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

Rigby, J. and Elmerhebi, E. and Diness, Y. and Mkwanda, C. and Tonthola, K. and Galloway, H. and Miles, R. and Henrion, M.Y.R. and Edwards, T. and Gauld, J. and Msefula, C. and Johnston, R. and Nair, S. and Feasey, N. and Elviss, N.C. (2021) Optimized methods for detecting Salmonella Typhi in the environment using validated field sampling, culture and confirmatory molecular approaches. Journal of Applied Microbiology. ISSN 1364-5072

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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 1980s. Supplementing clinical data with environmental screening offers the potential for enhanced surveillance, which might inform interventions and assess vaccination programmes.

Item Type:
Journal Article
Journal or Publication Title:
Journal of Applied Microbiology
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/1300/1305
Subjects:
ID Code:
159439
Deposited By:
Deposited On:
14 Sep 2021 14:15
Refereed?:
Yes
Published?:
Published
Last Modified:
22 Nov 2021 16:44