Clinical features of patients with beta-lactamase producing Haemophilus influenzae isolated from sputum

Ampicillin resistance amongst isolates of Haemophilus influenzae is of increasing concern but its clinical impact is unclear. We performed a retrospective study of 34 hospital patients with lower respiratory tract infection (LRTI) caused by beta-lactamase positive (beta+) H. influenzae and compared these with 34 control patients with LRTI caused by beta-lactamase negative (beta-) strains. Chronic obstructive pulmonary disease was the most common underlying condition in both groups (beta+ 23/24, beta- 25/34). A recent course of antibiotics, especially ampicillin/amoxycillin, was significantly (P < 0.05) more common in the beta+ group (beta+ 17/34, beta- 3/34). Other pathogens were isolated more frequently in the beta+ group (beta+ 10/34, beta- 4/34). There was no difference in outcome between the two groups.