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Infectious Diseases > Infective diarrhoea > Flashcards

Infective diarrhoea Flashcards

1
Q

Definition of diarrhoea

A

Three or more loose or liquid stools within a 24-hour period

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2
Q

Definition of Gastroenteritis

A

Inflammation of the stomach and intestinal epithelium

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3
Q

Definition of food poisoning

A

Development of vomiting and diarrhoea caused by eating food contaminated with microorganisms and/or toxins

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4
Q

Definitions of dysentery

A

Bloody diarrhoea with mucus, pain, fever usually caused by bacterial parasitic or protozoan infection

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5
Q

Incubation times for infective diarrhoea

A

• Less than 6 hours: preformed toxin of S. aureus or B. Cereus
• 6 to 24 hours: preformed toxin of C. perfringens and B. Cereus
• 16 to 72 hours: Noroviruses, Enterotoxigenic E coli, Vibrio, Salmonella, Shigella, Campylobacter, Cryptosporidium

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6
Q

Features of a medical emergency

A

• Severe dehydration
• Sepsis
• Acute bloody diarrhoea in a child
• Severe colitis with complications
• Neurological symptoms
• Febrile traveller from a malarial area –consider malaria

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7
Q

Features of a history to consider

A

•Age
•Immunocompromise or pregnancy (Listeria)
•Acute on chronic symptoms
•Recent food exposures –take aways, restaurant, BBQs
•Animal exposure, farms
•Recent antibiotic treatment
•Family or social contacts
•Travel history: Typhoid, parasites
•Consider non infective aetiology if there are chronic features i.e: Chron’s disease, ulcerative colitis, etc
•Consider diarrhoea associated with infection outwith the GI tract: sepsis, pyelonephritis, Legionellosis

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8
Q

Investigations of stool samples

A

-Microscopy (parasites)
-Culture and antimicrobial susceptibility testing
-Molecular: PCR/ sequencing
-Serology: latex agglutination (0157, salmonella)

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9
Q

Patterns of illness

A

•Acute vomiting
•Acute watery diarrhoea
•Diarrhoea with fever
•Enteric fever
•Persistent diarrhoea

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10
Q

Bacterial toxins in acute vomiting

A

-Bacillus cereus
-Staph aureus

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11
Q

Describe norovirus in acute vomiting

A

• Most common causative agent of viral gastroenteritis
• Seasonal predominance during winter in children and adults
• Person to person spread is common
• Outbreaks in hospitals, care homes, nurseries, cruise ships, refugee camps and military combat areas
• Viral identification by PCR in vomit and/or stool
• Supportive treatment, isolation, contact precautions
• Self-limiting disease lasts approx 3 days
• Can be severe in the immunocompromised

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12
Q

Describe acute watery diarrhoea

A

•Loose stools with mucus, no blood
•Occasional vomiting and anorexia, malaise, low grade fever
•Viruses: Norovirus, rotavirus (young children) and adenovirus

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13
Q

Bacteria in acute watery diarrhoea

A

-S.aureus
-Bacillus cereus
-Clostridium perfringens
-Enterotoxigenic E coli
-Vibrio cholerae
-Cryptosporidium

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14
Q

S. aureus in acute watery diarrhoea

A

• Heat stable enterotoxin
• contaminated ready to eat food

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15
Q

Bacillus cereus in acute watery diarrhoea

A

• Produces two toxins: emetic and diarrhoeal toxin
• Presents with sudden vomiting followed by diarrhoea later
• Present in food multiplies quickly if left at room temperature: i.e. rice left over, sauce
• Self-limiting – supportive measures
-Complications= ruptured oesophagus

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16
Q

Clostridium perfringens in acute watery diarrhoea

A

• Shot incubation 6-24 hours
• Toxin generated in the gut after ingestion
• Contaminated meat, sauce in poor storage conditions
• Abdominal cramps and diarrhoea, no vomiting
• Supportive measures

17
Q

Enterotoxigenic E coli in acute watery diarrhoea

A

• Leading cause of bacterial diarrhoea in the tropics and returning traveller
• Watery diarrhoea, abdominal cramps
• Self resolving in 2 – 4 days
• Supportive measures

18
Q

Vibrio cholerae in acute watery diarrhoea

A

• Toxin mediated disease: increase in cyclic AMP blocks absorption of Na and chloride in the small intestine
=Two serogroups O1 and O139
• Related to contaminated water / undercooked shelfish, natural disasters, social conflict areas
• Endemic in tropical areas: India, central America and Africa
• Severe watery diarrhoea “rice water stool” in a patient residing in an endemic area or returning traveller
• Fulminant disease due to hypovolaemic shock and death
• Treatment: rehydration
=Antibiotics shorten the duration of the illness
=Isolation
• Notifiable to public health

19
Q

Cryptosporidium in acute watery diarrhoea

A

• Protozoan parasite: C. homini and C. parvum
• Occurs through direct exposure to infected people or animals
• Resistant to chlorine – swimming pools
=Contaminated water
=Contact with lambs and calves
• Usually asymptomatic
• Children or student vets
• Can cause watery diarrhoea
• Self resolving 1-2 weeks
• Can be severe in immunocompromised: HIV / infants
• Treatment:
=Oral rehydration
=Nitazoxanide
• Advice patients to avoid swimming pools for 14 days after symptoms stopped

