Foodborne Pathogens

Question 1

gram -ve bacteria

Answer 1

salmonella
campbylobacter
verocytotoxinigenic escherichia coli
sheigella spp.
yersinia enterocolitica
vibrio spp.

Question 2

gram +ve bacteria

Answer 2

listeria monocytogenes
staphylococcus aureus
clostridium perfringens
clostridium botulinum
bacillus cereus

Question 3

2 types of infection

Answer 3

toxicoinfection

invasive infection

Question 4

intoxification

Answer 4

chemical or poisonous plants/animals or fungii (mycotoxins), bacterial, algal (biotoxins)
diarrhoeic enterotoxins,neurotoxins

Question 5

foodborne intoxificaiton

Answer 5

organism produces specific toxins/toxic metabolites in the food that is ingested (cl. botulimum (adults), staph.aureus, B. cereus (emetic syndrome)

Question 6

foodborne infection

Answer 6

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)

Question 7

most common in UK

most deaths

Answer 7

campbylobacter
salmonella
yersinosis
VTEC
listeriosis (most deaths)

Question 8

enterobacteriaceae (facultatively anaerobe), grame -ve pathogens

others

Answer 8

salmonella
yersinia enteroclitica
E.coli 0157
shigella

Other:
campbylobacter (micro-aerophilic)
vibrio spp (facultatively anaerobic)

Question 9

what causes yersiniosis

Answer 9

yersinia enterocolitica

Question 10

what was bubonic plague

Answer 10

yersinia pestis

Question 11

characteristics of yersinia enterocolitica

Answer 11

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

Question 12

infection routes for humans of yersinia enterolitica

Answer 12

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

Question 13

yersiniosis

Answer 13

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

Question 14

pigs and pork exposure of yersinia

Answer 14

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

Question 15

control measures in the pre-harvest phase for yersinia

Answer 15

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

Question 16

control masures for yersinia in the harvest phase

Answer 16

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

Question 17

control measures for yersinia in the post harvest phase

Answer 17

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

Question 18

3 vibrio species

Answer 18

vibrio cholerae
vibrio parahaemolyticus
vibrio vulnificus

Question 19

vibrio cholerae

Answer 19

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

Question 20

cause of cholera

Answer 20

incubation= 6hrs- 5 days
toxico infection
10 to the 6 infectious dose (high)

Question 21

symptoms of cholerae

Answer 21

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

Question 22

sources of vibrio cholerae

Answer 22

poor santiation, contaminated water for food or drining
shellfish- filtrate seawater nd concentrate V. cholerae
raw and lightly cooked seafood

Question 23

vibrio parahaemolyticus

Answer 23

similar affects to V. cholearae
invades gut epithelial cells- haemolytic cytotoxin leading to diarrhoea
similar sources
incubation- 12-24hrs
milder sysmptoms
self limiting

Question 24

vibrio vulnificus

Answer 24

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

Question 25

listeria monocytogenes

Answer 25

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)

Question 26

characteristics of listeria monocytogenes

Answer 26

``` 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 ```

Question 27

sources of listeria

Answer 27

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

Question 28

invasive listeriosis

Answer 28

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

Question 29

non- invasive listeriosis

Answer 29

enteric diarrhoea, mild fever, headacheand myalgia short incubation 1-3 days healthy- at risk for non-invasive liseriosis

Question 30

toxgenic foodborne bacteria

Answer 30

intoxifcation due to toxin produced in the food B. cereus, B. botulinum, S. aureus generally toxin mediated posioning has amore rapid onset

Question 31

min. toxic dose for: S. aureus C. botulimnum B. cereus

Answer 31

10 to the 6 10 to 4- 10 to 5 10 to 7- 10 to 8

Question 32

staphylococcus aureus

Answer 32

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 ```

Question 33

symptoms of staph. aureus

Answer 33

6-24hrs | nasuea, vomitting, diarhoea, abdominal pain, no fever, collapse and dehrdation in severe

Question 34

charcteristics of S. aureus toxin and how to cook

Answer 34

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

Question 35

sources of staph. aureaus

Answer 35

poor hygiene food handling skin infections, nostrils post cooking contamination

Question 36

clostridium botulism

Answer 36

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

Question 37

2 types of foodborne disease of C. botulinum

Answer 37

``` botulissm (intoxification) infant botulism (toxico-infection) ```

Question 38

main sources of C.botulinum

Answer 38

soil, water, veg | animal and human faeces (asymptomatic)

Question 39

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?

Answer 39

non-proteolytic non-proteolytic type- less than 0.1 min, proteoyltic type 2.5 mins

Question 40

symptoms of C.botulinum

Answer 40

nausea, vomitting, visual distrubances, vertigo

Question 41

the botulinum cook

Answer 41

12D reeduction of C.botulinum spores 2.5 mins at 121degres

Question 42

thermal resistance of C. botulinum toxins

Answer 42

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

Question 43

infant botulism

Answer 43

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

Question 44

what are the 2 sydromes of bacillus cereus

Answer 44

diarrhoeal and emetic syndrome

Question 45

bacillus food poisoning- charactristics of bacteria

Answer 45

gram +ve spore forming motile rod produces 2 toxins which are heat stable associated with pulses and rice

Question 46

thermal resistanance of B. cereus

Answer 46

highly resistant spores and toxins 0. 02-0.06 mins at 121 degrees 0. 3- 27 mins at 100 degrees

Question 47

sources of B. cereus

Answer 47

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

Question 48

emetic syndrome of B. cereus

Answer 48

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

Question 49

diarrhoeal syndrome of B. cereus

Answer 49

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

Question 50

control measures for B. cereus

Answer 50

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

Question 51

clostrideum perfringens

Answer 51

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

Question 52

C. perfringens toxico infection

Answer 52

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