scholarly journals Lac+plasmids are responsible for the strong lactose-positive phenotype found in many strains ofKlebsiellaspecies

1973 ◽  
Vol 22 (3) ◽  
pp. 329-333 ◽  
Author(s):  
E. C. R. Reeve ◽  
J. A. Braithwaite
Keyword(s):  
Escherichia Coli ◽  
Bacterial Strain ◽  
Common Ancestor ◽  
Galactosidase Activity ◽  
Macconkey Agar ◽  
New Host ◽  
E Coli ◽  
Compatibility Group ◽  
Diverse Origin ◽  
Low Efficiency

SUMMARYA variety ofKlebsiellastrains examined all show either a strong (ML+) or a weak (ML−/+) lactose-positive phenotype on MacConkey agar. ML+Klebsiellae have about 10 times the β-galactosidase activity of ML−/+strains in cultures both induced and not induced for this enzyme. Of 14 ML+strains of diverse origin tested, at least 13 carry alacoperon on a plasmid which can be transferred toEscherichia coli. The seven plasmids so far studied in detail all belong to the F compatibility group but are unable to promote their own transfer. To explain these results it is suggested that theKlebsiellagroup derive from a common ancestor with a chromosomallacoperon of low efficiency, which was made good by the acquisition of alacoperon from another bacterial strain, probablyE. coli: the newlacgenes remained as a plasmid, possibly because they could not be integrated in the new host.

Comparison of a New Enrichment Procedure for Shiga Toxin–Producing Escherichia coli with Five Standard Methods

2005 ◽  
Vol 68 (8) ◽  
pp. 1593-1599 ◽  
Author(s):  
MICHAEL A. GRANT
Keyword(s):  
Escherichia Coli ◽  
Real Time ◽  
Shiga Toxin ◽  
Real Time Pcr ◽  
Target Cells ◽  
Macconkey Agar ◽  
Standard Methods ◽  
E Coli ◽  
Canadian Health ◽  
Health Products

A new procedure for enrichment of Escherichia coli O157:H7 and other Shiga toxin–producing E. coli was compared to five standard methods: the British Public Health Laboratory Service, International Standard Method, U.S. Department of Agriculture, Canadian Health Products and Food Branch, and U.S. Food and Drug Administration. The new procedure was comparable to the standard methods in its ability to detect target cells inoculated into foods at approximately 1 CFU g−1. Comparisons were also made of the ability of the six enrichment procedures to detect E. coli O157:H7 against a large background of competitor microorganisms. In these experiments the new procedure yielded more target cells than the other five enrichments by two to three orders of magnitude as determined by enumeration on sorbitol MacConkey agar with tellurite and cefixime and Rainbow agar with tellurite and novobiocin and by verification of presumptive colonies by real-time PCR. For example, the population of enterohemorrhagic E. coli strain 6341 recovered on sorbitol MacConkey agar with tellurite and cefixime after enrichment with the experimental method was 2.42 × 108 CFU ml−1 and 1.80 × 106 CFU ml−1 after enrichment with the Canadian Health Products and Food Branch method, the second most effective in this experiment. In addition, broth cultures resulting from each of the six enrichment procedures were used to prepare templates for real-time PCR detection of stx1/stx2. Resulting threshold cycle (Ct) values after the experimental enrichment were similar to positive control values, whereas the five standard methods produced delayed Ct values or were not detected.

High sensitivity detection of Escherichia coli based on the measurement of β-galactosidase activity by microchip capillary electrophoresis combined with field-amplified sample injection

2019 ◽  
Vol 11 (11) ◽  
pp. 1558-1565 ◽  
Author(s):  
Yan Zhang ◽  
Yating Zhang ◽  
Luqi Zhu ◽  
Pingang He ◽  
Qingjiang Wang
Keyword(s):  
Escherichia Coli ◽  
Capillary Electrophoresis ◽  
High Sensitivity ◽  
Laser Induced Fluorescence ◽  
Galactosidase Activity ◽  
Microchip Capillary Electrophoresis ◽  
Sample Injection ◽  
E Coli ◽  
High Sensitivity Detection ◽  
Sensitivity Detection

A sensitive strategy developed for the detection of Escherichia coli (E. coli) by microchip capillary electrophoresis (MCE) combined with laser-induced fluorescence (LIF) is described in this paper.

scholarly journals Enzyme Characteristics of β-d-Galactosidase- and β-d-Glucuronidase-Positive Bacteria and Their Interference in Rapid Methods for Detection of Waterborne Coliforms andEscherichia coli

