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Finals Revision > Infectious diseases > Flashcards

Infectious diseases Flashcards

1
Q

What does HIV stand for

A

Human immunodeficiency virus

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2
Q

What does AIDS stand for

A

Acquired immunodeficiency syndrome

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3
Q

What type of virus is HIV?

A

RNA retrovirus

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4
Q

Pathology of HIV

A

HIV enters & destroys the CD4 T helper cells

Initial seroconversion flu like illness occurs within a few weeks of infection

infection then becomes asymptomatic until it progresses & patient becomes immunocompromised

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5
Q

How is HIV transmitted?

A
  • Unprotected anal, vaginal or oral sexual activity.
  • Mother to child at any stage of pregnancy, birth or breastfeeding. This is referred to as vertical transmission.
  • Mucous membrane, blood or open wound exposure to infected blood or bodily fluids such as through sharing needles, needle-stick injuries or blood splashed in an eye.
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6
Q

Name some AIDS defining illnesses

A 
Kaposi’s sarcoma
Pneumocystis jirovecii pneumonia (PCP)
Cytomegalovirus infection
Candidiasis (oesophageal or bronchial)
Lymphomas
Tuberculosis
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7
Q

Why do AIDS defining illnesses occur in late stage HIV?

A

The CD4 count has dropped to a level that allows for unusual opportunistic infections and malignancies to appear

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8
Q

How is HIV screened for?

A

Everyone admitted to hospital with infectious disease regardless of risk factors

Anyone with risk factors

only need verbal consent before testing

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9
Q

When are antibody tests positive for HIV?

A

may not be present in early infection, but most people develop antibodies to HIV at 4-6 weeks but 99% do by 3 months

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10
Q

How is HIV tested for?

A
  1. Antibody testing - ELISA test and confirmatory Western Blot Assay
  2. p24 antigen - appears early in the blood as viral RNA rises, positive from 1 week to 3/4 weeks after infection
  3. Combination tests - p24 antigen + HIV antibody. If it’s positive, repeat to confirm.
  4. Can do PCR testing for HIV RNA levels - directly quantifies the amount of HIV in the blood and gives a viral load
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11
Q

When should someone asymptotic be tested for HIV after exposure?

A

4 weeks after possible exposure, then repeat at 12 weeks if there’s a negative result

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12
Q

What are the symptoms of HIV seroconversion illness?

A 
sore throat
lymphadenopathy
malaise, myalgia, arthralgia
diarrhoea
maculopapular rash
mouth ulcers
rarely meningoencephalitis
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13
Q

when do people have HIV seroconversion illness after exposure to the virus?

A

3-12 weeks after infection

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14
Q

in what % of people is initial HIV seroconversion symptomatic?

A

60-80%

increased symptomatic severity is associated with poorer long term diagnosis

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15
Q

How is HIV monitored?

A

1) CD4 count - CD4 cells are destroyed by the virus, lower the count the higher the risk of opportunistic infection.
500-1200 cells/mm3 normal
<200 cells/mm3 = AIDS & high risk of opportunistic infections

2) Viral load - number of copies of HIV RNA per ml of blood. Undetectable = viral load below the labs recordable range.

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16
Q

Tx for HIV and what’s the goal of it?

A

Antiretroviral therapy (ART) with the aim of achieving a normal CD4 count and undetectable viral load.

Highly active anti-retrovirus therapy (HAART) medication classes:

  1. Protease inhibitors (PIs)
  2. Integrase inhibitors (IIs)
  3. Nucleoside reverse transcriptase inhibitors (NRTIs)
  4. Non-nucleoside revisers transcriptase inhibitors (NNRTIs)
  5. Entry inhibitors (Els)

Usually start with 2 NRTIs (tenofovir & emtricitabine) + a 3rd agent

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17
Q

What additional management if needed for people with HIV?

A

prophylactic co-trimoxazole - for CD4 count <200 to protect against pneumocystis jirovecii pneumonia (PCP)

Monitor CVD risks & give statins

Yearly cervical smears - HIV predisposes to HPV

Keep up with vaccinations but avoid live vaccines

Advise condons and dams (unlikely to pass on virus if undetectable viral load)

C-section unless undetectable viral load

No breastfeeding unless undetectable viral load

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18
Q

Mx of children born to HIV positive mothers

A

ART for 4 weeks to reduce risk of vertical transmission

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19
Q

What is post exposure prophylaxis for HIV?

A

used after exposure to HIV to reduce the risk of transmission

not 100% effective

Needs to be started within 72 hours, sooner its started the better

Do HIV test initially & at 3 months to confirm negative status

Protected sex until confirmed negative at 3 months

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20
Q

What is given as post exposure prophylaxis for HIV?

A

Truvada (emtricitabine + tenofovir) & raltegravir for 28 days

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21
Q

Name some neurocomplications of HIV

A 
Toxoplasmosis
Primary CNS lymphoma 
TB
Encephalitis
Cryptococcus 
Progressive multifocal leukoencephalopathy 
AIDS dementia complex
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22
Q

What is toxoplasmosis?

A

A disease caused by the toxoplasma gondii parasite that can be picked up from raw meat, water or unwashed fruit/veg. Cats carry the parasite.

It accounts for 50% of cerebral lesions in patients with HIV

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23
Q

Symptoms and Ix for toxoplasmosis

A

Constitutional symptoms
HEadache
Confusion
Drowsiness

CT - single/multiple ring enhancing lesions, mass effect may be seen

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24
Q

Mx of toxoplasmosis

A

sulfadiazine and pyrimethamine

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25
Q

What is primary CNS lymphoma associated with?

A

EBV

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26
Q

what is seen on CT for primary CNS lymphoma?

A

single or multiple homogenous enhancing lesions

27
Q

mx for primary CNS lymphoma

A

steroids - reduce tumour size
chemotherapy - methotrexate
whole brain irradiation
surgical excision

28
Q

How to tell the difference between toxoplasmosis and lymphoma

A

Toxoplasmosis = thallium SPECT negative, ring/nodular enhancement on CT & multiple lesions

Lymphoma = thallium SPECT positive, solid (homogenous) enhancement on CT and single lesion

29
Q

What is crytococcus?

A

Most common fungal infection of CNS

30
Q

What is the Most common fungal infection of CNS?

A

crytococcus

31
Q

symptoms of crytococcus

A

headache, fever, malaise, nausea/vomiting, seizures, focal neurological deficit

32
Q

what is seen on LP for crytococcus?

A

High opening pressure

India ink test positive

33
Q

what is seen on CT of crytococcus?

A

meningeal enhancement, cerebral oedema

34
Q

What is Progressive multifocal leukoencephalopathy (PML)?

A

widespread demyelination

due to infection of oligodendrocytes by JC virus (a polyoma DNA virus)

35
Q

Symptoms of progressive multifocal leukoencephalopathy

A

subacute onset : behavioural changes, speech, motor, visual impairment

36
Q

Imaging results for progressive multifocal leukoencephalopathy

A

Ct single or multiple lesions, no mass effect, don’t usually enhance.

MRI is better - high-signal demyelinating white matter lesions are seen

37
Q

What GI upset is seen in HIV?

A

Diarrhoea is common in patients with HIV. This may be due to the effects of the virus itself (HIV enteritis) or opportunistic infections

38
Q

causes of diarrhoea in HIV positive patients

A 
HIV enteritis 
Cryptosporidium + other protozoa (most common)
Cytomegalovirus
Mycobacterium avium intracellulare
Giardia
39
Q

What test can be done on the stool to diagnose cryptosporidium in HIV?

A

A modified Ziehl-Neelsen stain (acid-fast stain) of the stool may reveal the characteristic red cysts of Cryptosporidium.

40
Q

What infections do you see in HIV patients with a CD4 cell count of 200-500?

