Microbiological Survey of Domestically-produced Sprouts Available at Retail in Canada

Introduction: Since 1990, sprouts have been linked to 38 documented outbreaks in North America, and, more recently, were implicated in French and German outbreaks in which a novel Escherichia coli pathovar caused spectacular levels of morbidity and mortality. Despite well-recognized food safety issues with sprout production, sprouts remain popular and are frequently consumed without cooking.

Purpose: Examine the microbiological quality and safety of retail sprouts in Canada, and to determine whether antimicrobial resistance (AMR) is a concern in retail sprouts.

Methods: Domestically produced sprouts (n=44) were obtained from five cities across Canada. Total microbial counts, coliforms and E. coli were determined by standard methods. In addition, E. coli O157:H7 and Salmonella were detected using Reveal kits and conventional testing methods, respectively. Enrichment was used to recover enterococci, with all isolates screened for AMR using a panel of 15 antimicrobials.

Results: Overall, total microbial loads were high, with 80% of samples possessing ≥ 2x10⁸ CFU/g. Coliforms were detected in 50% of all samples, with one sample (2.3%) positive for generic E. coli. Neither E. coli O157:H7 nor Salmonella were detected. Enterococci were recovered from 93% of samples; 7% of the isolates were En. faecalis, 24% En. faecium and 68% Enterococcus spp. AMR examination revealed resistance to clinically relevant antibiotics, including kanamycin, nitrofurantoin, penicillin, and quinupristin.

Significance: Overall, the observed levels of total bacterial and coliform levels were similar to previous reports. However, the observed prevalence of enterococci and associated AMR represent an ill-considered transmission source of antimicrobial resistance.