Skip to main content
ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Food Safety and Enteric Pathogens Research » Research » Publications at this Location » Publication #108099
Title: EVALUATION OF INVASION-CONFERRING GENOTYPES AND ANTIBIOTIC-INDUCED HYPERINVASIVE PHENOTYPES IN MULTIPLE ANTIBIOTIC RESISTANT SALMONELLA TYPHIMURIUM DT104

Author
item CARLSON, STEVEN
item WILLSON, RUTH
item Crane, Amy
item FERRIS, K - USDA, APHIS, NVSL

Submitted to: Microbial Pathogenesis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Antibiotic resistance in pathogenic bacteria is a problem in both developed and developing countries. This problem is especially evident in Salmonella typhimurium, a foodborne pathogen that causes disease throughout the world. Salmonella typhimurium further poses a major health concern due to its apparent enhanced ability to acquire multiple antibiotic resistance genes and its putative enhanced ability to cause disease. Recently, we demonstrated that multiresistant Salmonella typhimurium do not appear to be more efficient at physically invading intestinal cells, a process that underlies the disease-causing acumen of Salmonella. In the present study, we evaluated the presence of an important Salmonella virulence marker in over 400 isolates of multiresistant Salmonella typhimurium. Also, we used a tissue culture assay to evaluate a potential relationship between antibiotic exposure and an enhanced ability to invade cells. Our studies revealed that the virulence marker of interest is similar in multiresistant and nonresistant Salmonella typhimurium. Furthermore, we failed to identify any isolates that were more invasive in the presence of any of the five antibiotics commonly part of the resistance profile of multiresistant S. typhimurium. These results further indicate that the putative hypervirulent nature of multiresistant Salmonella typhimurium is not likely to occur at the level of intestinal cell invasion. The results from this study will be helpful to scientists and to clinicians. Specifically, these studies show that antibiotic use does not influence the initial phase of Salmonella virulence.

Technical Abstract: Antibiotic resistance in pathogenic bacteria is a problem in both industrialized and developing countries. This is especially evident in S. typhimurium, a foodborne pathogen that causes gastrointestinal and systemic disease throughout the world. S. typhimurium DT104 further poses a major health concern due to its apparent enhanced ability to acquire multiple antibiotic resistance genes and its putative hypervirulent phenotype. Recently, we demonstrated that multiresistant S. typhimurium do not appear to be more invasive than nonresistant cohorts. In the present study, we evaluated the presence of Salmonella pathogenicity island 1 (SPI1) flanking and internal sequences in over 400 isolates of multiresistant S. typhimurium. With these same isolates, we also used a tissue culture invasion assay to evaluate a potential relationship between antibiotic exposure and a hyperinvasive phenotype. Our studies revealed that SPI1 flanking sequences are similar in multiresistant and nonresistant S. typhimurium. Furthermore, we failed to identify any isolates that were hyperinvasive in the presence of any of the five antibiotics commonly part of the antibiogram of multiresistant S. typhimurium. These results further indicate that the putative hypervirulence of multiresistant S. typhimurium is not likely to occur at the level of invasion.