SUMMARY OF THESIS
Molecular characterization of toxins in Staphylococcus aureus isolated from milk and "coalho" cheese in cities from the Agreste region of Pernambuco
LUZ, Isabelle da Silva - Caracterização molecular das toxinas em Staphylococcus aureus isolados de leite e queijo de coalho em municípios da região agreste de Pernambuco. Recife, 2008. (Dissertação de Mestrado - Centro de Pesquisas Aggeu Magalhães, Fundação Oswaldo Cruz).
Milk and cheese have an important role in human nutrition and when consumed without proper hygienic/sanitary precautions, they can cause disease due to the presence of pathogenic microorganisms, particularly Staphylococcus aureus. The involvement of this bacterium in the epidemiology of food-borne diseases is due to its high prevalence and risk of producing thermostable enterotoxins that are responsible for food poisoning. S. aureus can produce other toxins of interest to human health such as toxic shock syndrome toxin-1, responsible for toxic shock syndrome in humans and the exfoliative toxins, causative agents of scalded skin syndrome. Some have applied molecular analyses of the coagulase gene to subdivide S. aureus based on the polymorphism of this gene. Bacterial resistance to antibiotics is a serious problem for the Public Health Department because resistant bacteria can be transmitted to humans through contaminated foods. The aims of this study were to isolate S. aureus obtained from milk and "coalho" cheese from the Agreste region of Pernambuco, characterize the antimicrobial sensitivity profile, research the presence of genes responsible for toxins, investigate the expression of the toxigenic genes in isolates of S. aureus and correlate molecular typing by the coagulase gene with the presence of toxigenic genes. The antimicrobial sensitivity profile demonstrated that the majority of the S. aureus isolates was sensitive to vancomycin, sulfa + trimethoprim and enrofloxacin, and some demonstrated a high level of resistance to other antibiotics tested. The analysis of the gene coa in 94 S. aureus isolates allowed their distribution into two coagulotypes, coa1 = ~750 bp and coa2 = ~1000 bp, suggesting the spread of clones restricted to the Agreste region of Pernambuco. Among the 88 S. aureus isolates positive by PCR, the following genotypes were found: seg, seh, sei, seg + seh, seg + sei, seg + sej, seh + sei, seg + seh + sei, seg + sei + sej and seg + seh + sei + sej. These results suggest the existence of a geographic variation in distribution of S. aureus carrying toxigenic genes. Of these, 20 isolates were selected for analysis by RT-PCR. The transcripts obtained in 12/20 were seg, seh, sei, seg + seh, seg + sej and seg + sei + sej, and coa1 and coa2. The S. aureus isolates positive by PCR and RT-PCR examined in this study expressed genes responsible for enterotoxins and showed potential to cause a clinical picture of food poisoning.
Isabelle da Silva LUZ
Publication Dates
-
Publication in this collection
16 June 2009 -
Date of issue
June 2009
