Can Clostridium innocuum Masquerade as Clostridioides difficile?

To the Editor—Darkoh et al [1] recently described high-level vancomycin resistance (≥32 μg/mL) in Clostridioides difficile isolates that were recovered from Houston, Texas, and Nairobi, Kenya. The authors concluded that C. difficile isolates with a reduced susceptibility to vancomycin are circulating within a broad population. They further concluded that the increasing presence of these isolates with reduced vancomycin susceptibility may result in therapeutic failures, thus calling for increased screening for C. difficile vancomycin resistance [1]. The authors report that 38% of the 536 stool samples acquired from patients with acute diarrhea had C. difficile growth on a screening medium containing 4-μg/mL vancomycin. These results are counter to previously reported vancomycin minimum inhibitory concentration (MIC) data from clinically relevant C. difficile isolates [2]. The investigators used a screening media that included vancomycin to select for isolates with an elevated vancomycin MIC (≥4 μg/mL) [...