USMLE Step3 Infectious Disease

Instructions:

• Answer 50 questions in 15 minutes.
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• Match each statement with the correct term.
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This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. How long abx is given in pseudomonas infection?
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
<5000 copies/ml
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w


2. How to dx progressive multifocal leukoencephalopathy
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
AA gradient >35 or Po2 <70
Reddish orange discoloration of urine - feces - sweat - tears - sputum


3. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
<500 copies/ml


4. reddish colored papules with central umbilication in HIV or immunocompromised patient
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Think about cutaneous cryptococous; lesions looks like molluscus contagiousm. present in face/trunk/anywherer; dx biopsy of lesion which shows granulomatous inflammation with multinucleated giant cell
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.


5. which heart valve is closer to ventricular conduction system/
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Aortic valve; endocardiits of AR p/w AV block and LBBB
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid


6. What is characteristic for dx of rocky mountain spotted fever?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
High risk 19-64; 1-2 dose - above 65; one dose
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin


7. What is the Tx of cryptococcal meninngitis
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
CD4 less than 350 and RPR >1:32; HIV infected patient with syphilis >1 yr should have CSF exam before tx. if csf normal tx with benzathine penicillin weekly for 3 weeks.
Pt who have been treated before for latent TB
Either TB or aspergillosis


8. When not to tx asymptomatic bacteriura?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Do EBV antibody test
Td every 10 years - tdap once before 65 and after 65
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx


9. what if monospot test is neg in IM?
6-12 weeks
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Do EBV antibody test
Viral load and CD4 count


10. What are the subjective /objective measure of encephalopathy?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Pegylated interferon and lamivudine
HBIG hep B immunoglobulin


11. How to dx lyme arthritis?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
ELISA and western blot of synovial fluid.
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
<5000 copies/ml


12. after recent exposure - negative ELISA - How to confirm?
Voriconazol. mycetoma-surgical removal
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.


13. thrombocytopenia in HIV
<500 copies/ml
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Monospot test which screen heteropile ab that agglutinate horse rbc
Similar pathophysiology as ITP - tx zidovudine


14. causative organisms of uti
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Oropharyngeal secretions; hence named as kissing disease


15. where TB normally affects
Aortic valve; endocardiits of AR p/w AV block and LBBB
Upper lobes; any fibrosis in this area suggestive of latent TB
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -


16. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
HBIG hep B immunoglobulin
Type 1: patient with dm and pvd; caused by staph/GAS/ e coli/bacteroids; type2 - no associated medical illness - caused by laceration - trauma - surgery - IV drug abuse - caused mainly by GAS
Cd4 count
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.


17. hypertriglyceridemia in HIV
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Ampicillin-sublactam; most bites contain eikenella
AA gradient >35 or Po2 <70


18. INH
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Viral load and CD4 count


19. How to dx adequate response to HBV vaccine
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Pts with pseudomonas bacerimia have this. they have perivascular bacterial invasion of the media and adventitia of arteries and veins. then ishcemic necrosis; skin and mucous membrane have nodular patches wtih hemorrhage and ulceration
Vaccine titer >10mU/ml
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w


20. how im is transmitted?
Immune mediated; circulating IgG and IgM to penicillin derivatives
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Oropharyngeal secretions; hence named as kissing disease
<500 copies/ml


21. How to tx TSS?
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Oropharyngeal secretions; hence named as kissing disease


22. when western blot is done for HIV testing
<5000 copies/ml
Within 6 months viral load will be <50
If a sample is ELISA positive - it is tested fro western blot for confirmation
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits


23. if a patient received BCG vaccine - how big is his PPD induration


24. When to give abx to prevent recurrent uti
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
More than two UTI in six months or more than 3 uti in a year; cipro/bactrim/nitrofurantoin; abx may be given continuous or postcoital


25. pneumococcal vaccine indication?
Need lumbar puncture to relieve pressure; they have high opening pressure >350
High risk 19-64; 1-2 dose - above 65; one dose
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
ELISA and western blot of synovial fluid.


