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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. acute febrile reaction develops after starting penicilin tx to syphilis patient
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Vaccine titer >10mU/ml

2. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
PML; focal neurological deficit like MM; no specific tx; regress with HAART
HBIG hep B immunoglobulin
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.
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

3. How to tx TSS?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
6-12 weeks
If a sample is ELISA positive - it is tested fro western blot for confirmation
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

4. What is the indication of corticosteroid in pcp infection?
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
AA gradient >35 or Po2 <70
Rifampin600mg q12. or cipro
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

5. what would be viral load after 4 weeks
<5000 copies/ml
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Similar pathophysiology as ITP - tx zidovudine

6. what if monospot test is neg in IM?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
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
Do EBV antibody test
Within 6 months viral load will be <50

7. which heart valve is closer to ventricular conduction system/
Aortic valve; endocardiits of AR p/w AV block and LBBB
Either TB or aspergillosis
Pegylated interferon and lamivudine
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

8. How to tx pseudomonas?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
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
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

9. hypertension in children
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
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
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
<500 copies/ml

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

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11. worsening of TB after starting HAART in HIV
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
High risk 19-64; 1-2 dose - above 65; one dose
HBIG hep B immunoglobulin
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

12. pathophysiology of toxic shock syndrom?
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
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
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

13. after recent exposure - negative ELISA - How to confirm?
Upper lobes; any fibrosis in this area suggestive of latent TB
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Voriconazol. mycetoma-surgical removal

14. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
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
ELISA; initial visit - 6 - 12 and 24 weeks;

15. when HIV patient develop pcp?
When cd4 count falls below 200. 2p in pcp =200
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 lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
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

16. 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
Td every 10 years - tdap once before 65 and after 65
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

17. rifampin
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Reddish orange discoloration of urine - feces - sweat - tears - sputum

18. How to tx IM?
Ampicillin-sublactam; most bites contain eikenella
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
High risk 19-64; 1-2 dose - above 65; one dose

19. what would be viral load after 2-4m of HAART?
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
ELISA and western blot of synovial fluid.
<500 copies/ml
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

20. gas gangrene
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Clostridium perfringens after penetrative injuries/wounds
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

21. When to tx influenza with antiviral therapy?
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
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Clostridium perfringens after penetrative injuries/wounds
Pegylated interferon and lamivudine

22. How to dx IM?
Vaccine titer >10mU/ml
Aortic valve; endocardiits of AR p/w AV block and LBBB
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

23. where TB normally affects
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Upper lobes; any fibrosis in this area suggestive of latent TB
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

24. What are the behavioral interventions decrease the risk of UTI
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
Postcoital voiding - increased intake of cranberry juice
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

25. How to dx?
Mainly clinical - epidemiological and seasonal setting
Bronchoalveolar washing and transbronchial biopsy
Do EBV antibody test
Blastomycosis

26. wisconsin - missisipi - ohio
Blastomycosis
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

27. What is tetanus - diptheria - pertusis recommendation?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Pregnacy - urologic procedure - hip arthoplastu
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Td every 10 years - tdap once before 65 and after 65

28. How to dx adequate response to HBV vaccine
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Vaccine titer >10mU/ml
HBIG hep B immunoglobulin
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

29. clinical manifestation of mucomycosis
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

30. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Others lesions are ring enhancing and have mass effect while PML don't
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

31. systolic HTN in elderly
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Upper lobes; any fibrosis in this area suggestive of latent TB
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

32. aspergillosis
Voriconazol. mycetoma-surgical removal
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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Vaccine titer >10mU/ml

33. foot infections in DM
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

34. How to dx lyme arthritis?
ELISA and western blot of synovial fluid.
Similar pathophysiology as ITP - tx zidovudine
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
PML; focal neurological deficit like MM; no specific tx; regress with HAART

35. How to differentiate different types of necrotizing fascitis?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Clostridium perfringens after penetrative injuries/wounds
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

36. What is the mch of ampicillin induced rash in IM
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Immune mediated; circulating IgG and IgM to penicillin derivatives
Viral load and CD4 count
6-12 weeks

37. Tx of choice for human bites
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
If a sample is ELISA positive - it is tested fro western blot for confirmation
Ampicillin-sublactam; most bites contain eikenella
Every 3-4 hours to determine appropritate time to start HAART

38. 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
Immune mediated; circulating IgG and IgM to penicillin derivatives
Ampicillin-sublactam; most bites contain eikenella
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

39. What is the pathophysiology of Meningococcal meningitis?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Either TB or aspergillosis
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Aortic valve; endocardiits of AR p/w AV block and LBBB

40. chshould we tx IM with abx (ampicilin) if throat cx is positive?
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
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Pt who have been treated before for latent TB

41. How to confirm chlamydia infection?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Every 3-4 hours to determine appropritate time to start HAART
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.
Others lesions are ring enhancing and have mass effect while PML don't

42. What is fatal consequence of RMSF?
6-12 weeks
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Aortic valve; endocardiits of AR p/w AV block and LBBB
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

43. dame that has already occurred
Cd4 count
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Vaccine titer >10mU/ml
Monospot test which screen heteropile ab that agglutinate horse rbc

44. infiltrate in upper lobe of lung?
Blastomycosis
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Acyclovir
Either TB or aspergillosis

45. How to dx cryptococal meninggits
<500 copies/ml
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

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

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47. What is tx for herpes zoster
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Acyclovir
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

48. How to differentiate gonococcal and nongonoccal urethritis?
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
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
Non pregnant premanopausal - elderly - dm - sci - chronic foley

49. How to tx pcp?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Monospot test which screen heteropile ab that agglutinate horse rbc
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Rifampin600mg q12. or cipro

50. How long abx is given in pseudomonas infection?
Pt who have been treated before for latent TB
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Oropharyngeal secretions; hence named as kissing disease
Monospot test which screen heteropile ab that agglutinate horse rbc