Abstract:
Microbial dynamics on commercially grown white button mushrooms is of importance in terms of food safety
assurance and quality control. The purpose of this study was to establish the microbial profile of fresh white
button mushrooms, with the focus on potential presence of food-borne pathogens. The total microbial load was
determined through standard viable counts. Presence and isolation of gram-negative bacteria including
coagulase positive Staphylococci were performed using a selective enrichment approach. Dominant and presumptive organisms were confirmed using molecular methods. Total mushroom microbial counts ranged
from 5.2 to 12.4 log cfu g-1, with the genus Pseudomonas being most frequently isolated (45.37% of all
isolations). In total, 91 different microbial species were isolated and identified using Matrix assisted laser
desorption ionisation time of flight mass spectrophotometry, PCR and sequencing. Considering current food
safety guidelines in South Africa for ready-to-eat fresh produce, coliform counts exceeded the guidance
specifications for fresh fruit and vegetables. Based on our research and similar studies, it is proposed that
specifications for microbial loads on fresh, healthy mushrooms reflect a more natural microbiome at the pointof-
harvest and point-of-sale.
