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Expression of the hil A Salmonella typhimurium gene in a poultry Salm. enteritidis isolate in response to lactate and nutrients
Author(s) -
Durant J.A.,
Corrier D.E.,
Stanker L.H.,
Ricke S.C.
Publication year - 2000
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1046/j.1365-2672.2000.01089.x
Subject(s) - biology , salmonella enteritidis , virulence , microbiology and biotechnology , salmonella , lactose , gene expression , bacteria , biochemistry , gene , genetics
Pathogens express virulence genes in response to the combination of environmental conditions present in the host environment. The crop is the first gastrointestinal environment encountered in birds. However, feed withdrawal alters the crop environment resulting in an increased pH, and decreased concentrations of lactate, glucose and amino acids compared with unmoulted birds. Salmonella enteritidis infections increase significantly in hens that have been force moulted by feed withdrawal. The present study examined the effects of pH, carbohydrate sources, amino acids and lactate on expression of Salm. enteritidis virulence by measuring expression of hil A. The hil A gene encodes a transcriptional activator that regulates expression of Salmonella virulence genes in response to environmental stimuli. HilA expression was determined using a poultry isolate of Salm. enteritidis carrying a hil A ‐lac ZY transcriptional fusion from Salm. typhimurium . The media used were Luria Bertani (LB) broth and LB broth diluted 1 : 5 (DLB). The expression of hil A was 2·9‐fold higher in DLB broth compared with LB broth which suggested that there is a nutritional component to the regulation of hil A. Addition of 0·2% glucose, fructose or mannose to LB and DLB reduced hil A expression 1·5 to twofold. Addition of 0·2% Casaminoacids, arabinose, fucose, or lactose had little effect on hil A expression. Lactate (25 and 50 mmmol l −1 ) reduced hil A expression at pH 6, 5 and 4, with the lowest expression occurring at pH 4. Based on these results it appears that the composition of the crop lumen could potentially influence Salm. enteritidis virulence expression.