[Occurrence of Listeria monocytogenes in raw milk, pasteurized type C milk and minas frescal cheese commercialized in Piracicaba-São Paulo]. / Ocorrência de Listeria monocytogenes em leite cru, leite pasteurizado tipo C e queijo minas frescal comercializados em Piracicaba-S.P.

Samples of raw milk, pasteurized C type milk and minas frescal cheese were analyzed for the presence of Listeria monocytogenes by a method developed for dairy products by Lovett (1) and by Lovett & Hitchins (2). A total of 20 samples of each product and from different commercial brands were analyzed, obtained from various retail stores in Piracicaba, SP. According to the pattern of sampling and methodology adopted, none of the samples of the aforesaid products was positive for the presence of L. monocytogenes or another species of the genus. It was possible to observe differences in the degree of selectivity of the selective media utilized, notwithstanding the LPM agar showing to be superior to MMA. Based on the literature and on the result obtained, becomes evident the need of a more suitable method for the detection and isolation of L. monocytogenes from foods, even when the patogen appears in low numbers, with purpose to obtain rapid, reliable and reproducible results.