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Sensitivity of gentamicin-resistant Enterobacteriaceae to cefamandole and cefoxitin
Abstract:
A collection of gentamicin-resistant Enterobacteriaceae strains was significantly more resistant to cefamandole than a species-matched collection of gentamicin-sensitive organisms. Cefamandole and gentamicin resistance could be simultaneously transferred by conjugation from four different species, Citrobacter freundii, Escherichia coli, Klebsiella pneumoniae and Serratia marcescens, to a recipient E. coli strain. Plasmids specifying linked resistance to cefamandole and gentamicin are thus commonly present in the environment of our medical center despite the fact that cefamandole has never been used here. Gentamicin-resistant organisms were not more resistant to cefoxitin than gentamicin-sensitive isolates. Conjugal transfer of cefoxitin resistance could not be demonstrated. Relative resistance to cefoxitin was nevertheless common among Enterobacter and Serratia isolates.
Insights
Gentamicin-resistant bacteria often show increased resistance to cefamandole, with resistance genes transferable between species. This linked resistance is common, even where cefamandole isn't used.
Area of Science:
- Microbiology
- Antimicrobial Resistance
- Molecular Biology
Background:
- Enterobacteriaceae are common causes of healthcare-associated infections.
- Antibiotic resistance, particularly to gentamicin, is a growing concern.
- The relationship between gentamicin and cefamandole resistance in Enterobacteriaceae is not fully understood.
Purpose of the Study:
- To investigate the co-occurrence and transferability of gentamicin and cefamandole resistance in Enterobacteriaceae.
- To compare cefamandole and cefoxitin resistance patterns in gentamicin-resistant versus gentamicin-sensitive strains.
Main Methods:
- Phenotypic characterization of antibiotic resistance in clinical isolates.
- Conjugation experiments to assess the transferability of resistance genes.
- Species identification and characterization of Enterobacteriaceae.
Main Results:
- Gentamicin-resistant Enterobacteriaceae exhibited significantly higher resistance to cefamandole compared to gentamicin-sensitive strains.
- Simultaneous transfer of cefamandole and gentamicin resistance via conjugation was demonstrated from multiple Enterobacteriaceae species.
- Linked resistance plasmids for cefamandole and gentamicin were prevalent in the hospital environment, despite cefamandole's absence.
- No significant difference in cefoxitin resistance was observed between gentamicin-resistant and sensitive isolates, and cefoxitin resistance was not transferable via conjugation.
Conclusions:
- Plasmids carrying linked cefamandole and gentamicin resistance are common in Enterobacteriaceae within healthcare settings.
- The presence of these plasmids suggests a potential for co-selection and spread of resistance, even without direct antibiotic pressure.
- Cefoxitin resistance appears to be mediated by different mechanisms and is not directly linked to gentamicin resistance transfer.