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USMLE Step3 Infectious Disease

Subjects : health-sciences, usmle-step-3

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 to dx?
Mainly clinical - epidemiological and seasonal setting
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Postcoital voiding - increased intake of cranberry juice

2. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
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
Every 3-4 hours to determine appropritate time to start HAART
PML; focal neurological deficit like MM; no specific tx; regress with HAART
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

3. how HAART therapy affects HIV viral loads?
Pregnacy - urologic procedure - hip arthoplastu
ELISA; initial visit - 6 - 12 and 24 weeks;
Within 6 months viral load will be <50
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

4. how im is transmitted?
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
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Oropharyngeal secretions; hence named as kissing disease
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

5. What is the criteria for Spontaneous bact peritonitis
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Pt who have been treated before for latent TB
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
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

6. pathophysiology of toxic shock syndrom?
ELISA and western blot of synovial fluid.
When cd4 count falls below 200. 2p in pcp =200
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

7. after recent exposure - negative ELISA - How to confirm?
<500 copies/ml
AA gradient >35 or Po2 <70
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

8. What is the classic signs of nec fasc?
No skin changes but pain out of proportion; infection spreads along fascial plane rapidly with blister - erythema - and bullae formation; marked tenderness on palpation - and CREPITUS
Ampicillin-sublactam; most bites contain eikenella
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
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

9. low grade fever - maculopapular rash - lymphadenopathy
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
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.
Rifampin600mg q12. or cipro
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

10. acute febrile reaction develops after starting penicilin tx to syphilis patient
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

11. aspergillosis
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Voriconazol. mycetoma-surgical removal

12. dame that has already occurred
Mainly clinical - epidemiological and seasonal setting
Every 3-4 hours to determine appropritate time to start HAART
Cd4 count
Aortic valve; endocardiits of AR p/w AV block and LBBB

13. what would be viral load after 4 weeks
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
<5000 copies/ml
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

14. When to tx asymptomatic bacteriurea >100 -000?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Pregnacy - urologic procedure - hip arthoplastu
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

15. What is lag time to develop lyme arthritis after exposure to vector
Others lesions are ring enhancing and have mass effect while PML don't
Gonococcal with purulent discharges and presence of multiple diplococi and neurotrophils in urethral swab; non gonoccal (chlamydia) are watery disch - swab abacterial - sometimes have intracellular organism
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
AA gradient >35 or Po2 <70

16. What are the subjective /objective measure of encephalopathy?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

17. What is fatal consequence of RMSF?
Rifampin600mg q12. or cipro
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Gonococcal with purulent discharges and presence of multiple diplococi and neurotrophils in urethral swab; non gonoccal (chlamydia) are watery disch - swab abacterial - sometimes have intracellular organism
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

18. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Every 3-4 hours to determine appropritate time to start HAART

19. INH
<5000 copies/ml
Pt who have been treated before for latent TB
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Vaccine titer >10mU/ml

20. When to give prophylaxis against MAC
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Acyclovir
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

21. How to dx IM?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Mainly clinical - epidemiological and seasonal setting
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
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

22. antibiotic with good prostate penetration?
Acyclovir
Voriconazol. mycetoma-surgical removal
Cd4 count
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

23. How to differentiate different types of necrotizing fascitis?
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
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
Cd4 count
When cd4 count falls below 200. 2p in pcp =200

24. When to tx influenza with antiviral therapy?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
High risk 19-64; 1-2 dose - above 65; one dose
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
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

25. rifampin
When cd4 count falls below 200. 2p in pcp =200
Reddish orange discoloration of urine - feces - sweat - tears - sputum
AA gradient >35 or Po2 <70
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

26. hypertension in children
Pegylated interferon and lamivudine
Within 6 months viral load will be <50
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

27. What is difference between uti relapse versus recurrence?
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
High risk 19-64; 1-2 dose - above 65; one dose
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

28. How to tx IM?
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
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
Every 3-4 hours to determine appropritate time to start HAART

29. How to tx TSS?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Blastomycosis
Cd4 count
Aortic valve; endocardiits of AR p/w AV block and LBBB

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

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31. How often HIV postiive patients CD4 count needs to be evaluated?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
AA gradient >35 or Po2 <70
Every 3-4 hours to determine appropritate time to start HAART

32. systolic HTN in elderly
Pregnacy - urologic procedure - hip arthoplastu
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

33. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

34. worsening of TB after starting HAART in HIV
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Cd4 count
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
<5000 copies/ml

35. What are the behavioral interventions decrease the risk of UTI
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Postcoital voiding - increased intake of cranberry juice
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

36. when not to give INH therapy if ppd positive and patient asyptomatic
Pt who have been treated before for latent TB
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Vaccine titer >10mU/ml

37. when western blot is done for HIV testing
If a sample is ELISA positive - it is tested fro western blot for confirmation
Rifampin600mg q12. or cipro
ELISA; initial visit - 6 - 12 and 24 weeks;
PML; focal neurological deficit like MM; no specific tx; regress with HAART

38. INH
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Pt who have been treated before for latent TB
Do EBV antibody test
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

39. 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
Do EBV antibody test
Non pregnant premanopausal - elderly - dm - sci - chronic foley
<5000 copies/ml

40. How long we tx chronic prostatis?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Either TB or aspergillosis
Similar pathophysiology as ITP - tx zidovudine
6-12 weeks

41. When not to tx asymptomatic bacteriura?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Bronchoalveolar washing and transbronchial biopsy
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

42. gas gangrene
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
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
Postcoital voiding - increased intake of cranberry juice
Clostridium perfringens after penetrative injuries/wounds

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

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44. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Similar pathophysiology as ITP - tx zidovudine
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
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

45. causative organisms of uti
<500 copies/ml
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
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

46. What are indicators for progression of HIV
Viral load and CD4 count
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
ELISA and western blot of synovial fluid.

47. where TB normally affects
Upper lobes; any fibrosis in this area suggestive of latent TB
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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

48. What is the indication of corticosteroid in pcp infection?
AA gradient >35 or Po2 <70
Clostridium perfringens after penetrative injuries/wounds
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
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

49. can HIV transmitted through human bite?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Bronchoalveolar washing and transbronchial biopsy
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

50. reddish colored papules with central umbilication in HIV or immunocompromised patient
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
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
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes