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United States Department of Agriculture

Agricultural Research Service

Title: Exposure to Rumen Protozoa Leads to Enhancement of Pathogenicity of and Invasion by Multiple-Antibiotic-Resistant Salmonella Enterica Bearing Sgi1

Authors
item Rasmussen, Mark
item Carlson, Steven
item Franklin, Sharon
item McCuddin, Zoe
item Wu, M - WALTER REED ARMY INST RES
item Sharma, Vijay

Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 15, 2005
Publication Date: August 20, 2005
Citation: Rasmussen, M.A., Carlson, S.A., Franklin, S.L., McCuddin, Z.P., Wu, M.T., Sharma, V.K. 2005. Exposure to rumen protozoa leads to enhancement of pathogenicity of and invasion by multiple-antibiotic-resistant Salmonella enterica bearing SGI1. Infection and Immunity. 73(8):4668-4675.

Interpretive Summary: Multiple antibiotic resistant Salmonella enterica serotype Typhimurium is a foodborne pathogen that has been purported to be more virulent (i.e., hypervirulent) than antibiotic sensitive counterparts. The paradigm for this multiresistance/hypervirulence is Salmonella enterica serotype Typhimurium phagetype DT104 (DT104). For DT104, the basis for the multiresistance is related to a cluster of chromosomal genes called an "integron". Factors underlying hypervirulence, however, have not been completely identified. Since protozoa, single cell eukaryotic micro-organisms, have been implicated in the alteration of virulence in other pathogens, we attempted to assess the possibility that protozoa may contribute to the putative hypervirulence of DT104. Our study reveals that DT104 can be more virulent, as determined by a tissue culture invasion assay, after surviving within protozoa originating from the bovine rumen. The enhancement of invasion was correlated with hypervirulence in a neonatal calf infection model in which we observed a more rapid progression of disease and a greater recovery rate for the pathogen. This protozoa-mediated augmentation of virulence was additionally observed in other Salmonella possessing the integron structure found in DT104.

Technical Abstract: Multiple antibiotic resistant Salmonella enterica serotype Typhimurium is a foodborne pathogen that has been purported to be more virulent than antibiotic sensitive counterparts. The paradigm for this multiresistant/hyperpathogenic phenotype is Salmonella enterica serotype Typhimurium phagetype DT104 (DT104). For DT104, the basis for the multiresistance is related to an integron structure but factors underlying hyperpathogenicity have not been completely identified. Since protozoa have been implicated in the alteration of virulence in Legionella and Mycobacterium, we attempted to assess the possibility that protozoa may contribute to the putative hypervirulence of DT104. Our study reveals that DT104 can be more invasive, as determined by a tissue culture invasion assay, after surviving within protozoa originating from the bovine rumen. The enhancement of invasion was correlated with hypervirulence in a neonatal calf infection model in which we observed a more rapid progression of disease and a greater recovery rate for the pathogen. This protozoa-mediated phenotype was additionally observed in other Salmonella possessing the integron structure found in DT104.

Last Modified: 11/1/2014