A

Oral thrush - candida albicans
Shingles - herpes zoster
Hairy leukoplakia - EBV
Kaposi sarcoma - HHV-8

41
Q

What infections do you see in HIV patients with a CD4 cell count of 100-200?

A 
Crytosporidiosis - diarrhoea
Cerebral toxoplasmosis
Progressive multifocal leukoencephalopathy 
Pneuocystis jirovecii pneumonia
HIV dementia
42
Q

What infections do you see in HIV patients with a CD4 cell count of 50-100?

A

Aspergillosis - caused by aspergillus fumigatus
Oesophageal candidiasis - candida albicans
Cryptococcal meningitis
Primary CNS lymphoma

43
Q

What infections do you see in HIV patients with a CD4 cell count of <50?

A

Cytomegalovirus retinitis

Mycobacterium avium-intracellulare infection

44
Q

What CD4 cell counts is seen in patients with oesophageal candidiasis?

A

Less than 100

45
Q

Symptoms of oesophageal candidiasis

A

dsyphagia - difficulty swallowing

Odynophagia - painful swallowing

46
Q

Tx for oesophageal candidiasis

A

fluconazole + itraconazole

47
Q

What causes Kaposi’s sarcoma in HIV patients?

A

HHV-8 : human herpes virus 8

48
Q

Presentation of Kaposi’s sarcoma

A

Purple papules or plaques on the skin or mucosa (GI tract and respiratory tract)

Skin lesions may ulcerate

Respiratory involvement = haemoptysis and pleural effusion

49
Q

Mx for Kaposi’s sarcoma

A

Radiotherapy and resection

50
Q

Symptoms of PCP

A 
Features
dyspnoea
dry cough
fever
very few chest signs

Pneumothorax is a common complication of PCP.

Extrapulmonary manifestations are rare (1-2% of cases), may cause
hepatosplenomegaly
lymphadenopathy
choroid lesions

51
Q

What is pneumocystis jiroveci pneumonia?

A

Called PCP

Generally classified as a fungus but some consider it a protozoa

Most common opportunistic infection in AIDS

52
Q

Who should get prophylaxis against PCP?

A

all patients with a CD4 count < 200/mm³ should receive PCP prophylaxis

53
Q

Ix for PCP

A

CXR - bilateral interstitial pulmonary infiltrates / lobar consolidation / can be normal

Exercise induced desaturation

Sputum often fails to show PCP, need bronchoalveolar lavage
- silver stain shows characteristic cysts

54
Q

Mx of PCP

A

Co-trimoxazole

IV pentamidine in severe cases

55
Q

What is MRSA?

A

Methicillin resistant staphylococcus aureus

56
Q

Who gets screened for MRSA?

A

Elective admissions before coming in

Emergency admissions

57
Q

How are patients screened for MRSA?

A

Nasal swab (5 seconds around rim of patients nose) and skin lesions/wounds

58
Q

How should you treat a carrier of MRSA?

A

Nose = mupirocin 2% in white soft paraffin, TDS for 5 days

Skin = chlorhexidine gluconate OD for 5 days, apply all over but particularly to axilla, groin and perineum

59
Q

Abx for MRSA infections

A

Vancomycin
Teicoplanin
Linezolid

60
Q

What causes syphilis?

A

Treponema pallidum

61
Q

What happens in the primary stage of syphilis?

A

painless ulcers (chancre)

62
Q

What is lymphogranuloma venereum (LGV)?

A

An SiT caused by chlamydia trachomatis

Primary infection = single painless pustule which develops into an ulcer

Second stage of infection = painful inguinal lymphadenopathy. Classic GROOVE SIGN

third stage of infection = proctocolitis. Risk factors: MSM & HIV infection

63
Q

Symptoms of proctocolitis

A

Rectal bleeding and discharge

Ulceration around the anus

64
Q

Mx of LGV (lymphogranuloma venereum)

A

doxycycline

Finals Revision (18 decks)

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