Toxigenic Clostridioides difficile and Their Antibiotic Susceptibility in Bulgarian Patients during and Post-COVID-19 Pandemic

Abstract

The COVID-19 pandemic boosted antibiotic use in Bulgaria. The aim of the study was to evaluate for the first time in our country, the influence of the COVID-19 pandemic on both characteristic, prevalence and antibiotic susceptibility of Clostridioides difficile. We investigated 75 C. difficile strains isolated since the pandemic compared with 52 strains from 2013–2019. In 2020–2023, the toxigenic strains (TCDs) were 92.0% of all strains vs. 57.7% of those isolated beforehand. In 2020–2023, TCD resistance was metronidazole 5.8%, vancomycin 1.4%, and fidaxomicin 1.6%, without significant differences between the two periods. We observed a 5.5-fold increase in the prevalence of hypervirulent (HCD) strains. In HCD strains in 2020–2023, metronidazole resistance was 7.9%. Notably, resistance to levofloxacin 1 and 32 mg/l was 91.9% and 75.8%, respectively, in TCD strains from 2020–2023. Briefly, the increase in both TCD and HCD strains and the presence of resistance to all three antibiotics for treating C. difficile infections imply the need for susceptibility testing of all TCD isolates. The strikingly high levofloxacin resistance was linked to fluoroquinolone consumption in Bulgaria. The results stress the need for regular monitoring of antibiotic susceptibility of TCD strains, and strict adherence to the antibiotic policy.