Assessing the relationship between organic farming practices and microbiological characteristics of organic lettuce varieties (Lactuca sativa L.) grown in Sao Paulo, Brazil.

AIMS

This study aimed to gather information on farming practices employed in organic lettuce fields in Sao Paulo, Brazil and associate these practices with the microbiological characteristics of the products.

METHODS AND RESULTS

Practices were surveyed using a questionnaire applied in ten farms, where 200 heads of lettuce were collected and submitted to enumeration of total coliforms and generic Escherichia coli and tested for Salmonella spp. using culture and molecular (qPCR) methods. Based on the responses, the farms could be clustered in two groups: group 1, comprised by six farms, where chicken manure was used as fertilizer in most of them and the composting process was not performed on site; and group 2, comprised by four farms, where other types of fertilizer were used, and the composting process was performed on site. Generic E. coli was detected in 56 (28%) samples, with an average of 1·1 ± 0·7 log MPN per g. Salmonella DNA was detected in two (1%) samples by qPCR.

CONCLUSIONS

The prevalence and bacterial loads of generic E. coli, and the occurrence of Salmonella, even at low populations undetectable by conventional culture methods, highlight the need for control measures during farming practices to reduce microbial contamination and risks of foodborne illnesses. These measures include the use of properly composted manure and appropriate washing procedures for leafy vegetables before consumption.

SIGNIFICANCE AND IMPACT OF THE STUDY

The obtained data contribute to a better understanding of the farming practices of organically grown lettuces in Sao Paulo, Brazil.