20
Q

Most common organisms in traveller’s diarrhoea

A

• Enterotoxigenic E coli (ETEC)
• Campylobacter
• Salmonella
• Shigella
• Vibrio cholerae
• Chronic diarrhoea:
=Giardia
=Cryptosporidium
=Cyclospora belli

21
Q

Describe acute dysentery syndromes

A

Diarrhoea associated with fever suggests an acute inflammatory
enteritis.
•Dysentery: frequent small stools accompanied by blood, mucus with
pain and tenesmus
•High risk of person-to-person transmission:
=Day-care centres, institutions, poor hygiene

22
Q

Organisms causing acute dysentery syndromes

A

• Campylobacter
• Invasive E coli (0157)
• Salmonella / Typhoid fever
• Entamoeba histolytica

23
Q

Campylobacter in acute dysentery syndromes

A

•Campylobacter jejuni
=Undercooked poultry
=Incubation: 1 to 3 days
=Bloody stool, abdominal cramps, fever
•Complications:
=Bacteraemia (immunocompromised)
=Guillain-barre syndrome (1200 cases per annum in the UK)
•Self-limiting
•Rarely requires antimicrobial treatment

24
Q

Salmonella in acute dysentery syndromes

A

•Non typhoidal Salmonella
• Eggs – imported / poultry/ meat/ pets
• Incubation: 6 - 72 hours
• Diarrhoea and vomiting, high fever
• Complications:
=Bacteraemia
=Aortitis
=Osteomyelitis
=Meningitis
=Splenic cyst
• Requires blood cultures and stool sample
• Intravenous antimicrobials when invasive: ceftriaxone

•Typhoid is travel related and presents usually with fever and constipation

25
Q

Shiga toxin producing E coli diagnosis

A

-Serious clinical and Public Health problem- E coli O157:H7 and non- O157
STEC
-Haemolytic uraemic syndrome (HUS)in 10-15%, usually aged <16 years or
>60 years
-Diagnosis: Culture or molecular tests (PCR) stool/ Serology on clotted blood (antibody detection)

26
Q

Clinical presentation and management of STEC

A

-Clinical presentation:
• Acute abdominal pain, fever, pallor, petechiae
• If there is oliguria: maker of severe disease

-Management:
• Seek urgent advice
• Blood tests: FBC, blood film, U&Es, CRP, LDH
• Submission of stool sample is essential
• Do not give antimicrobials / NSAIDs or anti-motility drugs (interfere with clearance)
• Encourage oral fluids prior referral
• Inform microbiology and public health

27
Q

Shigella in acute dysentery syndromes

A

•Shigella sonnei/ Flexneri/ dysenteriae/ boydii
•Low infectious dose: 10 to 100 organisms
•Risk group: children / MSM
•Causes dysentery and bloody diarrhoea
•Fever, vomiting and abdominal pain
•Travellers returning from India / Pakistan
•Important public health problem especially in developing countries
•Treatment: ceftriaxone or ciprofloxacin

28
Q

Examples of parasites

A

-Amoebiasis
-Giardiasis

29
Q

Describe entamoeba hystolitica (amoebiasis)

A

• Orofaecal infection
• Tropical areas – poor sanitation
• Human reservoir
• Returning travellers in the UK and MSM (men that have sex with men)
• Clinical presentation
=Asymptomatic 80%
=Loose stool and abdominal cramps
= +++ Bloody stools and abdominal cramps: colitis with ulcer formation (potential perforation)

30
Q

Diagnosis and treatment of amoebiasis

A

•Stool samples for ova cysts and parasites
• Pus samples and stool for trophozoites require urgent examination
• PCR
•Serology for liver disease
•Liver aspirate: No evidence of parasites

-Treatment:
• Metronidazole
• Paronomycin – clears intraluminal parasites

31
Q

Extraintestinal infections of amoebiasis

A

Liver abscess:
◦ More common in men
◦ Fever, abdominal pain and pleuritic pain
◦ Single large abscess
◦ 80% right lobe, can cause pleural effusion
◦ Treatment:
=Drainage
=High dose metronidazole

32
Q

Describe Giardiasis

A

•Asymptomatic
•Abdominal pain, diarrhoea – subacute – chronic
•Malabsorption (lactose)
•Examination of stools for ova, cysts as parasites
=PCR
•Management: Albendazole

33
Q

Infection control measures

A

•Single room accommodation with En- suite toilet
•Wash hands with soap and water
=alcohol gel not sufficient in many cases
•PPE/ linen and waste disposal
•Dedicated equipment
•Bristol stool charts
•Drugs/ interventions that worsen diarrhoea (anti-motility drugs, stop laxatives)

34
Q

Public health actions

A

•Contact tracing
•Exclusion of infected individuals from
=pre-school nurseries
=Healthcare settings
=Workplace – food handlers
• Clearance samples may be required prior to returning to work

Infectious Diseases (25 decks)

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