Detection of Clostridium difficile toxin in various tissue culture monolayers.

Thirty stool filtrates known to contain Clostridium difficile toxin based on previous testing on McCoy cells were tested for toxicity on primary African green monkey kidney (AGMK), McCoy, MRC-5, primary rhesus monkey kidney (RMK), and Vero cells. All 30 filtrates showed cytotoxic effect at greater than or equal to 1:100 dilution on McCoy and Vero cells. A total of 22 filtrates were positive on MRC-5 monolayers, while only 16 and 10 filtrates showed positive cytotoxic effect on AGMK and RMK cells, respectively. Another 630 stool specimens were tested on McCoy and Vero cells only. Of these stool filtrates, 70 were positive and 560 were negative with both cell lines, which thus gave 100% agreement. Vero cells can be used interchangeably with McCoy cells for the detection of C. difficile toxin in stool filtrates.