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Analiza zymodemów pasożytniczych

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The aim of the study was the characterization of selected virulence markers of Shiga toxin-producing Escherichia coli originated from raw beef by the use of PCR. The identification of Stx variants (stx₂c, stx₂d, stx₂e and stx₂f) was done with the stx2 -positive E. coli strains, resulting in the detection of the stx2d gene in 13 STEC isolates out of which 3 strains also had the stx₂c gene. None of the isolates possessed the stx2f or stx2e genes. The intimin marker (γ variant) was observed in all E. coli O157:H7, whereas β variant in E. coli O26 isolates. The genotypic factors such as katP, toxB and efa1 were detected in all O157:H7 as well as in one O26 isolate. Fifteen STEC were iha-positive and five saa-positive. None of the saa-positive isolates belonged to the O157 or O26 groups. The simultaneous presence of the lpfAO₁₅₇/OI₋₁₄₁ and lpfAO₁₅₇/OI₋₁₅₄ genes was noted in 8 O157:H7 and in one O26 STEC. The lpfAO₁₅₇/OI₋₁₄₁ gene alone was present in 4 other STEC tested, including one E. coli O26. None of E. coli O157:H7 had the lpfAO113 marker that was observed in the all remaining STEC. In one isolate belonging to the E. coli O26 group, for the first time a simultaneous presence of the lpfAO₁₅₇/OI₋₁₄₁, lpfAO₁₅₇/OI₋₁₅₄ and lpfAO₁₁₃ was noted.
For the last 25 years, Shiga toxin-producing E. coli (STEC) has been a serious cause of human diseases, responsible for the progression of hemorrhagic colitis (HC), hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Cattle and other ruminants are the main reservoirs of these bacteria. The infections are mainly associated with strains belonging to serogroups O157, O26, O103, O111 and O113. The main source of the bacteria is contaminated food of animal origin (especially beef) but water and person-to-person transmission may play a significant role in human infections. Large outbreaks connected to STEC can affect many people causing serious morbidity and mortality, making this bacteria one of the most significant food-borne pathogens. In this paper several plasmid and chromosomal genes responsible for the expression of important virulence determinants of STEC have been described. Among them, Shiga toxin (Stx) encoded by the stx genes is the best characterized pathogenic marker. This review should improve the knowledge of STEC and the function of the virulence markers described, but further studies are needed to evaluate the role of STEC genes in e.g. apoptosis or quorum sensing processes.
Shiga toxin-producing E. coli (STEC) are a serious cause of human diseases. The infections are mainly associated with strains belonging to serogroups O157, O26, O103, O111 and O113, while the main source of infection is contaminated food of animal origin (especially beef). In this study the molecular identification methods for STEC were used which enabled detection of STEC in raw beef using multiplex PCR (mPCR) assays, isolation of individual bacterial colonies with digoxigenin (DIG)-labeled DNA probe and characterization of the virulence markers by the use of mPCR. The molecular method was used to examine 272 raw beef samples obtained from slaughterhouses. After the mPCR-1 analysis 16 stx-positive samples (5.88%) were detected. The STEC isolates were then tested using the mPCR and PCR assays. Eight of them belonged to O157:H7 serotype by the presence of the rfbO157 and fliCн₇ genes. The stx₁ marker was observed in all E. coli O157:H7 and in four of the non-O157:H7 isolates tested. Moreover, the stx₂ gene was detected in all E. coli O157:H7 and in seven of the non-O157:H7, three of them also possessed the stx₁ marker. Eight of the rfbO157-negative STEC were examined with the mPCR-3 assay to detect the rfbO111, rfbO113 and O26wzx markers, three of them produced the characteristic amplicon for the O26 group. These isolates also carried the stx₁ (one strain) or stx₂ genes (two isolates). Among the STEC tested, none belonged to the O111 or O113 groups. The amplification with the mPCR-4 assay showed that all isolates harbored the enterohemolysin (ehlyA) gene whereas the intimin marker (eaeA) was observed in all E. coli O157:H7 and O26 isolates.
Z tusz kurcząt izolowano termotolerancyjne szczepy Campylobacter, określano ich przynależność gatunkową, a następnie badano w nich obecność sekwencji DNA kojarzonej z inwazyjnymi właściwościami tych szczepów.
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