Incidence of the Aerobactin Iron Uptake System Among Escherichia coli Isolates From Infections of Farm Animals

Abstract

To assess the importance of aerobactin-mediated iron uptake as a bacterial virulence determinant in animal infections, a total of 576 strains of Escherichia coli isolated from cattle, chickens, sheep and pigs were screened by colony hybridization to determine the presence of the aerobactin genetic determinants, and by a bioassay to detect aerobactin secretion in iron-limited conditions. Results obtained by the two complementary methods correlated well. The incidence of the aerobactin system was very high among septicaemia isolates, particularly those from cattle and chickens, an observation that strongly suggests an important role for this mechanism of iron assimilation in pathogenesis. On the other hand, the incidence of the aerobactin system among mastitis strains was not significantly higher than among faecal isolates from healthy animals. No classical enterotoxigenic E. coli strains tested carried the aerobactin genetic determinants. Although most strains that produced aerobactin were also able to make colicin V, the fact that the two characteristics existed separately in a significant minority of isolates suggested that colicin testing alone could not be reliably used to determine the presence of the aerobactin system.

Genes associated with pathogenicity of avian Escherichia coli (APEC) isolated from respiratory cases of poultry

“…The presence of operon aerobactin is in general related to ColV plasmids, although it can be chromosomal (Linggood et al 1987, Johnson 1991. Table 2 shows that iut A gene, which codifies outer membrane protein aerobactin receptor, was detected in 45.8% of the samples.…”

Inhibition of Biological Activities of the Aerobactin Receptor Protein in Rough Strains of Escherichia coli by Polyclonal Antiserum Raised against Native Protein

“…Possession of the aerobactin system by pathogenic bacteria has been implicated as a virulence factor by epidemiological evidence (Montgomerie et al, 1984;Carbonetti et al, 1986;Linggood et al, 1987;Jacobson et al, 1988) and by studies using laboratory strains in experimental infections (Williams, 1979). We believe, however, that this paper contains the first report in which the aerobactin genes alone, isolated from other potential virulence factors encoded, for example, by ColV plasmids, have been studied in the genetic background of a clinical E. coli isolate.…”

“…Escherichia coli (O'Brien & Gibson, 1970) and other members of the Enterobacteriaceae (Pollock et al, 1970;Perry & San Clemente, 1979) synthesize the phenolic siderophore enterochelin (enterobactin), but some clinical isolates of enteric bacteria also possess a second high-affinity iron-uptake system mediated by the hydroxamate siderophore aerobactin (Braun, 1981 ;Warner et al, 1981 ;Roberts et al, 19866;Martinez et al, 1987). The ability to make and use aerobactin increased the virulence of E. coli K12 strains in experimental infections (Williams, 1979), and a number of epidemiological studies showed significantly higher incidence of the aerobactin system among bacteria isolated from extraintestinal infections than among isolates from the faeces of healthy individuals (Montgomerie et al, 1984;Carbonetti et al, 1986;Linggood et al, 1987;Jacobson et al, 1988).…”

Studies on avian pathogenic Escherichia coli in commercial broiler chicken in South East Queensland

“…An early study conducted on one-day-old chickens suggested a positive association between low iron levels, APEC survival and the pathogenicity of the tested APEC strains (Lafont et al, 1987). Furthermore, several studies have suggested that the expression of an iron acquisition system occurs mainly in APEC compared with AFEC (Dias da Silveira et al, 2002;Dozois et al, 1992;Emery et al, 1992;Linggood et al, 1987). Among APEC strains, iron acquisition systems can be encoded by genes located on plasmids (Sabri et al, 2008;Skyberg et al, 2006) or by chromosomal PAIs (Kariyawasam et al, 2006a).…”

“…Previous studies have indicated that the aerobactin system is found in more than 72% of APEC isolates (Emery et al, 1992;Linggood et al, 1987). The aerobactin iron acquisition system consists of hydroxamate siderophore aerobactin and ferric aerobactin uptake proteins, which are encoded by iucA and iucC genes that are located on ColV plasmids (Boerlin and White, 2013).…”