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J3 > Spijsvertering > Flashcards

Spijsvertering Flashcards

1
Q

Name two bacterial pathogens that grow in foods and produce toxins

A

Bacillus cereus

Staphylococcus aureus

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2
Q

Dysentery

A

o Inflammatory disorder of the large bowel

o Blood and pus in faeces

o Pain, fever and abdominal cramps

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3
Q

Diarrhoea

A

o Abnormal frequency and/or fluid stool

o Usually indicates small bowel disease

o Causes fluid and electrolyte loss

o Severity varies from mild self-limiting to severe/fatal

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4
Q

Gastroenteritis

A

inflammation of the stomach and intestines, typically resulting from bacterial toxins or viral infection and causing vomiting and diarrhoea.

Symptoms: Nausea, vomiting, diarrhoea and abdominal discomfort

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5
Q

Enterocolitis

A

inflammation of both the small intestine and the colon

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6
Q

zoonotic definition

A

can be transmitted from animals to people

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7
Q

What are the 3 Fs of Faecal-oral transmission?

A

1) Food
o Contamination – Farm to fork
o Cross-contamination – Distribution chain or domestic kitchen

2) Fluids
o contaminated Water

3) Fingers
o Importance of washing hands

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8
Q

What is Enrichment broth?

A

Contains nutrients that promote preferential growth of the pathogen

used for laboratory diagnosis

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9
Q

What are Selective media?

A

o culture mediumthat is enriched with a particular substance to allow the growth of particular
strains of organisms.

o Used to isolate or identify particular organisms.

o i.e. Suppress growth of background flora while allowing growth of the pathogen

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10
Q

What are Differential media?

A

used to differentiate between closely related organisms or groups of organisms.

due to the presence of certain dyes or chemicals in the media, the organisms will produce characteristic changes or growth patterns that are used for identification or differentiation

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11
Q

How will MacConkey’s agar look with both lactose and non-lactose fermenting colonies?

A

Lactose fermenting colonies (E.coli)
are pink

non-lactose fermenting ones (Shigella spp.) are colourless.

Remember: Non-lactose fermenting have No colour

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12
Q

Who should get antibiotics for GI infections?

A

Very ill patients

Sepsis or evident bacteraemia

Significant co-morbidity
o Patients with minimal ability to handle physiological upset of several days of diarrhoea

C. difficile associated diarrhoea (metronidazole)

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13
Q

Campylobacter gram stain

A

Gram-negative

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14
Q

Campylobacter carriers and transmission

A

Large animal reservoir (poultry, cattle, sheep, rodents & wild birds)

Infection transmitted via contaminated food (especially poultry), milk or water

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15
Q

Campylobacter Pathogenesis

A

bacterial invasion of the small and large bowel, causing:
o Inflammation
o ulceration
o bleeding

Bacteraemia can occur

Rarely causes post-infectious Guillain-Barre and reactive arthritis

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16
Q

Campylobacter Clinical Presentation

A

 Bloody diarrhoea
 Cramping abdominal pain
 Fever

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17
Q

Campylobacter Treatment

A

Fluid replacement is sufficient in most cases

Clarithromycin for severe/persistent disease

Quinolone (ciprofloxacin) or aminoglycoside (gentamicin) for invasive disease

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18
Q

Salmonella gram stain + causative species

A

Gram-negative

Majority of human infection caused by single species Salmonella enterica

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19
Q

Salmonella carriers and transmission

A

wide range of warm and cold blooded animals

Acquired via contaminated food, especially pork, poultry & other meat/dairy products

Secondary spread via person-to-person transmission

NB: S. Typhi & S. Paratyphi (enteric fever) do not have an animal reservoir

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20
Q

Salmonella Pathogenesis

A

invasion of epithelial cells in the distal small intestine, and subsequent inflammation

Bacteraemia can occur

metastatic infection:
o e.g. osteomyelitis
o septic arthritis
o meningitis

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21
Q

Salmonella Clinical Presentation

A

 Watery diarrhoea
 Vomiting
 Fever usually associated with invasive disease

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22
Q

Salmonella Treatment

A

Fluid replacement is sufficient in most cases

Antibiotics reserved for severe infections and bacteraemia

Beta-lactams, quinolones or aminoglycosides may be used

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23
Q

Salmonella Prevention

A

immunisation of poultry

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24
Q

Shigella gram stain and species

A

Gram-negative bacilli

4 species
Shigella dysenteriae - most severe disease

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25
Q

Shigella Epidemiology

A

Mainly associated with diarrhoeal disease in children

S. dysenteriae in developing world

Humans are only reservoir

Person-to-person spread via faecal-oral route

Low infectious dose

Recent outbreaks associated with MSM

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26
Q

Shigella Pathogenesis

A

Organisms attach to and colonise mucosal epithelium of terminal ileum & colon

No systemic invasion

S. dysenteriae produces potent exotoxin (Shiga toxin)
o damages intestinal epithelium
o can cause renal failure as part of HUS

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27
Q

Shigella Clinical Presentation

A

 Dysentery
 Initially watery diarrhoea followed by bloody diarhoea
 cramping abdominal pain
 Fever

