All bacteria / virus / prions Flashcards
Staphylococcus Aureus
S Aureus is commonly found in humans and animals. True or False?
True. In humans, commonly found on nose and skin
Staphylococcus Aureus
What are the characteristics of S.Aureus?
- gram positive or negative
- spore forming or not
- What conditions does it survive in (temp,pH, salt)
- what metabolites it produce
- Gram positive cocci
- Most resistant, non-spore-forming species : grow in wide range of temperatures, pH and salt resistant (10%)
- Produce highly heat-stable enterotoxins (proteins) that are not destoryed by proteases (trypsin, pepsin) and remain intact in GI tract.
Staphylococcus Aureus
For S Aureus, what is the
- disease type
- infectious dose
- incubation period
- illness period
- Intoxication
- < 10 micrograms of enterotoxin (around 10^5 organisms / g of food)
- Incubation period : 1/2 to 6h
- illness period : few hours - 1 day
Staphylococcus Aureus
What are the 2 main transmission routes for S Auerus?
- Person to person : contamination of food from infected workers with S Auerus strains that can produce toxins on their skin
- Temperature abuse : improper storage temperatures, cooling not rapid enough
Staphylococcus Aureus
What are the symptoms for S Aureus for
1. mild cases [4]
2. severe cases [4]
Mild cases
- diarrhoea, nausea + vomit, abdominal pain
Severe cases
- Dehydration (from diarrhoea and vomiting)
- Headache
- Muscle cramps
-** Change in blood pressure and pulse rate**
Staphylococcus Aureus
What is the main category of food that is incriminated for S Aureus?
Foods that have considerable preparation steps.
Includes a wide range of RTE / chilled products
- Meat and meat products
- Poultry and egg products
- Milk and dairy products
- Salads
- Bakery products
Staphylococcus Aureus
What are 5 ways to diagnose S Aureus?
- Serologicalmethods to determine enterotoxicity (For S.Auereus strains)
- Detection of enterotoxin
- Detecting presence of large no of coagulase positive S Aureus from contaminated food samples
- Interviews with victims
- gathering of epidemiological data in case of outbreaks
Staphylococcus Aureus
Why is detecting presence of large no of coagulase positive S Aureus from contaminated food samples not a good way to diagnose it?
In some cases, Staph Aureus may not be detected as it may have been killed through cooking. However, absence of S Aureus does not mean that it is NOT the cause of disease, since toxin is present in the food. It is more important to detect toxin
Staphylococcus Aureus
How to detect enterotoxin in S Aureus? [2]
- Concetrate toxin by restoring serological activity and identify with antiserum
- Rapid methods to detect 1 nanogram toxin / g food (v low LOD) : using antibodies such as ELISA
C. Perfringens
Is clostridium perfringens
1. Gram positive or negative
2. Spore forming or not
Gram positive, spore forming
C. Perfringens
Clostridium perfringens is widely distributed in the environment. True or False?
True
C. Perfringens
where can C. Perfringens and its spores be naturally found?
C.Perfringens : intestines of humans and many domestic animals
Spores : soil / sediments / areas subject to human or animal faecal pollution
C. Perfringens
What is the:
1. Disease type (infection? intoxication?)
2. Infective dose (hint : per g of food)
3. Infection / illness period
- Infection
- 108 vegetative cells ;; for 100 g of food : 106 cells / g of food
- Symptoms last for 1-2 weeks in vulnerable populations
C. Perfringens
What are the 2 different types of disease related to C. Perfringens?
- Perfringens food poisoning (gastroenteritis) – infection. Type A strands produce Clostridium Perfringens Enterotoxin (CPE)
- Pig bel disease – Type C strands produce beta toxin (intoxication)
Pig bel disease – pig belly – belly swell
C. Perfringens
What are the symptoms for C.
Perfringens food poisoning [2] and whats the incubation period?
Gastroenteritis
- watery diarrhea and abdominal cramps 8-12h after consumption of affected food
C. Perfringens
What are the symptoms for C.Perfringens for
Pig Bel disease? [4, 2 common 2 characteristic]
- Swollen belly (like pig -> pig bel)
- Necrosis (death) of small intestine
- Diarrhoea
- Vomit
C. Perfringens
What are the incriminated foods for C. Perfringens?
Cooked meat products, especially with gravy. (catered food)
C. Perfringens
What is the main cause behind C. Perfringens food poisoning?
Due to temperature abuse of cooked foods, causing rapid multiplication and formation of spores.
- Spores survive cooking, germinate after heat shock. and multiply rapidly due to slow cooling / improper storage temp.
C. Perfringens
how to diagnose C.Perfrignens? [3]
1) Symptoms and history of eating temperature abused foods
Confirmation
2) Detecting CPE toxin in faeces of patients through serological assays
3) Detection of presence of large qty of organisms in contaminated food or patient’s stools
Bacillus cerus
Is bacillus cerus :
- gram positive or negative
- spore forming or not
- Gram positive
- Spore forming
(Usually gram +ve = spore forming except for staph aureus : gram +ve BUT not spore forming)
Bacillus cerus
What is the disease type for Bacillus cerus? (Infection / intoxication / toxicoinfection)
Intoxication, ingestion of pre-formed toxin
Bacillus cerus
What are the 2 types of disease that Bacillus cerus can cause? Which type is more common?
- Emetic type (more common)
- Diarrhoeal type
Bacillus cerus
For the emetic type B. cerus, it is caused by the ingestion of?
Low molecular weight heat stable peptide known as cereulide
- heat-resistant emetic toxin
Bacillus cerus
What are the symptoms of emetic type B.cereus? [4] What is the incubation period and length of intoxication?
Similar to S. Auerus intoxication : Nausea and vomitting (occasional cramps and diarrhoea)
- 1/2 - 6h after ingestion of food, with occassional cramps and diarrhoea.
- Length of intoxication : < 24h (v fast)
Bacillus cerus
What is the main type of food related to emetic type B.Cereus? What is the main cause of illness?
“Chinese fried rice syndrome”
- starchy foods like rice, noodles
- Due to improper storage of cooked rice (at room temp), and reheating of cooked rice for fried rice but toxin already formed.
Bacillus cerus
The diarrhoeal type of B.Cereus affects what kinds of foods?
A wide variety of foods
- Meats, milk, vege, fish
- Food mixtures like sauces, puddings, soups
Bacillus cerus
What are the 3 ways of confirmation of B Cerus in foods?
- Isolation of strains of the same serotype from food and faeces / vomitus of patient
- Isolation of large numbers of common food poisoning B Cereus serotype in food / faeces / vomitus
- Isolation of B Cereus from food and determing enterotoxigenicity by serological / biological tests
Vibrio Parahaemolyticus
Bacillus cerus
What is a way to diagnose the emetic form of B Cerus?
Rapid onset of vomitting symptoms + history of food consumption
Vibrio Parahaemolyticus
All forms of Vibrio Parahaemolyticus are pathogenic. True or False?
False, they occur naturally in marine environments, and some strains are non-pathogenic.
Vibrio Parahaemolyticus
What is the
1. Disease type
2. Infectious dose
3. Incubation period
4. Illness period
For V.Parahaemolyticus?
- Infection
- 10^6 organisms
- Incubation period : average of 15h (:O thats fast, 4-96h)
- Illness period : 2.5 days
Vibrio Parahaemolyticus
What are the symptoms of V Parahaemolyticus?
V Parahaemolyticus gastroenteritis
- Nausea, vomiting, abdominal cramps, watery diarrhoea (ocean = water)
- Headache, fever, chills (the sea v cold 🥶)
Vibrio Parahaemolyticus
What are the incriminated foods?
Oysters, clams and raw fish (seafood)
Vibrio Parahaemolyticus
What are the main reasons for V Parahaemolyticus gastroenteritis? [2]
- Raw, undercooked or recontaminated fish and shellfish
- Improper refrigeration, temp abuse
Vibrio Parahaemolyticus
How to:
1. Diagnose
2. Analyse foods
for V Parahaemolyticus
- Diagnosis : Isolation of organism from patient’s stool
- Food analysis : cultivation of organism + demonstrate pathogenicity (bc it is present doesn’t mean it caused the illness! There are non-pathogenic forms too!!)
Hepatitis A
What is the infective dose and incubation period for Hep A?
