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BDS2 HHD - Microbiology > 14. Infections of the GI tract > Flashcards

14. Infections of the GI tract Flashcards

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Biology 101 flashcards
1
Q

Healthy stomach features

A

sterile, contains only a few organisms because of low pH and enzymes

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2
Q

Healthy small intestine features

A

streptococci, lactobacilli and yeasts, the proportions of which depend on dietary habits

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3
Q

Healthy large intestine features

A

dense population of varied flora
* strep faecalis, bacteroides, enterobacteriaceae, clostridium spp, anaerobic streptococci

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4
Q

GASTROENTERITIS
1. What is it?
2. Symptoms?
3. Age and location prevalence?

A

1
Acute gastrointestinal illness usually due to infection
2
Vomiting and diarrhoea
Often associated with food poisoning
3
Can occur at all ages, but infants principal group
More common in countries with poor hygiene standards, water sanitation problems
Sporadic or epidemic forms

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5
Q

Diff bacteria incubation period and duration of symptoms?

A
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6
Q

Other causes of gastroenteritis (pathogen, type, incubation, duration)

A
  1. Not just cause by bacteria, also caused by pathogens
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7
Q

Risk groups FOR GASTROENTERITIS

A
  • Enteric hygiene difficulties
  • Pre-school, creche children
  • Food workers
  • Health care staff
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8
Q

CAMPYLOBACTER

  1. What is it?
  2. Symptoms
  3. Recurrent infection?
  4. How spread?
A

1
Commonest bacterial gastroenteritis in Western world - C. jejuni, C. coli
Curved, slender, Gram negative bacilli

2
Fever, myalgia, abdo pain, severe diarrhoea
Prolonged carriage can occur

3
Recurrent infection can occur in up to 25% of patients
Low infective dose

4
* Foods - poultry (gut of bird), raw milk and dairy products. May be contaminated by kittens and puppies.
* Caused by enterotoxin

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9
Q

CAMPYLOBACTER

  1. Diagnosis
  2. Treatment
  3. Post infection complications
A

1
Diagnosis - Selective media, low Ox, 43C.
* Gram, Biochemical.

2
Treatment - Erythromycin for prolonged symptoms or worsening symptoms, dysentery, pyrexia, bacteraemia, pregnant women and persons at risk for complications

3
Post-infectious complications, rare: * Guillain-Barre, RA, Convulsions
Prevention is key

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10
Q

SALMONELLOSIS

  1. How many serotypes?
  2. Incubation period?
  3. Symptoms
  4. Source?
A

1
2500 serotypes:
* S.enteritidis (non-typhoidal)
* S.typhi/S.paratyphi (typhoidal)

2
Incubation period- 1-2days

3
Nausea, vomiting, diarrhoea, fever, abdominal pain.
Disseminated sepsis

4
Source - ingestion of contaminated food/water
Found in domestic animals and poultry * Poultry, swine, cattle.
* Handling exotic pets- reptiles, turtles

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11
Q

SALMONELLOSIS

  1. Age
  2. Duration
  3. How
A

1
Infants, elderly, decreased stomach acid

2
Duration 1-7 days

3
Organisms enter gut mucosal cells and produce enterotoxin which acts in jejunum, ileum and colon.
Gastroenteritis - 75% of infections
Bacteremia - 5% to 10% of infections, often resulting in distant infections (eg, central nervous system infections, endocarditis, or osteomyelitis)

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12
Q

SALMONELLOSIS

  1. Diagnosis
  2. Treatment
  3. Second spread
A

1
Diagnosis - Enrichment and selective media
* Biochemical and serological

2
Treatment - Rehydration. Treatment rarely necessary (Antibiotic therapy is contraindicated- prolongs the carriage of the organism in the convalescent phase)

