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
Describe the current treatment of HIV infection with anti viral agents.
antivirals for AIDS illness = return back to HIV infection state
> PrEP
PEP for Sexual Exposure
> ART - combination pill (cART)
req. 90% adherence
- poor adherence = viral mutation and adherence
*NUCLEOSIDE: reverse transcriptase
!marrow tox., neuropathy, lipodystrophy
*NON-NUCLEOSIDE: reverse transcriptase
!skin rashes, hypersens, drug interactions
*PROTEASE inhibitors
!drug-drug, diarrhoea, lipodystrophy, hyperlipidaemia
*INTEGRASE inhib.
!rashes, disrupted sleep
- start all pt. at dx
- lifetime
Describe the ethical issues involved in HIV testing
1) Sensitivity
2) Informed Consent -
3) Confidentiality balance with possible risk to others
4) Patients may request their status is hidden from other practice staff
List the infections which may be transmitted by needlestick injuries.
HIV
Hep B, Hep C
Outline the recommended procedure following a needlestick injury.
- Wash off splashes on skin with soap and running water.
- Encourage bleeding if the skin has been broken, but do not suck.
- Wash out splashes in the eye, nose or mouth.
- Assessment of the risk of virus transmission by someone other than the victim.
- Report the incident.
Signficance of 1º HIV / seroconversion
abrupt onset 2-4w post exposure; self-limiting
non-specific
Flu-like illness
Fever
malaise lethargy
Signficance of Pneumocystis jiroveci pneumonia
Commonest late stage AID infection
CD4 <200
Classical history of dry cough and increasing breathlessness over seveal weeks
-CXR, sputum, broncoscopy
> COTRIMOXAZOLE
PENTAMIDINE
Define PUO
temperature of greater than 38.3oC on multiple occasions during a period longer than three weeks that defied one week’s evaluation of the patient in hospital
• 3 outpatient/inpatient +
• 1 week of outpatient investigation
+Nonsocomial
+Neuropenic - fever w/ neutrophil <500 undiagnosed after 3 days of investigation
+HIV-associated PUO - 3days inpatient / 4w outpatient
List the major disease categories which can present with a PUO.
INFECTION
MALIGNANCY
INFLAMMATORY
Outline the approach to the PUO patient - important aspects of history taking, examination and preliminary investigations.
urines, fbcs, CRP AND ESR (acute phase reactants), blood cultures
Appreciate some of the contemporary imaging techniques available for use in investigating PUO.
CXR
Echocadiography (new murmur)
CT PET
- cannot always differentiate between infection and inflamm
- anatomical change may not develop in imm compr.
Understand the place of the “therapeutic trial” in PUO patients.
Suspected myobacterial infection
suspected vasculitis or connective tissue disorder
Common causes of HIV-PUO
Mycobacterium tuberculosis
Mycobacterium avium
Mix of causatives
Unknown
Next stage of investigating PUO
Invasive investigations
- tissue culture and histology
- BM, liver = blind investigation
Outcomes of PUO
Spontaneous resolution (younger more common)
Alternatively respond to NSAIDs or steroids