- Infectious dose : 10-100 particles
- Incubation period : average of** 30 days (1 month)**
Hepatitis A
What are the common symptoms [4= 2+2] and characteristic symptoms [2] of Hep A?
Symptoms
- Sudden onset of fever, nausea, abdominal discomfort, loss of appetite
- Characterisitic : dark urine, jaundice
iLLNESS IS MILD
Hepatitis A
Hep A affects children very seriously. True or False?
How long does recovery in children?
False.
- Most are asymptomatic
- Recovery 1-2 weeks
Hepatitis A
Is Hep A more/less serious in adults as compared to children? How long does Hep A symptoms last in adults?
- More serious in adults
- Lasts for < 2 months, but may last as long as** 6 months** in some
Hepatitis A
What are the incriminated foods (or categories) for Hep A? [5]
Contaminated water/ foods (raw / RTE)
- Shellfish : oysters and clams –> MOST COMMON
- cold cuts and sandwiches (RTE)
- Fruit and fruit juice
- Vegetables and salads
- Milk and milk products
Oral faecal route
Hepatitis A
What is the main transmission routes for Hep A? [2]
1) Oral-faecal route
- Uninfected person ingests food or water that has been contaminated with the faeces of an infected person.
2) Person to person
- Food contaminated by infected workers in food plants
How to diagnose Hep A? [4]
1) Presence of immunoglobulin M, igM, (antibody to fight off Hep A virus) during acute / early stage + presence of igG indicates old infection
2) Virus-specific diagnosis with serological test
3) Commericially available test kits
4) Clinical signs and food consumption history
Hepatitis A
How to treat hepatitis A? Will one get immunity after Hep A infection?
To treat Hep A, can get HAV (Hep A Virus) vaccination within 2 weeks of exposure (stimulates body to produce specific antibodies to fight virus)
Yes, one can get lifelong immunity aft hep A infection
Hepatitis A
How to prevent / control Hep A? [4]
Not in lect slides but yea
- Maintain proper hygiene
- Sick workers take leave
- Ensure safe supply of non-contaminated foods.
- Do not eat raw oysters
Norovirus
What are the characterisitics of norovirus?
- Strand
- Envelope
- Geno groups
- Single stranded RNA
- Non-enveloped
- 5 geno groups : Group 1 - 5
Norovirus
What is the
1. Disease type
2. Infectious dose
3. Incubation period
4. Illness period
for norovirus?
- Infection
- 10 particles
- 24-48h incubation period
- illness last for 2-3 days (48-72 h)
Norovirus
What are the 3 main routes of transmission for norovirus?
- Oral faecal route (ingestion of contaminated foods)
- Person to person (poor hygiene of infected person, in contact with infected person’s faecal matter)
- Air transmission - inhalation of virus particles when someone vomit on surface like table / floor.
Norovirus
What are the characteristic symptoms for norovirus? [3] What is the most common complication?
- Explosive diarrhea and/or vomiting
- low-grade fever
- headache
- Most common complication : dehydration
Norovirus
What are the 3 main types of incriminated foods for norovirus?
- Contaminated water
- RTE foods contaminated by infected workers
- Foods contaminated at source
- Oysters
- Fruits and vege (contaminated water used to irrigate the crops)
Norovirus
How to diagnose/detect norovirus? [2]
- Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR)
- Detection of Norovirus RNA in contaminated food / stool or vomitus (within 48-72h of onset of symptoms) of infected person / environmental swabs
Norovirus
Norovirus can be totally prevented. True or False?
False. Norovirus is resistant to environmental changes
- resistant to chemical disinfectants like chlorine
Norovirus
What are 2 main control measures to control norovirus?
1. Provision of safe food and water
2. Simple measures
- Ensuring good hygiene and proper handling of foods
- Infected workers to take leave
- Environmental disinfection
Zoonoses - Salmonella spp
Salmonella spp / Salmonella Enteritidis is commonly found in nature. True or False? If yes, where is it found?
True.
Salmonella spp can be found in:
1. intestinal tracts of humans and animals (livestock, wildlife and pets)
2. The environment
Zoonoses - Salmonella spp
What is the
1. disease type
2. incubation period
3. illness period
for Salmonella spp?
