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1 Fd Micrbilgy MODULE 4 - FOODBORNE BACTERIAL PATHOGENS AND THERMAL DESTRUCTION Objective On cmpletin f this mdule, participants will be able t: Identify the primary public health cntrls fr sme bacteria that are majr causes f fdbrne illness Define D value Relate the D value t the cking temperatures required by the Fd Rules Define pasteurizatin as nrmally used fr fd Overview Mdules 1 and 2 prvided an verview f micrbilgy. This mdule will be specific and discuss varius fdbrne bacterial pathgens. The bacterial pathgens can be brken int tw grups: (1) gram-negative rds, and (2) gram-psitive rds and ccci. The pathgens within each grup have sme similarities in additin t the way they stain. Fr example, gram negative rds are nnspre frmers and tend t have a fecal surce. On the ther hand, gram-psitive rds and ccci can be spre frmers and are typically assciated with envirnmental surces like sil and sediments. Gram Negative Rds The gram-negative rds cvered in this mdule are: Campylbacter jejuni, Yersinia spp., Salmnella spp., Shigella spp., Escherichia cli and Vibri spp., Plesimnas shigellides Gram Psitive Rds The gram-psitive rds and ccci cvered in this mdule are: Bacillus cereus, Listeria mncytgenes, Clstridium perfingens, Clstridium btulinum, Staphylcccus, Streptcccus, Aermnas hydrphila, Miscellaneus enterics BETC participants are nt expected t knw micrrganisms by Gram type, this is prvided fr infrmatin nly. 1

2 Fd Micrbilgy This sectin cntains backgrund infrmatin n specific fdbrne bacterial pathgens. An understanding f the grwth characteristics and surces f bacterial pathgens in fds is essential t cnducting a hazard analysis f a fd prduct. The CONTROLS and RESERVOIR fr thse bacterial agents yu are mst likely t investigate as assciated with a fd brne illness are belw. The web address indicated fr each micrrganism is fr additinal infrmatin abut the micrrganism. Pathgenic bacteria Campylbacter jejuni CONTROLS FOR CAMPYLOBACTER JEJUNI: Sanitatin t prevent recntaminatin (including handwashing and preventin f crss cntaminatin); cking; pasteurizatin; water treatment RESERVOIR: Chickens; cws; flies; cats; puppies. Yersinia enterclitica and Yersinia pseudtuberculsis CONTROLS FOR YERSINIA: Sanitatin t prevent recntaminatin (including handwashing and preventin f crss cntaminatin); cking; pasteurizatin; water treatment; prper hlding temperatures. RESERVOIR: Animals and their feces; lakes; streams; vegetatin; sil; birds. Salmnella spp. CONTROLS FOR SALMONELLA: Sanitatin t prevent recntaminatin (including handwashing and preventin f crss cntaminatin); cking; pasteurizatin; prper hlding temperatures. RESERVOIR: Dmesticated animals and feces; water; sil; insects. Shigella spp. CONTROLS FOR SHIGELLA: Sanitatin t prevent recntaminatin (including handwashing and preventin f crss cntaminatin); cking; water treatment; prper hlding temperatures. RESERVOIR: Humans, fr all practical purpses. 2

3 Fd Micrbilgy Entervirulent Escherichia cli Grup (EEC Grup) The EHEC grup is the ne f mst interest fr Public Health Envirnmentalists; this grup includes E. cli O157:H7. The ther grups belw are presented fr infrmatin. Escherichia cli - entertxigenic (ETEC) Escherichia cli - enterinvasive (EIEC) Escherichia cli - enterpathgenic (EPEC) Escherichia cli O157:H7 enterhemrrhagic (EHEC) CONTROLS FOR EHEC: Sanitatin t prevent recntaminatin (including handwashing and preventin f crss cntaminatin); cking; pasteurizatin; persnal hygiene; prper hlding temperatures; preventing fecal cntaminatin f animal carcasses. RESERVOIR: Sme ruminants; e.g., cattle; sme ther animals. Can be spread persn-t-persn. Vibri chlerae O1 Vibri chlerae nn-o1 Vibri parahaemlyticus and ther vibris Vibri vulnificus NOTE THE CASE FATALITY RATE FOR V. VULNIFICUS DISEASE IS 50%. ALSO, V. VULNIFICUS IS A NATURAL COMPONENT OF WARM MARINE WATERS, IT IS NOT AN INDICATOR OF, OR ASSOCIATED WITH, POLLUTION OF THE SHELLFISH GROWING WATERS. CONTROLS FOR VIBRIOS: Cking; preventin f recntaminatin; preventin f time/temperature abuse; cntrl prduct surce. RESERVOIR: Estuarine waters. Plesimnas shigellides Bacillus cereus CONTROLS FOR BACILLUS CEREUS: Refrigeratin. RESERVOIR: Widely distributed in the envirnment. Listeria mncytgenes CONTROLS FOR LISTERIA MONOCYTOGENES: Sanitatin t prevent recntaminatin frm the envirnment; cking; pasteurizatin. RESERVOIR: Sil; ther envirnmental surces. 3

