Avaliação do método de disco-difusão e pontos de corte epidemiológicos para rifampicina, eritromicina e tetraciclina em isolados de Clostridioides difficile humanos e animais

Abstract

Clostridioides (prev. Clostridium) difficile is an enteropathogen responsible for causing diarrhea and pseudomembranous colitis, which can lead to death. Among the different risk factors for C. difficile infection, antibiotic therapy stands out. In addition to its relationship with the development of the disease, the use of antimicrobials exerts selective pressure on C. difficile, which has resulted in the development of strains classified as “hypervirulent”. Despite the relevance of antimicrobial resistance in the epidemiology and treatment of C. difficile, the susceptibility tests available for this pathogen still use the determination of the minimum inhibitory concentration (MIC), being expensive and laborious. Such methods are not optimized for routine laboratory work and are expensive. In this study, disk diffusion was used to assess the susceptibility of C. difficile to erythromycin, rifampicin and tetracycline. A total of 155 strains isolated in Brazil between 2011 and 2022 were tested using the disk diffusion and episolometer test (Etest) methods. Data such as isolates’ ribotypes, host of origin and year of isolation were used to assess possible associations with resistance to the antimicrobials tested. The present study suggests that disk diffusion can be an interesting tool for screening erythromycin and rifampicin-resistant C. difficile strains, showing a high correlation to the classification obtained through MIC evaluation. The present study suggests cutoff points at WT ≥ 20mm and WT ≥ 28 mm for classification of erythromycin and rifampicin, respectively. However, for tetracycline, disk diffusion did not perform satisfactorily, misclassifying 5,8% of the isolates. In the present study, isolates of ribotypes belonging to clade 5 were more likely to be resistant to erythromycin, tetracycline and rifampicin, while isolates from animals and non-toxigenic strains showed a higher percentage of resistance to tetracycline and rifampicin, respectively. Tetracycline-resistant isolates also showed a positive statistical association with being resistant to rifampicin as well. The present study suggests that disk diffusion can be a useful tool for assessing the sensitivity of C. difficile to erythromycin and rifampicin, however it is not suitable for tetracycline.