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MICR3215: Food Microbiology and Biotechnology > Foodborne Pathogens - Bacteria (MICR3215) > Flashcards

Foodborne Pathogens - Bacteria (MICR3215) Flashcards

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1
Q

What is foodborne infection?

A

Foodborne infection refers to the ingestion of food that contains living harmful microorganisms. These microorganisms multiply in the body, invade the intestinal walls, and cause illness. The time from ingestion to the onset of symptoms is relatively long because the infection is a result of the microorganisms’ growth in the body.

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2
Q

What are some examples of organisms that can cause foodborne infection?

A

Salmonella, Listeria monocytogenes, Campylobacter jejuni, and Yersinia enterocolitica

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3
Q

What is foodborne intoxication?

A

Foodborne intoxication refers to the ingestion of food that contains toxins produced by microorganisms, even if the microorganisms are no longer present in the food. The toxins present in the food are responsible for causing the illness.

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4
Q

Name some organisms that can cause foodborne intoxication.

A

Staphylococcus aureus, Bacillus cereus, and Clostridium botulinum

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5
Q

What is foodborne toxico-infection?

A

Foodborne toxico-infection occurs when a person consumes food containing a large number of noninvasive pathogens. These pathogens cause illness by producing toxins while growing in the intestines.

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6
Q

What microorganisms cause foodborne toxico-infection?

A

Clostridium perfringens, Bacillus cereus, E. coli 0157:H7, and Shigella.

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7
Q

What are the main characteristics of Campylobacter?

A
  • Gram-negative ,non-spore forming, curved, microaerophilic bacteria
  • Has a growth temp: 4 C to 45 C, optimum 42 C
  • pH range : 5.5 to 9.0
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8
Q

What species of Campylobacter are pathogenic?

A

C. jejuni, C. coli, C. lari, and C. upsaliensis

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9
Q

What are some examples of foods that are contaminated by Campylobacter?

A
  • unpasteurized milk and dairy products
  • raw meat/poultry
  • domestic pets
  • non - chlorinated or feacal contaminated water
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10
Q

What are some characteristics of the environment in which Campylobacter can survive?

A
  • modified atmosphere and vacuum packaging; optimal 3-5% oxygen and 2-10% carbon dioxide
  • chill temperatures (4 C)
  • Freezing does not kill viable cells
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11
Q

How is Campylobacter transmitted?

A
  • Feacal oral route
  • ingesting contaminated food or water
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12
Q

List some places where Campylobacter can be found.

A
  • gut of domestic and wild animals such as birds and ruminants (not found in the human intestines)
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13
Q

What is considered an infectious dose of Campylobacter and what are the Symptoms of infection?

A

Infectous dose: >/= 10^3 - 10^5 organisms
- There are 2-10 days incubation.

  • Symptoms last 1-4 days:
    1. bloody diarrhea
    2. fever
    3. nausea
    4. vomiting
    5. abdominal pain
    6. headache
    7. muscle pain
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14
Q

How can Campylobacter be detected and diagnosed?

A

Two ways:
1. Enumeration: direct plating on modified charcoal cefoperazone deoxycholate agar (mCCDA)
2. PCR Based methods: For the detection of highly conserved region of the 16S rRNA, whereas more specific loci are used for thr detection of Campylobacter species.

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15
Q

What prevention methods should be utilized for Campylobacter?

A
  • Thorough cooking of foods to minimum safe temperatures
  • use of only pasteurized milk and dairy products
  • elimination of animal waste as fertilizer
  • Good manufacturing and sanitation practices
  • Pasteurization of food
  • Use of approve water sources
  • Avoid cross contamination
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16
Q

What diseases are associated with Campylobacter infection?

A
  1. Campylobacter-related diarrhoea (self-limiting) characterized by symptoms such as bloody diarrhoea, fever, nausea, vomiting, abdominal pain, headache, and muscle pain
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17
Q

What is the infectious dose of Campylobacter and what is the incubation period?