3
High secondary spread
* Strict contact precautions
* Clinical surveillance of contacts

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13
Q

STAPHYLOCOCCUS AUREUS

  1. Source?
  2. Symptoms
  3. Incubation
  4. Diagnosis
  5. Treatment
A

1
Foods - cooked food not stored at 4 degrees or frozen immediately is the main source of infection
Source - generally from food handler. Organisms multiply in warm conditions
Caused by preformed heat - stable enterotoxins

2
Nausea and vomiting (and diarrhoea in 25% of
patients)

3
Incubation 1⁄2 to 6 hours. Duration 1-24 hours, rarely 48 hours

4
Diagnosis - faecal culture

5
Treatment - self-limiting, no treatment required

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14
Q

BACILLUS CERUS

  1. what?
  2. Source
  3. Types
  4. Symptoms
  5. Treatment
A

1
Aerobic spore-forming gram-positive bacillus

2
Foods - mainly rice, also other cereals, raw, dried
and processed foods.
Spores survive boiling - sporulation

3
Two types of poisoning: Emetic and diarrhoeal (rare)

4
Symptoms usually occur within 2 to 6 hours after ingestion of contaminated food. Last 6 to 10 hours.

5
No treatment required, self-limiting

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15
Q

BACILLARY DYSENTERY (SHIGELLOSIS)

(Make Q’s)

A
  • Shigella sonnei is the most common species in developed countries
  • Other 3 species S flexneri, S boydii, S dysenteriae usually acquired abroad
  • Mild intestinal illness - fever, malaise, self-limiting watery diarrhoea
  • The diarrhoea may decrease and become bloody with mucus and pus (ie. dysentery)
  • Requires low infecting dose acquired by direct contact
  • Short incubation period- within 48 hours
  • Is locally invasive in large bowel
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16
Q

BACILLARY DYSENTERY (SHIGELLOSIS)

diagnosis
Treatment

A
  • S dysenteriae infection is most likely to cause complications such as HUS, dysentery, and toxic megacolon.

1
Diagnosis - isolate organism on selective culture media

2
Treatment - rehydration. Antibiotics indicated for most patients- ciprofloxacin

17
Q

CRYPTOSPORIDIOSIS

A
  • A self limiting diarrhoeal illness in children
  • Nausea and vomiting
  • Drinking contaminated water containing cysts of - Crypto parvum
  • Source is infected cattle
  • Very resistant to chlorination
  • A more severe illness occurs in immunocompromised (AIDS)
  • Diagnosed by finding cysts in stool (acid ‘fast’)
  • No specific treatment
18
Q

CLOSTRIDIUM PERFRINGENS

A
  • Gas gangrene and food poisoning
  • Heat resistant spores survive in contaminated foods during the heating procedure. After food is ingested- sporulation occurs in the GIT and an enterotoxin is produced
  • Abdominal pain and watery diarrhoea
  • Treatment - symptomatic, no antibiotics
  • Prevention - good food hygiene, adequate cooking of food to kill the organisms
19
Q

INFANTILE GASTROENTERITIS - principle causes

A

Viral
-rotavirus (the most common cause)

-noroviruses (Norwalk like)

Bacterial (Escherichia coli)

-enteropathogenic

-enterohaemorrhagic

-enterotoxigenic

-enteroinvasive

20
Q

VIRAL GASTROENTERITIS

A
  • Frequent cause of infantile gastroenteritis
  • Up to 50% of cases caused by rotaviruses in under 3 year olds
  • Short incubation of 2-4 days
  • Presents as acute diarrhoea of mild to moderate severity, may be vomiting
  • More common in winter months
  • Diagnosed by detection of rotavirus antigen in stool
  • Supportive care
21
Q

ENTEROPATHOGENIC E COLI (EPEC)

A
  • More than 20 (O) serotypes have been identified in outbreaks of infantile diarrhoea
  • Spread by contaminated food
  • Small intestine affected
  • Local destruction of intestinal epithelial cells
  • Infantile gastroenteritis, traveller’s diarrhoea
  • Fever, nausea, vomiting, non-bloody stools
  • Self-limiting, supportive care, no specific antibiotic treatment
22
Q

