Caracterização fenotípica e genotípica de staphylococcus aureus isolados de queijo minas frescal industrial e artesanal
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2015-08-28
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Universidade Federal de Goiás
Resumo
Staphylococcus aureus is an important foodborne pathogen, able to produce
extracellular toxins and to express antimicrobial resistance. Among the foods involved
in staphylococcal food poisoning, stands out the cheese, especially when
manufactured under improper hygienic and sanitary conditions. The objectives of this
study were to characterize Staphylococcus aureus isolated from artisanal and
industrialized Minas frescal cheeses, to determine their antimicrobial susceptibility
profile as well as the genetic similarity among the isolates. The isolates were also
tested for staphylococcal enterotoxins (SE) genes and other virulence factors. Fifty-six
artisanal raw milk cheeses sold at street fairs and 10 industrialized cheeses
commercialized in supermarkets of Goiânia, Goiás were analyzed between June and
August 2014. S. aureus was confirmed in 19 samples (33.9%) of artisanal cheese by
detection of femA gene, in which 29 isolates were obtained. These isolates were
submitted to the antimicrobial susceptibility test and classified into nine different
profiles (A - I). Thirteen isolates (44.8%) were resistant to penicillin and three (10.3%)
to tetracycline, with two (7.4%) resistant to both. The Multiplex PCR technique was
performed to detect virulence genes that code for the production of hemolysins (Hla
and Hlb), toxic shock syndrome toxin (TSST-1), exfoliative toxins (ETa and ETb) and
enterotoxins (SEA - SEE, SEG - SEJ, SEM - SEO). Genes encoding TSST-1 and
exfoliative toxins were not detected. All the isolates amplified for the hla gene and 14
(48.3%) for the hbl gene. The seh gene was the most frequently detected (n=11,
37.9%) followed by seo gene (n = 3; 10.3%), seg, sem and sen genes (n = 2, 6.9%)
and sec and sei genes (n = 1, 3.4%). In one isolate (3.4%), four enterotoxins genes
were detected, and in another, six (3.4%). The comparison performed by Pulsed Field
Gel Electrophoresis technique revealed 18 different DNA banding patterns which were
grouped into five clusters. The genotyping found high genetic similarity among the
isolates. Identical isolates were obtained from different samples and one sample
showed more than one genetically different isolate. It was identified up to four different
isolates from the same sample. The high prevalence of S. aureus in a widely consumed
product like Minas fresh cheese, as well as the detection of toxin encoding genes
identified in this study, warns of the necessity to reduce the contamination levels in this
type of cheese through monitoring and controling the production and trade of the
product.
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FERREIRA, M. A. Caracterização fenotípica e genotípica de staphylococcus aureus isolados de queijo minas frescal industrial e artesanal. 2015. 108 f. Dissertação (Mestrado em Nutrição e Saúde) - Universidade Federal de Goiás,Goiânia, 2015.