Microbiological analysis of pre-packed sweet basil (Ocimum basilicum) and coriander (Coriandrum sativum) leaves for the presence of Salmonella spp. and Shiga toxin-producing E-coli

摘要

Enteric pathogens, such as Salmonella spp. and pathogenic Escherichia coli, have been detected and associated with food borne outbreaks from (imported) fresh leafy herbs. Screening on imported herbs from South East Asian countries has been described. However, limited information on prevalence of these pathogens is available from other sourcing regions. Therefore, fresh pre-packed basil and coriander leaves from a Belgian trading company were investigated for the presence of Salmonella spp., Shiga toxin-producing Escherichia coli (STEC), generic Escherichia coli and coliforms. In total 592 samples were collected originating from Belgium, Israel and Cyprus during 2013-2014. Multiplex PCR followed by further culture confirmation was used for the detection of Salmonella spp. and STEC, whereas the Petrifilm Select E. coll. and VRBL-agar were used, respectively, for the enumeration of Escherichia coli and coliforms. Salmonella was detected in 10 out of 592 samples (25 g) (1.7%; 5 from basil and 5 from coriander), of which two samples were sourced from Israel and eight from Cyprus. The presence of STEC was suspected in 11 out of 592 samples (25 g) (1.9%; 3 basil and 8 coriander), due to the detection of stx and eae genes, of which one sample originated from Belgium, four from Israel and six from Cyprus. No STEC was isolated by culture techniques, but in three samples a serotype (026, 0103 or 0111) with its most likely associated eae-variant (beta or theta) was detected by PCR Generic Escherichia coli was enumerated in 108 out of 592 samples, whereby 55,32 and 13 samples respectively between 10-100, 100-1000 and 1000-10,000 cfu/g and 8 samples exceeding 10,000 cfu/g. Coliforms were enumerated in all herb samples at variable levels ranging from 1.6 to 7.5 log cfu/g. Further statistics indicate that the Escherichia coli class (categorized by level) was significantly correlated with the presence of Salmonella (p 0.001) or STEC (p = 0.019), whilEscherichia coliform counts were significant correlated with Salmonella (p 0.001), but not with STEC (p = 0.405). Generic Escherichia coli class is a better indicator for the presence of enteric pathogens than coliforms on fresh herbs, but the relationship between Escherichia coli and Salmonella or STEC was not strong enough to provide a threshold value for Escherichia coli to assure food safety (i.e. no pathogens present). Results indicate that fresh leafy herbs like basil and coriander sourced from different cultivation regions, may contain enteric pathogens and potentially pose a risk for human health. (C) 2015 Elsevier B.V. All rights reserved.