Micro: PCP, Toxo, MAC in AIDS Flashcards
What is a normal CD4 count?
450-1400
What are the 3 major clinical syndromes in pts w AIDS?
pulmonary - dyspnea and infiltrates (PCP most common)
neurologic - focal findings and mass lesion (toxo)
fever of unknown origin (FUO) - disseminated infections (MAC)
CXR has diffuse intersitial infiltrates what should you expect?
CXR has lobar infiltrate what should you suspect?
PCP (ground glass infiltrates)
s. pneumoniae
What is the phylogenetic status of PCP?
was believed to be parasite
it is actually a fungus
What is the microbiology of PCP?
2 prominent antigen groups, includes MSG complex
What is the life cycle/pathogenesis of PCP?
developmental stages: small pleomorphic trophozoite and cyst form (up to 8 intracystic bodies)
probably sexual phase
asexual replication by trophic form and sexual by cyst
MSG facilitates adherence to ECM, surfactant and mannose
MSG undergoes antigenic variation
What is the pathology of inf w PCP?
heavy airless lungs, thickened alveolar septa, foamy eosinophilic alveolar exudate w parasites
organism doesn’t invade lung tissue
How is PCP diagnosed?
CXR, PC in bronchopulmonary secretions by sputum or bronchoalveolar lavage
transbronchial or open lung biopsy may be necessary
LM: Giemsa stains nuclei of trophozoites, silver stains cyst walls, DFA, clusters of crushed ping pong balls
elevated LDH (up to 500)
+ beta-D-glucan
oxygen desaturation when exercising
PaO235 indicate severe dz and need for steroid treatment
What is the treatment for PCP?
high dose TMP-SMX (also used for prophylaxis if cd4 <200, once HAART raises this, can stop prophylaxis)
as organisms die can deteriorate due to dead contents filling alveolar spaces - combo w prednisone
What is the transmission of P. jiroveci?
person to person is rare
thought to be inhaled
What are lung symptoms that do NOT indicate PCP and necessitate search for a different dx?
lymphadenopathy pleural EFFUSIONS (PCP can have pneumothorax)
What are signs of a poor prognosis for PCP?
pts who AREN’T immunocompromised
pts who present w pneumothorax
What is the microbiology and basic life cycle of t. gondii?
obligate intracellular parasite
oocyst, trophozoite/tachyzoite, and bradyzoite forms
oocyst released into environment, develops four sporozoites which are ingested to cause infection
sexual and asexual phases (asexual in body responsible for dz = tachyzoites and bradyzoites)
What is the reservoir of infection for t. gondii?
cats - only definitive hosts for sexual stages
What are the different modes through which humans can become infected w t. gondii?
eating undercooked meat w cysts ingestion of oocyst from fecally contaminated hands or food organ transplant or blood transfusion transplacental accidental inoculation of tachyzoites
What does t. gondii do in the body?
gets into phagosome and prevents fusion w lysosome, differentiates into tachyzoite and divides rapidly
form cysts in skeletal muscle, myocardium, brain
What are the features of persistent infection w t. gondii?
dormant stage = bradyzoite
persistent inf w bradyzoites in immunocompetent, upon immunocompromise, cysts can reactive & cause symptoms
What are the clinical manifestations of toxo?
usually asymptomatic in immunocompetent
encephalitis in HIV+
congenital can be severe
How is toxo diagnosed?
serology - positive IgM in immunocompetent
AIDS - IgG+ on SERUM (IgM not helpful), ring enhancing lesion, PCR of CSF (negative doesn’t rule out)
usually improve w/i 10-14 days of rx, otherwise biopsy
tachyzoites on histology
What is the treatment of toxo?
not necessary in immunocompetent, not pregnant
for HIV/AIDS - sulfadiazine w pyrimethamine and leucovorin, continue until lesions and CD4 improve
CD4 less than 100 need TMP-SMX prophylaxis if IgG+
What is the microbiology of MAC?
slow growing, non-pigmented in culture
isolated from birds, fresh and salt water
What is the pathophysiology of MAC?
inhaled into respiratory tract, ingested into GI
translocates across mucosal epithelium, infects macrophages in LP and spreads lymphatically to local nodes
spreads hematogenously in immunocompromised
What are the clinical presentations of MAC?
immunocompetent: pulm dz
infects those w CF
in HIV: disseminated dz presents as nonfocal fever syndrome
What are the three different kinds of pulm dzs that occur in immunocompetent individuals w MAC?
elderly smokers (men) w pre-existing lung dz (COPD) - chronic cavitary pneumonia that resembles tb
elderly non-smoking females - mild lingular or RML infiltrates, productive cough and weight loss
single pulmonary nodule
What are the features of disseminated dz of MAC?
fever, night sweats, weight loss
lymphadenopathy, pancytopenia
abnormal liver fxn tests, watery diarrhea, RUQ pain
How is MAC diagnosed?
culture for AFB
DNA probe can differentiate from tb
What is the treatment for MAC?
either azithromycin (preferred) or clarithromycin + ethambutol and rifamyin (rifabutin has less interxns w HAART than rifampin) + HAART
What is the prophylaxis for MAC?
azithromycin
not needed w CD4 above 100