A

The infectious dose of Campylobacter is generally ≥10^3 - 10^5 organisms, and the incubation period ranges from 2 to 10 days.

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18
Q

How can Campylobacter transmission be controlled?

A

Campylobacter can be controlled by: 1. freezing contaminated carcasses,
2. employing chemical decontamination methods such as chlorine, chlorine dioxide, acidified sodium chlorite, trisodium phosphate, and peroxy acids.
3. Using preservatives (e.g., NaCl, lactic acid, ascorbic acid) and sanitisers (e.g., chlorine, gamma, and UV radiation) can also help prevent Campylobacter contamination in food production.

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19
Q

What are the main characteristics of Salmonella bacteria?

A
  • gram-negative, anaerobic, facultative, non-sporulating rod-shaped bacterium
  • grows between 5°C to 45°C
  • minimum water activity of 0.95
  • pH growth range of 4.0-9.0.
  • widely distributed in nature and can be found in the intestinal tracts of birds, reptiles, farm animals, humans, and insects.
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20
Q

What are the sources of Salmonella contamination?

A
  • water, soil, insects, domestic and wild animals, and the human intestinal tract.
  • high protein foods such as meat, poultry, fish, and milk, as well as egg and egg products.
  • commercially prepared and packed foods and raw produce contaminated by faecal matter.
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21
Q

How is Salmonella diagnosed and detected?

A
  1. selective media
  2. Serological tests
  3. PCR
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22
Q

What diseases are caused by Salmonella and what are their symptoms?

A

Salmonellosis, which is a foodborne illness characterized by symptoms such as:
1. diarrhoea,
2. fever,
3. abdominal cramps.

Salmonella also causes Typhoid fever with symptoms:
1. Fever
2. Diarrhea
3. Abdominal pain
4. Headache

Also causes Enterocolitis

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23
Q

What populations are vulnerable to Salmonella infection?

A

infants, the elderly, and individuals with weakened immune systems.

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24
Q

What control measures can be taken to prevent Salmonella contamination?

A

Prevention of Salmonella contamination involves measures such as:
1. proper cooking and storage of food, 2. practising good hygiene
3. ensuring proper sanitation in food handling and processing.
4. cross-contamination prevention between raw and cooked foods.
5. In some cases, the use of antibiotics may be necessary for treating infected individuals.

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25
Q

What are the main characteristics of Shigella bacteria?

A
  • gram-negative,
  • anaerobic,
  • non-sporulating rods,
  • facultative anaerobes
  • There are four species of Shigella that cause bacillary dysentery:
    1. S. dysenteriae,
    2. S. flexneri,
    3. S. boydii,
    4. S. sonnei.
  • Shigella can produce Shiga toxin, an enterotoxin associated with severe symptoms.
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26
Q

How is Shigella transmitted?

A
  • mostly transmitted through the faecal-oral route due to poor personal hygiene.
  • It can contaminate food through human error in food handling, especially in unprocessed products.
  • Flies can also serve as vectors for Shigella.
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27
Q

How is Shigella diagnosed and what are the symptoms of shigellosis?

A
  • Diagnosis is done through:
    1. stool cultures
    2. serologic tests
  • Shigella spp has a low infective dose (as low as 10 cfu).
  • The symptoms of shigellosis include: 1. dysentery (varying from mild to severe),
    2. diarrhoea (which may be bloody),
    3. abdominal pain,
    4. fever,
    5. nausea,
    6. cramps,
    7. vomiting,
    8. chills,
    9. fatigue,
    10. dehydration.
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28
Q

What diseases are caused by Shigella?

A

Bacillary dysentery, also known as shigellosis.

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29
Q

How can Shigella be controlled and prevented?

A
  1. Proper personal hygiene, including regular hand-washing with soap and water, is crucial in preventing the transmission of Shigella.
  2. Adequate toilet facilities and sanitation practices are also important in reducing the spread of bacteria.
  3. Treating fresh or raw produce with antimicrobial substances,
  4. Avoiding cross-contamination from unprocessed to processed products
  5. Proper disposal and treatment of sewage.
  6. Chlorination of water (0.5-1.5 mg/L or 250 ppm chlorine) and gamma radiation (3 kGy)
30
Q

What are the risk groups for shigellosis?

A

Risk groups for shigellosis include:
1. urban poor,
2. immigrants,
3. Native Americans,
4. individuals in daycare centres,

31
Q

How can Campylobacter and Salmonella infections be prevented in food production?

A

Prevention of Campylobacter and Salmonella infections in food production involves several measures including:
1. implementing good manufacturing practices and sanitation protocols,
2. maintaining proper temperature controls during food processing,
3. ensuring thorough cooking of meat and poultry products,
4. pasteurization of milk and dairy products,
5. practising strict personal hygiene among food handlers.
6. proper cleaning and sanitization of food preparation surfaces and equipment are essential to prevent cross-contamination.

32
Q

What are the different classes of Escherichia coli?

A

Pathogenic E. coli includes five classes: 1. enterotoxigenic,
2. enteroinvasive,
3. enteropathogenic,
4. enteroaggregative,
5. enterohaemorrhagic.

33
Q

What disease does enterotoxigenic E. coli cause?

A

traveller’s diarrhoea

34
Q

What disease does enteroinvasive E. coli cause?

A

shigella-like dysentery

35
Q

What disease does enteropathogenic E. coli cause?

A

diarrhoea in developing countries and summer infant diarrhoea.

36
Q

What disease does enteroaggregative E. coli cause?

A

infant diarrhoea, and clumps of cells form aggregative clumps.

37
Q

What disease does enterohaemorrhagic E. coli, such as E. coli O157:H7, cause?

A

gastroenteritis and can lead to severe complications, including kidney failure and death.

38
Q

What are the key control measures for preventing E. coli contamination?

A
  • Good agricultural practices,
  • proper hygiene practices,
  • prevention of faecal-oral route contamination
  • Other measures include providing proper hand-washing facilities, eliminating animal wastes and manure as fertilizer, and implementing raw material control.
39
Q

What are the pathogenic species of Vibrio?

A

Vibrio cholerae,
Vibrio parahaemolyticus,
Vibrio vulnificus.

40
Q

What are the common sources of Vibrio contamination?

A
  • Vibrio is commonly found in salty waters and is more prevalent in warmer months.
  • V. vulnificus is most commonly found in oysters and shellfish from the Gulf of Mexico.
  • Foods involved in Vibrio infections are raw or partially cooked oysters and shellfish.
41
Q

What disease does Vibrio cholerae cause?

A

Cholera

42
Q

What disease do Vibrio parahaemolyticus and Vibrio vulnificus cause?

A

Vibrio parahaemolyticus and Vibrio vulnificus cause gastroenteritis.

43
Q

What are the control measures for Vibrio contamination?

A
  1. Good hygiene, sanitation, and agricultural practices are important for controlling Vibrio contamination.
  2. It is necessary to use approved water sources and practice good manufacturing practices.
  3. Pasteurization of food products, proper sanitation, and cooking to a minimum temperature of 160°F (71°C) is crucial.
  4. It is important to avoid eating raw or undercooked seafood and cross-contamination.
  5. Keeping all seafood frozen until ready to eat.
  6. Additionally, cholera outbreaks can be reduced by maintaining proper sanitation and sewage disposal systems.
44
Q

What are the key characteristics of Yersinia?

A
  • gram-negative,
  • rod-shaped,
  • non-sporulating,
  • facultative aerobe bacterium.
  • It has a growth temperature range of -2 to 45 °C, with an optimum temperature of 29 °C.
  • water activity of >0.92 (5% NaCl)
  • pH growth range of 4.2 to 9.0, with an optimum of 7.4.
45
Q

What are the sources of Yersinia contamination?

A
  • Yersinia can be found in contaminated food, including vegetables, milk-derived products, oysters and fish, and meat contaminated with infected urine or faeces or non-contaminated, non-chlorinated water.
  • It can also be sourced from soil, water, domestic and wild animals, and rodents.
  • Yersinia is mostly associated with pigs.
46
Q

How is Yersinia transmitted?

A

Yersinia is most often transmitted through the ingestion of contaminated food, including undercooked meat and pork.
- It can also be transmitted through person-to-person contact.

47
Q

What are the symptoms of Yersinia infection?

A

Yersinia infection can cause symptoms such as:
ADULTS
1. abdominal pain,
2. headache,
3. fever,
4. diarrhoea,
5. nausea,
6. vomiting
CHILDREN
1. watery/mucoid diarrhoea.

48
Q

What disease is caused by Yersinia?

A

yersiniosis

49
Q

What are the control measures for Yersinia contamination?

A
  1. Thoroughly cook foods to minimum safe internal temperatures,
  2. avoid cross-contamination of surfaces and foods,
  3. use approved water sources, and practice good hygiene.
  4. Yersinia is sensitive to UV radiation and is inhibited by some herb and spice extracts, including cloves, allspice, sage, cinnamon, rosemary, and oregano when present at 4.1-4.7%.
  5. Growth can also be retarded by potassium sorbate up to 5000 ppm at pH 6.5.
50
Q

What are the main characteristics of Listeria monocytogenes?

A
  • gram-positive,
  • anaerobic,
  • non-spore-forming rod.
  • It grows at a temperature range of -1.5°C to 45°C, with its optimum growth temperature at 7°C.
  • It can be found in dairy, meat, poultry, fish, fruits, and vegetables.
51
Q

Where can Listeria monocytogenes be found?

A
  • soil, vegetation, and water.
  • It is commonly present in dairy, meat, poultry, fish, fruits, and vegetables.
52
Q

How is Listeria monocytogenes diagnosed or detected?

A
  • Symptoms include:
    1. nausea,
    2. vomiting,
    3. diarrhoea,
    4. headache,
    5. persistent fever,
    6. chills,
    7. backache,
    8. meningitis,
    9. encephalitis,
    10. septicemia.
  • Listeria monocytogenes can be detected through testing and screening methods.
53
Q

What diseases are associated with Listeria monocytogenes and what are the effects of these diseases?

A
  • Listeriosis
  • can lead to various serious infections, including abortion, neonatal meningitis, adult Listeriosis, and gastroenteritis.
  • primarily affects infants, pregnant women and their fetuses, as well as immune-compromised and organ transplant patients.
54
Q

How can Listeria monocytogenes be controlled?

A
  • through testing, screening, sanitation, and intervention strategies.
  • Intervention strategies include post-packaging pasteurization, growth inhibitors, and electronic or radioisotope irradiation of food products.
  • It is important to use pasteurized milk and dairy products, cook foods to proper internal temperatures, avoid cross-contamination, and clean and sanitize food contact surfaces.
55
Q

What are the main characteristics of Clostridium botulinum?

A
  • a gram-positive,
  • anaerobic,
  • spore-forming rod bacteria.
  • grows in temperatures ranging from 12.5°C to 50°C and has a pH range of ≥4.5.
  • found in soil, marine and lake sediments, faeces, carcasses, and various types of food.
  • can produce potent heat-labile neurotoxins that cause flaccid paralysis.
56
Q

What are the sources of contamination for Clostridium botulinum?

A
  • can be found in almost all foods, with soil and water being the initial sources of contamination.
  • It is commonly found in dairy, meat, poultry, fish, fruits, and vegetables.
  • Vegetables can be easily contaminated due to contact with soil and the presence of spores.
57
Q

How is Clostridium botulinum diagnosed or detected?

