CRONOBACTER IN FOOD AND STRATEGIES FOR CONTROL

Transcription

1 CRONOBACTER IN FOOD AND STRATEGIES FOR CONTROL Larry R. Beuchat Center for Food Safety, University of Georgia An International Meeting on Cronobacter (Enterobacter sakazakii) University College Dublin, Ireland - January

2 Overview Presence of Cronobacter in foods and beverages Survival and growth in dry and reconstituted infant formula and cereal Biofilm formation and resistance to disinfectants Survival and growth on fresh fruits and vegetables, and efficacy of sanitizers

3 Foods and beverages other than powdered infant formula, powdered milk and water from which Cronobacter has been isolated Animal origin: Beef, pork, poultry, sausage, camel, fish, shellfish, shrimp, cheese, eggs Plant origin: Cereal, flour, meal, grains, oilseeds, legumes, nuts, bakery products, herbs and spices, tea, lettuce, tomatoes, seed sprouts and other fresh produce, tofu, tempé, fermented beverages (attiéké, sobia, sous)

4 Survival in Powdered Infant Formula Ten-strain inoculum Five clinical isolates Four food isolates One environmental isolate Six powdered infant formulas Four milk-based formulas Two soy-based formulas a w range:. -. a w. -. (-strain inoculum) a w. -. ( clinical isolate and food isolate)

5 Powdered milk (a w.) was used as a carrier for inoculum Two inoculum populations. log CFU/g (. CFU/g). -. log CFU/g Three storage temperatures (,, and ºC) Five storage times (,,,, and months) Three replicate experiments

6 . E. C. sakazakii (log CFU/g). TSAP VRBGP agar. Ι. Storage time (months)

7 C Milk-based Formula Aformula a w. a w. a w. C. E. sakazakii (log CFU/g) C C I Storage time (months)

8 C Soy-based Formula Cformula a w. C. E. sakazakii (log (log CFU/g) C a w. a w. C I Storage time (months)

9 Detection (by enrichment) of C. sakazakii in a milk-based powdered infant formula initially containing. log CFU/g (. CFU/g) a w. Storage temp. (ºC) Storage time (months) a.. a Numbers indicate positive -g samples out of two tested ( month) or three tested ( - months)

10 C. E. sakazakii (log CFU/g) C Formula Milk-based A, strain formula (strain ) a w. a w. a w. a w. C C Storage time (weeks)

11 C. E. sakazakii (log CFU/g) C Formula Milk-based A, formula strain (strain ) a w. a w. a w. a w. C C Storage time (weeks)

12 Observations Rate of death of C. sakazakii in powdered infant formula increases with increased a w and temperature Rate of death of specific strains is unaffected by the composition of formulas but rate of death in a given formula may differ among strains When initially present in formulas (a w. -.) at populations as low as. CFU/g, C. sakazakii can survive for at least months

13 Survival in Dry Infant Cereal Ten-strain inoculum (all cereals) Four cereals Rice, barley, mixed grain, and oatmeal a w range. -. (rice cereal). -. (rice, barley, mixed grain, and oatmeal cereals) Rice cereal (a w.) was used as a carrier for the inoculum

14 Inoculum populations Rice cereal at a w. -. (. and. log CFU/g) Rice, barley, mixed grain, and oatmeal at a w. -. (. log CFU/g) Three storage temperatures (,, and ºC) Storage times (,,,, and months) Low a w :,,,, and months High a w :,,,,,, and weeks Three replicate experiments

15 C. sakazakii E. (log CFU/g) C C C Rice cereal a w. a w. a w. Storage time (months)

16 Rice Mixed grain C. E. sakazakii (log CFU/g) C a w. -. a w. a w. -. Barley Oatmeal Storage time (weeks)

17 C. sakazakii (log CFU/g) E. sakazakii (log CFU/g) Rice Barley C a w. -. a w. a w. -. Mixed grain Oatmeal Storage time (weeks)

18 Rice Mixed grain C. E. sakazakii (log CFU/g) Barley C a w. -. a w. a w. -. Oatmeal Storage time time (weeks)

19 Detection (by enrichment) of C. sakazakii in infant rice cereal initially containing. log CFU/g ( CFU/g) a w. Storage temp. (ºC) Storage time (months) a.. a Numbers indicate positive samples out of three tested

20 Observations At an initial population of. log CFU/g ( CFU/g), C. sakazakii was detected in infant rice cereal (a w. -.) stored for up to months, depending on storage temperature Rate of death increases with increased a w and storage temperature Rate of death was more rapid in rice, barley, mixed grain, and oatmeal cereals (a w. -.) than in rice cereal at a w. -.) Rate of death was unaffected by the composition of the cereals at a w. -.

