Micro: Opportunistic Mycoses in AIDS

Question 1

What is the most common fungal inf in AIDS pts?

Answer 1

oropharyngeal candidiasis (thrush)

Question 2

What is the microbiology of candida?

Answer 2

grows slowly as yeast in culture
oval budding cells in culture and blood
branching pseudohyphae in some species
can stain gram+ but are much larger than bacteria

Question 3

What are the symptoms of candidiasis in HIV?

Answer 3

altered taste, odynophagia, retrosternal pain, pseudomembranous thrush (can be scraped away), erythematous oral candidiasis, esophagitis

Question 4

What are important risk factors for candidemia and invasive candidiasis?

Answer 4

central venous lines, invasive procedures, broad spectrum abx
NOT more common in HIV, only mucosal inf

Question 5

How is candidiasis diagnosed?

Answer 5

clinical presentation
maybe endoscopy to rule out other sources
KOH prep - budding yeast and pseudohyphae
biopsy of oral lesions, esp if no response to Tx
culture not usually helpful b/c it is normal flora, culture of blood can confirm disseminated

Question 6

What is the general treatment for candidiasis?

Answer 6

Fluconazole, oral or IV - resistance not uncommon

treat underlying HIV

Question 7

What are important implications for candidiasis in HIV?

Answer 7

more common as CD4 falls, but can occur when higher
recurrent or resistant thrush is indication to start HIV treatment
esophageal candidiasis = AIDS defining condition

Question 8

What is the prevention of candidiasis?

Answer 8

prophylaxis w fluconazole not recommended due to resistance

Question 9

What is the microbiology/epidemiology of c. neoformans?

Answer 9

encapsulated yeast
worldwide distribution, soil and pigeon droppings
doesn’t infect birds
serotypes based on capsular agglutination rxns - A, B, C, or D (A and D most common in AIDS)
family includes c. gattii

Question 10

What is the pathogenesis of crypto?

Answer 10

portal of entry is lungs (also needle stick entry, transplant)
antiphagocytic capsule - prevents phagocytosis, depeletes complement, interferes with cell/cytokine response, prevents drainage of CSF
melanin made by yeast = virulence factor, tolerates oxidative stress

Question 11

What are the clinical manifestations of crypto?

Answer 11

meningitis - most common, signs usually -
increased ICP
pneumonia

Question 12

How is crypto diagnosed?

Answer 12

cryptococcal antigen in CSF and serum - detects part of capsule
smooth, yellow-tan colonies

Question 13

Who are the c. gattii hosts?

Answer 13

mostly in pts with “normal” immune system - may be subclinical problem
can be in HIV+

Question 14

What is the treatment of crypto?

Answer 14

amphoterecin B + flucytosine (5-FC)
oral regimens NOT preferred
in AIDS, IV for two weeks followed by oral maintenance
ampho B can reversibly raise creatinine
resistance rare unless using fluconazole
elevated CSF pressure - no meds, lumbar puncture

Question 15

What is the maintenance/prophylaxis for crypto?

Answer 15

maintenance: start w fluconazole at higher doses for 8-10 wks
continue at lower doses til CD4 over 200
primary prophylaxis NOT recommended

Question 16

What are the key points about histo?

Answer 16

ohio river valley, southeast (inc Dallas), in soil fertilized by bird or bat poop, inf through inhalation of spores
present intracellularly in phagocytic cells
acute and chronic pneumonias
no primary prophylaxis

Question 17

What are the key points about cocci?

Answer 17

endosporulating spherules in tissue, highly infectious
west texas to california, regions of mexico
inf after rainy seasons and dust storms
inf through inhalation of arthrospores
diffuse pneumonia and disseminated
dx by serology - immunodiffusion and complement fixation (IgG), seeing spherule, or culture
tx = ampho b for pneumonia, ampho + itraconazole for disseminated, LIFELONG fluconazole for meningitis

Question 18

What are the key points about blasto?

Answer 18

mississippi and ohio river valleys, not texas
exposure to moist soil
culture or antigen testing in urine and blood
pneumonia, extra-pulm in HIV (meningitis, mass lesions)
ampho b for severe, itraconazole for maintenance

Question 19

What are the key points about sporotrichosis?

Answer 19

inf from traumatic inoculation into skin
cutaneous manifestations, disseminated in AIDS (high mortality)
dx by culture, no antigen test

Question 20

What are the key points about penicillium marneffei (penicilliosis)?

Answer 20

red pigment in culture
southeast asia and southern china
tb-like pulm syndrome, dissemination, umbilicated lesions in skin and mucous membranes
no antigen test, dx by culture or biopsy
maintenance therapy for life

Question 21

What are the three main take home points?

Answer 21

candida in AIDS is usually mucosal
crypto is major cause of meningitis
disseminated dz is most common presentation of endemic mycoses

Question 22

What is antifungal diagnosis in a nutshell?

Answer 22

antigen testing for crypto and histo

serology for cocci

Question 23

What is antifungal therapy in a nuthsell?

Answer 23

ampho b for basically everything
fluconazole - the 3 C’s = crypto, cocci meningitis, candidiasis
itraconazole for histo, sporotrichosis, penicilliosis