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Microbiology > Infection In The Immunocompromised Patient > Flashcards

Infection In The Immunocompromised Patient Flashcards

1
Q

Immune Dysfunction Catagories - Neutropenia (Granulocytopenia) and Defects in Phagocyte Function

A
  • Acquired
    • Drugs
    • Radiation
    • Cancer
    • Haematopoietic stem cell transplant (HSCT)
  • Congenital
  • Defects in function
    • Leucocyte adhesion defects
    • Chemotactic defects
    • Abnormal phagocytosis
    • Defects in intracellular killing
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2
Q

Neutropaenic Sepsis

A
  • Defined as:
    • Neutrophil count = 0.5 x 109 plus
      • ​Temperature >/= 38°C OR
      • Other signs/symptoms consistent with sepsis
  • 1/3 due to bacteraemia
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3
Q

Neutropaenic Sepsis - Sources of Bacteraemia

A
  • 85% of infections are due to endogenous flora
  • Intravascular catheters
    • Most commonly colonised by coagulase negative staphylococci
  • Damaged mucosa
    • Viridans streptococci
    • Clostridium species
    • Escherichia coli and other coliforms
    • Pseudomonas aeruginosa
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4
Q

Neutropaenic Sepsis - Infectious Causes Other Than Bacteraemia

A
  • Upper aerodigestive tract infections
    • Candida species
    • Agents of mucormycosis
  • Lower respiratory tract infections
    • Especially Aspergillus species
  • Skin infections
    • Candida species
    • Trichosporan species
    • Fusarium species
    • Pseudomonas aeruginosa
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5
Q

Neutropaenic Sepsis - Investigation

A
  • History and examination
  • Full blood count
  • Kidney and liver function tests
    • Including albumin
  • C-reactive protein
  • Lactate
  • Blood culture
  • Relevant microbiological specimens
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6
Q

Neutropaenic Sepsis - Principles of Therapy

A
  • Fever in neutropaenia should be treated as infection unless proven otherwise
  • Promp initiation of antibiotic therapy essential
    • ‘Door to needle’ time <1 hour
  • A bactericidal antibiotic should be used - the immune system lacks capacity to kill
  • Antimicrobial regimen should be broad spectrum and directed against principal pathogens encountered
    • Subsequently adjust therapy in light of laboratory isolates
  • Recovery of neutrophils during therapy may be an important determinant of favourable response
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7
Q

Neutropaenic Sepsis - Therapeutic Options

A
  • Monotherapy:
    • Anti-pseudomonal beta-lactam
      • Piperacillin/tazobactam
      • Imipenem or meropenem
      • Ceftazidime
  • Combination therapy:
    • Anti-pseudomonal beta-lactam **+ **aminoglycoside:
      • Gentamycin
      • Ambikacin
      • Tobramycin
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8
Q

Neutropaenic Sepsis - Causes of Persistant Pyrexia

A
  • Pathogen resistant to empiric regiment
  • Dosage inadequate
  • Breakthrough bacteraemia
  • Failure of neutrophil count to rise
  • Line-related sepsis
  • Cryptic abscess
  • Fungal infection
  • Viral infection
  • Mycobacterial infection
  • Underlying disease
  • Graft-versus-host disesease
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9
Q

Neutropaenic Sepsis - Therapy Protocol

A
  • Confirmed neutropenic sepsis - begin empiric antibiotic therapy
    • Review in 48-72 hours - if persistent consider need to broaden antibiotic cover
      • Review in further 48-72 hours - if persisent consider need for antifungal therapy
  • Antibiotics may be stopped when the patient has responded to treatment - irrespective of neutrophil count
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10
Q

Neutropaenia - Infection Prevention

A
  • Prophylactic antibiotics
    • Ciprofloxacin given for duration of neutropaenia
  • Protective (reverse) isolation
    • Decrease nosocomial risk with:
      • Single room with HEPA-filtered air
      • Handwashing critical
    • Minimise exposure to potential exogenous pathogens
      • Neutropaenic diet
  • Granulocyte colony-stimulating factor (G-CSF)
    • Not used routinely
  • Approaches to reduce catheter-related infection
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11
Q

