Lecture 7 - Infections in Immunocompromised Host

Question 1

What causes predisposition to infection?

Answer 1

neutropenia
defects in the phagocytic defense
defects in cellular immunity
defects in humoral immunity

Question 2

Incidence and severity of infection are inversely proportional to the _____

Answer 2

absolute neutrophil count (ANC)

risk of infection is significant at ANC <500

Question 3

Phagocytic defenses help us protect against what types of pathogens?

Answer 3

gram negative rods: E. coli, psuedomonas, klebsiella

gram positive: staph, strep

fungi: candidi, asperguillus and mucor

Question 4

Which pathogens do you really only see as opportunistic pathogens?

Answer 4

Bacteria:
listeria, mycobacteria, nocardia, legionella, salmonella

Fungi:
cryptococcus, histoplasma, coccidioides, pneumocystis

Viruses:
VZV, HSV, CMV

Helminths: stronglyoids stercoralis

Question 5

Normally for FUO we do not treat with ABX until we know what is going on, however if they have neutropenia what do we do?

Answer 5

rapid initiation of empiric antimicrobial therapy = MANDATORY

if they’re not getting any better you should be thinking fungus

Question 6

What are common infections in the neutropenic pt?

Answer 6

oropharygneal infections (HSV, candida, bacterial infections)

pulmonary infections (CMV in the setting of bone marrow transplantation)

skin and soft tissue infections (pts often have long term IV devices, offending organism typically skin flora

Question 7

What are the principles of therapy for neutropenic pts?

Answer 7

initial: empiric
cover gram negative

recovery of neutrophil count is prognostic factor

if pt remains febrile despite antibacterial coverage – consider antifungal therapy

Question 8

In pts with HIV, pneumocystis jiroveci is an opportunistic infection when the CD4 count is what?

Answer 8

<200

Question 9

What infections are we seeing in HIV pts with a CD4 < 100?

Answer 9

cryptococcal infections 
MAI 
CMV
toxoplasma 
cryptosporidium

Question 10

CMV treatment

Answer 10

gancyclovir

major SE of gancyclovir is pancytopenia or neutropenia

Question 11

Which species is most commonly involved in oropharyngeal infections of HIV pts?

Answer 11

candidia albicans

this infection can occur at high CD4 counts

Question 12

How can you tell the difference between thrush and oral hairy leukoplakia?

Answer 12

oral hairy leukoplakia you can not scrap off

dx of thrush is via KOH prep

Question 13

Besides thrust and oral hairy leukoplakia, what other oral ulcers are seen in HIV pts?

Answer 13

HSV
CMV: large, shallow ulcers
Aphthous stomatitis: ulcerations with exudate at the base

Question 14

How are oral ulcers dx in pts with HIV?

Answer 14

cultures, biopsy
KOH prep: thrush
EM: CMV

Question 15

Which cutaneous infections are seen with HIV pts?

Answer 15

VZV, HSV, Bacillary angiomatosis, molluscum contagiosum

Question 16

How is genital HSV dx in an HIV pt?

Answer 16

PCR

same way to dx VZV

both of these can recur regardless of the CD4 count

Question 17

Bacillary angiomatosis

Answer 17

a skin infection see in HIV pts

bartonella henselae

Question 18

Mollusum contagiosum

Answer 18

a skin infection seen in HIV pts

poxvirus
small flesh-colored umbilicated lesions

Question 19

CMV retinitis

Answer 19

ocular infection seen in pts with HIV

sxs include progressive visual loss, blurring and “floaters”

fundoscopic exam reveals coalescing white exudates with surrounding hemorrhage and edema

without treatment will progress to retinal detachment and visual loss

Question 20

Which vaccine is given to HIV pts to decrease risk of recurrent PNAs?

Answer 20

Prevnar

Question 21

Which pulmonary infections are commonly seen in HIV pts?

Answer 21

bacterial (strep, staph, h. flu)
pneumocystis jiroveci (PJP)
fungal (aspergillus, histpolasma, crypto)
mycobacterial (MAC - MTB and MIA)

Question 22

PJP clinical manifestations

Answer 22

insidious onset of fever, sweats, fatigue, non-productive cough
dyspnea is initially exertional, but progresses with impairment of gas exchange

Question 23

How is PJP dx?

Answer 23

blood gases reveal reduced oxygen levels and commonly low PCO2 levels
CXR most commonly reveal diffuse interstitial infiltrates (80%), but lobar, nodular, cavitary, asymmetric patterns can also occur
sputum, bronchoalveloar lavage or biopsy specimens are sent for staining

Question 24

What is the most common non-tuberculous pulmonary mycobacterial infection seen in HIV pts?

Answer 24

m. kansasii

Question 25

CMV clinical manifestation

Answer 25

can affect the entire GI system: esophagitis, gastritis, colitis
pts present with odynophagia, diarrhea, proctitis, fever, abdominal pain
can cause acalculous cholescystitis

dx: PCR, endoscopy or colonoscopy with biopsy and EM

Question 26

Crypotosporidium

Answer 26

usually causes a persistent diarrheal disease
can also cause acalculous cholescytitis

dx: stool PCR

Question 27

What CNS infections are seen with HIV pts?

Answer 27

cryptococcus
toxoplasma
CMV
PML, JC virus

Question 28

How is Cryptococcal Meningitis dx?

Answer 28

CSF analysis with INDIA INK STAIN

Question 29

Toxoplasmosis

Answer 29

HA, confusion, behavior/mood changes
can also cause ocular disease
ring enhancing lesion or lesions on CT or MRI
in HIV it is reactivation – IgG will be positive for all, dx by CSF PCR

Question 30

India ink stain

Answer 30

used to dx cryptococcal meningitis

Question 31

MAC prophylaxis

Answer 31

Begin prophylaxis at CD4 count <50

Prophylaxis with azithromycin 1200mg weekly

Question 32

PCP prophylaxis

Answer 32

Being prophylaxis at CD4 count <200
Bactrim DS (trimethoprim-sulfamethoxazole)
Also protects against toxoplasma