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Yr 3 - December lectures 2018 > Infections in the immunocompromised > Flashcards

Infections in the immunocompromised Flashcards

1
Q

Define pathogen

A

a micro-organism causing disease

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2
Q

Define primary pathogen

A

common cause of disease in healthy non-immune hosts e.g. s aureus, s. pneumoniae

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3
Q

Define opportunistic pathogen

A

rare cause of disease in healthy individuals causes serious disease in compromised hosts e.g. pseudomonas aeruginosa

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4
Q

What is included in host defence?

A

immunological but also anatomical integrity and physiological defences of the body surfaces e.g peristalsis, muco-ciliary escalator, normal flora, normal urinary flow

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5
Q

What are examples of damage to physical defence mechanisms?

A 
burns
trauma 
breaching skin 
iatrogenic damage e.g. surgery 
foreign body insertion 
intubation
urinary catheter
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6
Q

What are some more unusual examples of damage to physiological defence?

A

antibiotic disturbance of normal flora

cytotoxic damage to the gut

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7
Q

What are the most common infections caused by burns?

A

pseudomonas aeruginosa and staphylococcus aureus
- spread into bloodstream
- treatment includes topical and systemic agents
prevention of infection
- topical prophylactic use of silver sulfadiazine
- burn wound excision

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8
Q

What are some examples of primary immunodeficiency?

A 
neutrophil defect: CGD
humoral B cell defects
humoral complement 
cell-mediated- T cells 
severe combined immunodeficiency
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9
Q

What are examples of secondary immunodeficiency?

A 
AIDS
neutropenia
post-transplant
BMT 
chemotherapy 
spenocetomised patient
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10
Q

What pathogens are involved in humoral defects?

A 
capsulated bacteria
- s. pneumoniae
- H.influenzae
- N. meningitidis
- S.aureus 
Enteroviruses
mycoplasma
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11
Q

What pathogens are involved in neutrophil defects?

A

s. aureus
candida
aspergillus

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12
Q

What pathogens are involved in cell mediated defects?

A

intracellular bacteria
- mycobacteria - salmonella, listeria, legionella
viruses
- herpes, respiratory and enteric viruses
fungi and protozoa
- candida aspergilus, pneumocysitis, cryptococcus, cryotosporidium, toxoplasma

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13
Q

What is the management for primary immunodeficiency ?

A 
correct the defect:
- immunoglobulins, cytokines
- BMT 
- gene therapy?
early aggressive antibiotic tx
prophylaxis
- daily co-trimoxazole 
- penicillin if complement deficiency 
- fluoxacillin in some neutrophil disorders
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14
Q

What are the differing presentations of AIDs in HIV- positive individuals in western population compared to africa?

A

western population
- pre-haart pneumocystitis carinii pneumonia
africa
- TB or slim disease (prolonged diarrhoea with a wasting illness)

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15
Q

How is AIDS diagnosed?

A

many pathogens are impossible to grow or difficult
some are inaccessible e.g. intracerebral
multiple infections are the rule
antigen detection (PCR DNA probe) + tissue diagnoses may be required

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16
Q

What is an indicator of disease progression in AIDS?

A

spectrum of infecting organisms relates to disease progression = CD4 count diminshes
CD4 count is boosted by HAART (triple therapy)
rational prophylaxis offered for PCP, MAI, CMV with falling counts

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17
Q

What are the different pathogens that normally infect people with AIDs?

A 
Fungi 
- pneumocystitis carinii
- candida spp
- cryptococcis neoformans 
Parasites
- cerebral toxiplasmosis 
- cryptosporidiosis 
Bacteria 
- mycobacterium avium 
- mycobacterium tuberculosis 
- salmonella 
Viruses
- CMV
- HSV
- HHVB/KSHV
18
Q

What is pneumocystitis carinii?

A

ubiquitous uncultivable fungus

  • 60% of people infected by age 4
  • complex life cycle involving cysts and trophozoites
  • most common infection in AIDs

presentation

  • non-productive cough, dyspnoea, fever
  • perihilar infiltrates
  • may progress to severe respiratory distress

diagnosis
- silver stain/monoclonal antibody detection in BAL or biopsy

19
Q

What is the treatment for pneumocystitis carinii?

A

high dose cotrimoxazole
ventilation
if sulphonamide allergy - pentamidine, dapsone, clindamycin plus primaquine, atovaquone

chemoprophylaxis

  • cotrimoxazole or inhaled pentamidine
  • ?? still needed on HAART
20
Q

What is mycobacterium tuberculosis ?

A

2-10% annual risk of infection in HIV positive
- worldwide most illness is reactivation of latent infection
in africa 50% of HIV infected are MTB infected

presentation

  • rapidly progressive disease on primary infection
  • extrapulmonary disease more likely as CD4 cells decline
21
Q

What is mycobacterium avium-intracellulare complex (MAI)?

A

M. avium- TB in birds
M. intracellulare - atypical human isolate - ubiquitous (soil, water, food, animals)
presentation
- pulmonary infection in non-aids pts
- disseminated in advanced AIDS
- fever, night sweats, weight loss, organ infiltration

22
Q

How is MAI diagnosed and treated?

A

diagnosis

  • culture after 1-4 incubation of sample from a sterile site
  • blood culture, bone marrow, lymph node, liver biopsy

therapy

  • problematic: resistance to antituberculous drugs
  • clarithomycin or azithromycin (macrolides) and ethambutol plus rifabulin (+/- clotozamine, rifampicin, ciprofloxacin, amikacin)

prophylaxis
- rifabulin at CD4 <0.1x10^9/L

23
Q

What is cerebral toxoplasmosis?

