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Heat as a disinfection method for poultry houses persistently infected with Salmonella – an outline of methods and results Kim O. Gradel Danmarks Veterinærinstitut,

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Presentation on theme: "Heat as a disinfection method for poultry houses persistently infected with Salmonella – an outline of methods and results Kim O. Gradel Danmarks Veterinærinstitut,"— Presentation transcript:

1 Heat as a disinfection method for poultry houses persistently infected with Salmonella – an outline of methods and results Kim O. Gradel Danmarks Veterinærinstitut, Århus Rengøring og Desinfektion af Stalde Hotel Australia, Vejle, November 2003

2 Background In general, heat rather than chemical disinfection of contaminated items is recommended whenever possible. It is difficult to clean animal houses and cover all areas by surface disinfection. Hypothesis: heat can be evenly distributed and it can penetrate organic matter without damaging materials. Environmental considerations.

3 Disposition Laboratory tests Field tests Materials and methods Results
Conclusions Field tests

4 Heat tests related to general disinfection factors
Micro- organism Disinfectant Surroundings Type ”State/condition” Organic matter Temperature pH Biofilm Concentration Heat project

5 Laboratory tests Aims: Principles:
To find a temperature-humidity-time treatment that kills Salmonella. Investigate correlations between susceptibility of spiked Salmonella and naturally occurring E. coli. Principles: Simulation of real-life conditions. Worst-case scenarios. Full factorial design.

6 Laboratory tests: factors
Salmonella (S. Enteritidis, PT8, S. Typhimurium, DT110, S. Infantis) Escherichia coli (naturally occurring in faeces) Organic matter (pelleted feed for layers, chicken faeces) Drying during 10-day period prior to heating (yes, no) Humidity at heating (low = 16-30%; high = 100%) Heating temperature (50, 55, 60, 65, 70 oC)

7 Laboratory tests: test protocol
Thirty gram test material (feed or faeces) were put in beakers, yielding a layer cm thick. Spiked with high numbers of Salmonella. Beakers at 20 oC and 30% RH during 10-day period, lidded (no drying) or un-lidded (drying). 10-day samples checked microbiologically, other samples moved to cooled incubator. Other samples checked microbiologically as for 10-day samples after varying time periods, cf. next slide.

8 Laboratory tests: overview of tests
0-hour samples 24-hour samples 48-hour samples 1 oC per hour Final heating temperature 20 oC 20 oC 10-day samples 72-hour samples

9 Laboratory tests: samples prior to heating

10 Laboratory tests: temperature control programme

11 Laboratory tests: heating of high humidity samples

12 Laboratory tests: microbiological procedures
From each beaker, traditional Salmonella procedures: pre-enrichment, selective enrichment, plating on Rambach agar. From all beakers with faeces: plating from pre-enrichment broth on MacConkey agar (presence/absence of E. coli).

13 Laboratory tests: replicate tests
For the ”gold” standard, i.e. a temperature-humidity-time scheme that killed all bacteria, replicate tests were made. Only S. Enteritidis was used, as there were few differences between the three Salmonella serotypes. Only samples dried in the 10-day period were used. Crumbled feed and egg yolk as well as pelleted feed and faeces were used. All tests were repeated four times. Three different selective enrichment procedures were applied.

14 Laboratory tests: overview of traditional Salmonella results

15 Salmonella spp. detected on Rambach agar?
Laboratory tests: correlations between results for Salmonella and E. coli E. coli detected? Salmonella spp. detected on Rambach agar? SUM Yes No Pure culture of Salmonella Salmonella- and non-Salmonella Growth of non-Salmonella Sterile 8 90 10 116 40 3 222 273 48 98 13 230 389

16 Laboratory tests: conclusions
Humidity, both before and during heating, was an important factor in the bacterial killing. In general, there was a higher survival in feed than in faeces. There were high correlations between the survival of spiked Salmonella and naturally occurring E. coli. No bacteria were detected at 60 oC and 100% RH after 24 hours of heating (i.e. ”gold” standard for field studies), including in replicate tests.

