Micro December 2018

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Thirty-one foods and two environmental surfaces were analyzed in the matrix study. The 2

foods and surfaces tested were pasteurized whole milk, butter, non-fat dry milk powder, fresh 3

raw ground pork (90% lean), lamb chop, fresh raw ground chicken (92% lean), chicken carcass 4

rinsate, shell eggs, liquid egg whites, powdered egg whites, sprouts, cranberries (frozen), 5

powdered infant formula with probiotics, powdered infant formula without probiotics, dry dog 6

kibble, flour (all-purpose), chocolate chip cookie dough, fresh raw ground beef (73% lean), raw 7

frozen chicken wings (bone in, skin on), raw milk, whole liquid egg, tuna sushi (tuna fillet, no 8

rice), smoked salmon, bunched spinach, pasteurized carrot juice, ready-made sandwiches 9

(turkey breast, provolone cheese, lettuce, red onion and multi-grain bread), raw vegetable with 10

salad dressing (coleslaw), chicken feed and soybean meal, stainless steel environmental surface 11

(type 304, food grade, sampled by sponge), sealed concrete environmental surface (sampled by 12

sponge). Each food matrix was purchased from a local distributor and pre-screened for natural 13

contamination of coliform and E. coli by the FDA BAM Chapter 4 reference method, and for 14

total aerobic count by the FDA Chapter 3 method (7). Results are listed in Table 9. All matrices, 15

except for the chicken carcass rinsate and sprouts, were found to be uncontaminated with E. 16

coli and non- E. coli coliforms, and therefore required artificial contamination. Low (10-100 17

CFU/g), medium (100-1,000 CFU/g) and high (1,000-10,000 CFU/g) contamination levels were 18

targeted for each inoculating strain and matrix. For chicken carcass rinsate and sprouts, three 19

contamination levels were tested, and an uncontaminated level was not required. Five replicate 20

portions for each level of each matrix were prepared and diluted in BPBD, as directed in BAM 21

Ch. 4, and then tested by the 3M Petrifilm Rapid E. coli /Coliform Count Plate and BAM Ch. 4. 22

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