Bacterial counts and the occurrence of parasites in lettuce (Lactuca sativa) from different cropping systems in Brazil

Abstract

a b s t r a c tThis study evaluated the microbiological quality of 180 lettuce samples (Lactuca sativa) of the iceberg variety from different cropping systems and examined the efficacy of two sanitizers in reducing the bacterial counts. The results showed high contamination by mesophilic aerobic bacteria in traditionally grown and organically grown samples, which also possessed thermotolerant coliforms above the recommended levels in 66% and 80% of samples, respectively. Salmonella sp. was not detected in any of the analyzed samples. Traditionally grown and organically grown samples also exhibited a high frequency of intestinal parasites, including the pathogenic Taenia sp. and the Entamoeba histolytica species. In contrast, only 20% of hydroponically grown lettuce samples were contaminated with parasites. Sodium hypochlorite and acetic acid at concentrations of 100 mg L À1 and 1%, respectively, were effective in reducing bacterial counts, even in samples with high levels of contamination.

A PCR procedure for the detection of Giardia intestinalis cysts and Escherichia coli in lettuce

“…; Gomes Neto et al . ); according to our results, their contamination rate may be at least 20 cysts g −1 .…”

“…Light microscopy detected cysts in eluates from 50 g of lettuce inoculated with a minimum of 10 3 cysts (20 cysts per gram). Previous studies used similar procedures to determine the incidence of Giardia infection in naturally contaminated lettuces (Daryani et al 2008;Abougrain et al 2010;Gomes Neto et al 2012); according to our results, their contamination rate may be at least 20 cysts g À1 .…”

Microbiology of organic and conventionally grown fresh produce

“…Studies have isolated pathogens including Salmonella spp., L. monocytogenes and pathogenic E. coli from fresh and fresh-cut vegetable samples in many countries 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49. Other studies have compared the microbiological quality of vegetables from organic and conventional production 21, 22, 24, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59. Ceuppens et al 51 assessed the microbiological quality of lettuce production in Brazil and detected generic E. coli more frequently and at higher average concentrations in lettuce samples from organic farms (23.1% and 3.22 log CFU/g) vs. conventional farms (16.7% and 2.27 log CFU/g).…”

“…Ceuppens et al 51 assessed the microbiological quality of lettuce production in Brazil and detected generic E. coli more frequently and at higher average concentrations in lettuce samples from organic farms (23.1% and 3.22 log CFU/g) vs. conventional farms (16.7% and 2.27 log CFU/g). Gomes Neto et al 52 evaluated the microbiological quality of 180 iceberg lettuce samples from conventional ( n  = 60), organic ( n  = 60) and hydroponic ( n  = 60) cropping systems in Brazil and observed that samples from organic systems were the most contaminated both by bacteria and intestinal parasites, while the lowest contamination level was observed in hydroponically grown lettuce. Maffei et al 24 analyzed 130 samples of different organic ( n  = 65) and conventional ( n  = 65) vegetable varieties (also in Brazil), and observed that some organic varieties had greater microbial counts with the highest incidence of generic E. coli in organic loose-leaf lettuce (90% of samples positive).…”

Influence of different sources of contamination on the microbiological quality of lettuce in the Teresópolis region, RJ, Brazil

“…Lettuce (Lactuca sativa) has been considered one of the most consumed vegetables in Brazil, mainly due to its organic characteristics, such as being low in calories and a rich fiber source, in addition to being a low cost food, qualifying for different diets (GOMES NETO et al, 2012). It is the most important vegetable with green leaves in Brazil's economy, with acreage of approximately 35,000 acres (KRINSKI; PELISSARI, 2012).…”