Reduced Virulence of an fliC Mutant of Shiga-Toxigenic Escherichia coli O113:H21

ABSTRACT The contribution of flagellin to the virulence of the O113:H21 Shiga-toxigenic Escherichia coli (STEC) strain 98NK2 was investigated in the streptomycin-treated mouse model. Groups of mice were challenged with either the wild-type STEC or a fliC deletion derivative thereof. There was no difference in the level of gut colonization by the two strains, but the fliC mutant was significantly less virulent than its parent; the overall survival rates were 43.7% and 81.2%, respectively (P < 0.025). This is the first report of a nontoxic accessory virulence factor contributing to a fatal outcome of STEC infection in this model. Although H21 FliC is known to be a potent inducer of CXC chemokines, including interleukin 8, there was no obvious difference in the recruitment of polymorphonuclear leukocytes to the intestinal epithelium of mice challenged with either strain. However, immunofluorescence microscopy suggested that the fliC mutant was less capable of forming a close association with the colonic epithelium. This may have reduced the uptake of Stx2 by mice infected with the mutant.

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In Vivo Titration of Mitomycin C Action by Four Escherichia coli Genomic Regions on Multicopy Plasmids

Journal of Bacteriology ◽

10.1128/jb.183.7.2259-2264.2001 ◽

2001 ◽

Vol 183 (7) ◽

pp. 2259-2264 ◽

Cited By ~ 26

Author(s):

Yan Wei ◽

Amy C. Vollmer ◽

Robert A. LaRossa

Keyword(s):

Escherichia Coli ◽

Mitomycin C ◽

Transcriptional Activation ◽

Efflux Pump ◽

Wild Type ◽

Potent Inducer ◽

E Coli ◽

Genomic Regions

ABSTRACT Mitomycin C (MMC), a DNA-damaging agent, is a potent inducer of the bacterial SOS response; surprisingly, it has not been used to select resistant mutants from wild-type Escherichia coli. MMC resistance is caused by the presence of any of four distinctE. coli genes (mdfA, gyrl, rob, andsdiA) on high-copy-number vectors. mdfAencodes a membrane efflux pump whose overexpression results in broad-spectrum chemical resistance. The gyrI (also called sbmC) gene product inhibits DNA gyrase activity in vitro, while the rob protein appears to function in transcriptional activation of efflux pumps. SdiA is a transcriptional activator of ftsQAZ genes involved in cell division.

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TheEscherichia coliO157:H7 Carbon Starvation-Inducible Lipoprotein Slp Contributes to Initial AdherenceIn Vitrovia the Human Polymeric Immunoglobulin Receptor

10.1101/429480 ◽

2018 ◽

Author(s):

Christine Fedorchuk ◽

Indira T. Kudva ◽

Subhashinie Kariyawasam

Keyword(s):

