Emergence of Salmonella epidemics: The problems related to Salmonella enterica serotyp Enteritidis and multiple antibiotic resistance in other major serotypes

Abstract

-Two major changes in the epidemiology of salmonellosis occurred in the second half of the 20th century: the emergence of food-borne human infections caused by S. Enteritidis and by multiple-antibiotic resistant strains of Salmonella. This review updates information on the S. Enteritidis pandemic and focuses on the emergence of Salmonella, carrying the SGI1 antibiotic resistance gene cluster, resistant to extended-spectrum cephalosporins, or resistant to fluoroquinolones. The factors responsible for the emergence of these Salmonella strains could be either of human origin or related to bacterial genome evolution. However, our increasing understanding of the molecular fluidity of the genome shows that any attempt to counteract bacteria results in further bacterial evolution or adaptation of other bacteria to take place in the new free ecological niche. In these conditions, we can ask who is faster: humans who want to eliminate bacterial pathogens or bacteria that continuously evolve to gain new niches.

Emerging or re-emerging bacterial zoonoses: factors of emergence, surveillance and control

“…Many national sanitary statistics have reported an increase in the prevalence and the incidence of some bacterial zoonoses [11,37,38,52], and the specific causes of such an increase are discussed by several authors in the present issue [7,10,25,46,48,54]. Indeed, an ensemble of causes favorable to the multiplication and diffusion of zoonotic bacteria exist that can be identified for most of these zoonoses, as previously reported [8,13,26,28,38,41,52,53].…”

“…Despite the considerable technological progress made during the last thirty years, there is still a risk of emergence of new bacterial zoonoses, notably those that are foodborne. Food-borne zoonoses account for most of the emerging bacterial zoonoses due to the globalization of food resources and their worldwide distribution, which can be illustrated by the emergence of Escherichia coli O157:H7 [10] or Salmonella Enteritidis [54]. In addition, new bacteria have recently been identified, giving a precise etiology to diseases that were already known or whose zoonotic characteristics were discovered or validated recently.…”

Salmonella spp. in poultry: a constant challenge and new insights

“…Out of more than the 2600 serovars known today, only 10% are found in the commercial poultry and egg industry. Two of them, S. Enteritidis and S. Typhimurium, are of paramount importance to human health and can colonize the intestines of chickens (Velge et al, 2005). In most cases, the infected chickens either do not have clinical symptoms or the symptoms remain unnoticed.…”

Cell invasion of poultry-associated Salmonella enterica serovar Enteritidis isolates is associated with pathogenicity, motility and proteins secreted by the type III secretion system

“…Young chickens less than 2 weeks of age often develop systemic disease with varying degrees of mortality (Duchet-Suchaux et al, 1995;Suzuki, 1994;Velge et al, 2005) whereas most adult hens colonized with S. Enteritidis become intestinal carriers and typically remain asymptomatic (Golden et al, 2008;Lister, 1988;Velge et al, 2005). S. Enteritidis can invade internal organs of laying hens and infect reproductive tissues leading to internal contamination of newly formed eggs (De Buck et al, 2004;Guard-Petter, 2001;Velge et al, 2005). It is believed that the specialized ability of S. Enteritidis to contaminate developing eggs acts as an ecological amplifier that facilitates dissemination of S. Enteritidis in the food chain and its eventual transmission to humans.…”