Table 2.

Summary of microbiological results of testing samples of raw milk and unpasteurised milk cheeses associated with incidents and outbreaks of infection

Incident or outbreak of infection number [references]	Description	Incriminated food	Samples collected	Results of microbiological analysis
Milk outbreak 1 [19, 20]	Seven cases of STEC O157:H7 PT 21/28 stx2 in 2017	Consumption of raw cow's milk from a single dairy	21 samples of raw cow's milk and two samples of cream collected from the dairy	STEC O157:H7 indistinguishable from that isolated from the cases and from cow faeces collected on the farm was isolated from three bulk tank milk samples. Statutory indicator bacteria tests (ACCs and coliforms) gave compliant results for all three samples from which STEC was isolated: borderline levels of CPS were detected in all three samples. Of the remaining 18 samples, 13 had borderline levels of CPS, three had unsatisfactory levels of coliforms and three had unsatisfactory levels of ACCs. None of the 21 samples were interpreted as being of satisfactory quality. The two samples of cream were of satisfactory quality and were tested for E. coli, Listeria and Salmonella.
Milk outbreak 2 [19]	Four cases of Campylobacter infection in 2017	Consumption of raw cow's drinking milk from a single dairy	31 samples of raw cow's milk collected from the dairy	Campylobacter jejuni MLST 22 was isolated from two milk samples which were indistinguishable from that infecting the patients: results for CPS were borderline for one sample and the level of coliforms was unsatisfactory for the other; all other microbiological parameters (ACC, L. monocytogenes, Salmonella and STEC) were satisfactory. For the remaining 29 samples, 12 were satisfactory for all parameters, four had borderline levels of CPS and 13 had unsatisfactory levels of coliforms.
Milk outbreak 3 [19]	Single sporadic case of S. enterica serovar Dublin in 2017	Consumption of raw cow's drinking milk at a childminders which was bought from a local on farm dairy	Four samples of raw cow's milk from the bulk tank and a filter sock removed following milking at the dairy	S. Dublin was detected in all the milk samples (as well as a filter sock) and isolates were found to be indistinguishable from the clinical isolate. All four milk samples from which S. Dublin was recovered were satisfactory for all other parameters (ACC, coliforms, Campylobacter, L. monocytogenes, CPS)
Cheese collected following an STEC outbreak associated with raw drinking milk consumption also from these premises [19, 21]	Sporadic case of S. enterica serovar Mbandaka (MLST: 413). STEC was also isolated from this patient, in 2014	This cheese was manufactured at the same farm that had previously been associated with an STEC outbreak	Seven samples of cow's milk cheese collected at the farm cheese manufacturing environment in 2015 which was co-located with the dairy producing the milk	S. Mbandaka indistinguishable from the patient was isolated from one cheese sample. Of all seven samples, Listeria, CPS, STEC and E. coli O157 were not detected. Two samples were satisfactory with respect to the presence of E. coli, one was borderline, and the remaining four (including the sample from which S. Mbandaka was isolated) were unsatisfactory, with results ranging from 102 to 104 cfu/g.
Cheese infection [19]	Sporadic case of listeriosis infected with L. monocytogenes serovar 1/2a, ST403 and SNP type 1.1.1.1.1.1.1 in 2016	The patient purchased the cheese from a farm shop which was co-located with the cheese production environment	28 samples of cow's milk cheese (five hard, five semi soft and 18 soft) from the dairy collected in 2016 and 2017	L. monocytogenes was detected in four samples of soft cheese all at end of production, two at <20 cfu/g, one at 2.3 × 103 cfu/g and one at 1.6 × 104 cfu/g: all isolates were shown to be indistinguishable from that recovered from the clinical samples from the case. Satisfactory results were obtained for all other microbiological parameters: CPS (13 samples), Salmonella (12 samples), STEC (five samples) and E. coli O157 (nine samples). Unsatisfactory results were obtained for E. coli in four soft and one hard cheese sample taken from this producer (levels 2.4 × 102–2.1 × 104 cfu/g): satisfactory E. coli levels were detected in six samples. L. monocytogenes was not detected in samples with unsatisfactory levels of E. coli.
Cheese contamination incident (PHE, unpublished)	Contamination with CPS in 2013	Hard goat's milk cheese which were condemned and did not enter the human food chain.	44 samples of a hard goat's milk cheese were collected over a 2-week period from two separate batches (at the end of production) and produced in the same dairy	S. aureus was detected in 40: seven at borderline levels of <104 cfu/g and the remaining 33 at unsatisfactory levels of between 104 and 107 cfu/g. Isolates of S. aureus were all shown to contain genes encoding the staphylococcal enterotoxin type C: samples of cheese were tested for staphylococcal enterotoxins which were not detected. Thirty of the samples were tested for other microbiological parameters: Salmonella and Listeria were not detected in any sample, while five had unsatisfactory levels of E. coli, all at <103 cfu/g.

ACCs, aerobic colony counts; CPS, coagulase positive staphylococci; MLST, multilocus sequence type; SNP, single-nucleotide polymorphism type; ST, sequence type; STEC, Shiga toxin-producing E. coli.