Comparação entre os meios de cultura Baird-Parker, Baird-Parker RPF e Petrifilm Staph Express na detecção de Staphylococcus coagulase positivo em leite cru naturalmente contaminado e em leite esterilizado inoculado com culturas específicas

Abstract

The reference methodology for Staphylococcus spp. enumeration recommends the use of the Baird-Parker agar (BP). However, others culture media may produce results in a shorter time, as Baird-Parker - RPF agar (bioMérieux, Marcy l'Etoile, France) and the PetrifilmTM Staph Express Count Plate - PSE - (3M Microbiology Products, St. Paul, USA). Thus, this work was carried out in order to compare the efficiency of the fore cited culture media for the enumeration of Staphylococcus spp. in raw milk and sterilized milk. The latter was inoculated with pure cultures of Staphylococcus aureus, Staphylococcus hyicus, and Staphylococcus intermedius in three different concentrations (107, 104, and 102 CFU/mL) with six repetitions for each treatment. Mean Staphylococcus spp. count obtained by PSE (2.50 Log10 CFU/mL) was lower (p<0.05) from those obtained by BP (4.12 Log10 CFU/mL) and RPF (3.86 Log10 UFC/mL) agars, being the latter two values considered similar (p>0.05). The mean counts in PSE for the enumeration of the three Staphylococcus species inoculated in sterilized milk were different (p<0.05) of those obtained in BP, however, they were similar (p>0.05) in BP and RPF agars. Therefore, the replacement of the BP by the RPF can be viable without altering the accuracy of the analysis