Growth and enterotoxin production of Staphylococcus aureus during the manufacture and ripening of Camembert-type cheeses from raw goats' milk.

Tests were carried out to determine the effect of manufacturing procedures for a Camembert-type cheese from raw goats' milk on the growth and survival of Staphylococcus aureus organisms added to milk at the start of the process, and to study the possible presence of staphylococcal enterotoxin A in these cheeses. The initial staphylococcal counts were, respectively, 2, 3, 4, 5 and 6 log cfu ml-1. Cheese was prepared following the industrial specifications and ripened for 41 d. Detection of enterotoxins was done by the Vidas SET test and by an indirect double-sandwich ELISA technique using antienterotoxin monoclonal antibodies. Generally, numbers of microbes increased at a similar rate during manufacture in all cheeses until salting. During the ripening period, the aerobic plate count population and Staph. aureus levels remained stable and high. There was an approximately 1 log reduction of Staph. aureus in cheeses made with an initial inoculum of Staph. aureus greater than 10(3) cfu ml-1 at the end of the ripening period (41 d) compared with the count at 22 h. The level of staphylococcal enterotoxin A recovered varied from 1 to 3.2 ng g-1 of cheese made with an initial population of 10(3)-10(6) cfu ml-1. No trace of enterotoxin A was detected in cheeses made with the lowest Staph. aureus inoculum used in this study.

Evaluation of the VIDAS methodology for detection of Escherichia coli O157 in food samples.

An automated enzyme-linked fluorescence immunoassay (ELFA), the VIDAS E. coli O157 method, was compared with immunomagnetic separation (IMS) followed by culture on cefixime tellurite sorbitol MacConkey agar (CT-SMAC) for detecting Escherichia coli O157 in artificially and naturally contaminated food samples including raw milk cheeses, poultry, raw sausages, and ground beef retail samples. Confirmation of the samples positive according to the ELFA was performed by use of an automated immunoconcentration system, VIDAS ICE, which allows selective capture and release of target organisms. A total of 496 retail food samples were examined. Seventeen food samples gave positive values with the ELFA method, and among them 9 food samples were confirmed by the ICE method. Eight were shown to contain sorbitol-positive, O157-positive, H7-negative, motile, non-verotoxin-producing E. coli. The ninth positive sample contained an O157-positive, H7-negative, sorbitol-negative, non-verotoxin-producing E. coli. The IMS technique only allowed confirmation of this sorbitol-negative, non-verotoxin-producing E. coli O157.

Detection of Escherichia cole O157 in French food samples using an immunomagnetic separation method and the VIDAS E. coli O157.

Two commercially available screening methods, an automated enzyme-linked fluorescent immunoassay (VIDAS E. coli O157) and an immunomagnetic separation followed by culture onto cefixime tellurite sorbitol MacConkey agar (CT-SMAC), were compared for detection of Escherichia coli O157 in naturally and artificially contaminated food samples. A total of 250 naturally contaminated food samples, including raw milk cheeses, poultry, raw sausages and ground beef retail samples, were examined. Four poultry, one raw sausage and one ground beef sample were found to be positive for E. coli O157 by both methods. Of the six positive samples, five were shown to contain sorbitol-positive, O157-positive, H7-negative, motile and non-verotoxin-producing E. coli.