FB pathogens 2 Flashcards
What is teh primary source of Yersinia and primary source of VIBRIO species
Yersinia - PIG GUTS, pig intestines.
As it is an
Vibrio - primary sourse is HUMANS as it is harboured in our intestines, we introdcue to human food chain by faecal contaminated water (marine water, esturies)
BOTH ARE Enterobacteriaceae, primary source is where bacteria harboured = INTESTINE
Growth characteristics Vibrio cholerae
• Facultatively anaerobic
• halophilics (0.5-10% NaCl) – grow in high salt conditions
• alkaliphilic (pH 7.8-8.6) – v alkali
• straight or curved, motile rods
NaCl is required for survival and growth
• Primary source is faecally contaminated water
Enterobacteriaceae
include • Salmonella spp. • Yersinia enterocolitica • E. coli O157 (and other VTEC) • Shigella spp. vibrio cholerae
What does Vibrio cholerae cause?
Incubation and what type of infection?
CHOLERA
• profuse watery diarrhoea with ‘rice water’ stools , very intensive (up to 10 litres per day)
• Severe abdominal pain, vomiting
• Fluid loss can lead to severe dehydration, acidosis, shock and circulatory collapse
• Death in few hours if not rehydrated
• Incubation 6 h -5 days
Infection: toxico-infection: enterotoxin
Symptoms of Vibrio cholerae
- profuse watery diarrhoea with ‘rice water’ stools , very intensive (up to 10 litres per day)
- Severe abdominal pain, vomiting
- Fluid loss can lead to severe dehydration, acidosis, shock and circulatory collapse
- Death in few hours if not rehydrated
Sources cholera
- Poor sanitation, using faecal contaminated water for food preparation or drinking
- Shellfish– filtrate sear water and concentrate V. cholerae
- Seafood, including raw, lightly cooked or recontaminated shellfish or fish
CONTROL MEASURES: Vibrio cholerae
- Consume only potable water.
- Dispose of sewage correctly.
- Use only potable water in seafood harvesting and preparation.
- Do not harvest seafood from waters containing V. cholerae.
- Avoid raw seafoods
- Chill seafood to <4°C at harvest and after.
- Exclude infected individuals from handling food.
Other species of Vibrio?
other than V. cholerae
2. Vibrio parahaemolyticus:
3. Vibrio vulnificus:
Theres are less common and both simialr to V cholerae but less severe those with lvier disease shoudln’t eat raw shellfish (oysters)
Listeriosis caused by what bacteria
Gram what?
and morphology
Listeria monocytogenes
Gram positive
Rods with slightly curved shape
Primary source of listeriosis
ENVIRONMENT, widespread, everywhere, on computer, desk etc. We ingest daily base but usually low dose. Not enough to lead to disease.
Main sources of Listeriamonocytogenes?
– Animal intestines (asymptomatic carriers) and human
– ubiquitous in the environment: soil, water, plants, silage
– Working surfaces in the food industry (can form persistent biofilms which are source for contamination)
– Main disease when listeria gets into food, multiples and we ingest
Characteristics of listeria monocytogenes
• Motile rod at 20-25°C, non-motile at 37°C
Gram positive
• Facultative anaerobe, but prefers a microaerophilic atmosphere if O2 is present
• Very resistant to drying
• 4°C (can grow at 0°C, even -1.5°C) to 45°C psychrophilic
• tolerate 10% NaCl – halophilic to some extent
• tolerate low aw (water activity) – can grow on v dru food stuff
• pH: 4.1 to 9.6
• Easily killed at 72 degs as don’t ahve spores
Incubation of Listeria monocytogenes
How does invasive listeria it cause listeriosis?
- Incubation 1-21 days
- Invade GI mucosa macrophages – bloodstream to CNS, or fetus
- bad for Immuno Compromised individuals (pregnant women, AIDS patients, cancer patients, young, elderly)
- In pregnant women is the main cause od abortion and miscarriage along with toxoplasmosis
- It leads to Septicaemia, meningitis, encephalitis and spontaneous abortion
Non-invasive listeriosis
When ingest lot of listeria but able to recover
• Symptoms mostly local enteric diarrhoea, mild fever, headache and myalgia
• The disease has a short incubation period (1 to 3 days).
• Healthy individuals are at risk for non-invasive listeriosis
Control measures: listeriosis
- Use GHP and HACCP in food production.
- Immunocompromised individuals and other target populations should avoid high-risk foods.
- Pasteurize milk and dairy products; don’t consume unpasteurized products.
- Prevent cross-contamination and recontamination of heat-treated foods.
