A bacteriological survey of fresh minced beef on sale at retail outlets in Scotland in 2019: three food-borne pathogens, hygiene process indicators and phenotypic antimicrobial resistance.

The health and economic burden of foodborne illness is high, with approximately 2.4 million cases occurring annually in the United Kingdom. A survey to understand the baseline microbial quality and prevalence of food-related hazards of fresh beef mince on retail sale could inform risk assessment, management and communication to ensure the safety of this commodity. In such a survey, a two-stage sampling design was used to reflect variations in population density and the market share of five categories of retail outlets in Scotland.  From January to December 2019, 1009 fresh minced beef samples were collected from 15 Geographic Areas. The microbial quality of each sample was assessed using Aerobic Colony Count (ACC) and generic E. coli count. Samples were cultured for Campylobacter and Salmonella and PCR was used to detect target genes (stx1 all variants, stx2 a-g, and rfbO157) for Shiga toxin-producing Escherichia coli (STEC). The presence of viable E. coli O157 and STEC in samples with a positive PCR signal was confirmed via culture and isolation. Phenotypic antimicrobial sensitivity patterns of cultured pathogens and 100 generic E. coli isolates were determined, mostly via disc diffusion. The median ACC and generic E. coli counts were 6.4 x 105 (Inter-quartile range (IQR):6.9 x 104 to 9.6 x 106) and <10 cfu per gram (IQR:<10 to 10) of minced beef respectively. The prevalence was 0.1% (95% confidence interval C.I. 0 to 0.7%) for Campylobacter, 0.3% (95% C.I. 0 to 1%) for Salmonella, 22% (95% C.I. 20% to 25%) for PCR positive STEC and 4% (95% C.I. 2 to 5%) for culture positive STEC. The evidence for phenotypic antimicrobial resistance (AMR) detected did not give cause for concern, mainly occurring in a few generic E. coli isolates as single non-susceptibilities to first-line active substances. The low prevalence of pathogens and phenotypic AMR is encouraging but ongoing consumer food-safety education is necessary to mitigate the residual public health risk.