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In vitro activity of cefoxitin and imipenem against Mycobacterium abscessus complex
1INSERM, U872, LRMA, Equipe 12 du Centre de Recherche des Cordeliers, Paris, France; Université Pierre et Marie Curie, UMR S 872, Paris, France; Université Paris Descartes, UMR S 872, Paris, France; Service de Microbiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, Paris, France.
This study compared cefoxitin and imipenem activity against Mycobacterium abscessus complex strains. Imipenem showed lower minimum inhibitory concentrations (MICs) but higher resistance rates, with variations observed between species and morphotypes.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- The Mycobacterium abscessus complex is an opportunistic pathogen, frequently causing difficult-to-treat infections, particularly in cystic fibrosis patients.
- Understanding the in vitro activity of key antibiotics like cefoxitin and imipenem is crucial for guiding treatment strategies.
Purpose of the Study:
- To compare the in vitro activity of cefoxitin and imipenem against clinical isolates of the Mycobacterium abscessus complex.
- To investigate factors influencing antibiotic susceptibility, including species and morphotype.
Main Methods:
- Minimum inhibitory concentrations (MICs) of cefoxitin and imipenem were determined for 43 Mycobacterium abscessus complex strains.
- Susceptibility testing was performed according to Clinical and Laboratory Standards Institute (CLSI) breakpoints.
- Strains were analyzed based on species (M. abscessus vs. M. bolletii) and morphotype (smooth vs. rough).
Main Results:
- Imipenem exhibited lower MICs compared to cefoxitin across the tested strains.
- However, a higher proportion of strains were classified as imipenem-resistant based on CLSI breakpoints.
- Cefoxitin MICs were significantly higher for Mycobacterium bolletii than for M. abscessus, and both antibiotics showed higher MICs for the rough morphotype.
Conclusions:
- In vitro activity profiles of cefoxitin and imipenem against Mycobacterium abscessus complex differ, with implications for resistance interpretation.
- Species and morphotype significantly influence the susceptibility to these beta-lactam antibiotics.
- Further clinical studies are needed to clarify the therapeutic impact of these observed in vitro differences.
