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Activity of erythromycin against Haemophilus influenzae from respiratory tract infections
Abstract:
Ampicillin and amoxycillin are very frequently used for treating respiratory infections due to Haemophilis influenzae, but the emergence of beta-lactamase producing strains of this organism may limit their use. Erythromycin would be a suitable alternative but to date variable absorptions and reported minimal inhibitory concentrations (MICs) outside the range of achievable blood levels of erythromycin have prevented its use. The purpose of this study was to determine the MICs of erythromycin for strains of H. influenzae isolated from patients with lower respiratory tract infection and the frequency of beta-lactamase production in these strains. Eighty-five of 100 strains were sensitive to erythromycin (MIC much less than 2.00 mg/L). Eleven strains were resistant to ampicillin and 10 of these produced beta-lactamase. Nine beta-lactamase producing strains had MICs to erythromycin of 2.0 mg/L or less. With the blood levels of erythromycin obtainable with new formulations, this antibiotic should prove of use in the treatment of respiratory infections due to H. influenzae.
Insights
Eighty-five percent of Haemophilus influenzae strains are sensitive to erythromycin, making it a viable alternative for respiratory infections. New formulations may improve erythromycin
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Ampicillin and amoxicillin are common treatments for Haemophilus influenzae respiratory infections.
- Beta-lactamase producing H. influenzae strains limit the efficacy of these antibiotics.
- Erythromycin is a potential alternative, but past concerns about absorption and minimal inhibitory concentrations (MICs) have hindered its use.
Purpose of the Study:
- To determine erythromycin MICs for H. influenzae strains from lower respiratory tract infections.
- To assess the prevalence of beta-lactamase production in these strains.
Main Methods:
- Isolating H. influenzae strains from 100 patients with lower respiratory tract infections.
- Determining the minimum inhibitory concentrations (MICs) of erythromycin for each strain.
- Testing strains for beta-lactamase production and ampicillin resistance.
Main Results:
- Eighty-five of 100 H. influenzae strains were sensitive to erythromycin (MIC < 2.00 mg/L).
- Eleven strains were ampicillin-resistant, with 10 producing beta-lactamase.
- Nine beta-lactamase producing strains exhibited erythromycin MICs of 2.0 mg/L or less.
Conclusions:
- Erythromycin demonstrates significant in vitro activity against H. influenzae, including beta-lactamase producing strains.
- Achievable blood levels with new erythromycin formulations suggest its clinical utility for H. influenzae respiratory infections.
- Erythromycin represents a promising therapeutic option where ampicillin resistance is a concern.