26. What are the behavioral interventions decrease the risk of UTI
HBIG hep B immunoglobulin
AA gradient >35 or Po2 <70
Viral load and CD4 count
Postcoital voiding - increased intake of cranberry juice


27. how HAART therapy affects HIV viral loads?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Bronchoalveolar washing and transbronchial biopsy
Monospot test which screen heteropile ab that agglutinate horse rbc
Within 6 months viral load will be <50


28. How to differentiat PML from toxoxplasmosis - cns lymphoma adn brain abscess


29. What is tetanus - diptheria - pertusis recommendation?
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Upper lobes; any fibrosis in this area suggestive of latent TB
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Td every 10 years - tdap once before 65 and after 65


30. How often viral load is monitored after HAART?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Every 3-4 hours to determine appropritate time to start HAART
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months


31. How to tx pcp?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer


32. drugs work well on hypertriglyceridia?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Oropharyngeal secretions; hence named as kissing disease


33. How to give postexposure prophylaxis for HIV
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Reddish orange discoloration of urine - feces - sweat - tears - sputum
When patient is older >65 - pregnant - cardiac of pulmonary disease; patient without above risks are treated when they come within 48 hours of symptom onset
Upper lobes; any fibrosis in this area suggestive of latent TB


34. acute onset +rusty sputum
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Postcoital voiding - increased intake of cranberry juice
<500 copies/ml
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles


35. dame that has already occurred
HBIG hep B immunoglobulin
Within 6 months viral load will be <50
Cd4 count
Every 3-4 hours to determine appropritate time to start HAART


36. after exposure of HIV when antibody testing is performed?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
ELISA; initial visit - 6 - 12 and 24 weeks;
CD4 less than 350 and RPR >1:32; HIV infected patient with syphilis >1 yr should have CSF exam before tx. if csf normal tx with benzathine penicillin weekly for 3 weeks.
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes


37. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Voriconazol. mycetoma-surgical removal
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region


38. How to confirm dx if pcp?
Pts with pseudomonas bacerimia have this. they have perivascular bacterial invasion of the media and adventitia of arteries and veins. then ishcemic necrosis; skin and mucous membrane have nodular patches wtih hemorrhage and ulceration
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Relapse: infecting organism is same as original infecting organism within 2 weeks of tx completion; recurrence: if the infecting organism is different from that of the original organism
Bronchoalveolar washing and transbronchial biopsy


39. foot infections in DM
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.


40. How to dx IM?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Within 6 months viral load will be <50
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6


41. How to tx IM?
Cd4 count
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Tx emptirically both gonococcus and chlamydia; 30% gono have coexsiting chlamydial infection; single dose ceftriaxone for gono and Azithromycin for chlamydia. if no improvement give metronidazol for trichomonas infection
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease


42. acute febrile reaction develops after starting penicilin tx to syphilis patient
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Postcoital voiding - increased intake of cranberry juice
<5000 copies/ml


43. pathophysiology of toxic shock syndrom?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Aortic valve; endocardiits of AR p/w AV block and LBBB
Type 1: patient with dm and pvd; caused by staph/GAS/ e coli/bacteroids; type2 - no associated medical illness - caused by laceration - trauma - surgery - IV drug abuse - caused mainly by GAS
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer


44. How to tx chronic hep B
Oropharyngeal secretions; hence named as kissing disease
<500 copies/ml
Pegylated interferon and lamivudine
When cd4 count falls below 200. 2p in pcp =200


45. What is the indication of corticosteroid in pcp infection?
Either TB or aspergillosis
AA gradient >35 or Po2 <70
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes


46. How to tx pseudomonas?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Bronchoalveolar washing and transbronchial biopsy
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles


47. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Tx emptirically both gonococcus and chlamydia; 30% gono have coexsiting chlamydial infection; single dose ceftriaxone for gono and Azithromycin for chlamydia. if no improvement give metronidazol for trichomonas infection
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w


48. When to tx influenza with antiviral therapy?
<5000 copies/ml
More than two UTI in six months or more than 3 uti in a year; cipro/bactrim/nitrofurantoin; abx may be given continuous or postcoital
When patient is older >65 - pregnant - cardiac of pulmonary disease; patient without above risks are treated when they come within 48 hours of symptom onset
ELISA; initial visit - 6 - 12 and 24 weeks;


49. What is tx for herpes zoster
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
<5000 copies/ml
Acyclovir
ELISA; initial visit - 6 - 12 and 24 weeks;


50. How to dx?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Either TB or aspergillosis
Mainly clinical - epidemiological and seasonal setting
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses