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| Author(s): |
Priscila Pedullo Alvares
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2011-04-14 |
| Examining board members: |
Mariza Landgraf;
Maria Teresa Destro;
Roxane Maria Fontes Piazza
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| Advisor: | Mariza Landgraf |
| Abstract | |
Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens that can cause since mild or severe and bloody diarrhea to serious complications, such as hemorrhagic colitis, hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. These microorganisms have been associated with numerous outbreaks and several sporadic cases worldwide due to consumption of contaminated food, especially meat. E. coli O157 is considered the main serogroup involved in disease outbreaks of STEC, however, many cases have been occurred worldwide due to non-O157, such as O26, O103, O111 and O145 strains. The aims of the present study were to determine the occurrence of STEC at three points of cattle slaughter for exporting and in refrigerated beef and poultry cuts commercialized in the Metropolitan area of Sao Paulo, Brazil; identify the genes that code for the virulence factors stx1, stx2, eaeA and ehxA; detect E. coli O157:H7 strains using uidA, rfbO157 and flicH7 genes; verify the citotoxicity in Vero cells and the enterohemolytic activity; evaluate the antimicrobial susceptibility profile; identify the STEC serotypes and evaluate the genetic diversity of STEC isolates. A total of 603 samples were collected from 201 animals at slaughter. The samples were taken from hide (201), carcass (201) and half-carcass (201) and were always collected from the breast region. At retail, 100 refrigerated beef cuts and 100 chicken cuts were analyzed. The detection of E. coli O157 samples were conducted according to the ISO methodology (16654) and for detection of O26, O103, O111 e O145 serogroups the Surveillance Group for Diseases and Infections of Animals methodology (NRM 006) was used. The isolates were confirmed as STEC by PCR technique. Among 201 animals sampled, two (1,0%) were positive for STEC, obtaining seven isolates from hide (three from animal number 399 and four from animal number 401). The microrganism was not detect in carcass and half carcass samples. The seven isolates carried stx2, uidA, eaeA, ehxA, rfbO157 and fliCH7 genes, so, they can be considered as enterohaemorrhagic E. coli (EHEC) O157:H7 serotype. None of the isolates produced the enterohemolytic activity and three (42,8%) isolates showed resistence to nalidixic acid and one (14,3%) to chloramphenicol. PFGE revealed that the seven STEC strains showed two distinct genetic profiles, with 75.3% of similarity between them. STEC was not detected from beef and poultry cuts commercialized at retail. These results suggest that, although present in animals hides, the STEC isolation at later stages of food chain was rare, probably due to effective sanitary measures to control contamination and transmission of this pathogen along the beef production chain until commercialization. (AU) | |