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Infections > Infectious Diarrhoea > Flashcards

Infectious Diarrhoea Flashcards

1
Q

Definitions of diarrhoea, gastro-enteritis, dysentery

A

Diarrhoea = SUBJECTIVE, FLUIDITY + FREQ.

Gastro-enteritis = OBJECTIVE, ≥ 3 LOOSE STOOLS/DAY + ACCOMPANYING FEATURES (at least 1 of: FEVER, VOMITING, PAIN, BLOOD/MUCUS in STOOLS)

Dysentery = OBVIOUS, LARGE BOWEL INFLAMMATION, BLOODY STOOLS

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2
Q

3 types of diarrhoeal illness

A

Non-inflammatory/secretory:

SECRETORY TOXIN-MEDIATED

* CHOLERA = INCREASES cAMP lvls + Cl SECRETION (causing MASSIVE H2O LOSSES) = increased cAMP results in loss of Cl from cells along w/ Na and K - osmotic effect leads to massive loss of H2O from gut
* ENTEROTOXIGENIC E. COLI (TRAVELLERS' DIARRHOEA)

FREQ. WATERY STOOLS + RAPID DEHYDRATION + LITTLE ABDO PAIN

REHYDRATION mainstay of therapy

Inflammatory:

INFLAMMATORY TOXIN DAMAGE + MUCOSAL DESTRUCTION

• BACTERIAL INFECTION/AMOEBIC DYSENTERY

PAIN (e.g. abdo) + FEVER + BLOODY STOOLS + SYSTEMIC UPSET

REHYDRATION ALONE OFTEN SUFFICIENT + ANTIMICROBIALS may be appropriate

Mixed Picture

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3
Q

Assessing pt. of gastro-enteritis

A

SYMPTOMS + THEIR DURATION (duration of diarrhoea, freq., quality of stool, other symptoms)

• 2/52 UNLIKELY to be INFECTIVE GASTRO-ENTERITIS

RISK of FOOD POISONING

• DIETARY, CONTACT, OCCUPATION, INSTITUTION, TRAVEL Hx, ANTIMICROBIALS

ASSESS HYDRATION

• POSTURAL BP (≥ 20 mmHg drop after standing), SKIN TURGOR, PULSE, URINE FLOW, PT. APPEARANCE, MUSCLE CRAMPS

FEATURES of INFLAMMATION (SIRS)

• FEVER, RAISED WCC, RAISED HR
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4
Q

Investigations of gastro-enteritis

A

• STOOL CULTURE ± MOLECULAR/Ag TESTING

* Difficult to find pathogen in midst of complex normal flora
* Selective + enrichment methods of culture necessary - variety of media + incubation conditions
* Takes 3 DAYS to COMPLETE ALL TESTS
  • BLOOD CULTURE
  • U+E (renal function as can be v. dehydrated)
  • FBC (blood count) = NEUTROPHILIA, HAEMOLYSIS (E. coli O157)
  • ABDOMINAL X-RAY/CT if ABDOMEN DISTENDED, TENDER (distended abdo - constipation, increased risk of perforation)
  • SEROLOGY
  • SIGMOIDOSCOPY
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5
Q

Management of gastro-enteritis

A

Rehydration - oral rehydration w/ salt and sugar solution/IV saline

Antibiotics - not for healthy pt. w/ non-invasive infection; for immunocompromised, severe sepsis/invasive infection, chronic illness

Fasting, treating complications

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6
Q

Epidemiology of gastro-enteritis

A
  • CONTAMINATION of FOOD-STUFFS - intensively farmed chicken + CAMPYLOBACTER
    • POOR STORAGE of PRODUCE - bacterial proliferation at room temp.
    • TRAVEL-RELATED INFECTIONS - e.g. SALMONELLA
    • PERSON-to-PERSON SPREAD - NOROVIRUS
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7
Q

Defenses against enteric infection

A
  • HYGIENE!!
    • STOMACH ACIDITY - can be affected by antacids + infection
    • NORMAL GUT FLORA - can be affected by C. difficile diarrhoea
    • IMMUNITY - can be affected by HIV + salmonella
    • GUT MOTILITY
    • AGE
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8
Q

DDx

A
  • INFLAMMATORY BOWEL DISEASE
    • SPURIOUS DIARRHOEA - SECONDARY to CONSTIPATION
    • CARCINOMA
    • DIARRHOEA + FEVER can occur w/ SEPSIS OUTSIDE GUT
      ○ LACK of ABDO PAIN/TENDERNESS goes AGAINST GASTRO-ENTERITIS
  ○ NO BLOOD/MUCUS in STOOLS
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9
Q

Campylobacter gastro-enteritis

A
  • UP TO 7 DAYS INCUBATION - DIETARY Hx may be UNRELIABLE + CLEARS UP IN 3 WEEKS
  • PRESENTATION: SEVERE ABDOMINAL PAIN ± COLITIC PICTURE
  • INVESTIGATIONS: STOOLS -VE w/I 6 WEEKSROUTINE BACTERIAL CULTURE for CAMPYLOBACTER: specialised culture conditions
      ○ 2 SPECIES CAUSE MOST INFECTIONS = 90% - C. jejuni; 9% - C. coli

• < 1% INVASIVE
POST-INFECTION SEQUELAE: GUILLAIN-BARRE SYNDROME, REACTIVE ARTHRITIS

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10
Q

Salmonella gastro-enteritis

A
  • SYMPTOM ONSET usually < 48HRS AFTER EXPOSURE
  • PRESENTATION: DIARRHOEA usually LASTS < 10 DAYS
  • INVESTIGATIONS: < 5% +VE BLOOD CULTURES; 20% PT. still have +VE STOOLS at 20/52
    • ROUTINE BACTERIAL CULTURE for SALMONELLA:○ 2 SPECIES in GENUS = S. enterica, S. bongori
      ○ COMMONEST ISOLATES in UK = Salmonella enteritidis + Salmonella typhimurium (many isolates are imported from abroad)

