Laboratory diagnosis of Clostridium difficile disease

Abstract

The laboratory diagnosis of Clostridium difficile-associated disease (CDAD) is based on culture and toxin detection in fecal specimens. Culture is performed on a commercially available selective media. C. difficile colony morphology is typical when viewed under a dissecting microscope. Definitive identification is best obtained by gas liquid chromatography. Culture is very sensitive but, when used alone without toxin testing, it leads to low specificity and misdiagnosis of CDAD when high rates of asymptomatic carriage exist. Toxin detection by a tissue culture cytotoxin assay followed by neutralisation with specific antiserum is often considered the standard. However, this approach lacks sensitivity and has not detected up to 30% of patients with confirmed CDAD. Multiple enzyme immunoassays (EIAs) have been introduced by various manufacturers for the detection of toxin A alone or for both toxins A and B. Some of these are designed to give results in less than 1 h. Comparative studies of EIA kits reported that the sensitivity and specificity are slightly lower than cytotoxin assays. Toxigenic culture tests C. difficile isolates for toxin production: colonies isolated on selective media are tested for in-vitro toxin production either by a cytotoxicity assay or by direct EIA. It has higher sensitivity than the cytotoxicity assay and equivalent specificity. In the routine laboratory, culture and toxin detection should be performed on every specimen and, in culture-positive and fecal toxin-negative cases, toxigenic cultures should be performed on isolated colonies.

Clostridium difficile infection: Early history, diagnosis and molecular strain typing methods

“…2) [8]. A laboratory diagnosis of CDI must be based on the detection of C. difficile toxins or on the isolation of toxigenic C. difficile strains from stool samples [150]. However, these results should be combined with the clinical findings to diagnose the disease.…”

“…The culture of samples is recognised as the most sensitive method for the detection of C. difficile, but its specificity for CDI is low because the rate of asymptomatic carriage of C. difficile among hospitalised patients is so high. This method is not clinically practical for routine diagnosis because it does not distinguish between toxigenic and non-toxigenic isolates and requires 24e48 h to obtain the first results [150]. However, stool culture testing permits the molecular typing of the isolated strains and antibiotic susceptibility determination, making it essential for epidemiological surveys [8,150].…”

“…However, stool culture testing permits the molecular typing of the isolated strains and antibiotic susceptibility determination, making it essential for epidemiological surveys [8,150]. Therefore, stool culture testing can be coupled with a cell cytotoxicity assay or EIA (enzyme immunoassay) to detect toxinproducing C. difficile strains (known as toxigenic cultures), resulting in increased specificity [150].…”

“…The cytotoxic activity is lost very quickly, meaning if the analysis of fresh specimens is not possible, the samples should be stored at 4 C or below. However, cultures are not affected by temporal conditions due to sporulation [150]. Formed stools only must be tested if they come from patients with ileus or potential toxic megacolon or in the case of epidemiological studies [150].…”

“…The original formulation has been extensively modified, including the replacement of egg yolk by blood [150]. The addition of 1 g/L of taurocholate, desoxycholate or cholate has also been shown to induce the germination of C. difficile spores when they are incorporated in CCF [152,153].…”