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:
1Heat as a disinfection method for poultry houses persistently infected with Salmonella – an outline of methods and resultsKim O. GradelDanmarks Veterinærinstitut, ÅrhusRengøring og Desinfektion af StaldeHotel Australia, Vejle, November 2003
2BackgroundIn 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.
3Disposition Laboratory tests Field tests Materials and methods Results ConclusionsField tests
4Heat tests related to general disinfection factors Micro-organismDisinfectantSurroundingsType”State/condition”Organic matterTemperaturepHBiofilmConcentrationHeat project
5Laboratory 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.
6Laboratory 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)
7Laboratory 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.
8Laboratory tests: overview of tests 0-hoursamples24-hoursamples48-hoursamples1 oCperhourFinal heatingtemperature20 oC20 oC10-daysamples72-hoursamples
11Laboratory tests: heating of high humidity samples
12Laboratory 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).
13Laboratory 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.
14Laboratory tests: overview of traditional Salmonella results
15Salmonella spp. detected on Rambach agar? Laboratory tests: correlations between results for Salmonella and E. coliE. coli detected?Salmonella spp. detected on Rambach agar?SUMYesNoPure culture of SalmonellaSalmonella- and non-SalmonellaGrowth of non-SalmonellaSterile89010116403222273489813230389
16Laboratory 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.
17Field testsAim: 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.
20Field tests: Overview of farms, houses and treatments HOUSE TYPETREATMENTNo. of Salmonella samplesChallenge samplesBeforeAfterAA1BarnSteam without F287288YesA2Battery302303BB1Steam with F100102B2Pulse fogging96NoB3Surface dis.CC1298308DD1289290EE1FF1150
21Field tests: results for Salmonella samples HOUSETREATMENTSalmonella (positive/sum)Non-sterile Rambach (positive/sum)RSBeforeAfterA1Steam, no F36/2876/288278/28794/2883.0AA2Steam,no F65/3020/303284/302114/3032.5B1Steam, +F0/1000/10241/1003/10214.1BB2Pulse fog.6/1000/9658/10033/961.7CB3Surface5/10068/1008/1008.5CDC137/2980/308180/2982/30892.9ED11/2890/29078/2891/29079.4FE140/308224/3089/30825.1DF116/1500/150146/1503/15048.7
26Field 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.
27Field tests: ”traditional” Danish heating: a typical temperature curve
29Field tests: ”traditional” heating: challenge samples and peak temperatures E. FaecalisFeedE. ColiEnterococciFaeces60-658/135/134/131/1355-6011/148/140/1428-556/95/92/9
30Field 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.
31Future 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
32Acknowledgments 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.