- Completely separate raw and cooked products during meat product manufacture.
- Re-heat ready-to-eat foods adequately.
Which bacteria is the main source humans?
Staphylococcus aureus and Vibrio cholerae
Which bacteria primary source is the environment?
Clostridium botulinum, C. perfringens, bacillus cereus
Soil, water, veg
What are toxigenic foodborne bacteria?
Bacteria that lead to intoxication due to toxin produced in the food depending on pathogenesis
Examples of toxigenic foodborne bacteria
- B. cereus
- Clostrium. botulinum
- SStaphylococcus aureus
Important to know about onset of toxin mediated poisoning
Has a more rapid onset generally
What is a toxin?
1. A poison found in some animals and plants and microorganisms 2. Mostly protein 3. Botulinum toxin is formed when C. botulinum grows, most toxic
Staphylococcus aureus and different types
There are 8 toxins but some aren’t food borne, cause respiratory/ skin/ pulmonary disease e.g. the very painful Bacterial caused staphylococcus dermatitis in equids
Staphylococcus aureus, what food borne disease does it cause and characteristics
- motile, atmosphere condition, where found etc
Not growth
• Foodborne intoxication staphyloenterotoxicosis • Non motile • Facultative anaerobe • Primary source: Environment and human • Main sources: o Skin, hands, anterior nares (30% to 50% people harbour S. aureus), skin lesions o Under nail o Milk (udder) o Environment (dust, vegetation) • Extremely resistant to desiccation HIGHLY HEAT RESISTANT
Staphylococcus aureus Optimal Growing conditions, pH, water activity
enterotoxin not produced <8°C
mesophilic, 37 degs
o 7-46°C
o pH: 4-9.8
o Tolerate low aw (water activity) can grow in dry environment
o Tolerate 10% NaCl (and produce enterotoxin A) halotolerant
How to tell different when looking at electron micrograph of Staphylococcus aureus vs streptococcus
o Cocci – round, Staphylococcus look like bunch of grapes vs streptococcus grow in a line
When does staphylococcus aureus cause illness?
- Growth of the pathogen in food is necessary, as large numbers of S. aureus (>105 CFU/g) are required to produce enough toxin in food to cause illness
- Sources: Poor hygiene amongst food handlers with skin infections, or those who carry the pathogen in their nostrils
- Post cooking contamination – poor hygeine
- Enterotoxin highly heat - resistant ( not inactivated by boiling at 100°C)
- Only can do is get rid of it
Control measures staphylococcus aureus
- Use good personal hygiene practices when handling foods.
- People with skin infections should not handle foods.
- Use GHP when handling foods.
- Chill cooked food rapidly in small quantities.
- Store cooked or heat-treated foods at <4°C or >60°C.
- Avoid extensive handling of foods.
- Avoid delays between cooking and eating.
BOTULISM caused by what bacteria
Clostridium botulinum
Characteristics clostridium botulinum
- what look on electron
- Red/ pink = spore survive in harsh environment
- Spores are found in a variety of environments
- Typically foodborne form caused by poorly canned, bottled foods or in honey
- Germinating spores in anaerobic environment lead to formation of vegetative cells that release a potent toxin: neurological toxin
- Toxin acts to block nerve synapsis causing paralysis and death
What disease does Clostridium botulinum bacteria cause?
Two types of foodborne diseases
- Botulism (intoxication in adults)
- Infant botulism (toxico-infection in babies up to 1
Primary and sec source of clostridium botulinum
• Primary- Main sources:
– PRIMARY: environment - Soil , water, vegetables
– Secondary source Animal and human faeces (asymptomatic)
Symptoms of clostridium botulinum
nausea, vomiting, visual disturbances, vertigo - gets into CNS
What is the difference between proteolytic and non-proteolytic botulism?
non proteolytic toxic dose is much higher than proteolytic
Onset and length of time BOTULISM disease
- onset - 12-36 hrs
2. duration days to several months
Thermal resistance of clostridium botulinum
toxin is sensitive to heat not like staphylo aureus
treatment at 80°C rapidly denatures toxin
approx. 1000 x reduction of types A and B in 1 minute
all toxins inactivated by heating at 80°C for 30 minutes
Infant botulism:
caused by clostridium botulinum bacteria
• Children under 1 year old do not have established gut microflora, so the pathogen may colonize more easily than in other individuals
• The organism is ingested and proliferates in the GIT, producing toxin
• Honey most common source- don’t give honey to babies and infants
• Their gut isn’t fully developed
• Neuromuscular symptoms similar to botulism, resulting in constipation, weak cry and respiratory distress
• Usually self limited not fatal
Control measures clostridium botulinum
- Avoid home canning of vegetables, fish and meats.