1998 ◽  
Vol 64 (3) ◽  
pp. 1018-1023 ◽  
Author(s):  
I. Tryland ◽  
L. Fiksdal
Keyword(s):  
Escherichia Coli ◽  
Enzyme Activity ◽  
Enzymatic Activity ◽  
Environmental Water ◽  
Coliform Bacteria ◽  
Galactosidase Activity ◽  
Fluorogenic Substrates ◽  
Rapid Methods ◽  
E Coli ◽  
Aerococcus Viridans

ABSTRACT Bacteria which were β-d-galactosidase and β-d-glucuronidase positive or expressed only one of these enzymes were isolated from environmental water samples. The enzymatic activity of these bacteria was measured in 25-min assays by using the fluorogenic substrates 4-methylumbelliferyl-β-d-galactoside and 4-methylumbelliferyl-β-d-glucuronide. The enzyme activity, enzyme induction, and enzyme temperature characteristics of target and nontarget bacteria in assays aimed at detecting coliform bacteria and Escherichia coli were investigated. The potential interference of false-positive bacteria was evaluated. Several of the β-d-galactosidase-positive nontarget bacteria but none of the β-d-glucuronidase-positive nontarget bacteria contained unstable enzyme at 44.5°C. The activity of target bacteria was highly inducible. Nontarget bacteria were induced much less or were not induced by the inducers used. The results revealed large variations in the enzyme levels of different β-d-galactosidase- and β-d-glucuronidase-positive bacteria. The induced and noninduced β-d-glucuronidase activities ofBacillus spp. and Aerococcus viridans were approximately the same as the activities of induced E. coli. Except for some isolates identified asAeromonas spp., all of the induced and noninduced β-d-galactosidase-positive, noncoliform isolates exhibited at least 2 log units less mean β-d-galactosidase activity than induced E. coli. The noncoliform bacteria must be present in correspondingly higher concentrations than those of target bacteria to interfere in the rapid assay for detection of coliform bacteria.

scholarly journals Purification and characterization of the class-II D-fructose 1,6-bisphosphate aldolase from Escherichia coli (Crookes' strain)

1978 ◽  
Vol 169 (3) ◽  
pp. 633-641 ◽  
Author(s):  
S A Baldwin ◽  
R N Perham ◽  
D Stribling
Keyword(s):  
Escherichia Coli ◽  
Common Ancestor ◽  
Class Ii ◽  
Purification And Characterization ◽  
Thiol Compounds ◽  
E Coli ◽  
Optimum Ph ◽  
Class Ii Aldolase ◽  
Fructose 1,6 Bisphosphate

A new form of the class-II D-fructose 1,6-bisphosphate aldolase (EC 4.1.2.13) of Escherichia coli (Crookes' strain) was isolated from an extract of glycerol-grown bacteria. It has a higher molecular weight (approx. 80000)than previous preparations of the enzyme and closely resembles the typical class-II aldolase from yeast in size and amino acid composition. On the other hand, its kinetic behaviour is not typical of a class-II aldolase. The enzyme has no requirement for thiol compounds either for stability or activity, added K+ ions have no effect, and the optimum pH for the cleavage activity is unusually high. The class-II enzymes from the prokaryote E. coli and the eukaryote yeast show no immunological identity. However, the similarity of their structures suggests that they have evolved from a common ancestor.

scholarly journals Detection of auto-transporter Sat and Vat genes among Escherichia coli strains isolated from urinary tract infections

2019 ◽  
Vol 23 (10) ◽  
pp. 40 ◽  
Author(s):  
Wisal R. Yaseen AL- Hayali1 ◽  
Alaa Younis Mahdy2 ◽  
Muhammad Abdul Zaraq Ibrahim3
Keyword(s):  
Escherichia Coli ◽  
Urinary Tract ◽  
Urinary Tract Infections ◽  
Duplex Pcr ◽  
Macconkey Agar ◽  
Biochemical Tests ◽  
E Coli ◽  
Genes Encoding ◽  
Tract Infections ◽  
Pcr Techniques

This study was designed to detect the presence of genes encoding autotranspoter proteins in E. coli that causes UTI by using PCR techniques. Seventy two urine sample were collected from patients infected with UTI whom attended to Salah-AL-deen general hospital in Tikrit city, during three months period (September to November 2016). All samples were cultivated on Blood agar and MacConkey agar. The 47(65.2%) E. coli isolates were confirmed using standard biochemical tests for E. coli. The results indicate the frequencies of Sat gene was 27 strains(57.5%) while Vat gene was 12 strains (25.5%) while the Duplex PCR detected 8(17%) strains of E. coli contained two genes. With this method, we confirmed that autotransporter genes are pathospecifically distributed among the E. coli strains studied.   http://dx.doi.org/10.25130/tjps.23.2018.167

scholarly journals Kinetics and mechanism of the bactericidal action of human neutrophils against Escherichia coli

