Infections in the Immunocompromised Host

Question 1

what is an immunocompromised host

Answer 1

*an ICH has impaired resistance to infection that is secondary to either:
-underlying disease
-treatment

Question 2

primary immune defects in immunocompromised hosts

Answer 2

1. neutropenia (ANC < 500)
2. decreased antibody production (impaired humoral immunity) [IgG level < 800]
3. decreased cell-mediated immunity (CD4 count < 200)
4. disrupted barriers (skin, mucosa, ec; ex. = burn patient)

Question 3

factors increasing likelihood of death in cancer patients with infection

Answer 3

*gram negative rods as cause of infection
*presence of severe sepsis or septic shock
*hematological malignancy
*HSCT
*multiple co-morbidities
*transfer to ICU

Question 4

prevention of infection in immunocompromised hosts

Answer 4

*prophylaxis for common pathogens:
-fluoroquinolones for bacteria
-fluconazole for fungi
-acyclovir for viruses

Question 5

common infections in immunocompromised hosts

Answer 5

*bacteria: S. aureus, S. epidermidis, GNRs
*fungi: candida, aspergillus
*viruses: herpes simplex, CMV

note - endogenous organisms are the most common cause of infection in immunocompromised hosts

Question 6

pathogenesis of infection in immunocompromised hosts

Answer 6

*endogenous > exogenous
*skin & mucosal surfaces are important points of entry
*predisposing factors include:
-loss of barrier integrity
-depletion of local immune defenses (phagocytic cells in submucosal tissues, Peyer’s patches, IgA)
-bacterial overgrowth on surfaces

Question 7

clinical manifestations of infection in immunocompromised hosts

Answer 7

*FEVER!!
*erythema
*warmth
*swelling
*pain

Question 8

how do we define fever in the immunocompromised hosts

Answer 8

*single temperature >38.3 C (101 F)
OR
*temperature >38 C (100.4 F) for > 1 hour

Question 9

common infectious “clinical syndromes” in immunocompromised hosts

Answer 9

*skin - cutaneous lesions
*HEENT - retinitis, stomatitis, sinusitis
*lungs - pneumonia
*GI tract - esophagitis, perianal infections
*CNS - meningitis/encephalitis
*blood - septicemia

Question 10

microbial causes of fever + skin lesions in immunocompromised hosts

Answer 10

*bacteria: S. aureus, Pseudomonas aeruginosa, Nocardia, M. tuberculosis
*viruses: HSV, varicella-zoster
*fungi: aspergillus, candida, crytpo

Question 11

fever + respiratory sx / abnormal CXR in immunocompromised hosts

Answer 11

*clinical syndrome = PNEUMONIA until proven otherwise
*etiologies: 75% infectious
*challenging to differentiate infection from non-infection

Question 12

microbial causes of fever + CNS findings in immunocompromised hosts

Answer 12

*bacteria: S. aureus, listeria
*viruses: varciella-zoster, HSV
*fungi: Cryptococcus, aspergillus
*parasites: toxoplasma, strongyloides

Question 13

timeline of infection in the neutropenic host

Answer 13

*early (1st 2 weeks of neutropenia): pyogenic extracellular bacteria & viruses
*later (after 2 weeks of neutropenia): bacteria + candida and invasive fungi