ICMSF methods studies. X. An international comparative study of four media for the enumeration of Staphylococcus aureus in foods.

An international comparative study, undertaken by six laboratories to assess the performance of four selective media commonly used for the enumeration of Staphylococcus aureus in foods, revealed that Baird-Parker agar performed most satisfactorily. There was no significant difference among milk salt, tellurite polymyxin egg yolk, and kalium rhodanid - actidione - natriumazid - eigelb - pyruvat (KRANEP) agars. The type of food examined appeared to influence the performance of the media, but no specific patterns could be determined.

[An agar medium for direct enumeration of Staphylococcus aureus: pork plasma medium for S. aureus (PPSA)].

A selective agar medium (pork plasma medium for S. aureus (PPSA)) enables the direct enumeration of coagulase-positive staphylococci. This medium is based on the Baird-Parker agar without egg yolk and is supplemented with pig plasma.

[Use of nitrates in cheese-making].

In the technology of semi-hard cheeses, nitrate is added to prevent thelate-blowing defect due to the growth of Clostridia. In normal technological conditions no risks must be encountered by the consumer. But if whey is re-used for feeding the amount of nitrate and nitrite in the whey must be controlled.