Avaliação da sensibilidade de cepas de Escherichia coli isoladas de mexilhões (Perna perna linnaeus, 1758) à antimicrobianos

Foram avaliadas 44 cepas de Escherichia coli isoladas de amostras cárneas de mexilhões capturados no município de Niterói, Estado do Rio de Janeiro, quanto a sua sensibilidade a antimicrobianos. Vinte e quatro antimicrobianos foram testados e padrões variáveis de comportamento frente aos mesmos foram observados. Todas as cepas avaliadas apresentaram sensibilidade total a apenas 41,66% dos antimicrobianos (R, Ac, C, To, Fx, Cz, Ct, Nt, Cp, Ge) e resistência total a 4,16% dos antimicrobianos (Ca). A cepa número 18 apresentou sensibilidade a 95,83% dos antimicrobianos, enquanto que a cepa número 30 aduziu resistência a 41,66% dos antimicrobianos. Frente aos resultados obtidos é importante ponderarmos sobre o risco à Saúde Pública associado ao hábito de ingerir pescado cru ou insuficientemente cozido, especialmente bivalves filtradores contaminados por bactérias com comprovada resistência a diferentes antimicrobianos, alimentos potencialmente envolvidos em processos de reinfecção do homem, no qual desencadeiam quadros de gastroenterite.

Analysis of virulence genes in Escherichia coli isolated from grated cheese

This research aimed to verify the presence of virulence genes in strains of Escherichia coli isolated from grated cheese sold in farmers' markets of Cuiabá-MT, Brazil. Forty samples of this food were submitted for microbiological analysis and 22 (55%) tested positive for E. coli. Next, 64 strains of E. coli were isolated from the positive samples and screened by the polymerase chain reaction (PCR) for the presence of the genes encoding the following virulence factors: stx1 and stx2 (verotoxin types 1 and 2), eae (intimin), lt1 (heat-labile toxin type 1), st1 (heat-stable toxin type 1), cnf1 and cnf2 (cytotoxic necrozing factor types 1 and 2), and cdtB (cytolethal distending toxin). All the isolates were negative for the genes stx1, stx2, eae, lt1, st1, cnf1, and cdtB, and five strains (7.81%) were positive for cnf2. A low prevalence of E. coli positive for virulence factors associated with the pathogenesis of diarrhoea was observed in this study. However, the presence of CNF-2 producing strains and the possibility of occurrence and scattering of other virulence factors that were not surveyed in the work indicate the risk related to the consumption of grated cheese from farmers' markets.

Molecular screening of bovine raw milk for the presence of Shiga toxin-producing Escherichia coli (STEC) on dairy farms

Milkborne transmission of Shiga toxin- producing Escherichia coli (STEC) has raised considerable concern due to recent outbreaks worldwide and poses a threat to public health. The aim of this study was to develop a sensitive and specific multiplex PCR assay to detect the presence of STEC in bovine raw milk. To identify E. coli (ATCC 25922) contamination, the gene uspA was used, and PCR sensitivity and specificity were accessed by testing diluted samples ranging from 2 to 2.0 × 10(6) CFU/mL. To detect STEC, the stx1 and stx2 genes were selected as targets. After reaction standardization, the multiplex assay was tested in raw milk collected from 101 cows on dairy farms. PCR assay for E. coli detection had a specificity of 100% and sensitivity of 79% (P<0.0001), with a lower detection limit of 2 CFU/mL. Multiplex PCR assay had 100% sensitivity for E. coli positive raw milk samples, and 31.1% were contaminated with STEC, 28.3% of stx2, and 1.9% of stx1. The multiplex PCR assay described in the present study can be employed to identify and screen E. coli harboring stx1 and stx2 genes in raw milk on dairy farms and in industries.

Survival of Shiga toxin-producing Escherichia coli O157:H7 in Minas frescal cheese

Shiga toxin-producing Escherichia coli (STEC) O157:H7 strains (isolated by cattle’s faeces and a reference strain, EDL933), were inoculated into pasteurized milk (102 and 103 cells.mL–1) to prepare the Minas frescal cheese. As control was used uninfected milk. Physicochemical and microbiological analyses were performed to milk and elaborated cheese. The O157:H7 strains were quantified in the stages of cheese processing and during 0, 2, 4, 5, 7, 10 and 15 storage days at 8 °C onto Sorbitol MacConkey Agar supplemented with potassium tellurite and cefixime (CT-SMAC). O157:H7 was not present in the pasteurised milk prior to the artificial inoculation. At the end of the processing the cheese had 10 to 100 times more STEC O157:H7 than the initial inoculum. During the storage, the Minas frescal cheese exhibited the largest population increase on the 4th and 5th day when inoculated with 102 and 103 cells.mL–1, respectively. Additionally, viable cells were found up to the 10th and 15th day, according to the amount of initial inoculum. This number of cells is able to cause infection in humans, and therefore, Minas frescal cheese, even when stored under refrigeration, is a potential vehicle of disease caused by STEC O157:H7.

