Hemophilus influenzae respiratory infection in adults

Once a Hemophilus influenzae isolate is identified as the cause of a respiratory tract infection in an adult, it should be tested for beta-lactamase production, ie, for ampicillin resistance. The incidence of ampicillin-resistant strains of H influenzae is increasing. The Centers for Disease Control in Atlanta estimates an average incidence nationwide of 18% to 22%; the rate varies considerably from community to community. Thus, practitioners should be aware of the ampicillin-resistance rate in their community and should keep this rate in mind especially when treating patients empirically. Patients with H influenzae infections who are acutely ill, who fail to respond to ampicillin, or who are known to have an ampicillin-resistant infection on the basis of laboratory findings should receive therapy designed to combat ampicillin-resistant strains.