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J Food Sci. 2014 May;79(5):M961-6. doi: 10.1111/1750-3841.12459. Epub 2014 Apr 24.

Assessment of microbiological contamination of fresh, minimally processed, and ready-to-eat lettuces (Lactuca sativa), Rio de Janeiro State, Brazil.

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Laboratory of Products, Microbiology Dept., National Inst. of Quality Control in Health, Oswaldo Cruz Foundation, Av. Brasil, 4365, Manguinhos, Rio de Janeiro - RJ, Brazil, CEP 21040 -900.


This study aimed to assess the microbiological contamination of lettuces commercialized in Rio de Janeiro, Brazil, in order to investigate detection of norovirus genogroup II (NoV GII), Salmonella spp., total and fecal coliforms, such as Escherichia coli. For NoV detection samples were processed using the adsorption-elution concentration method associated to real-time quantitative polymerase chain reaction (qPCR). A total of 90 samples of lettuce including 30 whole fresh lettuces, 30 minimally processed (MP) lettuces, and 30 raw ready-to-eat (RTE) lettuce salads were randomly collected from different supermarkets (fresh and MP lettuce samples), food services, and self-service restaurants (RTE lettuce salads), all located in Rio de Janeiro, Brazil, from October 2010 to December 2011. NoV GII was not detected and PP7 bacteriophage used as internal control process (ICP) was recovered in 40.0%, 86.7%, and 76.7% of those samples, respectively. Salmonella spp. was not detected although fecal contamination has been observed by fecal coliform concentrations higher than 10(2) most probable number/g. E. coli was detected in 70.0%, 6.7%, and 30.0% of fresh, MP, and RTE samples, respectively. This study highlights the need to improve hygiene procedures at all stages of vegetable production and to show PP7 bacteriophage as an ICP for recovering RNA viruses' methods from MP and RTE lettuce samples, encouraging the evaluation of new protocols that facilitate the establishment of methodologies for NoV detection in a greater number of food microbiology laboratories.


The PP7 bacteriophage can be used as an internal control process in methods for recovering RNA viruses from minimally processed and ready-to-eat lettuce samples.


RT-PCR; bacterial contamination; internal control; lettuce; norovirus

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