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      Primer aislamiento de Escherichia coli no O157 productor de toxina Shiga en carnes bovina y porcina en Venezuela Translated title: First isolation of non-O157 shiga toxin producing Escherichia coli in bovine and porcine meats in Venezuela


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          Escherichia coli productor de toxina Shiga (STEC), es un patógeno transmitido por alimentos. El serotipo O157:H7 se considera clínicamente el más importante, pero un 50% de las infecciones por STEC corresponden a serotipos no O157. En Venezuela, la presencia de cepas STEC no O157 en productos cárnicos no ha sido reportada, lo que motivó este trabajo. Se analizaron 70 muestras de carne molida (35 bovinas y 35 porcinas). El aislamiento de E. coli se llevó a cabo en agar MacConkey sorbitol, suplementado con cefixima y la identificación bioquímica según pautas de la FDA. Se realizó la extracción del ADN y ensayos de PCR para la identificación de cepas STEC O157:H7 y STEC no O157. De 70 muestras analizadas, 50 (71,4%) resultaron positivas al aislamiento de E. coli, lográndose identificar 47 cepas sorbitol positivas y 3 cepas sorbitol negativas. La PCR demostró ausencia de STEC O157:H7 y presencia de STEC no O157 productor de toxina Shiga Stx1 y Stx2 en el 4,3% de las muestras analizadas. Se demuestra, por primera vez en el país, la circulación de cepas STEC no O157 en productos cárnicos, lo que permite sugerir el establecimiento de estrategias de prevención asociadas a este patógeno.

          Translated abstract

          Shiga toxin producing Escherichia coli (STEC) is a food-transmitted pathogen. Serotype O157:H7 is considered the most clinically important, but 50% of STEC infections correspond to non-O157 serotypes. In Venezuela, presence of non-O157 STEC strains in meat products has not been reported, which was the reason for this study. Seventy ground meat samples were analyzed (35 bovine and 35 porcine). E. coli isolation was done in MacConkey sorbitol agar, supplemented with cefixim, and the biochemical identification was done according to FDA guidelines. DNA extraction and PCR assays were used for the identification of STEC O157:H7 and not O157 strains. Of the 70 samples analyzed, 50 (71.4%) were positive for E. coli isolation, and 47 sorbitol positive and 3 sorbitol negative strains were identified. PCR showed absence of STEC O157:H7 and presence of non-O157 STEC Shiga toxin Stx1 and Stx2 producers in 4.3% of the samples analyzed. This is the first time that the circulation of non-O157 STEC strains in meat products is demonstrated in this country, which suggests that prevention strategies associated to this pathogen should be established.

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          Most cited references44

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          Non-O157 Shiga toxin-producing Escherichia coli infections in the United States, 1983-2002.

          Shiga toxin-producing Escherichia coli (STEC) O157:H7 is a well-recognized cause of bloody diarrhea and hemolytic-uremic syndrome (HUS). Non-O157 STEC contribute to this burden of illness but have been underrecognized as a result of diagnostic limitations and inadequate surveillance. Between 1983 and 2002, 43 state public health laboratories submitted 940 human non-O157 STEC isolates from persons with sporadic illnesses to the Centers for Diseases Control and Prevention reference laboratory for confirmation and serotyping. The most common serogroups were O26 (22%), O111 (16%), O103 (12%), O121 (8%), O45 (7%), and O145 (5%). Non-O157 STEC infections were most frequent during the summer and among young persons (median age, 12 years; interquartile range, 3-37 years). Virulence gene profiles were as follows: 61% stx(1) but not stx(2); 22% stx(2) but not stx(1); 17% both stx(1) and stx(2); 84% intimin (eae); and 86% enterohemolysin (E-hly). stx(2) was strongly associated with an increased risk of HUS, and eae was strongly associated with an increased risk of bloody diarrhea. STEC O111 accounted for most cases of HUS and was also the cause of 3 of 7 non-O157 STEC outbreaks reported in the United States. Non-O157 STEC can cause severe illness that is comparable to the illness caused by STEC O157. Strains that produce Shiga toxin 2 are much more likely to cause HUS than are those that produce Shiga toxin 1 alone. Improving surveillance will more fully elucidate the incidence and pathological spectrum of these emerging agents. These efforts require increased clinical suspicion, improved clinical laboratory isolation, and continued serotyping of isolates in public health laboratories.
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            Sorbitol-MacConkey medium for detection of Escherichia coli O157:H7 associated with hemorrhagic colitis.

            Escherichia coli serotype O157:H7 is a recently recognized human pathogen associated with hemorrhagic colitis. Unlike most E. coli strains, E. coli O157:H7 does not ferment sorbitol. Therefore, the efficacy of MacConkey agar containing sorbitol (SMAC medium) instead of lactose as a differential medium for the detection of E. coli O157:H7 in stool cultures was determined in comparison with MacConkey agar. The relative frequency of non-sorbitol-fermenting (NSF) organisms other than E. coli O157:H7 in feces was low at 10 to 20% (95% confidence limits), and NSF organisms also occurred mostly in small numbers. In a field trial involving over 1,000 diarrheal stools, E. coli O157:H7 was isolated from 18 stools, all of which were from patients with bloody diarrhea. In every instance, the growth of E. coli O157:H7 on SMAC medium was heavy and occurred in almost pure culture as colorless NSF colonies in contrast to fecal flora, which are mostly sorbitol fermenting and hence appear pink on this medium, whereas on MacConkey agar cultures, the growth of E. coli O157:H7 was indistinguishable from fecal flora. SMAC medium permitted ready recognition of E. coli O157:H7 in stool cultures. Detection of E. coli O157:H7 on SMAC medium had a sensitivity of 100%, a specificity of 85%, and an accuracy of 86%. SMAC medium stool culture is a simple, inexpensive, rapid, and reliable means of detecting E. coli O157:H7, and we recommend routine use of SMAC medium especially for culturing bloody stools.
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              Direct detection and characterization of Shiga toxigenic Escherichia coli by multiplex PCR for stx1, stx2, eae, ehxA, and saa.

              We recently described a novel megaplasmid-encoded adhesin produced by certain Shiga toxigenic Escherichia coli (STEC) strains that lack the locus for enterocyte effacement (LEE) pathogenicity island. This adhesin, designated Saa (STEC autoagglutinating adhesin), may be a marker for a subset of LEE-negative STEC strains capable of causing severe gastrointestinal and systemic diseases in humans. In this study, we developed a pentavalent PCR assay for the detection of saa as well as other proven and putative STEC virulence genes (stx1, stx2, eae, and ehxA). The five primer pairs used in the assay do not interfere with each other and generate amplification products of 119, 180, 255, 384, and 534 bp.

                Author and article information

                Revista de la Sociedad Venezolana de Microbiología
                Rev. Soc. Ven. Microbiol.
                Organo Oficial de la Sociedad Venezolana de Microbiología. (Caracas, DF, Venezuela )
                December 2012
                : 32
                : 2
                : 107-111
                [01] orgnameUniversidad de Oriente orgdiv1Núcleo de Sucre Venezuela
                S1315-25562012000200006 S1315-2556(12)03200206


                : 01 February 2012
                : 21 June 2012
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 27, Pages: 5

                SciELO Venezuela

                Artículos Originales

                STEC no O157,PCR,carne bovina,carne porcina,Venezuela,non-O157 STEC,bovine meat,porcine meat


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