Escherichia Coli ◽

Immunofluorescence Microscopy ◽

Polymeric Immunoglobulin Receptor ◽

Wild Type ◽

Immunoglobulin Receptor ◽

E Coli ◽

Data Support ◽

Food Borne ◽

Food Borne Illness ◽

Adherence Mechanism

AbstractEscherichia coliO157:H7 is the most well-studied serotype of enterohemorrhagicE. coli(EHEC) class ofE. coliintestinal pathogens, and is responsible for many outbreaks of serious food-borne illness worldwide each year. Adherence mechanisms are a critical component of its pathogenesis, persistence in natural reservoirs, and environmental contamination.E. coliO157:H7 has a highly effective virulence operon, the Locus of Enterocyte Effacement (LEE), and its encoded intimate adherence mechanism is well characterized. However, factors involved in the preceding initial attachment are not well understood. In this study, we propose a mechanism of initial adherence used byE. coliO157:H7in vitro. We describe a bacterial protein not previously reported to be involved in adherence, Slp, and its interactions with the human host protein polymeric immunoglobulin receptor (pIgR). The human pIgR has previously been shown to act as an adherence receptor for some mucosal pathogens, and is highly expressed in the intestine. Following observation of significant colocalization betweenE. coliO157:H7 and pIgR location on Caco-2 cells, a co-immunoprecipitation (Co-IP) assay using a human recombinant Fc-tagged pIgR protein led to the identification of this protein. Disruption of Slp expression inE. coliO157:H7, through deletion of its encoding geneslp, produced a significant adherence deficiency to Caco-2 cells at early time points associated with initial adherence. Plasmid complementation ofslpfully restored the wild-type phenotype. Furthermore, immunofluorescence microscopy revealed evidence that this interaction is specific to the pathogenic strains ofE. colitested, and not the nonpathogenic strain E. coli K12. Additionally, deletion ofslpresulted in the absence of the corresponding protein band in further Co-IP assays, while the plasmid-encodedslpcomplementation of the deletion mutant strain restored the wild-type pattern. These data support the proposal that Slp directly contributes to initial adherence, with the pIgR protein as its proposed receptor.Author summaryEscherichia coliO157:H7 and other enterohemorrhagicE. coli(EHEC) are responsible for tens of thousands of cases of food-borne illness in the United States each year.E. coliO157:H7 has a particularly effective intimate adherence mechanism. However, the mechanisms of initial adherence, which facilitate attachment and virulence prior to the engagement of intimate adherence, are not well understood. In this study, we describe an initial adherence interaction between theE. coliO157:H7 Slp and the human polymeric immunoglobulin receptor (pIgR) expressed by the human colonic epithelial cell line Caco-2. The relationship was first demonstrated as a significant colocalization between the locations ofE. coliO157:H7 bacterial cells and pIgR protein using immunofluorescence microscopy. TheE. coliO157:H7 Slp protein was identified, and disruption of theslpgene resulted in a severe adherence deficiency to Caco-2 cells during initial adherence. This effect was reversed upon complementation of the Δslpstrain with a plasmid-encodedslpgene, and the constitutive over-expression ofslpresulted in hyper-adherence exceeding that of the wild-typeE. coliO157:H7. These data support the proposition that Slp directly contributes to initial adherence, with the pIgR protein as its proposed receptor.

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Loss of Resistance to Ingestion and Phagocytic Killing by O− and K− Mutants of a Uropathogenic Escherichia coli O75:K5 Strain

Infection and Immunity ◽

10.1128/iai.67.8.3757-3762.1999 ◽

1999 ◽

Vol 67 (8) ◽

pp. 3757-3762 ◽

Cited By ~ 35

Author(s):

Stacy M. Burns ◽

Sheila I. Hull

Keyword(s):

Escherichia Coli ◽

Polymorphonuclear Leukocytes ◽

Wild Type Strain ◽

Uropathogenic Escherichia Coli ◽

Wild Type ◽

O Antigen ◽

Loss Of Resistance ◽

Significant Difference ◽

The Difference ◽

Phagocytic Killing

ABSTRACT To determine the importance of the O75 O antigen and the K5 capsular antigen in resistance to phagocytosis and phagocytic killing, we used previously described O75− and K5−mutants from an O75+ K5+ wild-type uropathogenic Escherichia coli strain in phagocytosis assays with polymorphonuclear leukocytes (PMNs) and monocytes. At a 10-to-1 ratio of bacteria to phagocytes and in the presence of 10% serum, the parental strain GR-12 was resistant to both PMNs and monocytes over a 2-h incubation period. The O75− and K5− mutants were similar in sensitivity to killing by both PMNs and monocytes, decreasing in viability by 80% in the first hour. Yet, a significant difference in killing between the O75−and K5− mutants was observed in the first 15 min of incubation. The K5− mutant decreased in numbers by almost 60%, while the O75− mutant increased in numbers similarly to GR-12 in the first 15 min. The difference in killing was found not to be due to the rate of opsonization. To further determine the mechanism of resistance, a fluorescence assay was used to differentiate attached and internalized bacteria. The K5 capsule hindered the association of both the wild-type strain and the O75−mutant in the initial incubation time with PMNs. In conclusion, both the K5 capsule and O75 O antigen play crucial roles in resistance to phagocytosis over time.

