Investigation of Various Tissue Culture Monolayers Sensitivity in Detection of Clostridium difficile Toxin

Abstract: Backround: Clostridium difficile is the most common cause of nosocomial diarrhea. It is usually a consequence of antibi­otic treatment, but sporadic cases can occur. The purpose of this study was to investigate five tissue culture monolayers sen­sitivity in detection of C. difficile-toxin. A total of 402 stool samples from patients with nosocomial diarrhea hospitalized in three hospitals of Tehran Uni­versity of Medical Sciences (TUMS) were collected. The samples were cultured on a selective cycloserine cefoxitin fructose agar (CCFA) and incubated in anaerobic conditions, at 37 °C for 4 days. Isolates were characterized to species level by con­ventional biochemical tests. Bacterial cytotoxicity was assayed on five tissue culture monolayers. Our findings show that of the total patients, 24 toxigenic C. difficile (6%) were isolated. All 24 C. difficile toxins showed cytotoxic effect at ³ 1:10 dilution on Hela, Hep2, Vero, McCoy and Mdck cells after 16, 20, 24, 24 and 30 hours, re­spectively. C. difficile toxin showed cytotoxic effect at ³ 1:100 dilutions only on Hela cell monolayer after 48 hours. Hela cell monolayer may be a satisfactory substitute for the detection of C. difficile toxin in clinical specimens.