21 Survival and Growth in Reconstituted Infant Formula Ten-strain inoculum Six powdered infant formulas (four milk-based and two soy-based) One reconstitution liquid (water) Two inoculum populations Low:. CFU/ml ( CFU/ g, dry wt) High:. CFU/ml ( CFU/ g, dry wt) Four storage temperatures (,,, and ºC) Six storage times (,,,,, and h) Three replicate experiments

22 C. E. sakazakii (log CFU/ml) Formula A, low inoculum C C C C Formula B, low inoculum Formula C, low inoculum Storage time (h) Formula A, high inoculum Formula B, high inoculum Formula C, high inoculum - -

23 Observations Powdered infant formula reconstituted with water is an excellent medium for growth of C. sakazakii Growth occurs in reconstituted formulas held at,, and ºC, but not at ºC Growth is unaffected by composition of the formula

24 Survival and Growth in Reconstituted Infant Cereal Ten-strain inoculum Three cereals Rice, oatmeal, and rice with mixed fruit Two inoculum populations Low:. CFU/ml (. CFU/ g, dry wt) High:. CFU/ml ( CFU/ g, dry wt) Three reconstitution liquids Water, milk, and apple juice Four storage temperatures (,,, and ºC) Six storage times (,,,,, and h) Three replicate experiments

25 C. sakazakii E. (log CFU/ml) Rice, low inoculum Rice, high inoculum C C C Oatmeal, low inoculum Oatmeal, high inoculum Rice with mixed fruit, low inoculum Rice with mixed fruit, high inoculum Incubation time (h) Incubation time (h)

26 E. sakazakii (log CFU/ml) C. sakazakii (log CFU/ml) Rice, low inoculum Rice, high inoculum C C C Oatmeal, low inoculum Oatmeal, high inoculum Rice with mixed fruit, low inoculum Rice with mixed fruit, high inoculum Incubation time (h)

27 Observations C. sakazakii grows in infant cereals reconstituted with water or milk and held at,, and ºC, and in cereals reconstituted with apple juice and held at and ºC C. sakazakii, at an initial population of. CFU/ml, survives for at least h but does not grow in cereals reconstituted with water, milk, or apple juice and held at ºC Higher populations are reached in cereals reconstituted with milk than in cereal reconstituted with water, which in turn are higher than populations in cereals reconstituted with apple juice

28 Observations Rice and oatmeal cereals support better growth than do rice with mixed fruit cereal, regardless of reconstitution liquid C. sakazakii, at an initial population of. log CFU/ml ( CFU/ml), survives for at least days in rice cereal reconstituted with apple juice and held at ºC

29 E. sakazakii (log CFU/ml) C. sakazakii (log CFU/ml) C apple cantaloupe strawberry watermelon C C cabbage carrot cucumber lettuce tomato Time (h)

30 E. sakazakii (log CFU/ml) C. sakazakii (log CFU/ml) C apple cantaloupe strawberry watermelon C C cabbage carrot cucumber lettuce tomato Time (h)

31 Efficacy of Sanitizers in Killing C. sakazakii on Apples, Tomatoes, and Lettuce Treatment with chlorine, chlorine dioxide, and peroxyacetic acid reduced populations by. -. log CFU/apple, >. log CFU/tomato, and.. log CFU/ g of lettuce

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33 C. sakazakii (log CFU/coupon) Time (days) Populations of C. sakazakii in biofilm formed on stainless steel coupons immersed in M medium ( ) or RIF ( )

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35 Effectiveness of Disinfectants in Killing C. sakazakii Thirteen commercially available disinfectants used in hospitals, day-care centers, and foodservice kitchens were effective in killing planktonic cells (. log CFU/ml of water) within - min Reductions in reconstituted infant formula were only. -. log CFU/ml after min Presence of infant formula enhanced the resistance of C. sakazakii in biofilms or dried on the surface of stainless steel Overall order of resistance: Planktonic cells < cells dried on stainless steel < cells in biofilm

36 Publications from Which Presentation was Drawn J. Food Prot. :-, J. Food Prot. :-, J. Food Prot. :-, J. Food Prot. :-, J. Food Prot. :-, J. Food Prot. :-, Appl. Environ. Microbiol. :-, Appl. Environ. Microbiol. :-, Appl. Environ. Microbiol. :-, Food Microbiol. :-, Int. J. Food Microbiol. :-,

37 THANK YOU