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Bordetella pertussis isolates with a heterogeneous phenotype for erythromycin resistance
K E Wilson1, P K Cassiday, T Popovic
1Meningitis and Special Pathogens Branch, Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
Abstract:
Erythromycin is currently being used for both prophylaxis and treatment of pertussis infections. Erythromycin resistance was first recognized in Bordetella pertussis in Arizona in 1994, and since then, three additional resistant isolates have been identified in the United States. To better assess the potential public health impact of erythromycin-resistant B. pertussis, we used the disk diffusion assay to evaluate the frequency of erythromycin resistance among 1,030 recently circulating U.S. isolates and found the rate of occurrence to be <1%. We also describe a novel heterogeneous phenotype, with erythromycin-resistant colonies appearing only after a 7-day incubation period. To optimize patient management, we recommend that clinicians be alert to potential treatment failures and that laboratorians use a 7-day incubation period when screening for resistance. Our ongoing national surveillance will continue to monitor for resistant B. pertussis isolates and their potential association with changing pertussis epidemiology.
Insights
Erythromycin resistance in pertussis is rare (<1%) but emerging. A novel resistance phenotype requires a 7-day incubation for detection, crucial for effective treatment and surveillance.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Erythromycin is a key antibiotic for pertussis (whooping cough) prophylaxis and treatment.
- Erythromycin resistance in Bordetella pertussis was first identified in 1994 and has been sporadically reported since.
- Monitoring resistance is vital due to the public health implications of pertussis.
Purpose of the Study:
- To determine the frequency of erythromycin resistance in contemporary U.S. Bordetella pertussis isolates.
- To characterize any novel resistance phenotypes.
- To inform clinical management and laboratory diagnostics for pertussis.
Main Methods:
- Disk diffusion assay used to test 1,030 recent U.S. isolates of Bordetella pertussis.
- Evaluation of incubation time for optimal detection of resistance phenotypes.
Main Results:
- Erythromycin resistance was detected in less than 1% of the isolates tested.
- A novel heterogeneous resistance phenotype was observed, with resistant colonies appearing after 7 days of incubation.
- This contrasts with standard incubation periods, potentially leading to underdetection.
Conclusions:
- Erythromycin resistance in B. pertussis remains infrequent but warrants continued surveillance.
- Clinicians should consider treatment failure in patients on erythromycin.
- Laboratories should implement a 7-day incubation period for accurate screening of B. pertussis for erythromycin resistance.