- Infection
- incubation period of 12-36 h
- 4-7 days illness period
Although its infection, for ZOONOTIC diseases, incubation period is way shorter, < 48h
Zoonoses - Salmonella spp
What are the 2 main transmission routes for Salmonellosis?
- oral-fecal route
- cross contamination from processing environment
Zoonoses - Salmonella spp
For the oral fecal route, is it from animal to person / person to person?
1) Animal to person
- From faeces of animals (in raw meat / faeces on egg shells or pets)
- Consumption of raw and undercooked egg or products
2) Person to person
- in contact with faecal matter of other people due to poor hygiene (nvr wash hand properly after gg toilet)
Zoonoses - Salmonella spp
For the cross contamination leading to Salmonellosis, what are the 3 main ways it may spread in a processing facility?
- Infected food handlers have poor hygiene and infect the food with their faecal matter
- Cross contamination of raw and cooked foods
- Cross contamination from surfaces
Zoonoses - Salmonella spp
What are the 5 common symptoms of Salmonellosis?
1. Fever
2. Abdominal pain
3. Diarrhoea
4. Nausea
5. Vomitting
12-36 h after eating food
Zoonoses - Salmonella spp
What are 3 potential complications / characteristic symptoms of Salmonellosis?
- Dehydration + electrolyte imbalance
- Reactive arthritis
- Blood poisoning (septicaemia)
Zoonoses - Salmonella spp
- Salmonellosis is common in which groups of people?
- Salmonellosis has a high mortality rate, thus it is an important disease.True or False?
- Young, Old, Immunocompromised (YOPI without the P)
- False. It has <1% mortality rate but it is very widespread
Zoonoses - Salmonella spp
Salmonellosis is usually linked to what 2 broad categories of foods?
1) Animal products
- raw meat, poultry, eggs, milk
2) Fresh produce (because Salmonella is also present in envt)
Zoonoses - Salmonella spp
What 3 other products can cause Salmonellosis?
- Cocoa and chocolate
- Peanut butter
- Spices
Zoonoses - Salmonella spp
Only certain serotypes of Salmonella can cause disease in man. True or False?
False, all serotypes can cause disease in man.
Zoonoses - Salmonella spp
Prevention and control strategies for Salmonellosis only occurs at the processing stage in the farm to fork process. True or False?
False, it occurs from farm to fork
Zoonoses - Salmonella spp
What control measures can be put in place at the farms or during import of high risk products? [3]
- Obtain eggs from Salmonella free farms (locally)
- Foreign farms should have certification
- In farms, have low temperature pasteurisation of eggs, such that it is sufficient to kill Salmonella spp but insufficient to cook the eggs
Zoonoses - Salmonella spp
What are some control methods in processing facility to reduce the risk Salmonellosis?
HACCP :))))
1. Monitoring program
2. Refrigeration of raw meats / high risk products and proper handling (handling and storage)
3. Food handlers to have good hygiene practices
4. No cross contamination of foods
Can have regulatory measures also like SSOP etcetc, disinfecting surfaces
Zoonoses - Salmonella spp
How can consumers reduce their own risk of contracting Salmonellsis ? [2]
- Avoid eating raw meat, milk and fischery products + cook food well
- Wash fruits and vegetables if eaten raw, peel if possible
Zoonoses - Campylobacter jejuni
Campylobacter is normally / commonly present in?
Intestinal flora of warm blooded animals, esp chickens.
Zoonoses - Campylobacter jejuni
C. jejuni is sensitive to the processing envrionmen in terms of :
1. temp
2. pH
3. salt
4. disinfectants
True or False?
(Also state temp, pH, salt conditions)
True.
1. Tolerant to chilling, freezing will reduce but not eliminate it BUT sensitive to heat and drying
2. inhibited at pH < 4.9
3. inhibited at low salt conc (2%)
4. sensitive to disinfectants
Zoonoses - Campylobacter jejuni
What is the :
1. disease type
2. infective dose
3. incubation period
4. infection period
for campylobacteriosis?
- Infection
- 500 cells
- Incubation period : 2-5 days after consumption
- Infection period 2-10 days
Zoonoses - Campylobacter jejuni
What are the common symptoms [4] for campylobacteriosis and characterisitic symptom for the young/ weak?