Blood ◽  
1984 ◽  
Vol 64 (3) ◽  
pp. 635-641
Author(s):  
MN Hamers ◽  
AA Bot ◽  
RS Weening ◽  
HJ Sips ◽  
D Roos
Keyword(s):  
Escherichia Coli ◽  
Computer Program ◽  
Rate Constants ◽  
Bacterial Cell ◽  
Cell Envelope ◽  
Human Neutrophils ◽  
Galactosidase Activity ◽  
E Coli ◽  
Bacterial Proteins ◽  
Beta Galactosidase

A mutant strain of Escherichia coli (E. coli ML-35) was used to follow the kinetics of phagocytosis, perforation of the bacterial cell envelope, and inactivation of bacterial proteins by human neutrophils. This particular E. coli mutant strain has no lactose permease, but constitutively forms the cytoplasmic enzyme beta-galactosidase. This implies that the artificial substrate ortho-nitrophenyl-beta-D- galactopyranoside cannot reach the beta-galactosidase unless the bacterial cell envelope has been perforated. Thus, the integrity of the E. coli envelope can be measured simply by the activity of beta- galactosidase with this substrate. Indeed, ingestion of E. coli ML-35 by human neutrophils was followed by perforation of the bacteria (increase in beta-galactosidase activity). Subsequently, the beta- galactosidase activity decreased due to inactivation of the enzyme. With a simple mathematical model and a curve-fitting computer program, we have determined the first-order rate constants for phagocytosis, perforation, and beta-galactosidase inactivation. With 32 normal donors, we found an interdonor variation in these rate constants of 20% to 30% (SD) and an assay variance of 5%. The perforation process closely correlated with the loss of colony-forming capacity of the bacteria. This new assay measures phagocytosis and killing in a fast, simple, and accurate way; it is not hindered by extracellular bacteria. Moreover, this method also measures the postkilling event of inactivation of a bacterial protein, which permits a better detection of neutrophils deficient in this function. The assay can also be used for screening neutrophil functions without the use of a computer program. A simple calculation suffices to detect neutrophil abnormalities. Neutrophils from patients with chronic granulomatous disease (CGD) showed an impaired rate of perforation and thus also of inactivation. Neutrophils from myeloperoxidase-deficient patients or from a patient with the Chediak-Higashi syndrome only showed a retarded inactivation of beta-galactosidase, but normal ingestion and perforation. The role of myeloperoxidase in the killing process is discussed. Although myeloperoxidase does not seem to be a prerequisite for perforation, it probably plays a role in bacterial destruction by normal cells, because the inactivation of bacterial proteins seems strictly myeloperoxidase dependent.

scholarly journals Selective Isolation of eae-Positive Strains of Shiga Toxin-Producing Escherichia coli

2000 ◽  
Vol 38 (4) ◽  
pp. 1684-1687 ◽  
Author(s):  
Hiroshi Fukushima ◽  
Ken Hoshina ◽  
Manabu Gomyoda
Keyword(s):  
Escherichia Coli ◽  
Shiga Toxin ◽  
Acid Resistance ◽  
Selective Isolation ◽  
Macconkey Agar ◽  
Tellurite Resistance ◽  
E Coli

Culture on cefixime, tellurite, and sorbitol-MacConkey agar after HCl treatment facilitated the growth of 410 (94%) of 436eae-positive Shiga toxin-producing Escherichia coli (STEC) strains and 17 (16%) of 107 eae-negative STEC strains. This selectivity was closely related to acid resistance in E. coli and tellurite resistance ineae-positive STEC strains.

scholarly journals Coevolution of Bacteriophage PP01 and Escherichia coli O157:H7 in Continuous Culture

2003 ◽  
Vol 69 (1) ◽  
pp. 170-176 ◽  
Author(s):  
Katsunori Mizoguchi ◽  
Masatomo Morita ◽  
Curt R. Fischer ◽  
Masatoshi Yoichi ◽  
Yasunori Tanji ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Membrane Protein ◽  
Continuous Culture ◽  
Dilution Rate ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Escape Mutant ◽  
E Coli ◽  
Escape Mutants ◽  
Low Efficiency

