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Optimised methods for detecting Salmonella Typhi in the environment using validated field sampling, culture, and confirmatory molecular approaches

Rigby, Jonathan, Diness, Yohane, Mkwanda, Charity, Tonthola, Katalina, Galloway, Heather, Miles, Rory, Henrion, Marc, Edwards, Thomas, Gauld, Jillian, Msefula, Chisomo, Johnston, Rob, Nair, Satheesh, Feasey, Nicholas ORCID: https://orcid.org/0000-0003-4041-1405 and Elviss, Nicola (2021) 'Optimised methods for detecting Salmonella Typhi in the environment using validated field sampling, culture, and confirmatory molecular approaches'. Journal of Applied Microbiology. (In Press)

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Abstract

Aims
This study evaluated detection methods for Salmonella Typhi (S. Typhi) in the environment, to establish a novel pathway from field sampling to isolation of viable organisms and molecular confirmation from complex environmental samples, thus enabling environmental surveillance of typhoid.

Methods and Results
Multiple media were assessed using clinical isolates from the Public Health England’s (PHE) Culture collection. The culture pathway selected consisted of a primary 2% bile broth and secondary Selenite F broth, followed by modified Chromogenic Agar for Salmonella Esterase (mCASE). A qPCR assay was adapted from a validated S. Typhi PCR panel for confirmation of isolates, with comparison to biochemical and serological tests showing good specificity. Sampling locations in Blantyre, Malawi were used to compare sampling methods. Viable S. Typhi were isolated from a mixture of trap and grab river water samples on six occasions.

Conclusions
Culture of viable S. Typhi from environmental samples was possible using effective capture and culture techniques.
Significance and impact of study

Whilst several studies have attempted to detect S. Typhi from the environment, this is the first successful attempt to isolate the organism from river water since the 1980’s. Supplementing clinical data with environmental screening offers the potential for enhanced surveillance, which might inform interventions and assess vaccination programmes.

Item Type: Article
Subjects: QW Microbiology and Immunology > Environmental Microbiology > QW 55 Environmental microbiology
WA Public Health > Health Problems of Special Population Groups > WA 395 Health in developing countries
WA Public Health > Water > WA 675 Water. Water supply. Sources
WC Communicable Diseases > Infection. Bacterial Infections > Enteric Infections > WC 269 Salmonella infections
WC Communicable Diseases > Infection. Bacterial Infections > Enteric Infections > WC 270 Typhoid fever
Faculty: Department: Biological Sciences > Department of Tropical Disease Biology
Clinical Sciences & International Health > Clinical Sciences Department
Clinical Sciences & International Health > International Public Health Department
Clinical Sciences & International Health > Malawi-Liverpool-Wellcome Programme (MLW)
Digital Object Identifer (DOI): https://doi.org/10.1111/jam.15237
Depositing User: Faye Moody
Date Deposited: 23 Aug 2021 08:38
Last Modified: 23 Aug 2021 08:38
URI: https://archive.lstmed.ac.uk/id/eprint/18717

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