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Persistent infection with small colony variant strains of Staphylococcus aureus in patients with cystic fibrosis
B Kahl1, M Herrmann, A S Everding
1Institute of Medical Microbiology and Department of Pediatrics, University of Muenster Hospital and Clinics, Germany.
Abstract:
In a 34-month prospective study to determine the prevalence of Staphylococcus aureus small colony variants (SCVs) in cystic fibrosis (CF) patients, S. aureus SCVs or SCVs plus normal S. aureus were recovered from 26 of 78 patients; 27 patients harbored only normal S. aureus. By pulsed-field gel electrophoresis, clonal identity was demonstrated of SCV and normal strains isolated at the same time and of multiple S. aureus SCV and normal strains in consecutive specimens from individual patients. All S. aureus SCVs were resistant to antifolate antibiotics, while the corresponding parent strains were susceptible, and in 11 of 12 SCV/normal pairs, gentamicin was less active against S. aureus with the SCV phenotype than against the normal isolate. Analysis of the underlying auxotrophism of SCVs revealed hemin, thymidine, and/or menadione dependencies. Thus, S. aureus SCVs are highly prevalent in respiratory secretions of CF patients, persist over extended periods, and may contribute to S. aureus persistence in CF patients.
Insights
Staphylococcus aureus small colony variants (SCVs) are common in cystic fibrosis patients, persisting over time. These SCVs exhibit antibiotic resistance, potentially contributing to persistent S. aureus infections in CF patients.
Area of Science:
- Microbiology
- Infectious Diseases
- Pulmonology
Background:
- Cystic Fibrosis (CF) is a genetic disorder affecting multiple organs, primarily the lungs.
- Chronic respiratory infections are a major cause of morbidity and mortality in CF patients.
- Staphylococcus aureus is a common pathogen in CF airways, with persistent infections posing treatment challenges.
Purpose of the Study:
- To determine the prevalence of Staphylococcus aureus small colony variants (SCVs) in respiratory secretions of CF patients.
- To investigate the persistence and clonal relatedness of S. aureus SCVs in CF patients.
- To assess the antibiotic susceptibility profiles of S. aureus SCVs compared to normal strains.
Main Methods:
- Prospective study over 34 months.
- Isolation and identification of S. aureus and S. aureus SCVs from patient sputum.
- Pulsed-field gel electrophoresis (PFGE) for clonal analysis.
- Antimicrobial susceptibility testing.
Main Results:
- S. aureus SCVs were recovered from 26 of 78 CF patients.
- Clonal identity was confirmed between SCVs and normal S. aureus strains from the same or consecutive samples.
- S. aureus SCVs demonstrated resistance to antifolate antibiotics and reduced susceptibility to gentamicin compared to normal strains.
- Auxotrophism analysis revealed hemin, thymidine, and/or menadione dependencies in SCVs.
Conclusions:
- S. aureus SCVs are highly prevalent and persistent in CF respiratory secretions.
- SCVs may play a role in the long-term persistence of S. aureus infections in CF patients.
- The unique resistance patterns of SCVs highlight potential challenges in treating S. aureus infections in CF.