Common symptoms:
1. Fever
2. Nausea (w seldom vomit)
3. Diarrhoea
4. Abdominal pain
Characterisitic symptom for young and weak:
- mild to severe bloody diarrhoea
Zoonoses - Campylobacter jejuni
What are 3 long term complications for campylobacter jejuni?
- Reactive arthitis (joint inflammation) due to GI tract inflammation : 2%
- Guillain Barre Syndrome, GBS - myelin sheath broken and no signal transmission between nerves, muscles cannot move, including respiratory muscles -> cannot breathe and die(1/2000 cases)
- Blood poisoning, septicaemia(1.5/1000 cases)
Zoonoses - Campylobacter jejuni
What are the 2 main categories of transmission modes for C.jejuni?
- Oral faecal
- Zoonotic transmission
Zoonoses - Campylobacter jejuni
In the tranmission of C. Jejuni, what are the 3 sources in the oral faecal route?
- Surface waters from rivers and lakes – when people go CAMPing and drink unsafe water
- Consumption of raw chicken and turkeys (or milk/beef/pork)
- Contamination from infected animal (faecal matter from infected pet or in raw meat -> if slaughterhouse no proper hygiene practice)
Note:Cross contamination from infected human faecal matter due to poor hygiene – can theoretically occur but RARE, since it predominantly resides in GI tract of animals (vs others like salmonella;; reside in both human and animal GI tract)
Zoonoses - Campylobacter jejuni
In the zoonotic transmission of C. Jejuni, does it occur from human to animal or animal to human?
How does zoonotic transmission occcur and how to prevent it?
Goes both ways, although mostly is from animals to humans.
Zoonotic transmission occurs through pets, and can be prevented by not allowing pets into kitchen when handling food. (C.Jejuni found in intestines of warm blooded animals)
Zoonoses - Campylobacter jejuni
How to
1. diagnose
2. treat
disease from C.Jejuni?
- Diagnose : isolation and cultivation of C.Jejuni from stool sample
- Treatment : self-limiting
Zoonoses - Campylobacter jejuni
What are the 3 main categories of food that is affected by C.Jejuni?
- Surface water
- Poultry products - chicken and turkey
- Raw beef, milk, pork
Zoonoses - Campylobacter jejuni
What are 3 control measures for C.Jejuni?
- Obtain safe supply of water from approved sources
- Cook / pasteurise high risk products : raw milk, meat and poultry
- Maintain good personal hygiene practices, avoid cross contamination in kitchen and don’t allow pets into kitchen
Zoonoses - Avian influenza
Avian influenza has which 3 types? Which type is of concern?
- 3 types : type A,B,C
- Concerned with Type A
Zoonoses - Avian Influenza
Influenza Types (A/B/C) has subtypes. What are these subtypes classified on?
Haemagglutinin (H) and Neuraminidase (N) antigens.
Zoonoses - Avian Influenza
How many H subtypes and N subtypes are there in Type A influenza? How many different combinations are there in total?
H subtypes : 18
N subtypes : 11
Each virus can have unique combination of H and N subtypes (H1N1, H1N2….) and have 198 diff combinations in total (18 x 11)
Zoonoses - Avian Influenza
Domesticated birds are the natural reservoir for AI virus. True or False?
False. The main reservoir / natural carriers are wild waterfowls (migratory birds)
Zoonoses - Avian Influenza
How does the Avian Influenza (AI) spread among animals?
- AI is prevalent among bird species (wild waterfowl + domesticated species)
How it spreads :
- Migratory birds (wild waterfowl) may rest in water bodies when migrating from one end to another
- Other domesticated birds like ducks may go into the ponds and chill, and mingle with the migratory birds and get infected
- When the ducks return to the farm, they infect all the remaining chickens inside the farm
Zoonoses - Avian Influenza
AI viruses can be split into what 2 main categories? And which category are we more concerned with?
Categories
1. High pathogenicity Avian Influenza (HPAI)
2. Low pathogenicity Avian Influenza (LPAI)
- obviously, more concerned with HPAI, as it causes 90-100% mortality in poultry
- certain strands of LAPI can evolve into HPAI
Zoonoses - Avian Influenza
What 4 different H subtypes of HPAI of Type A influenza virus is of most concern to us?
