti-H. influenzae type b immunoglobulin M and G antibodies and confirmed by polymerase chain reaction.
Results: Seropositivity to anti-H. influenzae type b immunoglobulin G antibodies was observed in 26% pneumonic adult patients, 53.8% of whom also had anti-H. influenzae type b immunoglobulin M antibodies. Confirmatory polymerase chain reaction revealed that all 26 seropositive patients were positive, whereas only 2 of the patients seronegative for both immunoglobulin M and immunoglobulin G antibodies were positive to H. influenzae type b.
Conclusion: These findings indicated that H. influenzae type b is recently being considered as an important etiological agent of community-acquired idiopathic pneumonia in adults in Iraq; this change in the target population represents a demographic change in H. influenzae type b pathogenicity. Therefore, elderly patients must be included in the immunization schedule and therapeutic prophylaxis against H. influenzae type b infection.

Key words: Hib target group; Eastern Mediterranean region; Iraq