Test your basic knowledge |

USMLE Step3 Infectious Disease

Subjects : health-sciences, usmle-step-3

Instructions:

Answer 50 questions in 15 minutes.
If you are not ready to take this test, you can study here.
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. How to dx lyme arthritis?
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
If a sample is ELISA positive - it is tested fro western blot for confirmation
ELISA and western blot of synovial fluid.

2. hypertriglyceridemia in HIV
Voriconazol. mycetoma-surgical removal
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

3. How to dx adequate response to HBV vaccine
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Vaccine titer >10mU/ml
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

4. What is the criteria for Spontaneous bact peritonitis
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
HBIG hep B immunoglobulin
Rifampin600mg q12. or cipro
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

5. INH
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

6. What is fatal consequence of RMSF?
Similar pathophysiology as ITP - tx zidovudine
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

7. pneumococcal vaccine indication?
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
High risk 19-64; 1-2 dose - above 65; one dose
HBIG hep B immunoglobulin

8. infiltrate in upper lobe of lung?
When cd4 count falls below 200. 2p in pcp =200
Either TB or aspergillosis
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
PML; focal neurological deficit like MM; no specific tx; regress with HAART

9. gas gangrene
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Clostridium perfringens after penetrative injuries/wounds
Either TB or aspergillosis
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

10. causative organisms of uti
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
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
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

11. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Bronchoalveolar washing and transbronchial biopsy
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

12. when HIV patient develop pcp?
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
When cd4 count falls below 200. 2p in pcp =200
Oropharyngeal secretions; hence named as kissing disease
Acyclovir

13. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
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
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

14. HIV patient having fat deposition on back of neck and abdomen - like cushing
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
When cd4 count falls below 200. 2p in pcp =200
HIV viral load
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

15. what would be viral load after 2-4m of HAART?
Mainly clinical - epidemiological and seasonal setting
Pegylated interferon and lamivudine
<500 copies/ml
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

16. What is the mch of ampicillin induced rash in IM
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
ELISA; initial visit - 6 - 12 and 24 weeks;
Immune mediated; circulating IgG and IgM to penicillin derivatives

17. rifampin
HBIG hep B immunoglobulin
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Within 6 months viral load will be <50

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

19. How long we tx chronic prostatis?
Either TB or aspergillosis
<500 copies/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
6-12 weeks

20. hypertension in children
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Ampicillin-sublactam; most bites contain eikenella
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
PML; focal neurological deficit like MM; no specific tx; regress with HAART

21. How to dx progressive multifocal leukoencephalopathy
Aortic valve; endocardiits of AR p/w AV block and LBBB
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
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

22. When not to tx asymptomatic bacteriura?
Either TB or aspergillosis
High risk 19-64; 1-2 dose - above 65; one dose
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

23. worsening of TB after starting HAART in HIV
Others lesions are ring enhancing and have mass effect while PML don't
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

24. What are the subjective /objective measure of encephalopathy?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Every 3-4 hours to determine appropritate time to start HAART
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

25. antibiotic with good prostate penetration?
ELISA and western blot of synovial fluid.
Do EBV antibody test
Voriconazol. mycetoma-surgical removal
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

26. How to differentiate different types of necrotizing fascitis?
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
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

27. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Pegylated interferon and lamivudine
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.
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

28. What is lag time to develop lyme arthritis after exposure to vector
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Ampicillin-sublactam; most bites contain eikenella
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

29. What is the prognosis of lyme arthritis?
Vaccine titer >10mU/ml
Mainly clinical - epidemiological and seasonal setting
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Viral load and CD4 count

30. What are indicators for progression of HIV
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
Viral load and CD4 count
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

31. reddish colored papules with central umbilication in HIV or immunocompromised patient
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
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
High risk 19-64; 1-2 dose - above 65; one dose

32. What is characteristic for dx of rocky mountain spotted fever?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

33. acute febrile reaction develops after starting penicilin tx to syphilis patient
Either TB or aspergillosis
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

34. after recent exposure - negative ELISA - How to confirm?
Aortic valve; endocardiits of AR p/w AV block and LBBB
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.
Vaccine titer >10mU/ml

35. drugs work well on hypertriglyceridia?
Every 3-4 hours to determine appropritate time to start HAART
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Cd4 count
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

36. How to tx pseudomonas?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
High risk 19-64; 1-2 dose - above 65; one dose

37. aspergillosis
Voriconazol. mycetoma-surgical removal
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Oropharyngeal secretions; hence named as kissing disease
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

38. 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
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Do EBV antibody test
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

39. INH
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
If a sample is ELISA positive - it is tested fro western blot for confirmation
Viral load and CD4 count
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

40. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
HBIG hep B immunoglobulin
Pt who have been treated before for latent TB
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
AA gradient >35 or Po2 <70

41. clinical manifestation of mucomycosis
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

42. How to tx IM?
Td every 10 years - tdap once before 65 and after 65
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
AA gradient >35 or Po2 <70
Acyclovir

43. What is used for prophylaxis against meningo..meningitis?
Td every 10 years - tdap once before 65 and after 65
Rifampin600mg q12. or cipro
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
If a sample is ELISA positive - it is tested fro western blot for confirmation

44. How to dx IM?
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
6-12 weeks
Monospot test which screen heteropile ab that agglutinate horse rbc
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

45. what parameters increases risk of neurosyphilis in HIV patient
Vaccine titer >10mU/ml
Aortic valve; endocardiits of AR p/w AV block and LBBB
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.
HIV viral load

46. What is difference between uti relapse versus recurrence?
<5000 copies/ml
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Pregnacy - urologic procedure - hip arthoplastu
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

47. How to tx pcp?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Non pregnant premanopausal - elderly - dm - sci - chronic foley

48. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Similar pathophysiology as ITP - tx zidovudine
AA gradient >35 or Po2 <70
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

49. What is the pathophysiology of Meningococcal meningitis?
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Rifampin600mg q12. or cipro

50. How to dx cryptococal meninggits
ELISA; initial visit - 6 - 12 and 24 weeks;
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
HIV viral load
Vaccine titer >10mU/ml