4 Fd Micrbilgy Clstridium perfringens CONTROLS FOR C. PERFRINGENS: Prper cling, hlding, and reheating; educatin f fd handlers. RESERVOIR: Humans; dmestic and feral animals; sil; sediment. Clstridium btulinum NOTE THAT C. BOTULINUM TOXIN IS A NEUROTOXIN; ALSO NOTE THE ASSOCIATED FOODS AND INFECTIVE DOSE. CONTROLS FOR C. BOTULINUM: Destructin f spres; thermal prcessing; apprved surce. RESERVOIR: Sil; fresh-water and marine sediments; fish; mammals. Staphylcccus aureus NOTE THAT S. AUREUS TOXIN IS NOT DESTROYED BY ANY HEAT PROCESS ASSOCIATED WITH STANDARD COOKING TEMPERATURES. CONTROLS FOR S. AUREUS: Heating; prper emplyee hygiene; preventin f temperature abuse. RESERVOIR: Primarily humans; but als animals; air; dust; sewage; water. Streptcccus Aermnas hydrphila and ther spp. Miscellaneus enterics IMPORTANT POINTS FOR PUBLIC HEALTH ENVIRONMENTALISTS: The cmmn CONTROLS fr any micrrganism are effective fr ther micrrganisms. That is, PREVENTION OF RECONTAMINATION as a step t cntrl Campylbacter jejuni will als be effective against cntaminatin by Yersinia r any ther micrrganisms fr which this is a cntrl. Prper handwashing t prevent cntaminatin by Salmnella will als prevent cntaminatin by Shigella spp. BETC participants are nt expected t knw details f specific micrrganisms; hwever general cntrl mechanisms shuld be knwn. That is, participants shuld knw that preventin f temperature abuse is a cmmn cntrl mechanism, they d nt have t knw which micrrganisms fr which it is a cntrl. Thermal destructin f bacteria Fr the temperatures we find in nrmal kitchen peratins, r even fd prcessing peratins, there is n such thing as micrbilgical zer. At a given temperature fr a given time, the numbers f bacteria are reduced by a 4

5 Fd Micrbilgy percentage amunt. The expnential reductin in numbers f bacteria is referred t by D values. D value indicates the time required t destry 90% f the bacterial cells at a given temperature. Fr example, yu hld a theretical pathgen at 180 F and start with 1,000,000 (10 6 ) cells. At the end f 8 minutes, the number f bacterial cells has been reduced t 100,000 (10 5 ), after anther 8 minutes t 10,000 (10 4 ) and after 8 mre minutes t 1,000 (10 3 ) and s n. This is a typical pattern fr bacterial destructin by heat; the bacteria die ff lgarithmically. The D value is given fr a particular temperature; in this example, D 180 = 8 minutes. Fr cking temperatures, the micrrganism usually used t determine D values is Salmnella. Reducing the number f Salmnella rganisms frm 10 6 t 10 1 is a 5D reductin. The cking temperatures f the Fd Rules are designed t achieve 145 F fr 15 secnds: 3D reductin (99.9%) 155 F fr 15 secnds: 5D reductin (99.999%) 165 F fr 15 secnds: 7D reductin ( %) The explanatin fr the higher cking temperature fr pultry is that the expected bacterial lad is higher and this time-temperature cmbinatin will reduce that higher lad t a safe, nn-infective level, nt just because Salmnella can be expected t be fund n raw chicken. Salmnella can be expected t be fund n any raw fd frm an animal surce; the determining factr fr a predesignated cking temperature is the expected numbers at which it can be fund. Fr mst fds, when a time-temperature cmbinatin achieves a 5D reductin in Salmnella sp., the fd has been pasteurized. Time must be cnsidered with temperature in determining the D reductin: the higher the terminal temperature, the less time the fd must be held at that temperature t achieve an equivalent kill. NOTE: Pasteurizatin as it refers t milk has a D value established by the Milk Rules (Pasteurized Milk Ordinance) and sme ther fds may have a very specific meaning f pasteurized. Cmmercial canning peratins must reach a time-temperature cmbinatin t give a 12D reductin. This can nly be dne under pressure cking and is referred t as being cmmercially sterile. There are still sme spres even in canned prducts that can becme vegetative when heat shcked, such as being stred at abve 140 F. 5

6 Fd Micrbilgy The Z value is als referred t when designing a thermal destructin prcess fr fd. The Z value is the temperature change needed t change the D value by ne lg. The Z value lets yu cmpare r cnvert the lethality f a perid f time at ne temperature t the lethality f the same length f time at anther temperature. Frm the D value example abve (D 180 = 8 minutes) it takes 8 minutes at 180 F t reduce the bacterial lad by ne lg. Fr ur theretical example then, we want t knw the temperature necessary t reduce the bacterial lad by ne lg when held fr 80 minutes (increase time by a factr f 10). If it takes 80 minutes at 165 F t reduce the same bacterial lad by ne lg, the Z value is 15 ( ). Different micrrganisms have different Z values and Z values can be influenced by the prducts that are being prcessed. 6