TY - JOUR

T1 - Optimized methods for detecting Salmonella Typhi in the environment using validated field sampling, culture and confirmatory molecular approaches

AU - Rigby, J.

AU - Elmerhebi, E.

AU - Diness, Y.

AU - Mkwanda, C.

AU - Tonthola, K.

AU - Galloway, H.

AU - Miles, R.

AU - Henrion, M.Y.R.

AU - Edwards, T.

AU - Gauld, J.

AU - Msefula, C.

AU - Johnston, R.

AU - Nair, S.

AU - Feasey, N.

AU - Elviss, N.C.

PY - 2022/2/28

Y1 - 2022/2/28

N2 - 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.  

AB - 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.  

KW - bile broth

KW - biofilm

KW - biofilms

KW - Identification

KW - Malawi

KW - mCASE

KW - Moore swabs

KW - PCR (polymerase chain reaction)

KW - river water

KW - salmonella

KW - selenite broth

KW - typhoid

KW - water

U2 - 10.1111/jam.15237

DO - 10.1111/jam.15237

M3 - Journal article

VL - 132

SP - 1503

EP - 1517

JO - Journal of Applied Microbiology

JF - Journal of Applied Microbiology

SN - 1364-5072

IS - 2

ER -