Foodborne Pathogens Flashcards
gram -ve bacteria
salmonella campbylobacter verocytotoxinigenic escherichia coli sheigella spp. yersinia enterocolitica vibrio spp.
gram +ve bacteria
listeria monocytogenes staphylococcus aureus clostridium perfringens clostridium botulinum bacillus cereus
2 types of infection
toxicoinfection
invasive infection
intoxification
chemical or poisonous plants/animals or fungii (mycotoxins), bacterial, algal (biotoxins)
diarrhoeic enterotoxins,neurotoxins
foodborne intoxificaiton
organism produces specific toxins/toxic metabolites in the food that is ingested (cl. botulimum (adults), staph.aureus, B. cereus (emetic syndrome)
foodborne infection
invasive infection- bacteria ingested, organism invades and penetrates intestinal mucosa- local enteric or systemic infection
toxico infection- bacteria ingested through food consumption, the organisms produces toxin while in intestinal tract- ecoli o157, vibrio cholerae, cl.perfringens, B. cereus (diarrhoeal)
cl. botulinum (infant botulism)
most common in UK
most deaths
campbylobacter salmonella yersinosis VTEC listeriosis (most deaths)
enterobacteriaceae (facultatively anaerobe), grame -ve pathogens
others
salmonella
yersinia enteroclitica
E.coli 0157
shigella
Other:
campbylobacter (micro-aerophilic)
vibrio spp (facultatively anaerobic)
what causes yersiniosis
yersinia enterocolitica
what was bubonic plague
yersinia pestis
characteristics of yersinia enterocolitica
gram -ve,non sprogenic, rods facultatively anaerobic non motile at 35-37, usually at 22-25 degrees temp range 1-44 (28-29 op) can grow 5-7% salt pH 4-4.7
infection routes for humans of yersinia enterolitica
common in throat, tonsils and faeces of pigs
also in water, soil and dogs
PIGS- most important source
raw, minced pork
direct transmission through faecal - oral route and asymptomatic carriers
yersiniosis
acute disease with fever and gastroenteritis, sometimes with blood diarrhoea infectious dose less than 10 to the 4 1-1.5 days incubation psedoapendicitis liver and other abscesses secondary complications
pigs and pork exposure of yersinia
biotype 4, serotype O:3asymptomatic carrriers
evisceration (handling heads, tonsils and tongue)
psycotroph
raw pork products (meat, tongue)
also beef and milk (not pasturised)
veg and dogs and cats and wild rodents
water ponds and lakes
control measures in the pre-harvest phase for yersinia
prevent intro into farm
prevent spread
stress management, genotype resistance
biosecurity- hygienic husbandry, identification and removal of seropositive from herd, clean water and prevention of faecal contamination of water and feed
control masures for yersinia in the harvest phase
categorise pig according to risk
slaughter- hea removal before carcass splitting and removal of tongue- separate line for handling and inspection
avoid palpation and incision during inspection
tie rectum
control measures for yersinia in the post harvest phase
maintain cold chain (psyoctropic nature) pasurise cross contamination raw pork separate from other foods proper cooking (72 degrees 2-3 mins) personal hygiene cleaning and disinfection
3 vibrio species
vibrio cholerae
vibrio parahaemolyticus
vibrio vulnificus
vibrio cholerae
facultatively anaerobe halophilics
alkalphilic
straight or curved motile rods
seawater required for survival and growth
min 10-19 degrees in water
primary source= faecally contaminated water- marine water and estuaries
cause of cholera
incubation= 6hrs- 5 days
toxico infection
10 to the 6 infectious dose (high)
symptoms of cholerae
profuse watery diarrhoea- intensive up to 10L a day
severe abdominal pain and vomitting
fluid loss - can lead to severe dehration and acidosis , shock and circulatory collapse
death in a few hours if not rehydrated
sources of vibrio cholerae
poor santiation, contaminated water for food or drining
shellfish- filtrate seawater nd concentrate V. cholerae
raw and lightly cooked seafood
vibrio parahaemolyticus
similar affects to V. cholearae invades gut epithelial cells- haemolytic cytotoxin leading to diarrhoea similar sources incubation- 12-24hrs milder sysmptoms self limiting
vibrio vulnificus
similar to V. cholerae
similar sources
16-38hrs incubation
severe symptoms (septacaemia, necrotic skin lesions, death)
low infection dose 100 cells
simialr controls
liver disease or chronic disease no eat raw shellfish particulalry oysters
listeria monocytogenes
invasive infection listeriosis
main sources= animal instesitines and human
ubiquitous in the environment
working surfaces in food industry (persistent biofilms which are a source of contamination)
characteristics of listeria monocytogenes
motile rod at 20-25 degrees, non motile at 37 degrees facultative anaerobe prefers microaerophilic amosphere v resistant to drying growth - 4-45 degrees tolerate 10% NaCl tolerate low aw pH 4.1 to 9.6
sources of listeria
