scholarly journals Cloning of genes encoding colicin E2 in Lactococcus lactis subspecies lactis and evaluation of the colicin-producing transformants as inhibitors of Escherichia coli O157:H7 during milk fermentation

2011 ◽  
Vol 94 (3) ◽  
pp. 1146-1154 ◽  
Author(s):  
S.M. Liu ◽  
D.M. Miller ◽  
R.F. Roberts
Keyword(s):  
Escherichia Coli ◽  
Lactococcus Lactis ◽  
Escherichia Coli O157 ◽  
Milk Fermentation ◽  
Genes Encoding ◽  
Colicin E2

Persistence of Escherichia coli O157:H7 in Dairy Fermentation Systems

1998 ◽  
Vol 61 (12) ◽  
pp. 1602-1608 ◽  
Author(s):  
SEAN S. DINEEN ◽  
KAZUE TAKEUCHI ◽  
JANE E. SOUDAH ◽  
KATHRYN J. BOOR
Keyword(s):  
Escherichia Coli ◽  
Lactococcus Lactis ◽  
Dairy Products ◽  
Starter Cultures ◽  
Escherichia Coli O157 ◽  
Potential Health ◽  
E Coli ◽  
Lactococcus Lactis Subsp ◽  
Fermented Dairy Products ◽  
Fermented Dairy

We examined (i) the persistence of Escherichia coli O157:H7 as a postpasteurization contaminant in fermented dairy products; (ii) the ability of E. coli O157:H7 strains with and without the general stress regulatory protein, RpoS, to compete with commercial starter cultures in fermentation systems; and (iii) the survival of E. coli O157:H7 in the yogurt production process. In commercial products inoculated with 103 CFU/ml, E. coli O157:H7 was recovered for up to 12 days in yogurt (pH 4.0), 28 days in sour cream (pH 4.3), and at levels >102 CFU/ml at 35 days in buttermilk (pH 4.1). For the starter culture competition trials, the relative inhibition of E. coli O157:H7 in the experimental fermentation systems was, in decreasing order, thermophilic culture mixture, Lactobacillus delbrueckii subsp. bulgaricus R110 alone, Lactococcus lactis subsp. lactis D280 alone, Lactococcus lactis subsp. cremoris D62 alone, and Streptococcus thermophilus C90 alone showing the least inhibition. Recovery of the rpoS mutant was lower than recovery of its wild-type parent by 72 h or earlier in the presence of individual starter cultures. No E. coli O157:H7 were recovered after the curd formation step in yogurt manufactured with milk inoculated with 105 CFU/ml. Our results show that (i) postprocessing entry of E. coli O157:H7 into fermented dairy products represents a potential health hazard; (ii) commercial starter cultures differ in their ability to reduce E. coli O157:H7 CFU numbers in fermentation systems; and (iii) the RpoS protein appears to most effectively contribute to bacterial survival in the presence of conditions that are moderately lethal to the cell.

scholarly journals Identification and Characterization of Spontaneous Deletions within the Sp11-Sp12 Prophage Region of Escherichia coli O157:H7 Sakai

2013 ◽  
Vol 79 (6) ◽  
pp. 1934-1941 ◽  
Author(s):  
Chun Chen ◽  
Carrie R. Lewis ◽  
Kakolie Goswami ◽  
Elisabeth L. Roberts ◽  
Chitrita DebRoy ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Type Iii Secretion ◽  
Genomic Region ◽  
Escherichia Coli O157 ◽  
Content Type ◽  
E Coli ◽  
Food Borne ◽  
Genes Encoding ◽  
Identification And Characterization

ABSTRACTProphages make up 12% of the enterohemorrhagicEscherichia coligenome and play prominent roles in the evolution and virulence of this food-borne pathogen. Acquisition and loss of and rearrangements within prophage regions are the primary causes of differences in pulsed-field gel electrophoresis (PFGE) patterns among strains ofE. coliO157:H7. Sp11 and Sp12 are two tandemly integrated and putatively defective prophages carried byE. coliO157:H7 strain Sakai. In this study, we identified 3 classes of deletions that occur within the Sp11-Sp12 region, at a frequency of ca. 7.74 × 10−4. One deletion resulted in a precise excision of Sp11, and the other two spanned the junction of Sp11 and Sp12. All deletions resulted in shifts in the XbaI fragment pattern observed by PFGE. We sequenced the inducible prophage pool of Sakai but did not identify any mature phage particles corresponding to either Sp11 or Sp12. Deletions containingpchBandpsrC, which are Sp11-carried genes encoding proteins known or suspected to regulate type III secretion, did not affect the secretion levels of the EspA or EspB effector. Alignment of the Sp11-Sp12 DNA sequence with its corresponding regions in otherE. coliO157:H7 and O55:H7 strains suggested that homologous recombination rather than integrase-mediated excision is the mechanism behind these deletions. Therefore, this study provides a mechanism behind the previously observed genetic instability of this genomic region ofE. coliO157:H7.

