Limits...
Turn Up the Heat — Food and Clinical Escherichia coli Isolates Feature Two Transferrable Loci of Heat Resistance

View Article: PubMed Central - PubMed

ABSTRACT

Heat treatment is a widely used process to reduce bacterial loads in the food industry or to decontaminate surfaces, e.g., in hospital settings. However, there are situations where lower temperatures must be employed, for instance in case of food production such as raw milk cheese or for decontamination of medical devices such as thermo-labile flexible endoscopes. A recently identified locus of heat resistance (LHR) has been shown to be present in and confer heat resistance to a variety of Enterobacteriaceae, including Escherichia coli isolates from food production settings and clinical ESBL-producing E. coli isolates. Here, we describe the presence of two distinct LHR variants within a particularly heat resistant E. coli raw milk cheese isolate. We demonstrate for the first time in this species the presence of one of these LHRs on a plasmid, designated pFAM21805, also encoding type 3 fimbriae and three bacteriocins and corresponding self-immunity proteins. The plasmid was highly transferable to other E. coli strains, including Shiga-toxin-producing strains, and conferred LHR-dependent heat resistance as well as type 3 fimbriae-dependent biofilm formation capabilities. Selection for and acquisition of this “survival” plasmid by pathogenic organisms, e.g., in food production environments, may pose great concern and emphasizes the need to screen for the presence of LHR genes in isolates.

No MeSH data available.


Related in: MedlinePlus

Comparison of loci of heat resistance in FAM21805 (LHR1 and -2) and C604-10 (LHR2). ORFs present in all three LHRs are marked in gray (except for orf1 which is absent in LHR2FAM21805), ORFs unique to LHR2 are marked in blue, partially disrupted ORFs are marked with stripes, and mobile elements are marked in black. Regional nucleotide identities (%) are depicted. A 11.4 kb region containing the mcsSIAB cluster (Microcin S system, marked in red) has been inserted into LHR2FAM21805. For additional information on the ORFs, see Supplementary Table 1.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5383660&req=5

Figure 1: Comparison of loci of heat resistance in FAM21805 (LHR1 and -2) and C604-10 (LHR2). ORFs present in all three LHRs are marked in gray (except for orf1 which is absent in LHR2FAM21805), ORFs unique to LHR2 are marked in blue, partially disrupted ORFs are marked with stripes, and mobile elements are marked in black. Regional nucleotide identities (%) are depicted. A 11.4 kb region containing the mcsSIAB cluster (Microcin S system, marked in red) has been inserted into LHR2FAM21805. For additional information on the ORFs, see Supplementary Table 1.

Mentions: Whole genome sequencing (Illumina) analysis revealed that raw milk cheese isolate FAM21805 harbored an LHR (here designated LHR1) ~15 kb in size with a G+C content of 62% and highly similar (98–99%) to the one previously described in four heat resistant E. coli isolated from beef (Mercer et al., 2015). It contained fourteen putative ORFs and was flanked by mobile elements (Figure 1). We moreover detected additional homologs to several of these ORFs, strongly implying the presence of a second LHR in this isolate. However, de novo assembly failed to demonstrate the location of these homologs within a single genetic locus.


Turn Up the Heat — Food and Clinical Escherichia coli Isolates Feature Two Transferrable Loci of Heat Resistance
Comparison of loci of heat resistance in FAM21805 (LHR1 and -2) and C604-10 (LHR2). ORFs present in all three LHRs are marked in gray (except for orf1 which is absent in LHR2FAM21805), ORFs unique to LHR2 are marked in blue, partially disrupted ORFs are marked with stripes, and mobile elements are marked in black. Regional nucleotide identities (%) are depicted. A 11.4 kb region containing the mcsSIAB cluster (Microcin S system, marked in red) has been inserted into LHR2FAM21805. For additional information on the ORFs, see Supplementary Table 1.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383660&req=5

Figure 1: Comparison of loci of heat resistance in FAM21805 (LHR1 and -2) and C604-10 (LHR2). ORFs present in all three LHRs are marked in gray (except for orf1 which is absent in LHR2FAM21805), ORFs unique to LHR2 are marked in blue, partially disrupted ORFs are marked with stripes, and mobile elements are marked in black. Regional nucleotide identities (%) are depicted. A 11.4 kb region containing the mcsSIAB cluster (Microcin S system, marked in red) has been inserted into LHR2FAM21805. For additional information on the ORFs, see Supplementary Table 1.
Mentions: Whole genome sequencing (Illumina) analysis revealed that raw milk cheese isolate FAM21805 harbored an LHR (here designated LHR1) ~15 kb in size with a G+C content of 62% and highly similar (98–99%) to the one previously described in four heat resistant E. coli isolated from beef (Mercer et al., 2015). It contained fourteen putative ORFs and was flanked by mobile elements (Figure 1). We moreover detected additional homologs to several of these ORFs, strongly implying the presence of a second LHR in this isolate. However, de novo assembly failed to demonstrate the location of these homologs within a single genetic locus.

View Article: PubMed Central - PubMed

ABSTRACT

Heat treatment is a widely used process to reduce bacterial loads in the food industry or to decontaminate surfaces, e.g., in hospital settings. However, there are situations where lower temperatures must be employed, for instance in case of food production such as raw milk cheese or for decontamination of medical devices such as thermo-labile flexible endoscopes. A recently identified locus of heat resistance (LHR) has been shown to be present in and confer heat resistance to a variety of Enterobacteriaceae, including Escherichia coli isolates from food production settings and clinical ESBL-producing E. coli isolates. Here, we describe the presence of two distinct LHR variants within a particularly heat resistant E. coli raw milk cheese isolate. We demonstrate for the first time in this species the presence of one of these LHRs on a plasmid, designated pFAM21805, also encoding type 3 fimbriae and three bacteriocins and corresponding self-immunity proteins. The plasmid was highly transferable to other E. coli strains, including Shiga-toxin-producing strains, and conferred LHR-dependent heat resistance as well as type 3 fimbriae-dependent biofilm formation capabilities. Selection for and acquisition of this “survival” plasmid by pathogenic organisms, e.g., in food production environments, may pose great concern and emphasizes the need to screen for the presence of LHR genes in isolates.

No MeSH data available.


Related in: MedlinePlus