infectious dose more than 100 cells
regulalry consumed all the time ubiquitous
ready to eat (RTE) foods
raw milk, soft cheeses
post processing contamination of meat products after cooking (sliced deli products)
veg, salads, unpasteurized juices
invasive listeriosis
1-21 days incubation
GI mucosa- macrophages- bloodstream to CNS or fetus
immunocompromised (pregnant, aids, cancer, young and elderly)
septicaemia, menigitis, encephalits and sponatneous abortion
non- invasive listeriosis
enteric diarrhoea, mild fever, headacheand myalgia
short incubation 1-3 days
healthy- at risk for non-invasive liseriosis
toxgenic foodborne bacteria
intoxifcation due to toxin produced in the food
B. cereus, B. botulinum, S. aureus
generally toxin mediated posioning has amore rapid onset
min. toxic dose for:
S. aureus
C. botulimnum
B. cereus
10 to the 6
10 to 4- 10 to 5
10 to 7- 10 to 8
staphylococcus aureus
food borne intoxification staphyloenterotoxicosis
sources- skin, hands, anterior nares,skin lesions milk envrionment (dust, vegetation) non-motile facultative anaerobe resitance to desication 8 toxins 7-46 degrees 4-9.8 pH tolerate low aw tolerate 10% NaCl 1-6 hours incubation
symptoms of staph. aureus
6-24hrs
nasuea, vomitting, diarhoea, abdominal pain, no fever, collapse and dehrdation in severe
charcteristics of S. aureus toxin and how to cook
enterotoxin hgihly heat resitance (not inactivated by boilig at 100 degrees
growth in food necessary- large numbers required to produce enough toxin to cause illness
sources of staph. aureaus
poor hygiene food handling
skin infections, nostrils
post cooking contamination
clostridium botulism
spores found in variety of environments
canned, bottled or honey
germinating spores in anaerobic environment- lead to formation of vegetative cells that release a potent toxin
toxin- blocks nerve synapses causing paralysis and death
2 types of foodborne disease of C. botulinum
botulissm (intoxification) infant botulism (toxico-infection)
main sources of C.botulinum
soil, water, veg
animal and human faeces (asymptomatic)
which one of C.botulinum has the higher toxic dose- proteolytic or non-protyeoltic type?
which type has the lower decimal redcution time of spores at 100 degrees?
non-proteolytic
non-proteolytic type- less than 0.1 min, proteoyltic type 2.5 mins
symptoms of C.botulinum
nausea, vomitting, visual distrubances, vertigo
the botulinum cook
12D reeduction of C.botulinum spores 2.5 mins at 121degres
thermal resistance of C. botulinum toxins
toxin is sensitive to heat
treatment at 80 degrees rapidly denatures toxin
apporx 1000 x reduction of types a and b in 1 min
all toxins inactivated by heaing at 80 degrees for 30 mins
infant botulism
under 1 year not established gut microflora
prolifrates in GI tract, producing toxin
honey
neuromuscular symptoms similar to botulism- constipation , weak cry and respiratory distress
usually self limiting
what are the 2 sydromes of bacillus cereus
diarrhoeal and emetic syndrome
bacillus food poisoning- charactristics of bacteria
gram +ve spore forming motile rod
produces 2 toxins which are heat stable
associated with pulses and rice
thermal resistanance of B. cereus
highly resistant spores and toxins
- 02-0.06 mins at 121 degrees
- 3- 27 mins at 100 degrees
sources of B. cereus
soild, dust, water and vegetation
raw foods- cereals, dried veg, potatoes, milk, cream, rice and spices
cooked processed foods- toast, soups , cooked friend rice meals
emetic syndrome of B. cereus
high infectious dose (10 to the 5)
vegetative cells killed by cooking, spores not
if cooked rices not chilled spores germinate, bacteria grows and toxins produced- intoxification (ingestion of pre-formed toxin)
toxins are not destroyed by re-heating
emetic toxin induces rapid an dprofuse vomitting (15 mins after consumption
6-36hrs
diarrhoeal syndrome of B. cereus
spores of vegetative cells are ingested and toxin is produced in the GIT (toxico infection)
infectious dose high (10 to the 5 to 10 to the 8)
enteric toxin induces profuse , painful but short lived diarrhoea (4-6 hrs after consumption)
12-24hrs
control measures for B. cereus
prepare fod in small batches
chill cooked food rapidly in small quantities
stroe food under 5 or over 60
reheat cooked foods thoroughly to kill vegetative cells
clostrideum perfringens
type A starisn survive in GI tract of animal and soilds, water and dust
spores contaminate meat- may survive cooking
inadequately cooked and contaminated food coked in bul
xmas turkey
cooking activates C. perfringens spores which germinate in anaerboic conditions
gravy, logn cooking
ingestion leads to enterotoxin production in small intestine leading to diarrhoea
C. perfringens toxico infection
more than 10 to the 6 infection dose
incubation period 8-24hrs
ingested vegeative cells sporolate in SI, releasing entertoxin
sever abdominal pain with perfuse diarrhoea
last up to 2 days
