Salmonella, Listeria monocytogenes, and Indicator Microorganisms on Hass Avocados Sold at Retail Markets in Guadalajara, Mexico

Hass avocados may become contaminated with and at the farm and the packing facility or later during transportation and at retail. In Mexico, avocados are frequently sold in bulk at retail markets, where they are stored at room temperature for several hours or days and exposed to potential sources of microorganisms. These conditions may favor the entry, adhesion, survival, and biofilm formation of and . The aim of this study was to determine the occurrence of and other species and the levels of indicator microorganisms on the surface of avocados sold at retail markets. A total of 450 samples ( var. Hass) were acquired from retail markets located in Guadalajara, Mexico. One group of 225 samples was evaluated for the presence of and for enumeration of aerobic plate counts, yeasts and molds, coliforms, and . The other 225 samples were processed for isolation of and other species. Microbial counts (log CFU per avocado) were 4.3 to 9.0 for aerobic plate counts, 3.3 to 7.1 for yeasts and molds, 3.3 to 8.2 for 3.3 to 8.4 for coliforms, and 3.3 to 6.2 for . Eight samples (3.5%) were positive for spp. and were detected in 31 (13.8%) and 18 (8.0%) of 225 samples, respectively. and were isolated from 7.6, 1.3, and 0.9% of samples. These results indicate that avocados may carry countable levels of microorganisms and could be a vehicle for transmission of and .