scholarly journals Bile Salts Differentially Enhance Resistance of Enterohemorrhagic Escherichia Coli O157:H7 to Human Cationic Antimicrobial Peptides

2021 ◽  
Author(s):  
Crystal Gadishaw-Lue
Keyword(s):  
Escherichia Coli ◽  
Lipid A ◽  
Enterohemorrhagic Escherichia Coli ◽  
Escherichia Coli O157 ◽  
Salt Mixture ◽  
Two Component System ◽  
Two Component ◽  
Genes Encoding ◽  
Uremic Syndrome ◽  
Bacterial Outer Membrane

Enterohemorrhagic Escherichia coli (EHEC) causes severe food and water-borne illness associated with diarrhea, hemorrhagic colitis (HC), and hemolytic-uremic syndrome (HUS). Previously, we reported that treatment of EHEC with a physiologically relevant bile salt mixture (BSM) upregulates genes encoding a two-component system (TCS) (basRS) and a lipid A modification pathway (arnBCADTEF). The current study examines the effect of BSM treatment on EHEC resistance to human cationic antimicrobials, human defensin, HD-5 and cathelicidin, LL-37. Results show a significant increase in resistance to HD-5 when EHEC are pre-treated with BSM as compared to untreated EHEC. The BS-induced resistance phenotype is lost in each of the arnT and basS mutants. Interestingly, BSM treatment does not affect resistance to LL-37. The results of this study provide evidence that BS serve as an environmental cue by triggering changes via a TCS that result in protective modifications of the bacterial outer membrane, thereby increasing resistance to HD-5.

scholarly journals Novel Type of Fimbriae Encoded by the Large Plasmid of Sorbitol-Fermenting Enterohemorrhagic Escherichia coli O157:H−

2001 ◽  
Vol 69 (7) ◽  
pp. 4447-4457 ◽  
Author(s):  
Werner Brunder ◽  
A. Salam Khan ◽  
Jörg Hacker ◽  
Helge Karch
Keyword(s):  
Escherichia Coli ◽  
Gene Cluster ◽  
Enterohemorrhagic Escherichia Coli ◽  
Plasmid Replication ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Significant Homology ◽  
Genes Encoding ◽  
Uremic Syndrome ◽  
Six Genes

ABSTRACT Sorbitol-fermenting (SF) enterohemorrhagic Escherichia coli (EHEC) O157:H− have emerged as important causes of diarrheal diseases and the hemolytic-uremic syndrome in Germany. In this study, we characterized a 32-kb fragment of the plasmid of SF EHEC O157:H−, pSFO157, which differs markedly from plasmid pO157 of classical non-sorbitol-fermenting EHEC O157:H7. We found a cluster of six genes, termed sfpA,sfpH, sfpC, sfpD,sfpJ, and sfpG, which mediate mannose-resistant hemagglutination and the expression of fimbriae.sfp genes are similar to the pap genes, encoding P-fimbriae of uropathogenic E. coli, but thesfp cluster lacks homologues of genes encoding subunits of a tip fibrillum as well as regulatory genes. The major pilin, SfpA, despite its similarity to PapA, does not cluster together with known PapA alleles in a phylogenetic tree but is structurally related to the PmpA pilin of Proteus mirabilis. The putative adhesin gene sfpG, responsible for the hemagglutination phenotype, shows significant homology neither to papGnor to other known sequences. Sfp fimbriae are 3 to 5 nm in diameter, in contrast to P-fimbriae, which are 7 nm in diameter. PCR analyses showed that the sfp gene cluster is a characteristic of SF EHEC O157:H− strains and is not present in other EHEC isolates, diarrheagenic E. coli, or otherEnterobacteriaceae. The sfp gene cluster is flanked by two blocks of insertion sequences and an origin of plasmid replication, indicating that horizontal gene transfer may have contributed to the presence of Sfp fimbriae in SF EHEC O157:H−.

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