Flagella and curli fimbriae are important for the growth of Salmonella enterica serovars in hen eggs

Abstract

Salmonella enterica serovar Enteritidis is unable to multiply in the albumen of fresh eggs and must gain access to the yolk contents in order to multiply to a high level (>10 6 c.f.u. per ml egg contents). As human Salmonella infections resulting from the consumption of infected eggs more frequently involve serovar Enteritidis phage type (PT) 4 than other serovars or PTs, a number of isolates of various S. enterica serovars were examined for their ability to multiply to a high level in eggs over a period of 8 days storage at 20 6C. Their behaviour was compared to that of a range of defined fimbrial and flagella mutants of S. Enteritidis. Strains that did not express flagella were unable to multiply in eggs, and those deficient for curli fimbriae, including strains of S. Enteritidis PT6, displayed high-level growth in significantly fewer eggs than those able to express curli. Most S. Enteritidis strains multiplied to a high level in between 5 and 10 % of eggs during 8 days storage. One PT4 strain, though, showed high levels of growth in more than 25 % of eggs over this period, significantly higher than the other PTs or the two other isolates of PT4 tested. This ability may be important for the association of PT4 infection with the consumption of eggs. INTRODUCTIONSalmonella infection resulting from the consumption of contaminated eggs is a major public health problem in Europe and the USA and an emerging one in the Far East (Poppe, 1999). Salmonella enterica subspecies enterica serovar Enteritidis is responsible for the majority of eggassociated infections, and appears to possess factors that enable it to persist in the reproductive tissue of the hen so that it can contaminate the contents of intact eggs (Okamura et al., 2001a, b). Other serovars of S. enterica, such as Gallinarum and Pullorum, have in the past been widespread in laying flocks (Shivaprasad, 2000), without a concomitant high level of human infection.Salmonella enterica has the potential to elaborate numerous cell surface structures, including type 1 (SEF21), thin aggregative or curli (SEF17), SEF14, long polar (LPF) and plasmid-encoded (PEF) fimbriae, and flagella. Many of these have been shown to be important in the process of infection of the hen and in the colonization of the reproductive tissues. SEF14 fimbriae, which are only present in a few group D serovars (Turcotte & Woodward, 1993), mediate adherence to reproductive tissues (Ogunniyi et al., 1997) and may have a role in organ invasion and persistence (Rajashekara et al., 2000). There is some evidence that flagella are important in the subsequent invasion of internal tissues . Type 1 and curli fimbriae in Escherichia coli, analogous to SEF21 and SEF17 of S. Enteritidis, are associated with initial persistence in the avian gastrointestinal tract (La Ragione et al., 2000). There is little current evidence for a role for PEF and LPF in virulence or persistence in the chick model, or in laying hens. The role of any of these in the growth of Salmonella within the egg is not yet known. Salmonel...

Molecular insights into farm animal and zoonoticSalmonellainfections

“…A positive regulator of Type I fimbriae expression was also induced in the reproductive tract and in laid eggs (Gantois et al 2008b). A role for curli fimbriae and flagella in growth in eggs has also been reported (Cogan et al 2004), but the role of other surface structures, including T3SSs, in reproductive tract colonization requires further study. Recent studies have indicated that the SPI-2 regulator SsrA is required for colonization of the reproductive tract after intravenous inoculation of chickens (Bohez et al 2008), however potential for pleiotropic effects exists and the role of SPI-2 genes per se has not been reported.…”

The Salmonella Pathogenicity Island-1 and -2 Encoded Type III Secretion Systems

“…However, there is conflicting evidence for the contribution of flagella to virulence in S. Enteritidis. Flagellar mutants have been shown to be less proficient in colonizing eggs than wild-type S. Enteritidis (Cogan, et al, 2004). In 20-day-old chickens, Parker et al (Parker & Guard-Petter, 2001) observed that disruption of flagella (by deletion of transcriptional regulator FlhD) caused enhanced invasiveness upon oral challenge.…”

Quantitative estimation of the impact of setting a new target for the reduction of Salmonella in breeding hens of Gallus gallus

“…Quantitative estimation of the impact of setting a new target for the reduction of Salmonella in breeding hens of Gallus gallus numbers) include high molecular mass lipopolysaccharide and surface appendages such as curli, type I fimbriae and flagella (Cogan et al, 2004;De Buck et al, 2004;Guard-Bouldin et al, 2004;Guard-Petter, 2001). …”