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28
Q

Shigella Treatment

A

Fluid replacement is usually sufficient

Some cases of S.dysenteriae will require treatment of renal failure

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29
Q

Shigella Prevention

A

Only found in humans, so good standards of sanitation and personal hygiene are key measures

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30
Q

Vibrio cholerae gram stain

A

Gram-negative

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31
Q

Vibrio cholerae Pathogenesis

A

Flagellae and mucinase facilitate penetration of intestinal mucous

production of a potent protein exotoxin

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32
Q

Vibrio cholerae Clinical Presentation

A

Severe, profuse, watery diarrhoea (rice water stool)

 Profound fluid loss & dehydration:
o Hypokalaemia
o metabolic acidosis
o hypovolaemic shock
o cardiac failure

 Untreated -> mortality 30-40%

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33
Q

Vibrio cholerae Treatment

A

rehydration is lifesaving (mortality reduced to <1%)

Tetracycline antibiotics may shorten duration of shedding

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34
Q

Vibrio cholerae Prevention

A

Clean drinking water supply and proper sanitation

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35
Q

Vibrio cholerae Epidemiology

A

Endemic in parts of SE Asia, Africa, South America

Can live in fresh water

Only infects humans. Asymptomatic human reservoir

Spreads via contaminated food or water

person-to-person transmission uncommon

36
Q

Escherichia coli gram stain

A

Gram-negative

Important component of gut flora of man and animals

Some strains possess virulence factors which enable them to cause infections

37
Q

Enteropathogenic E. coli (EPEC) summary

A

Cause of some cases of “traveller’s” diarrhoea

adherence and formation of characteristic “attaching & effacing” lesion

o Watery diarrhoea with abdominal pain and vomiting
o Often accompanied by fever

38
Q

Enterotoxigenic E. coli (ETEC) summary

A

The major bacterial cause of diarrhoea in infants & children in developing world
o major cause of “travellers” diarrhoea

caused by toxin production
 Heat-labile (LT) analogue of cholera toxin
 Heat-stable (ST).

o Watery diarrhoea with abdominal pain and vomiting

39
Q

Enterohaemorrhagic E. coli (EHEC) summary

A

many types, but E. coli 0157 is most well known

Consumption of contaminated food, water and dairy products & direct environmental contact
with animal faeces e.g. petting zoos

Secondary person-to-person spread

Attaching and effacing lesion
Production of Shiga-like toxins.

o Bloody diarrhoea with abdominal pain and vomiting
o No associated fever
o Haemolytic uraemic syndrome (5-10% )

40
Q

Which bacterial are key causes of diarrhoea in children in the developing world?

A

EPEC & ETEC

Severity may be related to underlying malnutrition

ETEC may mimic cholera clinically

41
Q

Staphylococcus aureus gram stain

A

Gram-positive cocci

42
Q

Staphylococcus aureus carriers/transmission

A

food is contaminated by human carriers

Especially cooked meats, cakes and pastries

Bacteria multiply at room temperature and produce toxins

43
Q

Staphylococcus aureus pathogenesis

A

50% of S.aureus produce enterotoxins (types A-E)

Heat stable and acid-resistant protein toxins

44
Q

Staphylococcus aureus Clinical Presentation

A

 Profuse vomiting and abdominal cramps

 No fever and no diarrhoea

45
Q

Staphylococcus aureus prevention

A

Hygienic food preparation to minimise contamination

Refrigerated storage

46
Q

Bacillus cereus gram stain

A

Gram-positive

47
Q

Bacillus cereus pathogenesis

A

2 types of disease:

1) Emetic disease
o fried rice
o Heat stable toxin survives further frying

2) Diarrhoeal disease
o Ingested organisms produce a heat-labile toxin in the gut with similar mode of action to cholera toxin

48
Q

Bacillus cereus Clinical Presentation

A

Emetic disease
o Profuse vomiting with abdominal cramps and watery diarrhoea

 Diarrhoeal
o Watery diarrhoea with cramping abdominal pain, but no vomiting

49
Q

Clostridium perfringens gram stain

A

Gram-positive

50
Q

Clostridium perfringens pathogenesis

A

Organisms ingested & sporulate in large intestine with production of enterotoxin

Often involves bulk-cooking of stews, meat pies

51
Q

Clostridium perfringens Clinical Presentation

A

 Watery diarrhoea and abdominal cramps

52
Q

Clostridium perfringens control

A

 Rapid chilling/freezing of bulk-cooked foods

 Thorough re-heating before consumption

53
Q

Clostridium botulinum gram stain

A

Gram-positive

54
Q

Clostridium botulinum Clinical Presentation

A

Neuromuscular blockade results in flaccid paralysis & progressive muscle weakness

Involvement of muscles of chest/diaphragm causes respiratory failure

High mortality if untreated

55
Q

Clostridium botulinum pathogenesis

A

Produces powerful heat-labile neurotoxin

 Foodborne botulism- pre-formed toxin in food. associated with improperly processed canned
foods

 Infant botulism- organisms germinate in gut of babies fed honey containing spores, and toxins are
produced in gut

