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Incidence of ampicillin-resistant Hemophilus influenzae in otitis media
Abstract:
Ampicillin resistance in Hemophilus influenzae type b causing serious infections is appreciated, but little is known about ampicillin resistance in nonencapsulated strains causing otitis media. The ampicillin sensitivity of 984 middle-ear isolates of H. influenzae from children in Huntsville, Ala. obtained from 1970-1976, was examined: Nine AmpR isolates were found: one in 1973, two in 1974, three in 1975, and three in the first five months of 1976. Seven strains were nonencapsulated; two were type b. All nine produced beta-lactomase. The incidence of ampicillin resistance in strains causing otitis media increased from 0.6% in 1973 to 2.4% in 1976. AmpR H. influenzae infection should be suspected in situations where ampicillin therapy of otitis media is unsuccessful.
Insights
Ampicillin resistance in nonencapsulated Haemophilus influenzae, a cause of otitis media, is increasing. This beta-lactamase-producing resistance necessitates considering alternative treatments when ampicillin therapy fails.
Area of Science:
- Microbiology
- Infectious Diseases
- Otitis Media Pathogenesis
Background:
- Ampicillin resistance in Haemophilus influenzae type b is recognized, but data on nonencapsulated strains causing otitis media are limited.
- Otitis media is a common childhood infection often treated with ampicillin.
Purpose of the Study:
- To examine the incidence and trends of ampicillin resistance in middle-ear isolates of H. influenzae.
- To determine the characteristics of ampicillin-resistant H. influenzae strains causing otitis media.
Main Methods:
- Analysis of 984 middle-ear isolates of H. influenzae collected from children between 1970-1976.
- Testing for ampicillin sensitivity and beta-lactamase production in identified isolates.
Main Results:
- Nine ampicillin-resistant (AmpR) isolates were identified between 1973 and 1976.
- Seven of the nine AmpR strains were nonencapsulated; two were type b.
- All nine AmpR isolates produced beta-lactamase.
- The incidence of ampicillin resistance in H. influenzae causing otitis media rose from 0.6% in 1973 to 2.4% in 1976.
Conclusions:
- Ampicillin resistance in H. influenzae strains causing otitis media is an emerging concern.
- The increasing prevalence of beta-lactamase-producing, ampicillin-resistant H. influenzae necessitates clinical vigilance.
- Therapeutic failure of ampicillin for otitis media should prompt suspicion of AmpR H. influenzae infection.