Impaired Cellular Immunity

A
  • Cellular immunity = T-lymphocyte mediated
  • Defects may be:
    • Acquired
      • Drugs eg. cytotoxic chemotherapy, steroids
      • Radiation
      • Lymphoma
      • Hematopoietic stem cell transplantation
      • Infections eg. HIV
    • Congenital
  • May lead to infections that are:
    • Opportunistic
    • Intracellular
    • Emergence of latent infection or reactivation
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12
Q

Impaired Cellular Immunity - Viral Infections

A
  • Herpes simplex virus
  • Varicella zoster virus
  • Cytomegalovirus
  • Epstein-Barr virus
  • Respiratory viruses
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13
Q

Impaired Cellular Immunity - Bacterial Infections

A
  • Listeria monocytogenes
    • ​Occasional cause of severe meningitis
  • *Nocardia *species
    • May manifest as pneumonia or lung nodules
  • *Mycobacterium *species
    • Non-tuberculous mycobacteria may cause:
      • Line-related infections
      • Bacteraemia
      • Pneumonia
    • *M.tuberculosis *occurs predominantly in countries with high endemic rates
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14
Q

Impaired Cellular Immunity - Fungal Infections

A
  • Pneumocystis jirovecii
    • ​Sx - dyspnoea, cough, fever, bilateral infiltrates
    • Treat with co-trimoxazole
  • *Aspergillus *species
    • Commonly affects lungs and sinuses
  • Cryptococcus neoformans
    • Frequent cause of meningitis in HIV-infected patients
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15
Q

Impaired Cellular Immunity - Parasitic Infections

A
  • Toxoplasma gondii
    • May present as:
      • Fever
      • Encephalitis with focal cerebral lesions
      • Pneumonitis
      • Myocarditis
  • *Cryptosporidium *species
    • Mary lead to chronic or severe disease
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16
Q

Impaired Cellular Immunity - Diagnosis and Treatment of Infections

A
  • Diagnosis:
    • Pathogen appropriate clinical features
    • Ceulture
    • Serology
    • Biopsy/histology
    • Molecular tools eg. EIA, PCR
  • Treament:
    • Appropriate to pathogen
    • Empiric
17
Q

Impaired Cellular Immunity - Infection Prophylaxis

A
  • May be:
    • Primary
      • HIV infection when CD4 count is <200 cells/mm3
    • Secondary
  • Defined refimens in HIV and hematopoietic stem cell transplantation (HSCT)
18
Q

Impaired Humoral Immunity and Complement Deficiency

A
  • Mediated by B-lymphocytes
  • May be:
    • Primary - congenital
    • Secondary - acquired
      • Lymphoproliferative disorders
        • eg. Chronic lympocytic leukaemia, multiple myeloma
      • Hypo/asplenism
        • Splenectom
        • Sickle cell disease
      • Anti-cancer treatment
        • Cytotoxic chemotherapy
        • Radiotherapy
        • Hematopoietic stem cell transplantation
      • Drugs
      • Protein defiency
        • Protein-losing enteropathy
        • Nephrotic syndrome
        • Burns
19
Q

Impaired Humoral Immunity and Complement Deficiency - Infectious Pathogens

A
  • Bacteria
    • Encapsulated bacteria:
      • Streptococcus pneumoniae
      • Haemophilus influenzae
      • Neisseria meningitidis
    • *​**Capnocytophage canimorsus *- from animal bites
  • Parasites
    • Malaria
    • Babesiosis
20
Q

Impaired Humoral Immunity and Complement Deficiency - Presentation

A
  • Congenital
    • Usually presents with recurrent acute respiratory tract infections
      • Sinusitis
      • Otitis media
      • Pneumonia
        • May ==> to chronic disease
  • Acquired (eg. postsplenectomy sepsis)
    • Fever/rigors
    • Fulminating infection
21
Q

Impaired Humoral Immunity and Complement Deficiency - Management

A
  • Treatment
    • Antibiotics for infection
    • Identify underlying problem and correct
      • Immunoglobulin replacement
  • Prevention
    • Prophylactic antibiotics
      • Penicillin V
    • Vaccines
      • Pneumococcal
      • Meningococcal
      • Hib
      • Influenza

Microbiology (10 decks)

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