17 Field tests Aim: To test if the gold standard (60 oC & 100% RH during 24 hours) was valid in the field. Principles: Salmonella samples before and after heating. Salmonella results per se. Non-sterile Rambach agar plates (i.e. coliforms as possible indicator bacteria). Challenge samples, placed at sites where temperature was measured.

18 Field tests: principles I

19 Field tests: principles II

20 Field tests: Overview of farms, houses and treatments
HOUSE TYPE TREATMENT No. of Salmonella samples Challenge samples Before After A A1 Barn Steam without F 287 288 Yes A2 Battery 302 303 B B1 Steam with F 100 102 B2 Pulse fogging 96 No B3 Surface dis. C C1 298 308 D D1 289 290 E E1 F F1 150

21 Field tests: results for Salmonella samples
HOUSE TREATMENT Salmonella (positive/sum) Non-sterile Rambach (positive/sum) R S Before After A1 Steam, no F 36/287 6/288 278/287 94/288 3.0 A A2 Steam,no F 65/302 0/303 284/302 114/303 2.5 B1 Steam, +F 0/100 0/102 41/100 3/102 14.1 B B2 Pulse fog. 6/100 0/96 58/100 33/96 1.7 C B3 Surface 5/100 68/100 8/100 8.5 CD C1 37/298 0/308 180/298 2/308 92.9 E D1 1/289 0/290 78/289 1/290 79.4 F E1 40/308 224/308 9/308 25.1 D F1 16/150 0/150 146/150 3/150 48.7

22 Field tests: Salmonella ”hot” sites
POSITIVE/SUM % POSITIVE Beams/ledges 9/74 12.2 Droppings belts 5/48 10.4 Drip channels 12/51 23.5 Feed chain ”corner wheels” 6/33 18.2 Egg equipment 14/93 15.1 Floor related samples 103/507 20.3

23 Field tests: correlations between Salmonella and coliforms on house level

24 Field tests: correlations between Salmonella and coliforms on site level

25 Field tests: results for challenge samples

26 Field tests: ”traditional” Danish heating procedure
Practised for years in Danish poultry houses. Principle: a short steam and formaldehyde heating until the temperature reaches ca. 60 oC, after which the heating ceases. The house remains sealed for ca. 24 hours.

27 Field tests: ”traditional” Danish heating: a typical temperature curve

28 Field tests: ”traditional” Danish heating: challenge samples
E. Faecalis Feed E. coli Enterococci Faeces Barn 13 ppm Cage 22 ppm Par. 30 ppm 22 Pos / sum H 3/6 6/6 4/6 1/6 5/6 0/6 2/6 L S 7/12 12/ 12 6/12 4/12 11/ 3/12 0/12 1/12 2/12

29 Field tests: ”traditional” heating: challenge samples and peak temperatures
E. Faecalis Feed E. Coli Enterococci Faeces 60-65 8/13 5/13 4/13 1/13 55-60 11/14 8/14 0/14 28-55 6/9 5/9 2/9

30 Field tests: Conclusions
In tight houses, 60 oC and 100% RH was achieved minimum 10 cm above floor level within one hour and was easily maintained during 24 hours. 60 oC and 100% RH during 24 hours seemed effective in eliminating Salmonella and putative indicator bacteria. The addition of 30 ppm formaldehyde at the beginning of the process seemed to lower the lethal temperature by 2-5 oC. The occurrence of coliforms could be a guidance for the efficacy against Salmonella, although no cut-off values could be predicted. The ”traditional” Danish steam and formaldehyde procedure is ineffective.

31 Future perspectives Certification of heating procedures
Possible model: Danish Technological Institute has certified a heat treatment against Dry Rot in buildings. Companies that can document a time-temperature scheme with validated equipment are approved by this system. It also includes insurance against re-occurrence of Dry Rot See

32 Acknowledgments Kirsten Holm, DVI, Århus, Denmark.
Kirsten Christensen, DVI, Århus, Denmark. Staff at Landskontoret for Fjerkrærådgivning, Århus, Denmark. Staff at Danish Meat Research Institute, Roskilde, Denmark. Participating farmers.


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