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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 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
Aortic valve; endocardiits of AR p/w AV block and LBBB
HBIG hep B immunoglobulin
Every 3-4 hours to determine appropritate time to start HAART

2. what would be viral load after 4 weeks
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
<5000 copies/ml

3. acute onset +rusty sputum
Voriconazol. mycetoma-surgical removal
Either TB or aspergillosis
Vaccine titer >10mU/ml
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

4. 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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Upper lobes; any fibrosis in this area suggestive of latent TB
HBIG hep B immunoglobulin

5. after recent exposure - negative ELISA - How to confirm?
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
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
High risk 19-64; 1-2 dose - above 65; one dose

6. 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
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
<5000 copies/ml
Viral load and CD4 count

7. What is the prognosis of lyme arthritis?
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Viral load and CD4 count
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

8. What is difference between uti relapse versus recurrence?
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Monospot test which screen heteropile ab that agglutinate horse rbc
Acyclovir
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

9. When to give prophylaxis against MAC
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)
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
ELISA; initial visit - 6 - 12 and 24 weeks;

10. causative organisms of uti
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
<5000 copies/ml
AA gradient >35 or Po2 <70
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

11. What is the indication of corticosteroid in pcp infection?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
AA gradient >35 or Po2 <70
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Ampicillin-sublactam; most bites contain eikenella

12. What is tx for herpes zoster
Acyclovir
Monospot test which screen heteropile ab that agglutinate horse rbc
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
ELISA and western blot of synovial fluid.

13. How to dx IM?
Either TB or aspergillosis
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Monospot test which screen heteropile ab that agglutinate horse rbc
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

14. which heart valve is closer to ventricular conduction system/
Rifampin600mg q12. or cipro
Aortic valve; endocardiits of AR p/w AV block and LBBB
Oropharyngeal secretions; hence named as kissing disease
Every 3-4 hours to determine appropritate time to start HAART

15. What is the classic signs of nec fasc?
Postcoital voiding - increased intake of cranberry juice
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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
Similar pathophysiology as ITP - tx zidovudine

16. dame that has already occurred
Cd4 count
Td every 10 years - tdap once before 65 and after 65
Postcoital voiding - increased intake of cranberry juice
Upper lobes; any fibrosis in this area suggestive of latent TB

17. When not to tx asymptomatic bacteriura?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
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
Pregnacy - urologic procedure - hip arthoplastu
<5000 copies/ml

18. When to give abx to prevent recurrent uti
HBIG hep B immunoglobulin
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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
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

19. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Pregnacy - urologic procedure - hip arthoplastu
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
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
PML; focal neurological deficit like MM; no specific tx; regress with HAART

20. How to confirm chlamydia infection?
Bronchoalveolar washing and transbronchial biopsy
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Within 6 months viral load will be <50
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

21. when not to give INH therapy if ppd positive and patient asyptomatic
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Pt who have been treated before for latent TB
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

22. damae that is about to occur?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
HIV viral load
Monospot test which screen heteropile ab that agglutinate horse rbc
Voriconazol. mycetoma-surgical removal

23. What are the behavioral interventions decrease the risk of UTI
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Others lesions are ring enhancing and have mass effect while PML don't
Pregnacy - urologic procedure - hip arthoplastu
Postcoital voiding - increased intake of cranberry juice

24. What is the pathophysiology of Meningococcal meningitis?
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
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Acyclovir

25. How to tx IM?
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
When cd4 count falls below 200. 2p in pcp =200

26. hypertension in children
Others lesions are ring enhancing and have mass effect while PML don't
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

27. How to dx?
Mainly clinical - epidemiological and seasonal setting
Ampicillin-sublactam; most bites contain eikenella
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Td every 10 years - tdap once before 65 and after 65

28. hypertriglyceridemia in HIV
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Immune mediated; circulating IgG and IgM to penicillin derivatives
Oropharyngeal secretions; hence named as kissing disease
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

29. thrombocytopenia in HIV
<500 copies/ml
Pregnacy - urologic procedure - hip arthoplastu
Similar pathophysiology as ITP - tx zidovudine
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

30. How to give postexposure prophylaxis for HIV
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
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
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

31. What is the Tx of STD uretheritis?
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
6-12 weeks
Postcoital voiding - increased intake of cranberry juice
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

32. when HIV patient develop pcp?
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
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
When cd4 count falls below 200. 2p in pcp =200
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

33. worsening of TB after starting HAART in HIV
Oropharyngeal secretions; hence named as kissing disease
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
<500 copies/ml

34. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
When cd4 count falls below 200. 2p in pcp =200
HBIG hep B immunoglobulin
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
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

35. What is the Tx of cryptococcal meninngitis
Do EBV antibody test
Oropharyngeal secretions; hence named as kissing disease
ELISA; initial visit - 6 - 12 and 24 weeks;
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

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

37. INH
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

38. what would be viral load after 2-4m of HAART?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
<500 copies/ml
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

39. drugs work well on hypertriglyceridia?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
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
Pegylated interferon and lamivudine
Blastomycosis

40. How to dx cryptococal meninggits
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
If a sample is ELISA positive - it is tested fro western blot for confirmation
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

41. How often HIV postiive patients CD4 count needs to be evaluated?
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Bronchoalveolar washing and transbronchial biopsy
Similar pathophysiology as ITP - tx zidovudine
Every 3-4 hours to determine appropritate time to start HAART

42. Tx of choice for human bites
Upper lobes; any fibrosis in this area suggestive of latent TB
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
Ampicillin-sublactam; most bites contain eikenella
Reddish orange discoloration of urine - feces - sweat - tears - sputum

43. infiltrate in upper lobe of lung?
Acyclovir
Either TB or aspergillosis
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
Pregnacy - urologic procedure - hip arthoplastu

44. How to tx chronic hep B
Pegylated interferon and lamivudine
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Ampicillin-sublactam; most bites contain eikenella
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

45. What is characteristic for dx of rocky mountain spotted fever?
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
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Postcoital voiding - increased intake of cranberry juice
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

46. How to confirm dx if pcp?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Bronchoalveolar washing and transbronchial biopsy
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

47. How to tx pcp?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Td every 10 years - tdap once before 65 and after 65
Pt who have been treated before for latent TB

48. foot infections in DM
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Bronchoalveolar washing and transbronchial biopsy

49. How to tx pseudomonas?
Bronchoalveolar washing and transbronchial biopsy
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

50. what parameters increases risk of neurosyphilis in HIV patient
Every 3-4 hours to determine appropritate time to start HAART
Pt who have been treated before for latent TB
High risk 19-64; 1-2 dose - above 65; one dose
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.