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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. HIV patient having fat deposition on back of neck and abdomen - like cushing
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
ELISA and western blot of synovial fluid.
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

2. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Do EBV antibody test
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
6-12 weeks

3. gas gangrene
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Clostridium perfringens after penetrative injuries/wounds
Pt who have been treated before for latent TB
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

4. How to dx lyme arthritis?
Reddish orange discoloration of urine - feces - sweat - tears - sputum
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
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
ELISA and western blot of synovial fluid.

5. How to give postexposure prophylaxis for HIV
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
Vaccine titer >10mU/ml
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
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. What is the Tx of cryptococcal meninngitis
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

7. when western blot is done for HIV testing
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
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

8. 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
Blastomycosis
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

9. causative organisms of uti
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
High risk 19-64; 1-2 dose - above 65; one dose
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

10. acute febrile reaction develops after starting penicilin tx to syphilis patient
Clostridium perfringens after penetrative injuries/wounds
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

11. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Oropharyngeal secretions; hence named as kissing disease
HBIG hep B immunoglobulin
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

12. How to tx IM?
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Either TB or aspergillosis
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Non pregnant premanopausal - elderly - dm - sci - chronic foley

13. When to tx asymptomatic bacteriurea >100 -000?
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
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Pregnacy - urologic procedure - hip arthoplastu
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

14. dame that has already occurred
Cd4 count
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
HBIG hep B immunoglobulin
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

15. When to tx influenza with antiviral therapy?
High risk 19-64; 1-2 dose - above 65; one dose
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
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
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

16. How to dx bacterial meningitis from CSF study?

17. low grade fever - maculopapular rash - lymphadenopathy
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
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
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

18. drugs work well on hypertriglyceridia?
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Mainly clinical - epidemiological and seasonal setting

19. worsening of TB after starting HAART in HIV
6-12 weeks
PML; focal neurological deficit like MM; no specific tx; regress with HAART
High risk 19-64; 1-2 dose - above 65; one dose
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

20. infiltrate in upper lobe of lung?
Either TB or aspergillosis
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
AA gradient >35 or Po2 <70
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

21. What is tx for herpes zoster
Td every 10 years - tdap once before 65 and after 65
Acyclovir
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

22. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
High risk 19-64; 1-2 dose - above 65; one dose
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

23. how CMV presents in immunocompromised patients
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Viral load and CD4 count
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

24. What are the behavioral interventions decrease the risk of UTI
6-12 weeks
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
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

25. What are the subjective /objective measure of encephalopathy?
Either TB or aspergillosis
Monospot test which screen heteropile ab that agglutinate horse rbc
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

26. after exposure of HIV when antibody testing is performed?
Similar pathophysiology as ITP - tx zidovudine
ELISA; initial visit - 6 - 12 and 24 weeks;
Oropharyngeal secretions; hence named as kissing disease
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

27. What is the indication of corticosteroid in pcp infection?
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
6-12 weeks
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
AA gradient >35 or Po2 <70

28. What is the pathophysiology of Meningococcal meningitis?
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Voriconazol. mycetoma-surgical removal

29. what if monospot test is neg in IM?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Do EBV antibody test
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
Aortic valve; endocardiits of AR p/w AV block and LBBB

30. How to differentiate different types of necrotizing fascitis?
Similar pathophysiology as ITP - tx zidovudine
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
Voriconazol. mycetoma-surgical removal
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

31. How to dx?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Acyclovir
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Mainly clinical - epidemiological and seasonal setting

32. How to tx pcp?
Cd4 count
HIV viral load
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
High risk 19-64; 1-2 dose - above 65; one dose

33. How to tx chronic hep B
Upper lobes; any fibrosis in this area suggestive of latent TB
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Pegylated interferon and lamivudine

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

35. How to confirm chlamydia infection?
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Rifampin600mg q12. or cipro
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Td every 10 years - tdap once before 65 and after 65

36. How long abx is given in pseudomonas infection?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Pregnacy - urologic procedure - hip arthoplastu
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

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

38. after recent exposure - negative ELISA - How to confirm?
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
HBIG hep B immunoglobulin
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
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

39. wisconsin - missisipi - ohio
Need lumbar puncture to relieve pressure; they have high opening pressure >350
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
Blastomycosis
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

40. What is the classic signs of nec fasc?
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
Vaccine titer >10mU/ml
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

41. antibiotic with good prostate penetration?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Immune mediated; circulating IgG and IgM to penicillin derivatives
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

42. hypertension in children
Similar pathophysiology as ITP - tx zidovudine
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Postcoital voiding - increased intake of cranberry juice
Pegylated interferon and lamivudine

43. How to dx cryptococal meninggits
<500 copies/ml
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
When cd4 count falls below 200. 2p in pcp =200
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

44. What are indicators for progression of HIV
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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
Viral load and CD4 count
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

45. what would be viral load after 2-4m of HAART?
<500 copies/ml
Vaccine titer >10mU/ml
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
If a sample is ELISA positive - it is tested fro western blot for confirmation

46. What is lag time to develop lyme arthritis after exposure to vector
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
Similar pathophysiology as ITP - tx zidovudine
Blastomycosis

47. when HIV patient develop pcp?
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
When cd4 count falls below 200. 2p in pcp =200

48. What is tetanus - diptheria - pertusis recommendation?
Td every 10 years - tdap once before 65 and after 65
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
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

49. How to differentiate gonococcal and nongonoccal urethritis?
Blastomycosis
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
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Non pregnant premanopausal - elderly - dm - sci - chronic foley

50. what parameters increases risk of neurosyphilis in HIV patient
Others lesions are ring enhancing and have mass effect while PML don't
6-12 weeks
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.
Pt who have been treated before for latent TB