H1, H5, H7, H9
Zoonoses - Avian Influenza
What is the:
1. disease type
2. incubation period
3. illness period
caused by AI in man?
- (viral) infection
- incubation period : 2 days
- illness period : 4-7 days, but cough may persist for weeks
Zoonoses - Avian Influenza
What are the common symptoms of AI? [3+3 = 6 in total]
- Common flu symptoms : fever, cough, sore throat
- Diarrhea, abdominal pain, vomit
Zoonoses - Avian Influenza
What are 3 characterisitic symptoms / complications of AI?
- Conjunctvitis (eye infection)
- Pneumonia / acute respiratory distress
- Multiple organ failure and other life threatening complications
- Virus invades cells, and proteases unzip it and split the HA cleavage site → virus able to attack body cells
Zoonoses - Avian Influenza
What is the main transmission mode of AI virus?
Direct transmission from infected animal to human, when human are in close proximity with infected/dead chicken or contaminated surfaces w their faecal matter.
Zoonoses - Avian Influenza
In what 3 ways can direct transmission of AI virus occur?
- Inhalation of virus particles from air
- Through touching contaminated surfaces (with faecal matter of chicken), then touching eyes / nose
- Through direct contact with livestock / chickens, especially for abattoir workers (slaughterhouse) where they need to handle chickens and kill them.
Zoonoses - Avian Influenza
What is the treatment for Avian influenza?
4 types of antiviral drugs
Zoonoses - Avian Influenza
Name the 4 antiviral drugs used to combat AI.
- Amantadine
- Rimatadine
- Zanamivir
- Oseltamivir
Name the characteristics of Listeria Monocytogenes.
- Gram ? Spore?
- Serotypes and which is present in most outbreaks?
- Found commonly in?
- Gram positive rod, non spore-forming
- 13 serotypes ; 5 of which are of concern (1a,2a,1b,2b,4d)
- Most commonly found in soil. moist environments. As well as healthy human and animals, especially small ruminants like sheep.
Is Listeria monocytogenes a resistant bacteria? How to inhibit it?
Yes. It is resistant to extreme environment, survives well in :
- 10 % salt
- wide range of pH, acidic to neutral (5.5-9.0)
<br></br>
Listeria can be inhibited by high temp, particularly pasteurisation
What are the 2 main transmission route of Listeria Monocytogenes?
- Oral faecal route : contmainated from animal or human faecal matter.
- Cross contamination due to biofilm formation on surfaces.
Invasive illness - vulnerable groups
For Listeria Monocytogenes, what is the
- incubation period
- symptoms [3]
in vulnerable groups ?
Incubation period : 3 days - 3 months
<br></br>
Symptoms
1. Septicaemia (blood poisoning)
2. Meningitis (brain inflammation)
3. Miscarriage, still birth,** serious health issues in newborns** for pregnant women, > 80% fatality rate
Non-invasive illness - normal adults
For Listeria Monocytogenes, what is the
- incubation period
- symptoms [4]
in healthy adults?
Incubation period : 2-3 days
<br></br>
Symptoms : flu-like symptoms
1. fever and chills
2. nausea
3. vomit
4. SOMETIMES diarrhoea
Since Listeria Monocytogenes is not common, why is it still important?
High fatality rate in vulnerable groups (YOPI), > 50% fatality rate
What are the 4 main groups of incriminated foods for Listeria Monocytogenes?
- Dairy products : soft cheese, raw milk (sheep)
- RTE foods
- Raw / smoked fish
- Deli meats
What are the implications for Listeria in RTE foods?
Listeria monocytogenes can survive and grow in RTE foods, even under refrigeration. Long storage times in refrigerator increase the risk of contamination, making RTE foods a significant concern for vulnerable populations, especially since they are consumed without further cooking.
What are the control [2] and prevention [3] measures for Listeria Monocytogenes?
Control measures
1. Refrigeration temp should be at 1°C
2. Cooking and pasteurisation of raw milk etc
<br></br>
Prevention measures
1. Prevent cross contamination of RTE and raw foods
2. Prevent growth of Listeria through regular disinfection.
3. Regulatory measures
- reject positive consignments and suspend plant till disinfected
- Regular monitoring systems (HACCP) etc
