Ocorrência e avaliação do potencial enterotoxigênico de Staphylococcus isolados de derivados lácteos / Ocurrence and assessment of enterotoxigenic potencia of Staphylococcus isolated from dairy products

AUTOR(ES)
DATA DE PUBLICAÇÃO

2011

RESUMO

Staphylococcus are microorganisms widespread in nature and humans and animals are their main sources. Cross-contamination after milk pasteurization, caused especially by improper handling, is considered the most recurrent source of dairy products contamination by these pathogens. Staphylococus deserves our close attention due their ability to produce a large amount of extracellular proteins (enterotoxins), that if preformed in food and ingested, cause staphylococcal food poisoning. Although the Brazilian legislation (RDC 12/2001, Anvisa) only recommends coagulase-positive staphylococci count monitoring (relating coagulase production to the risk of enterotoxins production), previous researches showed that coagulase-negative species are also capable of producing enterotoxins in foods. Thus, this research aimed: i) to quantify and analyze the presence of coagulase-positive and coagulase-negative staphylococci from 104 dairy products samples, being: 24 homemade ice cream, 20 pasteurized dairy cream, 20 cheese pate, 20 Minas fresh cheese, and 20 Minas half cured cheese; ii) to identify phenotypically the species; iii) to evaluate the production of classic enterotoxins (SEA, SEB, Sec1, 2.3, SED and SEE) in vitro by using VIDAS system and correlate the results to the presence of possible coding genes of these enterotoxins, applying the PCR technique. The average staphylococcal preliminary count values in different food groups analyzed were: 5 x 103 CFU/g in ice cream, 2,9 x 105 CFU/g in dairy cream, 6,2 x 103 CFU/g in pate, 6,6 x 105 CFU/g in Minas fresh cheese and 6,4 x 105 CFU/g in Minas half cured cheese. From isolated strains, 83,6% (148/177) were classified as genus Staphylococcus and 16,4% (29/177) as Micrococcus. Staphylococcus were isolated from 43,3% (45/104) of samples, being found in 25 cheese samples, in 16 ice creams, in 3 pates and in just one dairy cream sample. Among staphylococcal strains, 74,3% (110/148) were coagulase-negative Staphylococcus and 25,7% (38/148) were coagulase-positive Staphylococcus, being these recovered only from cheeses samples. On 111 selected isolates (27 coagulase-positive and 84 coagulase-negative), were identified 13 staphylococcal species by using API-Staph system (bioMérieux-SA): S. aureus, S. auricularis, S. caprae, S. chromogenes, S. cohnii ssp cohnii, S. epidermidis, S. hominis, S. hyicus, S. lentus, S. saprophyticus, S. sciuri, S. warneri, S. xylosus. For classical staphylococcal enterotoxins detection was used VIDAS SET Staph- Enterotoxin immunoassay kit (bioMérieux-SA). From 111 isolates, just one (0,9%) produced enterotoxin, which was identified as S. aureus, coagulasepositive, isolated from Minas half cured cheese, whose count was 1,9 x 106 CFU/g. Contrary to expectations, no coding genes were present in isolates analyzed. Discrepancies between phenotypic and genotypic results of enterotoxin detection tests are common, requiring the application of other immunological and molecular tests for the confirmation of the results. Possible explanations would be that there are genes sequences variations or another enterotoxin that has immunological cross-reaction with classic enterotoxins. For this research, although the higher number of the isolates did not produce classical enterotoxins, the analyzed samples showed high staphylococcal concentration, that do not exclude a newly described enterotoxins risk production. It also demonstrates the lack of hygiene, health care and good practices during the production and commercialization of dairy products

ASSUNTO(S)

staphylococcus derivados do leite enterotoxinas perfil fenotípico perfil genotípico staphylococcus dairy products enterotoxins phenotypic profile genotypic profile

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