Affiliation:
1. Public Health Wales Microbiology, Singleton Hospital, Swansea, UK
2. Public Health Wales Microbiology, University Hospital of Wales, Heath Park, Cardiff, UK
Abstract
Introduction. A retrospective data analysis of 34 months (spanning 2016–2020) of 961573 diagnostic results obtained before and after nucleic acid amplification testing (NAAT) implementation, across the Public Health Wales microbiology network.
Hypothesis / Gap Statement. This is the first network-wide analysis of the implementation of enteric NAAT in diagnostic microbiology.
Aim. To assess the outcome of replacing microscopy and bacterial culture with NAAT as the primary test in the diagnosis of:
Campylobacter
spp., Salmonella sp.,
Shigella
spp., Shiga toxin-producing
Escherichia coli
(STEC), Cryptosporidium spp. and Giardia duodenalis infections.
Methodology. Following NAAT introduction, bacterial culture was performed as a secondary test, to provide further information from NAAT positive samples for epidemiological purposes. Primary detection rates and overall bacterial culture rates were calculated for each target pathogen using both testing regimes (Stage I) including a comparison of in-patient and out-patient diagnoses (Stage II).
Results. Stage I analysis showed that the primary detection rate significantly increased for
Campylobacter
spp. (P<0.0001),
Salmonella
sp. (P=0.0151),
Shigella
spp. (P<0.0001), STEC (P<0.0001), Cryptosporidium spp. (P<0.0001) and Giardia duodenalis (P<0.0001) when using NAAT compared to microscopy or bacterial culture. A significant decrease was seen in the overall rate of
Campylobacter
spp. isolation by bacterial culture (P<0.0001), whilst other targets remained unaffected. Stage II analysis showed that NAAT positive out-patient samples were more likely to be supplemented by a positive bacterial culture than NAAT positive in-patient samples for
Campylobacter
spp. (P<0.0001), Salmonella sp. (P=0.0004) and STEC (P=0.0039). However,
Shigella
spp. was more frequently isolated from NAAT positive in-patient samples (P=0.0005). A notable increase was seen for G. duodenalis detection from in-patient samples (P=0.0002). Reference laboratory data showed the NAAT assay can detect at least 53 serotypes of STEC but may not be able to detect some of the rarer species of Cryptosporidium seen in human infections.
Conclusion. The implementation of NAAT has significantly increased the primary detection rate of all target enteric pathogens in Wales and information gleaned previously from direct culture is largely unaffected.
Subject
Microbiology (medical),General Medicine,Microbiology
Cited by
4 articles.
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