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Glucose-6-phosphate dehydrogenase and ferredoxin-NADP(H) reductase contribute to damage repair during the soxRS response of Escherichia coli

Microbiology ◽

10.1099/mic.0.28612-0 ◽

2006 ◽

Vol 152 (4) ◽

pp. 1119-1128 ◽

Cited By ~ 51

Author(s):

Mariana Giró ◽

Néstor Carrillo ◽

Adriana R. Krapp

Keyword(s):

Escherichia Coli ◽

Survival Rates ◽

Multicopy Plasmid ◽

Wild Type ◽

Iron Sulfur Clusters ◽

Iron Sulfur ◽

Oxidative Challenge ◽

Glucose 6 Phosphate Dehydrogenase

The NADP(H)-dependent enzymes glucose-6-phosphate dehydrogenase (G6PDH) and ferredoxin(flavodoxin)-NADP(H) reductase (FPR), encoded by the zwf and fpr genes, respectively, are committed members of the soxRS regulatory system involved in superoxide resistance in Escherichia coli. Exposure of E. coli cells to the superoxide propagator methyl viologen (MV) led to rapid accumulation of G6PDH, while FPR was induced after a lag period of several minutes. Bacteria expressing G6PDH from a multicopy plasmid accumulated higher NADPH levels and displayed a protracted soxRS response, whereas FPR build-up had the opposite effects. Inactivation of either of the two genes resulted in enhanced sensitivity to MV killing, while further increases in the cellular content of FPR led to higher survival rates under oxidative conditions. In contrast, G6PDH accumulation over wild-type levels of expression failed to increase MV tolerance. G6PDH and FPR could act concertedly to deliver reducing equivalents from carbohydrates, via NADP+, to the FPR acceptors ferredoxin and/or flavodoxin. To evaluate whether this electron-transport system could mediate reductive repair reactions, the pathway was reconstituted in vitro from purified components; the reconstituted system was found to be functional in reactivation of oxidatively damaged iron–sulfur clusters of hydro-lyases such as aconitase and 6-phosphogluconate dehydratase. Recovery of these activities after oxidative challenge was faster and more extensive in transformed bacteria overexpressing FPR than in wild-type cells, indicating that the reductase could sustain hydro-lyase repair in vivo. However, FPR-deficient mutants were still able to fix iron–sulfur clusters at significant rates, suggesting that back-up routes for ferredoxin and/or flavodoxin reduction might be called into action to rescue inactivated enzymes when FPR is absent.

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Role ofrpoSin Escherichia coli O157:H7 Strain H32 Biofilm Development and Survival

Applied and Environmental Microbiology ◽

10.1128/aem.02149-12 ◽

2012 ◽

Vol 78 (23) ◽

pp. 8331-8339 ◽

Cited By ~ 16

Author(s):

Jessica R. Sheldon ◽

Mi-Sung Yim ◽

Jessica H. Saliba ◽

Wai-Hong Chung ◽

Kwok-Yin Wong ◽

...

Keyword(s):

