Microbiological analysis of lettuce (Lactuca sativa) from conventional and organic cultivation commercialized at fairs in Brazil

Abstract

Brazilian laws established regulatory limits in lettuce only to thermotolerant coliforms (fecal coliforms) and coagulase-positive Staphylococci of 10 MPN g and 10 CFU g respectively. The objective of this study was to evaluate and compare contamination of lettuce from conventional and organic cultivation, commercialized at fairs in south of Brazil, by the fecal coliforms, coagulase-positive Staphylococci, Salmonella spp. and Listeria monocytogenes. Eighty samples of traditionally and organically produced lettuce each were collected. The contaminated samples percent were 35 and 71.25, for fecal coliforms, 35 and 32,5 for coagulase-positive Staphylococci, 0 and 5 for Salmonella spp., 2.5 and 2.5 for Listeria monocytogenes, in conventional lettuce and organic lettuce, respectively. Results indicated that 35% of the samples of conventionally produced lettuce and 71.25% of the samples of organically produced one presented fecal coliform count above regulatory limits. Coagulasepositive Staphylococci counts above regulatory limits were verified in 28 and 26 samples from the conventional and organic agriculture, respectively. Salmonella spp. was present in 5% of organically produced samples and L. monocytogenes in 2.5% of lettuce samples from both types of agricultures. Obtained results highlight the importance of good practices from cultivation to commercialization to improve the hygienic-sanitary quality of vegetables.