A comparison of Clostridium difficile diagnostic methods for identification of local strains in a South African centre

Abstract

Accurate diagnosis of Clostridium difficile infection is essential for disease management.A clinical and molecular analysis of C. difficile isolated from symptomatic patients at Groote Schuur Hospital, South Africa, was conducted to establish the most suitable clinical test for the diagnosis and characterization of locally prevalent strains. C. difficile was detected in stool samples using enzyme-based immunoassays (EIA) and nucleic acid amplification methods, and their performance was compared with that of C. difficile isolation using direct selective culture combined with specific PCR to detect the C. difficile tpi gene, toxin A and B genes and binary toxin genes. Toxigenic isolates were characterized further by ribotyping. Selective culture isolated 32 C. difficile strains from 145 patients (22 %). Of these, the most prevalent (50 %) were of ribotype 017 (toxin A 2 B + ) while 15.6 % were ribotype 001 (toxin A + B + ). No ribotype 027 strains or binary toxin genes (cdtA and cdtB) were detected. The test sensitivities and specificities, respectively, of four commercial clinical diagnostic methods were as follows: ImmunoCard Toxins A & B (40 % and 99.1 %), VIDAS C. difficile Toxin A & B (50 % and 99.1 %), GenoType CDiff (86.7 % and 88.3 %) and Xpert C. difficile (90 % and 97.3 %). Ribotype 001 and 017 strains had a 100 % detection rate by Xpert C. difficile, 100 % and 93.3 % by GenoType CDiff, 75 % and 53.3 % by ImmunoCard and 75 % and 60 % by VIDAS, respectively. The overall poor performance of EIA suggests that a change to PCR-based testing would assist diagnosis and ensure reliable detection of locally prevalent C. difficile 017 strains. INTRODUCTIONOver the last decade, Clostridium difficile infection (CDI) has emerged as an important healthcare problem, both in the hospital setting and in the community. There has been growing concern over its rising incidence, disease severity and mortality. Major epidemics, causing significant loss of lives, have been reported in North America and Europe (Birgand et al., 2010; Healthcare Commission, 2006; Pépin et al., 2004). These epidemics have been attributed to virulent strains capable of producing more than ten times the amount of toxins than conventional strains (Kelly & LaMont, 2008;McDonald et al., 2005;O'Connor et al., 2009). In addition, the 'hyper virulent' 027 strain has developed resistance to antibiotics such as fluoroquinolones (Pépin et al., 2005).In South Africa, information on CDI remains scarce. Yet, there are some studies that have shown that CDI in this Abbreviations: CA, community acquired; CDI, Clostridium difficile infection; EIA, enzyme-based immunoassays; GDH, glutamate dehydrogenase; HA, hospital acquired; NLR, negative likelihood ratio; NPV, negative predictive value; PLR, positive likelihood ratio; PPV, positive predictive value. part of the world is not insignificant. In 2008, an institution in Pretoria reported a sudden increase in toxin-producing C. difficile, raising the alert of a possible outbreak and sensitizing its clinicians (Lekala...

Clostridium difficile infection perceptions and practices: a multicenter qualitative study in South Africa

“…However, CDI is understudied in low and limited resource settings, including nearly all African countries. Where limited data exists, a study at a tertiary hospital in Cape Town, South Africa found 22% of stool samples from patients with suspected CDI diarrhoea were C. difficile positive [2]. In addition, patients in South Africa are disproportionately affected by HIV and tuberculosis (TB) and therefore also experience known CDI risk factors of prior hospital and antibiotic exposure-exposures that can uniquely contribute to an increased risk of CDI and poor outcomes [3,4].…”

The impact of diagnostic methods on the diagnosis of Clostridiodes difficile infection

“…In a study from the Western Cape, SA, researchers attributed a lower CDI burden to strain diversity and low levels of toxin Incidence rate/10 000 days RESEARCH production. [3] In this study, the positivity rate of Xpert (21.13%) was almost double that of EIA (11.41%). Although toxin EIAs are rapid, widely available and inexpensive, they have poor sensitivity and are no longer recommended as stand-alone tests.…”

“…[9] Studies have shown that toxin EIA tests are less sensitive than PCR and results are variable owing to toxin degradation associated with delayed sample testing. [3] Delayed processing may have contributed to the lower positivity rate in the current study. In a study from the Western Cape, SA, researchers attributed a lower CDI burden to strain diversity and low levels of toxin Incidence rate/10 000 days RESEARCH production.…”

“…Risk factors include the use of broad-spectrum antimicrobials, gastric acid suppression, advanced age, prolonged hospitalisation, enteral feeds, chronic kidney disease and deficient immune status, all of which are associated with the development of CDI. [1,3,[14][15][16][17] Other units showing particularly high CDI incidence rates were the trauma, infectious diseases and gastrointestinal surgical units. Incidence rates were also elevated in the medical oncology, gastroenterology/haematology, renal transplant and renal/nuclear medicine units.…”

Accuracy of Xpert Clostridium difficile assay for the diagnosis of Clostridium difficile infection: A meta analysis

“…Because diagnostic tests performed with different reference methods occurred in the same article, 22 independent studies (including 9352 samples) were defined in the meta-analysis. Table 1 shows the characteristics of these included studies [16–35]. The prevalence of CDI across all studies ranged from 10% to 47.9%.…”