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 Veterin."— Presentation transcript:
Heat as a disinfection method for poultry houses persistently infected with Salmonella – an outline of methods and results Kim O. Gradel Danmarks Veterin æ rinstitut, Å rhus Reng ø ring og Desinfektion af Stalde Hotel Australia, Vejle, 11.-12. November 2003
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.
Disposition Laboratory tests Materials and methods Results Conclusions Field tests Materials and methods Results Conclusions
Heat tests related to general disinfection factors Micro- organism DisinfectantSurroundings Type State/condition Organic matter Temperature pH Biofilm Type Concentration Heat project
Laboratory tests Aims: 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.
Laboratory tests: factors Factor 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 o C)
Laboratory tests: test protocol 1. Thirty gram test material (feed or faeces) were put in beakers, yielding a layer 2-2.5 cm thick. 2. Spiked with high numbers of Salmonella. 3. Beakers at 20 o C and 30% RH during 10-day period, lidded (no drying) or un-lidded (drying). 4. 10-day samples checked microbiologically, other samples moved to cooled incubator. 5. Other samples checked microbiologically as for 10- day samples after varying time periods, cf. next slide.
Laboratory tests: overview of tests 10-day samples 0-hour samples 24-hour samples 48-hour samples 72-hour samples 20 o C 1 o C per hour Final heating temperature 20 o C
Laboratory tests: samples prior to heating
Laboratory tests: temperature control programme
Laboratory tests: heating of high humidity samples
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).
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.
Laboratory tests: overview of traditional Salmonella results
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 Yes 8 90108116 No4083222273 SUM489813230389
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 o C and 100% RH after 24 hours of heating (i.e. gold standard for field studies), including in replicate tests.
Field tests Aim: To test if the gold standard (60 o C & 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.
Field tests: principles I
Field tests: principles II
Field tests: Overview of farms, houses and treatments FARMHOUSE HOUSE TYPE TREATMENT No. of Salmonella samples Challenge samples BeforeAfter AA1BarnSteam without F287288Yes A2BatterySteam without F302303Yes BB1BarnSteam with F100102Yes B2BarnPulse fogging10096No B3BarnSurface dis.100 No CC1BatterySteam with F298308Yes DD1BatterySteam with F289290Yes EE1BatterySteam with F308 Yes FF1BatterySteam with F150 No
Field tests: Salmonella hot sites SITEPOSITIVE/SUM % POSITIVE Beams/ledges9/7412.2 Droppings belts5/4810.4 Drip channels12/5123.5 Feed chain corner wheels 6/3318.2 Egg equipment14/9315.1 Floor related samples103/50720.3
Field tests: correlations between Salmonella and coliforms on house level
Field tests: correlations between Salmonella and coliforms on site level
Field tests: results for challenge samples
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 o C, after which the heating ceases. The house remains sealed for ca. 24 hours.
Field tests: traditional Danish heating: a typical temperature curve
Field tests: traditional Danish heating: challenge samples E. Faecalis Feed E. coli Feed Enterococci Faeces E. coli Faeces Barn 13 ppm Cage 22 ppm Par. 30 ppm Barn 13 ppm Cage 22 ppm Par. 30 ppm Barn 13 ppm Cage 22 ppm Par. 30 ppm Barn 13 ppm Cage 22 ppm Par. 30 ppm Pos / sum H 3/66/64/61/65/6 0/65/62/60/61/60/6 L 4/66/62/63/66/62/63/66/61/60/6 2/6 S 7/12 12/ 12 6/124/12 11/ 12 7/123/12 11/ 12 3/120/121/122/12
Field tests: traditional heating: challenge samples and peak temperatures Peak tempe- rature E. Faecalis Feed E. Coli Feed Enterococci Faeces E. Coli Faeces 60-658/135/134/131/13 55-6011/14 8/140/14 28-556/9 5/92/9
Field tests: Conclusions In tight houses, 60 o C and 100% RH was achieved minimum 10 cm above floor level within one hour and was easily maintained during 24 hours. 60 o C 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 o C. 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.
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 www.vks-udvalget.dk
Acknowledgments Kirsten Holm, DVI, Å rhus, Denmark. Kirsten Christensen, DVI, Å rhus, Denmark. Staff at Landskontoret for Fjerkr æ r å dgivning, Å rhus, Denmark. Staff at Danish Meat Research Institute, Roskilde, Denmark. Participating farmers.