Pathogenic Enterobacteriaceae require multiple culture temperatures for detection in Cannabis sativa L.

Abstract

Background: Cannabis safety testing requires adequate detection of a broad class of bacteria known as Enterobacteria, from the family of Enterobacteriaceae. These organisms are responsible for many food-borne illnesses including gastroenteritis, and are common targets in the food testing industry. While all these organisms contain 16S DNA, not all of them grow on commercial culture-based platforms at a single culture temperature. Methods: We assessed four Enterobacteria (Aeromonas hydrophila, Pantoea agglomerans, Yersinia enterocolitica, Rahnella aquatilis) that vary in their preferred culture temperature, human pathogenicity and prevalence in cannabis. We cultured them on two different plating media and compared these results to two different qPCR assays. Results: All four bacteria grew on one plating medium at 30°C. 75% of them failed to grow at 36°C. Using a different plating medium, 75% grew at 30°C and zero grew at 36°C. Two different commercialy available quantitative PCR assays detected 100% of the organisms. Conclusions: Several Enterobacteria are highly medium- and temperature-sensitive, and can easily evade culture-based detection. Some of these bacteria are known to infect cannabis and may pose a clinical risk to cannabis trimmers or consumers. Quantitative PCR detected all of these species. Quantitative PCR is often criticized for failing to discern live versus dead DNA, but the definition of “live” is dependent on the culture medium and temperature used.