A

T gondii
- protozoal infection, usually asymptomatic (50% infected by middle age) or glandular fever
presentation in aids
- main cause of focal CNS lesions in AIDs
- pneumonitis and chorioretinitis may also occur
Empirical antitoxoplasma therapy if: I. ring enhancing lesions on CT/MRI

24
Q

What is the treatment for cerebral toxoplasmosis?

A

pyrimethamine plus folinic acid and sulphadiazine or clindamycin for 3-6 weeks acutely (expert advice needed)
prophylaxis
- secondary: prevent realpse pyrimethamine/dapsone
- primary: seropositive patients with low CD4 count

25
Q

What is cryptococcus neoformans?

A

capsulate urease-positive yeast

  • found in bird droppings
  • asymptomatic infection by pulmonary route

leading systemic fungal infection in AIDs

  • insidious meningitis - capsule inhibits alternate pathway of complement and little inflammation
  • skin and bone infections less common
26
Q

How is cryptococcus neoformans diagnosed and treated?

A

microscopy of CSF with india ink
antigen detection by latex agglutination in serum or urine (>90% sensitive)
csf or blood culture

treatment

  • amphoteracin B or fluconazole
  • lifelong fluconazole maintenance therapy required (even with HAART?)
27
Q

What is cryptosporidiosis?

A

c.parvum is an apicomplexan protozoan parasite
water borne outbreaks, faecal oral spread esp. farm animals
self-limiting infection (2-3 weeks) in normal children
chronic watery diarrhoea in AIDs can be life-threatening

28
Q

How is cryptosporidiosis diagnosed and treated?

A

diagnosis

  • modified acid-fast stain
  • monoclonal based immunofluorescence

prevention
- boil water if at risk

treatment

  • difficult
  • azithromycin with paromomycin shows promise
29
Q

What are the common viral infections in AIDs?

A

HSV - chronic mucocutaneous (oral and anogenital)
VZV - shingles
CMV- retinitis, encephalitis, hepatitis, pneumonia
treatment: aciclovir
HHV8 - kaposi’s sarcoma

30
Q

What are the causes of acquired immunodeficiency neutropenia?

A

iatrogenic- post-chemotherapy, post-BMT
aplastic anaemia - post chloramphenicol
other drugs - rarely high dose beta-lactams

31
Q

Why is acquired immunodeficiency neutropenia difficult to diagnose?

A

absence of pus/localisation

rely on fever as cardinal sign

32
Q

What is the empirical therapy for acquired immunodeficiency neutropenia?

A

febrile neutropenic cannot await culture results
URGENT bactericidal broad spectrum agents
anti-pseudomonal penicillin and aminoglycoside
add vancomycin (anti-gram-positive), then anti-fungal if no improvement

33
Q

What are the opportunistic mycoses in neutropenia?

A

aspergillus fumigatus

  • saprophytic mould in soil
  • inhaled spores infect lungs in prolonged neutropenia
  • necrotising pneumonia and dissemination
  • filamentous septate hyphae in tissues
  • common contaminant of culture media
    treatment: amphoteracin B (liposomal less toxic)

candida albicans
- yeast like fungus
- endogenous infection
- predispositions: diabetes, IV feeding, antibiotics
difficult to diagnose as blood cultures are only positive in 40%
treatment - amphorain B, fluconazole

34
Q

What are patients that have had a splenectomy susceptible to and what are the prevention approaches?

A

susceptible to capsulate bacteria

  • risk of systemic pneumococcal disease 25x , fatality 75x
  • functional splenectomy in sickle cell disease

prevention of infection

  • vaccination (preferably before splenectomy
  • prophylactic antibiotics - pen V or amoxicylin
35
Q

What are common infections in pregnancy?

A

ascending UTI
listeria monocytogenes
puerperal sepsis

36
Q

What can listeria monocytogenes cause in pregnancy and how is it avoided?

A

still birth, miscarrage or severe illness of newborn
septicaemia and meningitis in mother

Prevention
- pregnant women should avoid eating pate and soft cheeses

treatment/; amipicillin

37
Q

What form of sepsis is most important in pregnancy ?

A

groupe B
- maternal septicaemia, neonatal septicaemia and meningitis
higher risk in US than UK
prophylaxis with ampicillin during labour

38
Q

What are examples of congenital infections?

A 
toxoplasmosis 
rubella
CMV
HSV
hepatitis B, HIV 
parvovirus b19
syphilis 
ophthalmia neonatorum
39
Q

How are congenital infections managed?

A 
prevention 
- vaccination - rubella and hep B 
treatment
- antimicrobials = antiretrovirals, syphilis, aciclovir, spiramycin for toxo, silver nitrate ete dropes 
screening- syphilis, hep B  and HIV
vigilance and avoidance
40
Q

What are the implications of early onset infections in neonates?

A

<12 hours from birth

  • more severe, acquired in womb or at birth, usually disseminated infections (listeria or GBS)
  • increase risk if PROM, meconium stained liquor, maternal sepsis
41
Q

How are infections in neonates diagnosed and treated?

A

gastric aspirate, blood culture, CSF

treatment: ampicillin and gentamicin

Yr 3 - December lectures 2018 (15 decks)

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