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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 is the criteria for Spontaneous bact peritonitis
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Aortic valve; endocardiits of AR p/w AV block and LBBB

2. how HAART therapy affects HIV viral loads?
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Within 6 months viral load will be <50
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

3. How to dx adequate response to HBV vaccine
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Others lesions are ring enhancing and have mass effect while PML don't
Aortic valve; endocardiits of AR p/w AV block and LBBB
Vaccine titer >10mU/ml

4. wisconsin - missisipi - ohio
Blastomycosis
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

5. How to dx bacterial meningitis from CSF study?

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6. How long we tx chronic prostatis?
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
6-12 weeks
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

7. systolic HTN in elderly
<500 copies/ml
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
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.

8. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
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
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

9. When to give abx to prevent recurrent uti
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
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
6-12 weeks
Viral load and CD4 count

10. What is lag time to develop lyme arthritis after exposure to vector
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Do EBV antibody test
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Within 6 months viral load will be <50

11. thrombocytopenia in HIV
Similar pathophysiology as ITP - tx zidovudine
If a sample is ELISA positive - it is tested fro western blot for confirmation
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
<5000 copies/ml

12. after exposure of HIV when antibody testing is performed?
ELISA; initial visit - 6 - 12 and 24 weeks;
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
High risk 19-64; 1-2 dose - above 65; one dose
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

13. How to give postexposure prophylaxis for HIV
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
Oropharyngeal secretions; hence named as kissing disease
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

14. damae that is about to occur?
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 viral load
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

15. how im is transmitted?
Similar pathophysiology as ITP - tx zidovudine
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Oropharyngeal secretions; hence named as kissing disease
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

16. How to confirm chlamydia infection?
Acyclovir
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Monospot test which screen heteropile ab that agglutinate horse rbc
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

17. What are indicators for progression of HIV
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
ELISA; initial visit - 6 - 12 and 24 weeks;
Cd4 count
Viral load and CD4 count

18. foot infections in DM
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Bronchoalveolar washing and transbronchial biopsy
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
PML; focal neurological deficit like MM; no specific tx; regress with HAART

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

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20. How often HIV postiive patients CD4 count needs to be evaluated?
ELISA; initial visit - 6 - 12 and 24 weeks;
Postcoital voiding - increased intake of cranberry juice
Every 3-4 hours to determine appropritate time to start HAART
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

21. INH
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
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
<500 copies/ml
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

22. when not to give INH therapy if ppd positive and patient asyptomatic
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
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.
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Pt who have been treated before for latent TB

23. How to dx cryptococal meninggits
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Mainly clinical - epidemiological and seasonal setting
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

24. causative organisms of uti
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
<5000 copies/ml

25. reddish colored papules with central umbilication in HIV or immunocompromised patient
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
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
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
Do EBV antibody test

26. dame that has already occurred
Cd4 count
Pegylated interferon and lamivudine
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

27. what if monospot test is neg in IM?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Bronchoalveolar washing and transbronchial biopsy
Do EBV antibody test
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

28. 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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Cd4 count
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

29. can HIV transmitted through human bite?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
HIV viral load
Vaccine titer >10mU/ml
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

30. when HIV patient develop pcp?
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
When cd4 count falls below 200. 2p in pcp =200
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
<500 copies/ml

31. How to tx TSS?
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
Bronchoalveolar washing and transbronchial biopsy
ELISA; initial visit - 6 - 12 and 24 weeks;
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

32. When not to tx asymptomatic bacteriura?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Aortic valve; endocardiits of AR p/w AV block and LBBB
When cd4 count falls below 200. 2p in pcp =200
Non pregnant premanopausal - elderly - dm - sci - chronic foley

33. when western blot is done for HIV testing
If a sample is ELISA positive - it is tested fro western blot for confirmation
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
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
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

34. How to dx IM?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
HBIG hep B immunoglobulin
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

35. 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
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
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. if a patient received BCG vaccine - how big is his PPD induration

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37. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
PML; focal neurological deficit like MM; no specific tx; regress with HAART

38. How to tx IM?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Vaccine titer >10mU/ml
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

39. hypertriglyceridemia in HIV
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Pegylated interferon and lamivudine
Similar pathophysiology as ITP - tx zidovudine

40. What is tetanus - diptheria - pertusis recommendation?
Ampicillin-sublactam; most bites contain eikenella
Td every 10 years - tdap once before 65 and after 65
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Others lesions are ring enhancing and have mass effect while PML don't

41. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
HBIG hep B immunoglobulin
If a sample is ELISA positive - it is tested fro western blot for confirmation
High risk 19-64; 1-2 dose - above 65; one dose
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

42. What are the behavioral interventions decrease the risk of UTI
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
ELISA; initial visit - 6 - 12 and 24 weeks;
Postcoital voiding - increased intake of cranberry juice
Aortic valve; endocardiits of AR p/w AV block and LBBB

43. drugs work well on hypertriglyceridia?
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Pregnacy - urologic procedure - hip arthoplastu

44. what parameters increases risk of neurosyphilis in HIV patient
Acyclovir
Viral load and CD4 count
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

45. What is fatal consequence of RMSF?
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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Vaccine titer >10mU/ml
Immune mediated; circulating IgG and IgM to penicillin derivatives

46. What is tx for herpes zoster
6-12 weeks
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Acyclovir

47. 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
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Clostridium perfringens after penetrative injuries/wounds
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

48. pathophysiology of toxic shock syndrom?
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Mainly clinical - epidemiological and seasonal setting

49. rifampin
Reddish orange discoloration of urine - feces - sweat - tears - sputum
<500 copies/ml
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
HBIG hep B immunoglobulin

50. How to differentiate different types of necrotizing fascitis?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
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
Mainly clinical - epidemiological and seasonal setting
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.