- Discard cans with faulty seals.
- Heat any suspect food to 80°C for 15 minutes to destroy toxin.
- Store home-canned foods at <3°C.
- Do not feed honey to babies or infants.
- Do not feed infants non-heat treated foods
What bacteria causes DIARRHOEAL AND EMETIC SYNDROME
Bacillus cereus
Rod like
Diarrhoeal (toxico) and Emetic (intoxication)
Bacillus cereus
- characteristics
food poisoning:
• Bacillus cereus (and to a lesser extent B. subtilis)
• Gram positive spore forming, motile rod
• Produces two toxins which are heat stable not like C botulinum
• Associated with pulses and rice (though any food may be affected)
• Two syndromes:
– Emetic syndrome - intoxication
– Diarrhoeal syndrome - toxicoinfection
Sources of Bacillus cereus
• soil, dust, water, vegetation • raw foods cereals dried vegetables potatoes milk cream rice spices • cooked / processed foods roast / fried meat products soups cooked / fried rice meals
Bacillus pathogenesis – emetic syndrome:
- Infectious dose high (>105), so pathogen growth in food required
- Leave food stuff for few days at room temp
- Vegetative cells killed by cooking, spores are not
- If cooked rice/pulses are not chilled, spores can germinate, bacteria grows and toxins produced – ingestion of pre-formed toxin (intoxication)
- Toxins are not destroyed by re-heating
- Emetic toxin induces rapid and profuse vomitting (around 15 minutes after consumption)
Bacillus pathogenesis – diarrhoeal syndrome
- Spores or vegetative cells are ingested, and toxin is produced in the GIT (toxicoinfection)
- Infectious dose high (105 - 108), so pathogen growth in food required
- Enteric toxin induces profuse, painful but short-lived diarrhoea (4-6 hours after consumption)
When will disease caused by Bacillus cereus cause emetic vsdiarrhoeal?
Emetic or diarrhoeal depends on when ingest food, leave for longer at RT will produce emough toxin to emetic. If not too long after cooking it will polferate in gut and lead to diarrhoeal
Characteristics DIARRHOEAL syndrome due to bacillus cereus:
Onset symptoms
Duration symptoms
Symptoms
Onset symptoms: 4-16 hrs
Duration symptoms: 12-24 hrs
Symptoms: abdominal pain, watery diarrhoea
Characteristics Emetic syndrome due to bacillus cereus:
Onset symptoms
Duration symptoms
Symptoms
Onset symptoms: 1-14 hrs
Duration symptoms: 6-36 hrs
Symptoms: nausea and vomiting
Control measures: bacillus cereus
- Prepare food in small batches
- Chill cooked food rapidly in small quantities
- Store cooked food at <5°C or >60°C
- Re-heat cooked foods thoroughly to kill vegetative cells, (toxins won’t be inactivated by reheating!)
Clostridium perfringens
characteristics
Type of disease caused
- Main type A toxin producing strains survive in animal GI tract (asymptomatic carriers) and soils, water, dust
- Spores are red, unlike C bitulimum spore here is smaller than body and located centrally or near the end of the chain
Causes: toxicoinfection
How does Clostridium perfringens cause disease?
- Spores contaminate meat-may survive cooking (thermo resistant) survive cooking
- Contaminated foods, cooked in bulk and inadequately cooled
- Cooking activates C. perfringens spores which germinate in the anaerobic conditions
- Foods containing gravy, with long slow cooking, in bulk and in advance
- Poorly stored cooked meat (e.g. Xmas Turkey) including meat re-heated in mass catering allows germination and massive numbers of vegetative cells (>106)
- Ingestion leads to enterotoxin production in small intestine leading to diarrhoea (toxicoinfection)
C. perfringens toxicoinfection:
incubation
recovery?
symptoms?
- Infection dose >106 (growth in the food)
- Incubation 8-24 h
- Ingested vegetative cells sporulate in the small intestine, releasing enterotoxin
- Severe abdominal pain with profuse diarrhoea
- The illness last for up to 2 days, recovery is usually complete (could be fatal in IC people)
Control measures Clostridium perfringens
- Cook food thoroughly to kill vegetative cells
- Chill cooked food, especially meat dishes, rapidly in small quantities
- Store cooked food at <5°C or >60°C to prevent growth
- Limit the storage interval for cooked food to reduce growth of survivors
- Reheat food to at least 75°C to kill vegetative cells and to inactivate toxin if pre-formed in food