ABSTRACT The interaction between Escherichia coli O157:H7 and its specific bacteriophage PP01 was investigated in chemostat continuous culture. Following the addition of bacteriophage PP01, E. coli O157:H7 cell lysis was observed by over 4 orders of magnitude at a dilution rate of 0.876 h−1 and by 3 orders of magnitude at a lower dilution rate (0.327 h−1). However, the appearance of a series of phage-resistant E. coli isolates, which showed a low efficiency of plating against bacteriophage PP01, led to an increase in the cell concentration in the culture. The colony shape, outer membrane protein expression, and lipopolysaccharide production of each escape mutant were compared. Cessation of major outer membrane protein OmpC production and alteration of lipopolysaccharide composition enabled E. coli O157:H7 to escape PP01 infection. One of the escape mutants of E. coli O157:H7 which formed a mucoid colony (Mu) on Luria-Bertani agar appeared 56 h postincubation at a dilution rate of 0.867 h−1 and persisted until the end of the experiment (∼200 h). Mu mutant cells could coexist with bacteriophage PP01 in batch culture. Concentrations of the Mu cells and bacteriophage PP01 increased together. The appearance of mutant phage, which showed a different host range among the O157:H7 escape mutants than wild-type PP01, was also detected in the chemostat culture. Thus, coevolution of phage and E. coli O157:H7 proceeded as a mutual arms race in chemostat continuous culture.

scholarly journals Identification and Molecular Characterization of Class 1 Integrons in Multiresistant Escherichia coli Isolates from Poultry Litter

2012 ◽  
Vol 78 (15) ◽  
pp. 5444-5447 ◽  
Author(s):  
Elizabeth Ponce-Rivas ◽  
María-Enriqueta Muñoz-Márquez ◽  
Ashraf A. Khan
Keyword(s):  
Escherichia Coli ◽  
Poultry Litter ◽  
Class 1 Integron ◽  
Content Type ◽  
Gene Cassettes ◽  
E Coli ◽  
Class 1 ◽  
Chicken Litter ◽  
Diverse Origin

ABSTRACTThis study describes the prevalence of arrays of class 1 integron cassettes and Qnr determinants (A, B, and S) in 19 fluoroquinolone-resistantEscherichia coliisolates from chicken litter.qnrSandqnrAwere the predominant genes in these fluoroquinolone-resistant isolates, and an uncommon array ofaacA4-catB3-dfrA1gene cassettes from a class1 integron was found. Additionally,aadA1anddfrA1gene cassettes, encoding resistance to streptomycin and trimethoprim, constituted the most common genes identified and was located on megaplasmids as well on the chromosome. Antibiotic resistance, pulsed-field gel electrophoresis (PFGE), and plasmid data suggest a genetically diverse origin of poultryE. coliisolates.

scholarly journals Macrophage Class A Scavenger Receptor-Mediated Phagocytosis of Escherichia coli: Role of Cell Heterogeneity, Microbial Strain, and Culture Conditions In Vitro

2000 ◽  
Vol 68 (4) ◽  
pp. 1953-1963 ◽  
Author(s):  
Leanne Peiser ◽  
Peter J. Gough ◽  
Tatsuhiko Kodama ◽  
Siamon Gordon
Keyword(s):  
Escherichia Coli ◽  
Host Defense ◽  
Bacterial Strain ◽  
Chinese Hamster Ovary Cells ◽  
Culture Conditions ◽  
E Coli ◽  
Class A

ABSTRACT Macrophage class A scavenger receptors (SR-AI and SR-AII) contribute to host defense by binding polyanionic ligands such as lipopolysaccharide and lipoteichoic acid. SR-A knockout (SR-A−/−) mice are more susceptible to endotoxic shock and Listeria monocytogenes infection in vivo, possibly due to decreased clearance of lipopolysaccharide and microorganisms, respectively. We have used flow cytometry to analyze the role of SR-A and other scavenger-like receptors in phagocytosis of bacteria in vitro. Chinese hamster ovary cells stably transfected with human SR-A bound Escherichia coli and Staphylococcus aureus but ingested few organisms. Primary human monocyte-derived macrophages (Mφ) bound and ingested E. coli more efficiently, and this was partially but selectively blocked by the general SR inhibitor, poly(I). A specific and selective role for SR-A was shown, since bone marrow culture-derived Mφ from SR-A−/− mice ingested fewer E. coli organisms than did wild-type cells, while uptake of antibody-opsonized E. coli was unaffected. SR-A-dependent uptake of E. colivaried with the bacterial strain; ingestion of DH5α and K1 by SR-A−/− Mφ was reduced by 30 to 60% and 70 to 75%, respectively. Phagocytosis and endocytosis via SR-A were markedly down-modulated when Mφ were plated on serum-coated tissue culture plastic compared to bacteriologic plastic, where cell adhesion is mediated by SR-A and CR3, respectively. This paper demonstrates that SR-A can bind and ingest bacteria directly, consistent with a role in host defense in vivo, and highlights the importance of the source of the Mφ, bacterial strain, and culture conditions on receptor function in vitro.

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