Aspects of the hemes and modulation of hydrogen donors in catalases from bovine liver, yeast, and escherichia coli

Catalase is the enzyme which decomposes hydrogen peroxide to water and oxygen. Escherichia coli contains two catalases. Hydroperoxidase I (HPI) is a bifunctional catalase-peroxidase. Hydroperoxidase II (HPII) is only catalytically active toward H202. Expression of the genes encoding these proteins is controlled by different regimes. HPJI is thought to be a hexamer, having one heme d cis group per enzymatic subunit. HPII wild type protein and heme containing mutant proteins were obtained from the laboratory of P. Loewen (Univ. of Manitoba). Mutants constructed by oligonucleotidedirected mutagenesis were targeted for replacement of either the His128 residue or the Asn201 residue in the vicinity of the HPII heme crevice. His128 is the residue thought to be analogous to the His74 distal axial ligand of the heme in the bovine liver enzyme, and Asn201 is believed to be a residue critical to the function of the enzyme because of its role in orienting and interacting with the substrate molecule. Investigation of the nature of the hemes via absorption spectroscopy of the unmodified catalase proteins and their derived pyridine hemochromes showed that while the bovine and Saccharomyces cerevisiae catalase enzymes are protoheme-containing, the HPII wild type protein contains heme d, and the mutant proteins contain either solely protoheme, or heme d-protoheme mixtures. Cyanide binding studies supported this, as ligand binding was monophasic for the bovine, Saccharomyces cerevisiae, and wild type HPII enzymes, but biphasic for several of the HPII mutant proteins. Several mammalian catalases, and at least two prokaryotic catalases, are known to be NADPH binding. The function of this cofactor appears to be the prevention of inactivation of the enzyme, which occurs via formation of the inactive secondary catalase peroxide compound (compound II). No physiologically plausible scheme has yet been proposed for the NADPH mediation of catalase activity. This study has shown, via fluorescence and affinity chromatography techniques, that NADPH binds to the T (Typical) and A (Atypical) catalases of Saccharomyces cerevisiae, and that wild type HPII apparently does not bind NADPH. This study has also shown that NADPH is unlike any other hydrogen donor to catalase, and addresses its features as a unique donor by proposing a mechanism whereby NADPH is oxidized and catalase is protected from inactivation via the formation of protein radical species. Migration of this radical to a position close to the NADPH is also proposed as an adjunct hypothesis, based on similar electron migrations that are known to occur within metmyoglobin and cytochrome c peroxidase when reacted with H202. Validation of these hypotheses may be obtained in appropriate future experiments.

Clonación molecular de los DNAs complementarios que codifican para las hormonas de crecimiento de origen hipofisiario humano en Escherichia coli

Tesis (Maestría en Ciencias con Especialidad en Microbiología Médica) UANL

Biosíntesis de la hormona del crecimiento humano recombinante (HGHr) en Pichia pastoris y Escherichia coli

Tesis (Maestría en Ciencias con Especialidad en Biología Molecular e Ingeniería Genética) UANL

Expresión en Escherichia coli del DNA complementario de la hormona del crecimiento bovino

Tesis (Maestría en Ciencias con Especialidad en Biología Molecular e Ingeniería Genética) U.A.N.L.

Implementación de una técnica directa para la detección de la enterotoxina termolabil de Escherichia coli a partir de sus colonias en coprocultivo

Tesis (Maestría en Ciencias con Especialidad en Microbiología Médica) U.A.N.L.

Estudio sobre el efecto de diferentes concentraciones de alcoholes primarios sobre la viabilidad de Staphylococcus aureus y escherichia coli y la integridad de sus respectivos esferoplastos

Tesis de María Alicia Suárez Semour (Maestro en Ciencias con especialidad en Microbiología Médica) U.A.N.L.

Expresión de la proteína Omp31 recombinante de brucella ovis en el sistema de escherichia coli para su uso como antígeno en el diagnóstico de epididimitis contagiosa del carnero.

Tesis (Maestría en Ciencias con Acentuación en Inmunobiología) UANL, 2012.

Expresión y purificación de proteínas recombinantes y biofármacos en Escherichia coli utilizando la proteína SMBP como proteína de fusión.

Tesis (Maestría en Ciencias con orientación en Farmacia) UANL, 2014.

Activación del macrófago por Escherichia coli y Staphylococcus aureus bajo la influencia del zinc

Tesis (Doctorado en Ciencias con Especialidad en Inmunología) UANL

Adherencia e invasión de Escherichia coli septicémica aviar a células epiteliales

Tesis (Doctor en Ciencias con especialidad en Microbiología) U.A.N.L. Facultad de Ciencias Biológicas, 2007.

Gastric stability and oral bioavailability of colistin sulfate in pigs challenged or not with Escherichia coli O149: F4 (K88)

The aim of the present study was to investigate the in vitro gastric stability of colistin sulfate (CS) and its antimicrobial activity against Escherichia coli and to study the impact of ETEC O149: F4 (K88) infection in pigs on CS intestinal absorption. The stability profile of CS was evaluated in a simulated gastric fluid (SGF). Antimicrobial activity of CS and its degradation products were examined in a 96-well polystyrene microplate model. The effect of experimental infection with ETEC O149: F4 on CS intestinal absorption was determined by quantification of CS systemic concentration using a validated LC–MS/MS method. A rapid degradation of CS accompanied by an increase in CS antimicrobial activity by comparison with non-degraded CS (P < 0.0001) was observed in SGF. Additionally, CS levels were not quantifiable in systemic circulation using a highly sensitive method and concurrent oral challenge did not affect CS absorption in an induction model of subclinical post-weaning diarrhea (PWD).