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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.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

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. can HIV transmitted through human bite?
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
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Acyclovir
Aortic valve; endocardiits of AR p/w AV block and LBBB

2. acute febrile reaction develops after starting penicilin tx to syphilis patient
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Viral load and CD4 count
Oropharyngeal secretions; hence named as kissing disease
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

3. How to confirm dx if pcp?
Similar pathophysiology as ITP - tx zidovudine
Bronchoalveolar washing and transbronchial biopsy
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

4. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Cd4 count
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

5. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
6-12 weeks
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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

6. acute onset +rusty sputum
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
<5000 copies/ml
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

7. HIV patient having fat deposition on back of neck and abdomen - like cushing
Mainly clinical - epidemiological and seasonal setting
Pegylated interferon and lamivudine
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
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

8. How to dx IM?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Aortic valve; endocardiits of AR p/w AV block and LBBB
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
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

9. How to differentiate different types of necrotizing fascitis?
Oropharyngeal secretions; hence named as kissing disease
Rifampin600mg q12. or cipro
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
Bronchoalveolar washing and transbronchial biopsy

10. systolic HTN in elderly
<5000 copies/ml
Others lesions are ring enhancing and have mass effect while PML don't
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

11. How to tx pseudomonas?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
ELISA and western blot of synovial fluid.

12. How to dx adequate response to HBV vaccine
Vaccine titer >10mU/ml
Viral load and CD4 count
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

13. What is difference between uti relapse versus recurrence?
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Clostridium perfringens after penetrative injuries/wounds
Mainly clinical - epidemiological and seasonal setting
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

14. which heart valve is closer to ventricular conduction system/
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
6-12 weeks
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Aortic valve; endocardiits of AR p/w AV block and LBBB

15. when not to give INH therapy if ppd positive and patient asyptomatic
Vaccine titer >10mU/ml
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
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Pt who have been treated before for latent TB

16. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
6-12 weeks
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
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

17. 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
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Pegylated interferon and lamivudine
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

18. thrombocytopenia in HIV
Rifampin600mg q12. or cipro
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Similar pathophysiology as ITP - tx zidovudine

19. INH
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Pt who have been treated before for latent TB
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

20. clinical manifestation of mucomycosis
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Blastomycosis

21. How long we tx chronic prostatis?
Viral load and CD4 count
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Immune mediated; circulating IgG and IgM to penicillin derivatives
6-12 weeks

22. pneumococcal vaccine indication?
High risk 19-64; 1-2 dose - above 65; one dose
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
6-12 weeks
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

23. What is the mch of ampicillin induced rash in IM
Immune mediated; circulating IgG and IgM to penicillin derivatives
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Need lumbar puncture to relieve pressure; they have high opening pressure >350
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

24. antibiotic with good prostate penetration?
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
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

25. worsening of TB after starting HAART in HIV
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Immune mediated; circulating IgG and IgM to penicillin derivatives
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

26. How often HIV postiive patients CD4 count needs to be evaluated?
Cd4 count
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Every 3-4 hours to determine appropritate time to start HAART

27. dame that has already occurred
Cd4 count
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
6-12 weeks
Ampicillin-sublactam; most bites contain eikenella

28. what would be viral load after 2-4m of HAART?
Vaccine titer >10mU/ml
<500 copies/ml
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
6-12 weeks

29. How to dx bacterial meningitis from CSF study?

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30. pathophysiology of toxic shock syndrom?
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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
6-12 weeks
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

31. When to give prophylaxis against MAC
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

32. damae that is about to occur?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
HIV viral load
Postcoital voiding - increased intake of cranberry juice
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

33. When not to tx asymptomatic bacteriura?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Reddish orange discoloration of urine - feces - sweat - tears - sputum
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

34. What is the prognosis of lyme arthritis?
Immune mediated; circulating IgG and IgM to penicillin derivatives
Viral load and CD4 count
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
6-12 weeks

35. What is characteristic for dx of rocky mountain spotted fever?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Bronchoalveolar washing and transbronchial biopsy
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

36. how im is transmitted?
Oropharyngeal secretions; hence named as kissing disease
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Pt who have been treated before for latent TB
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

37. How to give postexposure prophylaxis for HIV
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
<500 copies/ml

38. hypertriglyceridemia in HIV
Bronchoalveolar washing and transbronchial biopsy
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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.
Upper lobes; any fibrosis in this area suggestive of latent TB

39. How to tx TSS?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

40. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

41. What is fatal consequence of RMSF?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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

42. How to dx cryptococal meninggits
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
Voriconazol. mycetoma-surgical removal
Upper lobes; any fibrosis in this area suggestive of latent TB

43. how HAART therapy affects HIV viral loads?
Within 6 months viral load will be <50
If a sample is ELISA positive - it is tested fro western blot for confirmation
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
<500 copies/ml

44. What are indicators for progression of HIV
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Blastomycosis
Viral load and CD4 count
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

45. How to differentiate gonococcal and nongonoccal urethritis?
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Pegylated interferon and lamivudine
Postcoital voiding - increased intake of cranberry juice
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

46. How to dx IM?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Monospot test which screen heteropile ab that agglutinate horse rbc
High risk 19-64; 1-2 dose - above 65; one dose
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

47. When to give abx to prevent recurrent uti
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
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
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

48. rifampin
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Ampicillin-sublactam; most bites contain eikenella
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Immune mediated; circulating IgG and IgM to penicillin derivatives

49. drugs work well on hypertriglyceridia?
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
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Others lesions are ring enhancing and have mass effect while PML don't
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

50. How often viral load is monitored after HAART?
Pegylated interferon and lamivudine
<500 copies/ml
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months