A
  • Symptoms of botulism, the food intoxication caused by Clostridium botulinum, typically appear 12 to 72 hours after consumption.
  • These symptoms include:
    1. nausea,
    2. vomiting,
    3. fatigue,
    4. dizziness,
    5. headache,
    6. dryness of skin, mouth, and throat,
    7. paralysis of muscles,
    8. double vision,
    9. difficulty breathing,
    10. dry mouth.
  • Diagnosis involves clinical evaluation of symptoms and the isolation of the bacteria from food samples or faeces.
58
Q

What diseases are associated with Clostridium botulinum?

A
  • Botulism: a serious illness characterized by paralysis and can be fatal.
59
Q

How can Clostridium botulinum be controlled?

A
  • proper canning of commercial and home-canned foods,
  • preventing the creation of anaerobic conditions, acidifying products to a pH below 4.6,
  • maintaining water activity below 0.93, storing food at temperatures below 40°F (4°C),
  • using salt levels of 10% (or less when combined with nitrites),
  • employing hurdle treatments that combine pH, temperature, and salt to inhibit bacterial growth.
60
Q

What are the main characteristics of Bacillus cereus?

A
  • gram-positive
  • aerobic bacteria
  • forms large spores and rods.
  • grow over a wide temperature range of 5°C to 48°C and a pH range of 4.9 to 9.3.
  • widely distributed in nature, particularly in soil and vegetation.
61
Q

What are the main sources of contamination for Bacillus cereus?

A
  • raw foods of plant origin and ready-to-eat foods.
  • It can cause both toxin-mediated infections and intoxication.
62
Q

What are the sources of contamination for Bacillus cereus?

A

soil, dust, air, cereal crops, water, decaying matter, herbs, spices, and can also cause skin infections.

63
Q

How is Bacillus cereus diagnosed or detected?

A
  • clinical symptoms and the isolation of the bacteria from food samples or faeces.
  • Detection methods include traditional microbiological methods, molecular methods, and immunological methods.
64
Q

What diseases are associated with Bacillus cereus?

A
  • Bacillus cereus can cause two food poisoning syndromes:
    1. The emetic syndrome is caused by a heat-stable toxin and results in symptoms such as nausea, vomiting, diarrhoea, and abdominal cramps within 1 to 6 hours of ingestion.
    2. The diarrheal syndrome is caused by heat- and acid-labile enterotoxin, leading to watery diarrhoea and abdominal cramps approximately 10 hours after ingestion.
65
Q

What control measures can be taken to prevent Bacillus cereus contamination?

A
  • Quick chilling methods to cool foods,
  • ensuring adequate cooking of foods, controlling raw materials and ingredients,
  • rapid cooling of heated foods
  • maintaining careful time and temperature control.
66
Q

What are the main characteristics of Staphylococcus aureus?

A
  • Gram-positive, aerobic cocci bacteria.
  • optimum temperature of 37 degrees C, with a growing range of 6-48 degrees C.
  • It can grow well in 7-10% NaCl and is resistant to drying.
  • can cause food poisoning and is commonly found in humans, animal bodies, and poultry.
67
Q

What are the sources of contamination for Staphylococcus aureus?

A

infected food handlers. Foods with high protein, sugar or salt content, low acidity, or moist fillings are at risk.

68
Q

How is Staphylococcus aureus diagnosed or detected?

A

Staphylococcus aureus can be cultured and identified from food or faecal samples. The detection of enterotoxins in food can also be used for diagnosis.

69
Q

What diseases are associated with Staphylococcus aureus?

A

Staphylococcus aureus causes staphylococcal food poisoning and staphyloenterotoxaemia infection.

70
Q

What control measures can be taken to prevent Staphylococcus aureus contamination?

A
  • using effective preservatives such as sorbate and benzoate,
  • employing chemical sanitisers like chlorine and quaternary ammonium compounds
  • ensuring proper time and temperature control.
  • Staphylococcus aureus is sensitive to UV radiation as well.

MICR3215: Food Microbiology and Biotechnology (10 decks)

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