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1.
J Food Prot ; 61(10): 1265-8, 1998 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-9798139

RESUMO

Beef tissues were contaminated with wet and dry manure. The manure was previously inoculated with Escherichia coli O157:H7 GFP, genetically modified with a plasmid encoding a protein that fluoresces green when exposed to long-wave ultraviolet light. After incubation at 37 degrees C for 5 days, the wet manure was spread on the surface of beef tissues at an average E. coli O157:H7 GFP level of 6.62 log CFU/cm2. Dry manure was obtained by subjecting wet manure to natural drying (simulating dry manure adhering to the hides of cattle) and was also applied to the surfaces of beef tissues. The degree of removal of E. coli O157:H7 GFP by washing was compared to the removal of cells of the same strain that had been inoculated as a suspension. The E. coli O157:H7 mixed into feces of cattle adhered more strongly to meat surfaces than that applied as a suspension, complicating the removal by conventional washing procedures. The fate of the bacterium mixed into wet or dry manure was evaluated. An initial decrease of the inoculated population was observed; this was probably an effect of the changed environment represented by the manure. After adaptation, the inoculated bacteria grew in the wet manure; a maximum population was reached in 5 days at 37 degrees C; levels declined with drying. The use of the GFP marker was of great value, since it allowed enumeration of E. coli O157:H7 in the presence of the natural flora of manure.


Assuntos
Matadouros , Escherichia coli O157 , Microbiologia de Alimentos , Esterco/microbiologia , Carne/microbiologia , Ampicilina/farmacologia , Animais , Bovinos , Contagem de Colônia Microbiana , Resistência Microbiana a Medicamentos/genética , Escherichia coli O157/efeitos dos fármacos , Escherichia coli O157/genética , Escherichia coli O157/crescimento & desenvolvimento , Fezes/microbiologia , Manipulação de Alimentos , Proteínas de Fluorescência Verde , Proteínas Luminescentes/genética , Penicilinas/farmacologia
2.
J Food Prot ; 61(5): 547-50, 1998 May.
Artigo em Inglês | MEDLINE | ID: mdl-9709225

RESUMO

Beef lean, fat, and connective tissues were inoculated with Escherichia coli O157:H7 before and after a prewashing procedure to compare the efficacy of prewashing and no prewashing on bacterial adherence and, consequently, on the removal of bacteria from the inoculated surfaces. Prewashing consisted of spraying tissues with tap water before inoculation. Final washing with disinfectant solutions compared the efficacy of several chemicals for the removal or destruction of E. coli O157:H7. The results showed that prewashing was very effective in reducing the numbers of bacterial cells on beef tissues, mainly lean tissue, in the control samples which received final washing with water. An opposite effect of prewashing was observed when disinfectant solutions were used for final washing; this may be due to dilution by water carried on the tissues after prewashing. The efficacy of chemicals was dependent on the type of exposed tissue. Hydrogen peroxide (3%) was more efficient in the removal of E. coli O157:H7 from connective tissues, with reductions greater than 4 log CFU/cm2, compared to a normally washed control (P < 0.01). Chlorhexidine (0.1%) was very efficient on fat and lean tissues, causing reductions over 5 log CFU/cm2 on not prewashed fat and lean tissues, compared to the control (P < 0.01). Acetic acid (5%) was the least effective, decreasing the number of CFU by under 1 log/cm2 as compared to the control; and no statistically significant difference was found among tissues, even though the removal of bacteria seemed less in lean tissue compared to fat or connective tissues.


Assuntos
Clorexidina/farmacologia , Desinfetantes/farmacologia , Escherichia coli O157/efeitos dos fármacos , Microbiologia de Alimentos , Peróxido de Hidrogênio/farmacologia , Produtos da Carne/microbiologia , Tecido Adiposo/microbiologia , Animais , Bovinos , Contagem de Colônia Microbiana , Tecido Conjuntivo/microbiologia , Escherichia coli O157/isolamento & purificação , Manipulação de Alimentos , Reprodutibilidade dos Testes , Estados Unidos
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