Genetic Basis of Intestinal Persistence of Salmonella enterica

Salmonella is a leading cause of food borne illness, causing an estimated 1.4 million cases per year in the United States. Serovar Typhimurium is responsible for about 26% of these cases (CDC, 1998).  The vast majority of Salmonella infections in mammals and birds are the result of infection with S. enterica subspecies I serovars, yet very few genetic factors that are necessary for intestinal persistence in these reservoirs have been described. Intestinal persistence is critical for shedding and transmission of serovar Typhimurium in mammals and birds, yet this phenomenon and interaction of the organism with the host immune system during persistent infection is poorly understood. The long-term goal of our work is to understand the genetic basis of persistence and host range restriction ofSalmonella enterica serovar Typhimurium in its mammalian hosts. We are currently working on the following projects:

1. Functional Genomics of Salmonellae:  Generation of a Complete Deletion Library

We are generating a library of targeted deletions using λ red recombination in all non-essential genes of Salmonella enterica serotype Typhimurium ATCC14028 in collaboration with Michael McClelland (Sidney Kimmel Cancer Center, San Diego CA).  We currently have generated targeted deletions in 1032 genes specific to Salmonellae, or approximately ¼ of the genome, and are progressing to complete this collection.  This library will be used for in vitro and in vivo screening, and will be an outstanding resource for the field!

2. In vitro Screening of Complete Deletion Library.

We are interested in the ability of Salmonellae to perisist in the mammalian and avian intestine, thus we are interested in identification of mutants defective in all aspects of the lifestyle of this important pathogen in the host. We are currently screening our library of deletions to identify mutants with interesting phenotypes in vitro including:  motility (both reduced and enhanced), resistance to gastric contents, resistance to bile acids, resistance to NO, biofilm formation, and resistance to antimicrobial peptides. We welcome collaborators on these projects!!

3.  In vivo Screening of Complete Deletion Library.

We are currently screening our pooled library in various animals to identify new genes important for intestinal persistence in these models. Animal models we are using are Salmonella-sensitive BALB/c mice, Salmonella-resistant CBA/J mice and Chickens. We are actively pursuing collaborations for large animal livestock models as well, as livestock animals are the primary reservoir of Non-Typhoidal salmonellosis for humans and are thus an important food safety concern. We welcome collaborators on these projects!