• POST-INFECTIOUS IRRITABLE BOWEL is COMMON

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11
Q

E. coli O157

A
  • PRESENTATION: FREQ. BLOODY STOOLS, HAEMOLYTIC-URAEMIC SYNDROME (HUS = HAEMOLYTIC ANAEMIA + RENAL FAILURE + THROMBOCYTOPENIA) - complication w/I 10 DAYS
    • HUS more likely in elderly, children, immunocompromised, chronic illnesses
  • MANAGEMENT: HUS = SUPPORTIVE e.g. DIALYSIS, TRANSFUSIONS, antibiotics NOT indicated

produces shiga toxin, which enters blood causing HUS (stimulates platelet activation)

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12
Q

Other bacteria

A
  • SHIGELLA (4 spp. = S. sonnei, S. flexneri, S. boydii, S. dysenteriae) - OUTBREAKS of SHIGELLA SONNEI in CHILDREN’S NURSERIES (more childhood, travel - HUS and seizures may complicate)
  • E. COLI (several other forms cause diarrhoea) - ENTEROINVASIVE, ENTEROPATHOGENIC, ENTEROTOXIC (traveller’s diarrhoea - lasts < 1 week, but persistent diarrhoea > 30 days in few pt.)
  • ROUTINE DIAGNOSIS of these E. coli strains NOT POSS. - only O157 is easily distinguishable from ordinary E. coli (ordinary are sorbitol fermenting; nearly al O157 are non-sorbitol fermenters)
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13
Q

Occasional causes of food poisoning outbreaks

A

• S. AUREUS (toxin) - FEW HRS, QUICKER COURSE. SHORT-LIVED
• BACILLUS CEREUS (re-fried rice)
CLOSTRIDIUM PERFRINGENS (undercooked meat/cooked food left out - toxin accumulates in spore formation)

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14
Q

Clostridium difficile diarrhoea

A
  • DRUG Hx: pt. usually gives hx of PREVIOUS ANTIBIOTIC Rx
  • SEVERITY RANGES: MILD DIARRHOEA - SEVERE COLITIS (produces enterotoxin + cytotoxin)

MANAGEMENT:

• METRONIDAZOLE, ORAL VANCOMYCIN, FIDAXOMICIN, STOOL TRANSPLANTS, SURGERY may be req. (severe pseudomembranous colitis)

  • STOP PRECIPITATING ANTIBIOTIC if poss.
  • FOLLOW PUBLISHED TREATMENT ALGORITHM - ORAL METRONIDAZOLE if NO SEVERITY MARKERS; ≥ 2 SEVERITY MARKERS = ORAL VANCOMYCIN

PREVENTION:

* REDUCTION in BROAD SPECTRUM ANTIBIOTIC PRESCRIBING
* AVOID 4 Cs
* ANTIMICROBIAL TEAM (AMT) + LOCAL ANTIBIOTIC POLCY
* ISOLATE SYMPTOMATIC PT.
* WASH HANDS bwtn PT. - CONTACT PRECAUTIONS
* CLEANING ENVIRONMENT
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15
Q

Parasites (x3)

A

INVESTIGATIONS: diagnosis usually by MICROSCOPY (stools sent w/ request of parasites, cysts + ova or PCO)

UK PROTOZOA:

GIADIA DUODENALIS - CYSTS/TROPHOZOITES

* PRESENTATION: DIARRHOEA, GAS, MALABSORPTION, FAILURE to THRIVE
* INVESTIGATIONS: CYSTS seen on STOOL MICROSCOPY, TROPHOZOITES (DUODENAL BIOPSY tightly bound to villi/STRING TEST)
* MANAGEMENT: METRONIDAZOLE, TINIDAZOLE

CRYPTOSPORIDIUM PARVUM

* PRESENTATION: DIARRHOEA, N + V, ABDO PAIN
* INVESTIGATIONS: OOCYTES seen on MICROSCOPY
* MANAGEMENT: NO SPECIFIC Rx usually req.

IMPORTED PROTOZOA:

ENTAMOEBA HISTOLYTICA:

• PRESENTATION: AMOEBIC DYSENTERY (intestinal amoebiasis), INVASIVE EXTRA-INTESTINAL AMOEBIASIS (liver/pleuropulmonary/brain abscess) - MONTHS/YEARS LATER, USUALLY NO BOWEL SYMPTOMS

	○ May mimic ulcerative colitis

INVESTIGATIONS:

* MICROSCOPY = TROPHOZOITES in SYMPTOMATIC PT. (HOT STOOL); ASYMPTOMATIC PT. - CYSTS seen in FORMED STOOL
* ANTIBODY DETECTION (SERUM) = for INVASIVE DISEASE

MANAGEMENT (intestinal disease): METRONIDAZOLE + LUMINAL AGENT (FURAMIDE) to clear colonisation

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16
Q

Viruses

A

ROTAVIRUS: CHILDREN < 5YRS

* COMMON in WINTER
* INVESTIGATIONS: diagnosis by ANTIGEN DETECTION in STOOL
* ROTAVIRUS VACCINE AVAILABLE (8 + 12 WEEKS)

NOROVIRUS: common cause of OUTBREAKS

* PRESENTATION: VOMITING, DIARRHOEA, commonly in WINTER
* INVESTIGATIONS: diagnosis by PCR
* STRICT INFECTION CONTROL MEASURES

Infections (6 decks)

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