title: Antimicrobial susceptibility of Brazilian Clostridium difficile strains determined by agar dilution and disk diffusion.
abstract: Clostridium difficile is a leading cause of diarrhea in hospitalized patients worldwide. While metronidazole and vancomycin are the most prescribed antibiotics for the treatment of this infection, teicoplanin, tigecycline and nitazoxanide are alternatives drugs. Knowledge on the antibiotic susceptibility profiles is a basic step to differentiate recurrence from treatment failure due to antimicrobial resistance. Because C. difficile antimicrobial susceptibility is largely unknown in Brazil, we aimed to determine the profile of C. difficile strains cultivated from stool samples of inpatients with diarrhea and a positive toxin A/B test using both agar dilution and disk diffusion methods. All 50 strains tested were sensitive to metronidazole according to CLSI and EUCAST breakpoints with an MIC90 value of 2μg/mL. Nitazoxanide and tigecycline were highly active in vitro against these strains with an MIC90 value of 0.125μg/mL for both antimicrobials. The MIC90 were 4μg/mL and 2μg/mL for vancomycin and teicoplanin, respectively. A resistance rate of 8% was observed for moxifloxacin. Disk diffusion can be used as an alternative to screen for moxifloxacin resistance, nitazoxanide, tigecycline and metronidazole susceptibility, but it cannot be used for testing glycopeptides. Our results suggest that C. difficile strains from São Paulo city, Brazil, are susceptible to metronidazole and have low MIC90 values for most of the current therapeutic options available in Brazil.
authors.affiliation: Universidade de São Paulo (USP), Faculdade de Medicina, Departamento de Moléstias Infecciosas e Parasitárias, São Paulo, SP, Brazil.
authors.forename: Edmir Geraldo
authors.initials: EG
authors.lastname: Fraga
authors.affiliation: Universidade de São Paulo (USP), Faculdade de Medicina, Departamento de Moléstias Infecciosas e Parasitárias, São Paulo, SP, Brazil. Electronic address: ac_nicodemo@uol.com.br.
authors.forename: Antonio Carlos
authors.initials: AC
authors.lastname: Nicodemo
authors.affiliation: Fleury Medicina e Saúde, Seção de Microbiologia, São Paulo, SP, Brazil; Universidade de São Paulo (USP), Faculdade de Farmácia, São Paulo, SP, Brazil. Electronic address: sampaio@usp.br.
authors.forename: Jorge Luiz Mello
authors.initials: JL
authors.lastname: Sampaio
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D058491:Bacterial Load; D001938:Brazil; D016360:Clostridioides difficile / Q000187:drug effects* / Q000302:isolation & purification; D003015:Clostridium Infections / Q000382:microbiology; D015169:Colony Count, Microbial / Q000379:methods; D052978:Disk Diffusion Antimicrobial Tests / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D024841:Fluoroquinolones / Q000494:pharmacology; D006801:Humans; D008297:Male; D008795:Metronidazole / Q000494:pharmacology; D008875:Middle Aged; D008911:Minocycline / Q000031:analogs & derivatives / Q000494:pharmacology; D000077266:Moxifloxacin; D009574:Nitro Compounds; D012016:Reference Values; D015203:Reproducibility of Results; D017334:Teicoplanin / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D000078304:Tigecycline; D014640:Vancomycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D009574:Nitro Compounds; D013844:Thiazoles; D008795:Metronidazole; D017334:Teicoplanin; D014640:Vancomycin; D000078304:Tigecycline; D008911:Minocycline; C041747:nitazoxanide; D000077266:Moxifloxacin
keywords: Agar dilution; Clostridium difficile; Disk diffusion; Susceptibility testing