Escherichia Coli ◽

Lake Water ◽

Biofilm Formation ◽

Survival Rates ◽

Confocal Scanning Laser Microscopy ◽

Wild Type ◽

Minimal Growth ◽

Content Type ◽

Biofilm Development

ABSTRACTThe protein RpoS is responsible for mediating cell survival during the stationary phase by conferring cell resistance to various stressors and has been linked to biofilm formation. In this study, the role of therpoSgene inEscherichia coliO157:H7 biofilm formation and survival in water was investigated. Confocal scanning laser microscopy of biofilms established on coverslips revealed a nutrient-dependent role ofrpoSin biofilm formation, where the biofilm biomass volume of therpoSmutant was 2.4- to 7.5-fold the size of itsrpoS+wild-type counterpart in minimal growth medium. The enhanced biofilm formation of therpoSmutant did not, however, translate to increased survival in sterile double-distilled water (ddH2O), filter-sterilized lake water, or unfiltered lake water. TherpoSmutant had an overall reduction of 3.10 and 5.30 log10in sterile ddH2O and filter-sterilized lake water, respectively, while only minor reductions of 0.53 and 0.61 log10in viable counts were observed for the wild-type form in the two media over a 13-day period, respectively. However, the survival rates of the detached biofilm-derivedrpoS+andrpoSmutant cells were comparable. Under the competitive stress conditions of unfiltered lake water, the advantage conferred by the presence ofrpoSwas lost, and both the wild-type and knockout forms displayed similar declines in viable counts. These results suggest thatrpoSdoes have an influence on both biofilm formation and survival ofE. coliO157:H7 and that the advantage conferred byrpoSis contingent on the environmental conditions.

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Contribution of Copper Ion Resistance to Survival of Escherichia coli on Metallic Copper Surfaces

Applied and Environmental Microbiology ◽

10.1128/aem.01938-07 ◽

2007 ◽

Vol 74 (4) ◽

pp. 977-986 ◽

Cited By ~ 168

Author(s):

Christophe Espírito Santo ◽

Nadine Taudte ◽

Dietrich H. Nies ◽

Gregor Grass

Keyword(s):

Escherichia Coli ◽

Metallic Copper ◽

Survival Rates ◽

Copper Ion ◽

Copper Surface ◽

Bacterial Inactivation ◽

Wild Type ◽

Copper Surfaces ◽

Detoxification Systems ◽

Copper Chelators

ABSTRACT Bacterial contamination of touch surfaces poses a serious threat for public health. The use of bactericidal surface materials, such as copper and its alloys, might constitute a way to aid the use of antibiotics and disinfectants, thus minimizing the risk of emergence and spread of multiresistant germs. The survival of Escherichia coli on metallic copper surfaces has been studied previously; however, the mechanisms underlying bacterial inactivation on copper surfaces have not been elucidated. Data presented in this study suggest that bacteria are killed rapidly on dry copper surfaces. Several factors, such as copper ion toxicity, copper chelators, cold, osmotic stress, and reactive oxygen species, but not anaerobiosis, influenced killing rates. Strains deleted in copper detoxification systems were slightly more sensitive than was the wild type. Preadaptation to copper enhanced survival rates upon copper surface exposure. This study constitutes a first step toward understanding the reasons for metallic copper surface-mediated killing of bacteria.

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Superselective Radioembolization of Hepatocellular Carcinoma: 5-Year Results of a Prospective Study

Nuklearmedizin ◽

10.1055/s-0038-1629756 ◽

1994 ◽

Vol 33 (05) ◽

pp. 206-214 ◽

Cited By ~ 1

Author(s):

J. Triller ◽

H. U. Baer ◽

Livia Geiger ◽

H. F. Beer ◽

C. Becker ◽

...

Keyword(s):

Hepatocellular Carcinoma ◽

Survival Rates ◽

Absorbed Dose ◽

Pulmonary Complications ◽

Pulmonary Shunt ◽

Recurrent Tumour ◽

Activity Distribution ◽

A Prospective Study ◽

Overall Survival Rates

SummaryTwenty patients with unresectable hepatocellular carcinoma (HCC) were followed up to 5 years after transarterial radiotherapy with 90Y-resin particles. Diagnostic radioembolizations of 99mTc-macroaggregates facilitated scintigraphic assessment of activity distribution, dose evaluation and final procedural verification. The overall survival rates were 56, 38 and 14% (after 1, 2 and 3 years, resp.). Patients with unifocal HCC and a single feeding artery (n = 7) even presented 83, 67 and 40% (2 alive after 2.75 and 4 years). With multiple arteries (n = 7), the longest survival was 26 months. Patients with multifocal HCC survived up to 33 months after selective radioembolization. Quality of life was improved in all. Survival was positively correlated with absorbed dose but residual/recurrent tumour occurred even after ≥300 Gy. Post-treatment symptoms were minimal (35 applications), pulmonary shunt rates were correctly predicted and pulmonary complications avoided.

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