Purpose: The aim of this work was to determine the microbiological quality of tilapia ceviche and shrimp ceviche sold at the metropolitan area of San José, Costa Rica, as well as the raw material used in its elaboration.
Methods: 25 samples of tilapia ceviche and 27 samples of shrimp ceviche were analyzed; same number of raw material was analyzed. Also, the behavior of some of the spoilage populations was analyzed in 25 samples of shrimp and same number of tilapia ceviche during its storage at 4ºC. Analysis included the evaluation of indicators and of different potential pathogens including Listeria monocytogenes, Salmonella, Escherichia coli, Vibrio parahaemolyticus and V. cholera.
Results: The results obtained from the raw material and ceviche analysis show that, although there is an important bacterial contamination present in raw material, and that the ceviche is a product that includes manipulation, there is an important reduction in the bacterial charges present in the end product, especially referring to total aerobic psychrofilic plate count and total coliforms; but not to fecal coliforms. Escherichia coli was isolated from 15% of the tilapia's ceviche and 4% from shrimp's ceviche, 3 strains of Listeria monocytogenes were isolated from tilapia, one from shrimp, 3 strains of V. parahaemolyticus were isolated from shrimp and 2 from its ceviche. Salmonella spp. were not isolated. The pH of ceviche plates stored at 4ºC for one week showed a trend towards stability or slight increase of this parameter. Same way, the concentration of spoilage microorganisms suffered slight variations; nevertheless, the low number of Pseudomonas spp present in tilapia's ceviche is an outstanding result since this population is associated to spoilage of the product.
Significance: Although there is an important reduction in the number of bacteria present in ceviches compared to raw material, the isolation of potential pathogens show that these products may represent a risk for public health.