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?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Oropharyngeal secretions; hence named as kissing disease
Mainly clinical - epidemiological and seasonal setting
Pegylated interferon and lamivudine

2. when HIV patient develop pcp?
High risk 19-64; 1-2 dose - above 65; one dose
Clostridium perfringens after penetrative injuries/wounds
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
When cd4 count falls below 200. 2p in pcp =200

3. What is the Tx of cryptococcal meninngitis
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
If a sample is ELISA positive - it is tested fro western blot for confirmation
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

4. What is difference between uti relapse versus recurrence?
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Others lesions are ring enhancing and have mass effect while PML don't
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

5. 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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
<5000 copies/ml
Reddish orange discoloration of urine - feces - sweat - tears - sputum

6. How to dx adequate response to HBV vaccine
Monospot test which screen heteropile ab that agglutinate horse rbc
Vaccine titer >10mU/ml
<5000 copies/ml
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

7. What are the behavioral interventions decrease the risk of UTI
Oropharyngeal secretions; hence named as kissing disease
Postcoital voiding - increased intake of cranberry juice
Others lesions are ring enhancing and have mass effect while PML don't
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

8. systolic HTN in elderly
High risk 19-64; 1-2 dose - above 65; one dose
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
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Within 6 months viral load will be <50

9. acute onset +rusty sputum
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Do EBV antibody test
Pt who have been treated before for latent TB

10. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
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
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
HBIG hep B immunoglobulin

11. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
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
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
PML; focal neurological deficit like MM; no specific tx; regress with HAART

12. How often viral load is monitored after HAART?
Pregnacy - urologic procedure - hip arthoplastu
HIV viral load
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

13. When to tx asymptomatic bacteriurea >100 -000?
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Monospot test which screen heteropile ab that agglutinate horse rbc
ELISA; initial visit - 6 - 12 and 24 weeks;
Pregnacy - urologic procedure - hip arthoplastu

14. where TB normally affects
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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

15. When not to tx asymptomatic bacteriura?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Blastomycosis
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Td every 10 years - tdap once before 65 and after 65

16. 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
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

17. How to dx progressive multifocal leukoencephalopathy
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
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
ELISA and western blot of synovial fluid.

18. What is lag time to develop lyme arthritis after exposure to vector
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

19. What is characteristic for dx of rocky mountain spotted fever?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Blastomycosis
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

20. pneumococcal vaccine indication?
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
PML; focal neurological deficit like MM; no specific tx; regress with HAART
High risk 19-64; 1-2 dose - above 65; one dose

21. can HIV transmitted through human bite?
HBIG hep B immunoglobulin
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
<5000 copies/ml
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

22. How to tx pseudomonas?
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
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
6-12 weeks
<500 copies/ml

23. INH
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
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
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

24. when we see echym gangrenosum?
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
Bronchoalveolar washing and transbronchial biopsy
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

25. hypertriglyceridemia in HIV
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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
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

26. foot infections in DM
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
If a sample is ELISA positive - it is tested fro western blot for confirmation
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

27. Tx of choice for human bites
Ampicillin-sublactam; most bites contain eikenella
Oropharyngeal secretions; hence named as kissing disease
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
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

28. How often HIV postiive patients CD4 count needs to be evaluated?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Every 3-4 hours to determine appropritate time to start HAART
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
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

29. How to dx IM?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
HBIG hep B immunoglobulin
Monospot test which screen heteropile ab that agglutinate horse rbc

30. How to dx cryptococal meninggits
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Ampicillin-sublactam; most bites contain eikenella
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

31. reddish colored papules with central umbilication in HIV or immunocompromised patient
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
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Rifampin600mg q12. or cipro

32. When to tx influenza with antiviral therapy?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
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
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

33. which heart valve is closer to ventricular conduction system/
Aortic valve; endocardiits of AR p/w AV block and LBBB
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
<500 copies/ml
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

34. dame that has already occurred
Pt who have been treated before for latent TB
Cd4 count
Monospot test which screen heteropile ab that agglutinate horse rbc
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

35. gas gangrene
Clostridium perfringens after penetrative injuries/wounds
Aortic valve; endocardiits of AR p/w AV block and LBBB
Cd4 count
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

36. What is the mch of ampicillin induced rash in IM
Immune mediated; circulating IgG and IgM to penicillin derivatives
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

37. How long abx is given in pseudomonas infection?
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
High risk 19-64; 1-2 dose - above 65; one dose
Mainly clinical - epidemiological and seasonal setting
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

38. What is used for prophylaxis against meningo..meningitis?
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Rifampin600mg q12. or cipro
<5000 copies/ml
HIV viral load

39. How to dx IM?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Every 3-4 hours to determine appropritate time to start HAART
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
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

40. How to differentiate different types of necrotizing fascitis?
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
Vaccine titer >10mU/ml
Pegylated interferon and lamivudine
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

41. after recent exposure - negative ELISA - How to confirm?
6-12 weeks
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.
ELISA; initial visit - 6 - 12 and 24 weeks;

42. What is the pathophysiology of Meningococcal meningitis?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

43. INH
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Pregnacy - urologic procedure - hip arthoplastu
6-12 weeks

44. What are indicators for progression of HIV
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
If a sample is ELISA positive - it is tested fro western blot for confirmation
Similar pathophysiology as ITP - tx zidovudine
Viral load and CD4 count

45. How to tx pcp?
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Monospot test which screen heteropile ab that agglutinate horse rbc
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
High risk 19-64; 1-2 dose - above 65; one dose

46. what parameters increases risk of neurosyphilis in HIV patient
Ampicillin-sublactam; most bites contain eikenella
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.
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

47. What is fatal consequence of RMSF?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
ELISA and western blot of synovial fluid.
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

48. pathophysiology of toxic shock syndrom?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
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

49. thrombocytopenia in HIV
Similar pathophysiology as ITP - tx zidovudine
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
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

50. wisconsin - missisipi - ohio
Blastomycosis
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Either TB or aspergillosis
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma