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

Abstract

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.

Agricultural practices in Brazilian organic farms and microbiological characteristics of samples collected along the production chain

“…The estimated population of Salmonella spp. in the positive enriched culture sample (1.1 log CFU per ml) was low and similar to that reported by Maffei et al, (2019) in Brazil: 1.0 and 1.2 log CFU per gram in two out of 200 enriched cultures of lettuce samples. Despite the growing number of FBD outbreaks associated with vegetables contaminated by Salmonella spp.…”

“…asburiae and Klebsiella pneumoniae in organic fertilizers may be related to the lack of standardization and validation of the composting method in the farms, particularly, ingredients used for formulation. The use of chicken manure, as detected in this study and also in the study of Maffei et al (2019), may explain these observations. Maffei et al (2019) detected higher populations of generic E .…”

“…The use of chicken manure, as detected in this study and also in the study of Maffei et al (2019), may explain these observations. Maffei et al (2019) detected higher populations of generic E . coli in lettuces that were grown in a chicken manure‐amended soil in comparison to samples cultivated using cattle, swine or mixed manure.…”

“…in lettuce and fertilizer samples was evaluated according to the ISO 6579:2002 method (International Organization for Standardization, 2007), whereas the ISO 19250:2010 (International Organization for Standardization, 2010) was used for water samples. Additionally, the pre-enriched lettuce and water samples were submitted to qPCR for quantitative estimation of Salmonella spp., as described by Maffei et al (2019). Total DNA was extracted from 1 ml of the pre-enriched samples using mericon DNA Bacteria Kit (Qiagen), following the manufacturer's instructions.…”

“…Salmonella spp., from the Enterobacteriaceae family, are frequently reported as vegetable contaminants (Ceuppens et al, 2014; Denis et al, 2016; Maffei et al, 2019; Ni et al, 2018; Rodrigues et al, 2014; Richter et al, 2019; Yang et al, 2020). Enterobacteriaceae comprises a large family of bacteria that includes the major food‐related enteric pathogens and species reported as multidrug‐resistant and opportunistic human pathogens.…”