W07 - Clinical 1 - Diarrhoea, Outbreak, HIV, PUO Flashcards
List the bacteria that are sought by routine culture of stools from patients with diarrhoea in the UK and outline their epidemiology.
CAMPYLOBACTER
C. jejuni (common), C. coli (less)
E. coli
enterotoxic (travellers diarrhoea
List other bacteria that cause diarrhoea, indicate the availability of routine tests for them & outline their epidemiology.
CAMPYLOBACTER
List the parasites commonly detected in stool specimens in the UK by microscopy and outline their epidemiology.
Protozoa, Helminths
*dx by microscopy; duodenal biopsy for trophozoites
Parasites, cysts, and ova request
- Giardia duodenalis (cysts/trophozoites)
- C parvum
- diarrhoea, gas, malabs., failure to thrive
> METRONIDAZOLE (giarda)
*ENTAMOEBA HISTOLYTICA = amoebic dysentry / invasive (ab detection)
> METRONIDAZOLE + LUMINAL AGENT TO CLEAR COLONIZATION
*Liver abscess
List the viruses that commonly cause diarrhoea and outline their epidemiology and how they are detected.
SALMONELLA
S. enteritidis
S. typhimurium
*S. typhi / paratyphi = enteric fever (typhoid/paratyphoid) NOT gastroent.
- rotavirus, Norovirus, Adenovirus
- seasonal
- ag detection in stool / PCR
Define food-poisoning, gastro-enteritis, dysentery and colitis.
GASTRO-ENTERITIS
3+ loose stooles/day + features
DYSENTERY
large bowel inflamm., bloody stools
Appreciate the normal bowel flora and the host’s natural defences against enteric
infections.
Cl. difficile diarrhoea - disruptions to normal gut flora
Understand the epidemiology of bacterial and viral gastro-enteritis.
Contaminated foodstuffs; intensive farming - CAMPYLOBACTER (commonest bact.)
Travel - SALMONELLA
The mechanisms by which infecting organisms can produce diarrhoea - toxin mediated, invasion, attachment
NON-INFLAMMATORY (toxin-med)
-Cholera: toxin retrograde endocytosis = ⇧cAMP and Cl secretion
- ENTEROTOXIGENIC E. COLI (traveller’s)
- frequent watery stools
INFLAMMATORY
- toxin dmg and mucosal destruction = pain & fever
*bact. infection/amoebic dysentry
Outline the principles of managing gastro-enteritis - history taking, assessing
dehydration,
> Rehydration therapy essential +/- Abx
> Salt/sugar solution (NaCl, KCl, Glucose)
* SGLT1 co-transporter; GLUT2; draws water in
- 2w = unlikely to be infective fastro-enteritis
- ?risk of food poisoning
- Hydration = postural BP, skin turgor, pulse
- Inflamm = fever, raised WCC
!Hyponatraemia; Hypokalaemia
Describe the potential complications of E. coli O157 infection.
Haemolytic-uraemic syndrome (shiga toxin in blood) = haemolytic anaemia and RenFailure; thrombocytopoenia; shistocytes
- freq bloody stools
- Seizures
- microangiopathy
> Supportive Tx only
Investigations of patient
Stool culture +/- molecular/Ag testing
Blood culture
Renal function
Blood count = haemlysis with E Coli O157
XR/CT with abdo distension
Diff. Dx to gastroent.
IBD
Spurious diarrhoea - 2º to constipation
Carcinoma
Nil abdo pain/tenderness = not gastroenteritis
Campylobacter gastroent. features
7d incubation; dietary hx may be unreliable
Abdo pain
Post-infection sequelae = Guillain-Barre sndrome, Reactive Arthritis
Salmonella gastroent. features
<48hr post-exposure onset; quicker
<10d diarrhoea
- +ve stooled at 20w (20% of patients - ?gallstones)
- post-infectious irritable bowel common
Abx indications
Gastroent:
- imm compr.
- severe sepsis/invasive infection
- chronic illness e.g. malignancy
Significance of Abx use and C diff diarrhoea
‘4 C’s’ (clindamycin, cephalosporins, co-amoxiclav and ciprofloxacin) associated with a higher risk of C. difficile infection. Often two or more antibiotics are prescribed at the same time and in the case of osteomyelitis for a minimum course of 4–6 weeks
- severe colitis
- enterotoxin A & cytotoxin B
> Metronidazole
Oral vancomycin
Stool transplants
Fidaxomicin
Difference between Non-inflamm Vs Inflamm
Non-inflammatory:
- Toxin-mediated usually
- Watery stools, rapid dehydration, relatively little abdo pain
- Rehydration mainstay of treatment
Inflammatory:
- Bacterial infection usually
- Abdo pain, bloody stools, sytemic upset
- Rehydration and (sometimes) antimicrobials required
Definition of confirmed, probable, possible cases
Confirmed – patient has predetermined signs and symptoms or positive lab test
Probable - patient has predetermined signs and symptoms or close contact
Possible – patient has one or few predetermined signs and symptoms
Criteria to declare a COVID-19 cluster/incident in an inpatient setting
Two or more patient and/or staff cases of COVID-19 within a specific setting where nosocomial infection and ongoing transmission is suspected
Outline the basic virological features of HIV.
CD4+ destruction = TH, macrophages, monocytes, cells in the brain, skin
• ⇧HIV viral load ⇩CD4 count
- ⇧risk of developing infection esp as CD4 declines
- AIDS dx occur at CD4 <200
=> Symptomatic HIV infection = viral load > CD4
+ opportunistic infection
Describe the modes of transmission and epidemiology of HIV infection
- sexual transmission
- injection/drug misuse
- blood products
- vertical transmission
- organ transplant
Describe the clinical presentations of HIV infection.
Pt wt. loss, lymphadenoapthy, thrush, skin and oral disease
- acute infection = seroconversion
- HIV infection = asymptomatic
- HIV related illness
- AIDS = symptomatic infection/tumour
1) asymptomatic
+ PERSISTENT GENERALISED LYMPHADENOPATHY
2) WT LOSS <10% OF BODY WEIGHT
+mucocutaenous manifestations (seborrheic dermatitis, prurigo, fungal nai infections, oral ulcerations)
+ Herpes zoster
+ recurrent URT infections
symptomatic but normal activity
3) WT LOSS >10% of BODY WT.
chronic diarrhoea >1mos
prolonged fever >1mos
oral candidiasis; oral leuoplakia, pulmonary TB
bedridden (performance scale 3)
4) HIV wasting syndrome • pneumocystic carinii pneumonia • toxoplasmosis of brain • HSV >1mos • Kaposi's sarcoma disseminated.
performance scale 4
List the laboratory tests used to diagnose HIV infection & describe the clinical significance of viral load measurement
POC = blood sample finger prick
Describe laboratory and clinical monitoring of HIV disease.
Monitoring HIV Ag and HIV Ab
HIV viral load used to monitor efficacy of ART
Viral nucleic acid used to dx in babies via vertical transmission