ENTEROHEMORRHAGIC E COLI (EHEC)

A
  • Enterohemorrhagic E coli (EHEC) produce Shiga toxin (STEC) or verotoxin (VTEC)
  • Over 100 serogroups, 0157:H7 commonest.
  • Diarrhoea, bloody colitis, HUS (5%).
    • Haemolytic anaemia, thrombocytopenia, ARF.
  • Ingestion of undercooked hamburger, salami,
  • sprouts, and unpasteurized milk
  • Low infective dose
  • Antibiotics and antimotility agents should be avoided if EHEC infection is suspected clinically
23
Q

ENTEROTOXIGENIC E COLI (ETEC)

A
  • Common cause of diarrhoea in travellers and in children in developing countries.
  • Organism attaches to the small bowel and causes diarrhoea through enterotoxins.
  • Mild to severe watery diarrhoea, cramps
  • Antibiotics (quinolones, TMPSMX, and rifaximin) often are given empirically for moderate to severe traveller’s diarrhoea
24
Q

ENTEROINVASICE E COLI (EIEC)

A
  • Fever, watery diarrhoea, cramps
  • Develops to (bacillary) dysentery, bloody stools
  • Large bowel affected, by invasion and local destruction of epithelial cells
  • Not enteropathogenic serotypes or enterotoxin producers
25
Q

GIARDIASIS

A
  • Caused by Giardia lamblia
  • Flagellate protozoan
  • Ingestion of cysts in contaminated food or water (resists chlorination)
  • These develop into trophozoites in duodenum
  • Find cysts or rarely trophozoites in stool
  • Symptoms of cramping abdo pain, flatulence, - diarrhoea
  • Metronidazole is antimicrobial of choice
26
Q

CLOSTRISIUM DIFFICILE

A
  • Antibiotic associated pseudomembraneous colitis
  • Antibiotics (clindamycin, cephalosporins) suppress normal flora, C. diff to multiply, produce toxins
  • Yellow ‘pseudomembranes’
  • Normal commensal in 3 % population
  • Diagnosis - sigmoidoscopy, toxin in stool samples
  • Treatment - withdraw offending antibiotic, replace fluids, metronidazole, oral vancomycin
  • Prevention – wash hands/surfaces, selective use of antibiotics, isolate infected patients
27
Q

AMOEBIC DYSENTERY

A
  • Causative organism: Entamoeba histolytica
  • Indian sub Continent, Africa (but Worldwide
    distribution)
  • Acquired from eating food contaminated with cysts
  • Can be severe diarrhoea with blood and mucus in stool
  • Can progress to cause perforation of large bowel and peritonitis
  • Also, liver involvement with hepatitis or liver abscess
  • Treatment with metronidazole
28
Q

CHOLERA

A
  • Caused by Vibrio cholerae
  • Typically water borne
  • Infects only humans
  • Short incubation period
  • A severe diarrhoeal illness with ‘rice water’ stools +/- vomiting and nausea
  • Dehydration, electrolyte loss, circulatory and renal failure
  • Mortality 40% without treatment
  • Treat by rehydration and antibiotics (tetracycline or ciprofloxacin)
29
Q

HELICOBACTER PYLORI

A
  • Chronic gastritis and gastroduodenal ulceration, some cases of gastric carcinoma
  • Gram negative bacterium
  • Treatment of H. pylori infection usually involves 7 days’ therapy with two antibiotics (clarithromycin, metronidazole, and amoxicillin are often used) together with a proton pump inhibitor (omeprazole)
30
Q

Prevention of foodborne illnesses

A

Recognition of possible sources

  • Thorough cooking of food
  • Segregation of foodstuffs
  • Rapid cooling and good refrigeration
  • Store food so as to prevent multiplication
  • Treatment of foods likely to be contaminated
  • Exclusion of insects and other pests and vermin
  • Handwashing and hygienic practices

BDS2 HHD - Microbiology (12 decks)

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