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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. What is the prognosis of lyme arthritis?
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

2. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Vaccine titer >10mU/ml
Need lumbar puncture to relieve pressure; they have high opening pressure >350

3. systolic HTN in elderly
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Immune mediated; circulating IgG and IgM to penicillin derivatives
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

4. foot infections in DM
Pt who have been treated before for latent TB
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
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
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

5. INH
6-12 weeks
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Do EBV antibody test

6. What is fatal consequence of RMSF?
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

7. What is the indication of corticosteroid in pcp infection?
Blastomycosis
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
AA gradient >35 or Po2 <70
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

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

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9. How to dx bacterial meningitis from CSF study?

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10. How to tx pseudomonas?
When cd4 count falls below 200. 2p in pcp =200
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Do EBV antibody test
6-12 weeks

11. When to give abx to prevent recurrent uti
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
Oropharyngeal secretions; hence named as kissing disease
6-12 weeks
Immune mediated; circulating IgG and IgM to penicillin derivatives

12. What is lag time to develop lyme arthritis after exposure to vector
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
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
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.

13. 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
Oropharyngeal secretions; hence named as kissing disease
High risk 19-64; 1-2 dose - above 65; one dose
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

14. thrombocytopenia in HIV
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Similar pathophysiology as ITP - tx zidovudine
Every 3-4 hours to determine appropritate time to start HAART

15. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Pregnacy - urologic procedure - hip arthoplastu
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

16. gas gangrene
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Clostridium perfringens after penetrative injuries/wounds
Rifampin600mg q12. or cipro
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

17. What is the Tx of cryptococcal meninngitis
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
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

18. low grade fever - maculopapular rash - lymphadenopathy
Viral load and CD4 count
Clostridium perfringens after penetrative injuries/wounds
HIV viral load
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

19. How to dx adequate response to HBV vaccine
Similar pathophysiology as ITP - tx zidovudine
Vaccine titer >10mU/ml
Pegylated interferon and lamivudine
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

20. When not to tx asymptomatic bacteriura?
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Others lesions are ring enhancing and have mass effect while PML don't
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Acyclovir

21. What are indicators for progression of HIV
Viral load and CD4 count
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
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

22. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
<500 copies/ml
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
PML; focal neurological deficit like MM; no specific tx; regress with HAART

23. hypertension in children
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
HBIG hep B immunoglobulin

24. When to tx asymptomatic bacteriurea >100 -000?
Clostridium perfringens after penetrative injuries/wounds
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Pregnacy - urologic procedure - hip arthoplastu

25. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
High risk 19-64; 1-2 dose - above 65; one dose
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
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Similar pathophysiology as ITP - tx zidovudine

26. How to differentiate gonococcal and nongonoccal urethritis?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
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

27. How to dx?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Mainly clinical - epidemiological and seasonal setting
Rifampin600mg q12. or cipro
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

28. When to tx influenza with antiviral therapy?
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Mainly clinical - epidemiological and seasonal setting
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
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

29. which heart valve is closer to ventricular conduction system/
Aortic valve; endocardiits of AR p/w AV block and LBBB
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

30. What are the behavioral interventions decrease the risk of UTI
Postcoital voiding - increased intake of cranberry juice
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Bronchoalveolar washing and transbronchial biopsy
Within 6 months viral load will be <50

31. How often HIV postiive patients CD4 count needs to be evaluated?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Every 3-4 hours to determine appropritate time to start HAART
ELISA and western blot of synovial fluid.
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

32. What is tetanus - diptheria - pertusis recommendation?
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Others lesions are ring enhancing and have mass effect while PML don't
Td every 10 years - tdap once before 65 and after 65
Immune mediated; circulating IgG and IgM to penicillin derivatives

33. What is the mch of ampicillin induced rash in IM
Immune mediated; circulating IgG and IgM to penicillin derivatives
Clostridium perfringens after penetrative injuries/wounds
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
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.

34. what would be viral load after 2-4m of HAART?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Need lumbar puncture to relieve pressure; they have high opening pressure >350
<500 copies/ml
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

35. How to give postexposure prophylaxis for HIV
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

36. antibiotic with good prostate penetration?
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
When cd4 count falls below 200. 2p in pcp =200

37. How often viral load is monitored after HAART?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Viral load and CD4 count
6-12 weeks

38. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
ELISA and western blot of synovial fluid.

39. aspergillosis
Acyclovir
Within 6 months viral load will be <50
HIV viral load
Voriconazol. mycetoma-surgical removal

40. How to tx chronic hep B
<5000 copies/ml
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Pegylated interferon and lamivudine
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

41. How to tx pcp?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

42. rifampin
Vaccine titer >10mU/ml
ELISA and western blot of synovial fluid.
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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

43. How to dx IM?
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Pregnacy - urologic procedure - hip arthoplastu
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

44. How to tx IM?
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

45. how im is transmitted?
Ampicillin-sublactam; most bites contain eikenella
Mainly clinical - epidemiological and seasonal setting
Oropharyngeal secretions; hence named as kissing disease
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

46. 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
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Immune mediated; circulating IgG and IgM to penicillin derivatives

47. When to give prophylaxis against MAC
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

48. worsening of TB after starting HAART in HIV
Monospot test which screen heteropile ab that agglutinate horse rbc
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Pt who have been treated before for latent TB

49. how CMV presents in immunocompromised patients
Upper lobes; any fibrosis in this area suggestive of latent TB
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Acyclovir

50. when we see echym gangrenosum?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes