Adhesion of Salmonella enterica var Enteritidis strains lacking fimbriae and flagella to rat ileal explants cultured at the air interface or submerged in tissue culture medium

Abstract

Rat ileal air interface and submerged explant models were developed and used to compare the adhesion of Salmonella enterica var Enteritidis wild-type strains with that of their isogenic single and multiple deletion mutants. The modi®ed strains studied were defective for ®mbriae,¯agella, motility or chemotaxis and binding was assessed on tissues with and without an intact mucus layer. A multiple a®mbriate=a¯agellate (®m 2 =¯a 2 ) strain, a ®mbriate but a¯agellate (¯a 2 ) strain and a ®mbriate=¯agellate but non-motile (mot 2 ) strain bound signi®cantly less extensively to the explants than the corresponding wild-type strains. With the submerged explant model this difference was evident in tissues with or without a mucus layer, whereas in the air interface model it was observed only in tissues with an intact mucus layer. A smooth swimming chemotaxis-defective (che 2 ) strain and single or multiple a®mbriate strains bound to explants as well as their corresponding wild-type strain. This suggests that under the present experimental conditions ®mbriae were not essential for attachment of S. enterica var Enteritidis to rat ileal explants. However, the possession of active¯agella did appear to be an important factor in enabling salmonellae to penetrate the gastrointestinal mucus layer and attach speci®cally to epithelial cells.

Lack of flagella disadvantages Salmonella enterica serovar Enteritidis during the early stages of infection in the rat

“…The fimÀ/fla+ mutant (EAV26) was able to colonize the rat gut and invade to the systemic tissues as effectively as its fimbriate parent strain (S1400, fim+/fla+). This was consistent with earlier findings, that these strains bound equally well to rat and chick gut explants (AllenVercoe & Woodward, 1999; Robertson et al, 2000) and caused similar levels of infection in 1-day-old chicks (AllenVercoe et al, 1999). The results suggest that, whilst SEF14, SEF17, SEF21, pef, lpf can have significant roles in the early stages of infection (Ohl & Miller, 2001;Darwin & Miller, 1999;Humphries et al, 2001;Baumler et al, 1996Baumler et al, , 1997, their presence is not a prerequisite in all cases.…”

“…This was consistent with the findings of other studies in vivo Schmitt et al, 2001). However, it contrasted with earlier results in vitro (AllenVercoe & Woodward, 1999;Robertson et al, 2000), where the aflagellate strains were found to be less able to attach to rat ileum or chick gut explants Robertson et al, 2000). The numbers of S. Enteritidis associating with the explants were, however, greatly influenced by the mucus layer , which is particularly deep at the ileum (Atuma et al, 2001).…”

“…Mediation of attachment primarily by bacterial (fimbrial) adhesins has been suggested (Kingsley & Baumler, 2000;Darwin & Miller, 1999;Humphries et al, 2001). However, recent studies suggest that other factors might also be involved Robertson et al, 2000;Robertson, 2000). S. Enteritidis mutant strains unable to express functional flagella were less able to attach to explants in vitro and less pathogenic to chicks in vivo AllenVercoe & Woodward, 1999;Robertson et al, 2000;Robertson, 2000).…”

Correlation between cluster analyses ofSalmonellastrains isolated from diarrhetic patients in Kuwait and biofilm formation

“…The possession of active flagella combined with chemotaxis is also an important factor in the pathogenicity of Salmonellae (Khoramian et al [7]; Jones et al [6]). Thus, variability in genotypic or phenotypic surface adhesion-related characteristics of different subspecies is expected to affect the establishment of Salmonellae populations in different hosts (Robertson et al [13]) and thus its ability to cause outbreaks. One mechanism for ensuring survival in the host might be the differential biofilm-forming potential within a natural Salmonellae population.…”

“…An important factor influencing the pathogenicity of Salmonella is its ability to adhere to the host's intestinal surfaces prior to invasion (Robertson et al [13]). This interaction is thought to depend upon bacterial-like adhesins recognizing specific glycoconjugate receptors on host cell surfaces.…”