Evaluation of the respiratory route as a viable portal of entry for Salmonella in poultry via intratracheal challenge of Salmonella Enteritidis and Salmonella Typhimurium

Abstract

Experimental and epidemiological evidence suggests that primary infection of Salmonella is by the oral-fecal route for poultry. However, the airborne transmission of Salmonella and similar enteric zoonotic pathogens has been historically neglected. Increasing evidence of Salmonella bioaerosol generation in production facilities and studies suggesting the vulnerabilities of the avian respiratory architecture together have indicated the possibility of the respiratory system being a potential portal of entry for Salmonella in poultry. Presently, we evaluated this hypothesis through intratracheal (IT) administration of Salmonella Enteritidis and Salmonella Typhimurium, as separate challenges, in a total of 4 independent trials, followed by enumeration of cfu recovery in ceca-cecal tonsils and recovery incidence in liver and spleen. In all trials, both Salmonella Enteritidis and Salmonella Typhimurium, challenged IT colonized cecae to a similar or greater extent than oral administration at identical challenge levels. In most trials, chickens cultured for cfu enumeration from IT-challenged chicks at same dose as orally challenged, resulted in an increase of 1.5 log higher Salmonella Enteritidis from ceca-cecal tonsils and a much lower dose IT of Salmonella Enteritidis could colonize ceca to the same extent than a higher oral challenge. This trend of increased cecal colonization due to IT challenge was observed with all trails involving week-old birds (experiment 2 and 3), which are widely considered to be more difficult to infect via the oral route. Liver-spleen incidence data showed 33% of liver and spleen samples to be positive for Salmonella Enteritidis administered IT (106 cfu/chick), compared with 0% when administered orally (experiment 2, trial 1). Collectively, these data suggest that the respiratory tract may be a largely overlooked portal of entry for Salmonella infections in chickens.

Salmonella spp. in Wild Free-Living Birds from Atlantic Forest Fragments in Southern Bahia, Brazil

“…Salmonella spp. are usually found in the intestinal tract of humans and animals, and they are transmitted through feces that eliminate the agent and contaminate water and food [9].…”

Poultry Body Temperature Contributes to Invasion Control through Reduced Expression of Salmonella Pathogenicity Island 1 Genes in Salmonella enterica Serovars Typhimurium and Enteritidis

“…In general, oral administration of S. Typhimurium or S. Enteritidis to poultry results in poor localization and colonization of systemic tissues such as the liver and spleen compared to bacterial concentration within the ceca [16][17][18][19][20]. Although the reasons for these results are likely multifactorial, the 3 to 5°C difference in the body temperature of poultry (41°C to 42°C) compared to susceptible mammals (37°C to 39°C) may be a factor contributing to the lack of systemic localization by these serovars in poultry.…”

Effect of dexamethasone on bacteriostatic activity of turkey monocytes and implications for food safety

“…While Salmonella is generally considered as having a fecal-oral mode of transmission, the respiratory route has recently been shown to be important in establishing colonization of internal tissues (Kallapura et al, 2014a) and ceca (Kallapura et al, 2014b) and the authors suggest that dissemination by respiratory macrophages may be of critical importance in transmission of Salmonella under field conditions (Kallapura et al, 2014b).…”