 Wound botulism- organisms implanted in wound produce toxin

Absorbed toxins spread via bloodstream and enter peripheral nerves where they cause neuromuscular
blockade at the synapses

56
Q

Clostridium botulinum treatment

A

Urgent intensive supportive care due to difficulties breathing and swallowing

Antitoxin

57
Q

Clostridium botulinum control

A

 Proper manufacturing controls in canning industry
 Hygienic food preparation
 Proper cooking
 Refrigerated storage

58
Q

Clostridium difficile Microbiology

A

Gram-positive

Spores resistant to heat, drying, disinfection, alcohol

59
Q

Clostridium difficile pathogenesis

A

Infection requires disruption of the normal “protective” gut flora

Clinical features due to production of potent toxins

60
Q

Clostridium difficile clinical presentation

A

 Mild to severe with abdominal pain
 Severe cases -> pseudomembranous colitis
 Fulminant cases -> colonic dilatation and perforation
 Severe cases may be fatal
 Relapses are common and may be multiple

61
Q

Clostridium difficile treatment

A

Stop precipitating antibiotics

 Oral metronidazole (mild [0 severity markers]).
 Oral vancomycin (severe [≥ 1 severity markers or no improvement after 5 days metronidazole])

 Refractory recurrent disease may require faecal transplant

62
Q

Clostridium difficile prevention

A

Antimicrobial stewardship

minimise use of “high risk” antibiotics
 Cephalosporins
 Fluoroquinolones
 Clindamycin
 Co-amoxyclav

Infection Prevention & Control measures
o Source isolation
o Hand hygiene
o Use of Personal Protective Equipment

 Cleaning/disinfection with hypochlorite disinfectants

63
Q

Clostridium difficile Severity markers

A 
o Colonic dilatation >6cm
o WCC >15 x10^9 /L
o Creatinine >1.5 x baseline
o Temp >38.5 C
o Immunosuppression
64
Q

Listeria monocytogenes gram stain

A

Gram-positive

65
Q

Listeria monocytogenes Epidemiology

A

Widespread among animals and the environment

Pregnant women, elderly and immunocompromised

Overall number of cases small, but mortality high

Infection associated with contaminated foods, especially unpasteurised milk and soft cheeses, pate,
cooked meats, smoked fish, and coleslaw

66
Q

Listeria monocytogenes pathogenesis

A

Invasive infection from GIT results in systemic spread via bloodstream

67
Q

Listeria monocytogenes Clinical presentation

A

 Initial flu-like illness, with or without diarrhoea

Majority of cases present with severe systemic infection
o Septicaemia
o Meningitis

68
Q

Listeria monocytogenes treatment

A

Intravenous antibiotics (usually Ampicillin and synergistic gentamicin) is required

69
Q

Listeria monocytogenes Control

A

Susceptible groups should avoid high risk foods

Observe use by dates

Wash raw fruit and vegetables and avoid cross contamination

70
Q

Helicobacter pylori gram stain

A

Gram-negative

71
Q

Helicobacter pylori clinical presentation

A

 Infection is asymptomatic unless peptic ulceration develops

 Now established as cause of >90% of duodenal ulcers, and 70-80% of gastric ulcers

 Gastric cancer risk

72
Q

Stool cultures take at least 48 hours. Which antibiotic (group) is usually used for empirical treatment of GI infections?

A

Ciprofloxacin (Quinolones)

73
Q

Which antibiotic is used to treat C. difficile infection?

A

metronidazole

74
Q

What are some methods for breaking the chain of infection?

A

public health measures - sanitation and clean water
education - hand hygiene
pasteurisation of milk

75
Q

What is the Commonest bacterial foodborne infection in the UK?

A

campylobacter

76
Q

Which GI infection can cause post-infectious Guillain-Barre Syndrome?

A

Campylobacter

Can also cause reactive arthritis

77
Q

Salmonella types

A

salmonella typhi/paratyphi - invasive, usually cause bloodstream infections and require antibiotic therapy

all other salmonella species - usually self-limiting and don’t behave invasively

78
Q

Which organisms only have a human carrier?

A

typhoid/paratyphoid (salmonella typhi/paratyphi )

Shigella dysenteriae

Vibrio cholerae

Helicobacter pylori

79
Q

What are 4 causes of bloody diarrhoea?

A

shigella
E. coli 0157
Campylobacter
salmonella

80
Q

What’s the major cause of traveller’s diarrhoea?

A

Enterotoxigenic E. coli (ETEC)

81
Q

Which bacterial infections cause a vomiting illness?

A 
salmonella
EPEC
ETEC
EHEC
Staphylococcus aureus
Bacillus cereus
82
Q

Name 3 bacteria that can cause bacteraemia from GI infection

A

campylobacter
salmonella
listeria

83
Q

Name 2 bacteria that can cause meningitis from GI infection

A

listeria

salmonella

84
Q

Name 2 bacteria that can cause Microangiopathic haemolytic anaemia from GI infection

A

E.coli O157:H7 causes haemolytic uraemic syndrome

Shigella causes haemolytic uraemic syndrome

“Shiga toxin”

85
Q

most common cause of GI infection in the UK

A

norovirus

J3 (18 decks)

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