Blinded application of microscopy, bacteriological culture, immunoassays and PCR to detect gastrointestinal pathogens from faecal samples of patients with community-acquired diarrhoea

Abstract

A blinded trial in two different laboratories was performed to compare the detection of selected enteric pathogens in 92 unselected faecal samples collected from patients with community-acquired diarrhoea by conventional and PCR-based techniques. Conventional techniques detected a single potential etiological agent in 15% of the samples, whereas results of PCR detected evidence of at least one agent in 41% of the samples. Overall, the detection rates for the different pathogens were as follows: adenovirus serogroup F, 1%; Campylobacter spp., 7.6%; Salmonella spp., 4%; enteroaggregative Escherichia coli, 9.8%; enteropathogenic E. coli, 6.5%; enterotoxigenic Clostridium perfringens, 3%; Cryptosporidium spp., 13%; and Giardia spp., 11%. Results for the detection of Salmonella spp., Campylobacter spp. and C. perfringens were similar by both techniques, whereas Cryptosporidium and Giardia spp. were detected 22 times more often by PCR than by conventional microscopy. It was not possible to compare the results for detection of enteroaggregative E. coli and enteropathogenic E. coli since these were only investigated by PCR. The results of this small study clearly demonstrate the advantages of PCR-based methods compared to conventional techniques for the detection of gastrointestinal pathogens.

Detection of enteroaggregative Escherichia coli in faecal samples from patients in the community with diarrhoea

“…Baudry et al (1990) first used the aat gene (referred to as the CVD432 EAEC probe) as a target for the identification of EAEC, and claimed that the probe was 89 % sensitive. Although subsequent studies have shown that the sensitivity varies between 15 and 90 % (Okeke & Nataro, 2001), the aat gene has remained the most popular target in molecular assays for the detection of EAEC (Schmidt et al, 1995;Cerna et al, 2003;Pabst et al, 2003;Amar et al, 2004). In this study, seven patients with aatpositive strains were known to have recently travelled outside the UK to destinations that included Nepal, Pakistan, Egypt, Sri Lanka and Mexico.…”

A study of the prevalence and genotypes of Giardia duodenalis infecting kennelled dogs

“…Given that the PCR detection method was more sensitive than microscopy, particularly when the level of infection was low (McGlade et al, 2003;Amar et al, 2004), only PCR detection data were used to evaluate associations with the other variables (Table 1).…”

Prevalence and genotyping of human isolates of Giardia duodenalis from Albania

“…However, considering that the fifty samples selected contain all of microscopy positives, the infection rates observed by immunofluorescence and PCR may overestimate the prevalence of Giardia infection. Nevertheless, more sensitive techniques such as PCR may indeed detect Giardia infection with low parasitic load or evidence the parasite when it is undetectable in stool sample [14,15]. Values of prevalence observed from rural and urban areas are identical, suggesting a comparable risk of infection in both the environment.…”