Diversity of binary toxin positive Clostridioides difficile in Korea

Abstract

The objective of this study is to determine the trend and diversity of binary toxin-positive Clostridioides difficile over 10 years in Korea. Binary toxin-positive strains were selected from a tertiary hospital in Korea in 2009-2018. The multi-locus sequence typing and antibiotic susceptibility test were performed. Among the 3278 isolates in 2009-2018, 58 possessed binary toxin genes (1.7%). The proportion of CDT- positive isolates was 0.51-4.82% in 2009-2018, which increased over the 10-year period (P = 0.023). Thirteen sequence types (STs) were identified; ST5 (14 [24%]), ST11 (11 [19%]), ST221 (10 [17%]), ST201 (7 [12%]) and ST1 (5 [9%]) were popular. All 58 isolates were susceptible to vancomycin and piperacillin/tazobactam, and clindamycin and moxifloxacin were active in 69.0% and 62% of isolates, respectively. ST1 strains were resistant to several antibiotics, including moxifloxacin (80%), clindamycin (60%) and rifaximin (60%). Moreover, four of five ST1 presented a metronidazole minimum inhibitory concentration of 4 µg/mL. Moxifloxacin resistance was highest (72.3%) for ST11. In conclusion, binary toxin-positive strains are non-prevalent in Korea and involve diverse STs. ST1 strains were resistant to several antibiotics.

Figure 1

Annual percentage of binary toxin-positive Clostridioides difficile among all the isolates by year.

Figure 2

Distribution of (A) sequence types (ST) and (B) clades by year, 2009–2018.

Figure 3

Neighbor-joining tree constructed using the concatenated sequences of the seven loci used in multi-locus sequence typing. Bootstraps were generated using 1000 replicates, and low values were removed for clarity. Sequence types (STs) are shown as numbers. The STs cluster into four groups, designated 2, 3, 5 and unknown.