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Cefoperazone-treated Mouse Model of Clinically-relevant Clostridium difficile Strain R20291
Published on: December 10, 2016
Comparative analysis of Clostridium difficile clinical isolates belonging to different genetic lineages and time
Patrizia Spigaglia1, Paola Mastrantonio1
1Department of Infectious, Parasitic and Immunomediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
Abstract:
Recent studies have shown that Clostridium difficile strains with variant toxins and those with resistance to macrolide-lincosamide-streptogramin B (MLSB) are increasingly causing severe disease and outbreaks in hospital settings. Here, the pathogenicity locus (PaLoc), the acquisition of binary toxin, and the genotypic and phenotypic characteristics of antibiotic resistance of 74 C. difficile clinical strains isolated from symptomatic patients in Italy during different time periods were studied. These strains were found to belong to two different lineages, and those isolated before 1991 were genetically unrelated to the more recent strains. The majority of recent C. difficile strains showed variations in toxin genes and in the toxin negative regulator (tcdC) and had the binary toxin. In 62 % of them, variations in tcdC and the presence of the binary toxin were associated. Five classes of susceptibility/resistance pattern (EC-a to -e) for erythromycin and clindamycin were identified in all strains studied. Most of the recent isolates belonged to EC-d and EC-e and, although erythromycin-resistant in vitro, did not harbour the commonly associated ermB determinant. Interestingly, two strains of the EC-d class were resistant to clindamycin only after induction with subinhibitory concentrations of the antibiotic. A decrease in tetracycline and chloramphenicol MIC values was also observed in the recently isolated strains, associated with less frequent detection of the catD and tetM genes. Two tetM-positive strains were resistant in vitro only after induction with subinhibitory concentrations of the antibiotic. The acquisition of the binary toxin, the possible increase in toxin production due to a mutated negative regulator and a decrease in the fitness cost as a result of lower levels of antibiotic resistance or other mechanisms may have led to the successful establishment of these new phenotypes, with potentially serious clinical implications.
Insights
Recent Clostridium difficile strains exhibit variant toxins and macrolide-lincosamide-streptogramin B (MLSB) resistance, leading to severe hospital outbreaks. These new strains possess binary toxins and altered toxin regulators, suggesting increased pathogenicity and clinical implications.
Area of Science:
- Microbiology
- Infectious Diseases
- Genetics
Background:
- Clostridium difficile strains with variant toxins and macrolide-lincosamide-streptogramin B (MLSB) resistance are increasingly causing severe disease and hospital outbreaks.
- Understanding the genetic and phenotypic characteristics of these emerging strains is crucial for effective clinical management and infection control.
Purpose of the Study:
- To investigate the pathogenicity locus (PaLoc), binary toxin acquisition, and antibiotic resistance profiles of 74 clinical Clostridium difficile strains isolated in Italy.
- To compare genetic and phenotypic characteristics between older and recent C. difficile isolates to identify factors contributing to increased pathogenicity.
Main Methods:
- Analysis of the pathogenicity locus (PaLoc), binary toxin presence, and tcdC gene variations in 74 C. difficile clinical strains.
- Genotypic and phenotypic characterization of antibiotic resistance to erythromycin, clindamycin, tetracycline, and chloramphenicol.
- Determination of minimum inhibitory concentration (MIC) values and detection of specific resistance genes (ermB, catD, tetM).
Main Results:
- Recent C. difficile strains showed variations in toxin genes and tcdC, frequently possessing the binary toxin, often associated with tcdC variations.
- Most recent isolates exhibited MLSB resistance (EC-d, EC-e) without the common ermB determinant; some showed inducible clindamycin resistance.
- A decrease in tetracycline and chloramphenicol MIC values was observed in recent strains, with less frequent detection of catD and tetM genes; some tetM-positive strains showed inducible resistance.
Conclusions:
- Acquisition of binary toxin, altered toxin regulation, and reduced antibiotic resistance fitness costs likely contribute to the successful establishment of new, potentially more virulent C. difficile phenotypes.
- These findings highlight the evolving nature of C. difficile and underscore the need for ongoing surveillance and updated treatment strategies to address emerging resistance and pathogenicity.
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