Antimicrobial susceptibility of Clostridioides difficile. An Argentinian multicenter study of isolates from human patients.

Clostridioides difficile is an etiological agent of diarrhea, and the use of antibiotics is one of the main risk factors for infection. Antimicrobials used for treatment are vancomycin (VAN), metronidazole (MET), and fidaxomicin. Resistant strains have been detected, exhibiting regional and institutional differences. The aim of this work was to determine the susceptibility profile of C. difficile clinical isolates to 14 antimicrobials, and to compare resistance among participating centers. A total of 208 consecutive isolates recovered from seven Argentinian hospitals between January 2018 and March 2020 were studied. MIC was determined by the agar dilution method (CLSI-M100 29ED). Azithromycin (AZM), clindamycin (CLI), ertapenem (ETP), imipenem (IMI), levofloxacin (LEV), linezolid (LNZ), meropenem (MER), metronidazole (MET), moxifloxacin (MOX), piperacillin-tazobactam (PTZ), rifaximin (RFX), teicoplanin (TEI), tigecycline (TGC), and VAN, were tested. The results were analyzed with SPSS 21.0. Chi-square was used to compare data, and statistical significance was set at p<0.05. Susceptibility percentages were as follows: VAN, TEI, and MET, 100%; TGC, 97.6%; PTZ, 96.2%; LNZ, 95.2%; MER, 99.5%; ETP, 60.9%; IMI, 42.8%; RFX, 55.6%; LEV, 48.6%; MOX, 46.1%; CLI, 29.9%; and azithromycin, 17.8%. Significant differences in resistance among centers were observed for: RFX (16.7%-91.7%), CLI (41.2%-86.1%), MOX (22.9%-97.2%), IMI (0%-55.6%), and azithromycin (62.5%-97.2%). Multidrug resistance (MDR) was detected in 80 isolates (38.5%), of which 63 (78.7%) were resistant to three families of antimicrobial agents and 17 (21.3%) were resistant to four. The most frequent combinations were RFX-MOX-CLI, present in 48 (60.0%) isolates, and RFX-IMI-MOX-CLI in 17 (21.3%) isolates. VAN, TEI, and MET were the most active antimicrobials in vitro against C. difficile strains. MER was the most active carbapenem, whereas IMI was the least active. We highlight the differences across institutions that could reflect epidemiological characteristics, and/or the dissemination of clones in each institution.