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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. how CMV presents in immunocompromised patients
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Within 6 months viral load will be <50

2. wisconsin - missisipi - ohio
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
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
ELISA; initial visit - 6 - 12 and 24 weeks;
Blastomycosis

3. when HIV patient develop pcp?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Similar pathophysiology as ITP - tx zidovudine
When cd4 count falls below 200. 2p in pcp =200
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

4. How to dx IM?
Pegylated interferon and lamivudine
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Ampicillin-sublactam; most bites contain eikenella

5. 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
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Do EBV antibody test
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

6. Tx of choice for human bites
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Upper lobes; any fibrosis in this area suggestive of latent TB
Ampicillin-sublactam; most bites contain eikenella
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

7. What are the behavioral interventions decrease the risk of UTI
Postcoital voiding - increased intake of cranberry juice
Mainly clinical - epidemiological and seasonal setting
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

8. What is the mch of ampicillin induced rash in IM
Every 3-4 hours to determine appropritate time to start HAART
Vaccine titer >10mU/ml
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Immune mediated; circulating IgG and IgM to penicillin derivatives

9. what parameters increases risk of neurosyphilis in HIV patient
Upper lobes; any fibrosis in this area suggestive of latent TB
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.
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

10. How to dx lyme arthritis?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Voriconazol. mycetoma-surgical removal
ELISA and western blot of synovial fluid.
Viral load and CD4 count

11. HIV patient having fat deposition on back of neck and abdomen - like cushing
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)
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Ampicillin-sublactam; most bites contain eikenella

12. after recent exposure - negative ELISA - How to confirm?
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Upper lobes; any fibrosis in this area suggestive of latent TB
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
<500 copies/ml

13. INH
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
AA gradient >35 or Po2 <70
Clostridium perfringens after penetrative injuries/wounds
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

14. worsening of TB after starting HAART in HIV
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Do EBV antibody test
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Acyclovir

15. How to dx IM?
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
Monospot test which screen heteropile ab that agglutinate horse rbc
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

16. gas gangrene
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Clostridium perfringens after penetrative injuries/wounds
Postcoital voiding - increased intake of cranberry juice

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

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18. after exposure of HIV when antibody testing is performed?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
ELISA and western blot of synovial fluid.
Rifampin600mg q12. or cipro
ELISA; initial visit - 6 - 12 and 24 weeks;

19. What is the criteria for Spontaneous bact peritonitis
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

20. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Aortic valve; endocardiits of AR p/w AV block and LBBB
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Vaccine titer >10mU/ml
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

21. How to dx adequate response to HBV vaccine
Pegylated interferon and lamivudine
Aortic valve; endocardiits of AR p/w AV block and LBBB
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Vaccine titer >10mU/ml

22. can HIV transmitted through human bite?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
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
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

23. acute febrile reaction develops after starting penicilin tx to syphilis patient
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Pt who have been treated before for latent TB

24. When to give prophylaxis against MAC
HIV viral load
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
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
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 is difference between uti relapse versus recurrence?
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
When cd4 count falls below 200. 2p in pcp =200
Either TB or aspergillosis

26. What is the classic signs of nec fasc?
Within 6 months viral load will be <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
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Non pregnant premanopausal - elderly - dm - sci - chronic foley

27. antibiotic with good prostate penetration?
Do EBV antibody test
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

28. What is the prognosis of lyme arthritis?
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
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 -
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

29. What are indicators for progression of HIV
Cd4 count
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Viral load and CD4 count

30. How to confirm dx if pcp?
Bronchoalveolar washing and transbronchial biopsy
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
HIV viral load
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

31. What is characteristic for dx of rocky mountain spotted fever?
Pregnacy - urologic procedure - hip arthoplastu
Viral load and CD4 count
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

32. when western blot is done for HIV testing
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
If a sample is ELISA positive - it is tested fro western blot for confirmation
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

33. thrombocytopenia in HIV
Immune mediated; circulating IgG and IgM to penicillin derivatives
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Similar pathophysiology as ITP - tx zidovudine

34. What is tetanus - diptheria - pertusis recommendation?
Bronchoalveolar washing and transbronchial biopsy
Clostridium perfringens after penetrative injuries/wounds
Td every 10 years - tdap once before 65 and after 65
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

35. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
HBIG hep B immunoglobulin
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Within 6 months viral load will be <50

36. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

37. 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
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

38. How often HIV postiive patients CD4 count needs to be evaluated?
Upper lobes; any fibrosis in this area suggestive of latent TB
Every 3-4 hours to determine appropritate time to start HAART
Others lesions are ring enhancing and have mass effect while PML don't
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

39. What is the Tx of cryptococcal meninngitis
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
High risk 19-64; 1-2 dose - above 65; one dose
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

40. where TB normally affects
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Mainly clinical - epidemiological and seasonal setting
Upper lobes; any fibrosis in this area suggestive of latent TB
Blastomycosis

41. dame that has already occurred
ELISA; initial visit - 6 - 12 and 24 weeks;
Cd4 count
Rifampin600mg q12. or cipro
Others lesions are ring enhancing and have mass effect while PML don't

42. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Do EBV antibody test

43. When to tx asymptomatic bacteriurea >100 -000?
Pregnacy - urologic procedure - hip arthoplastu
Oropharyngeal secretions; hence named as kissing disease
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

44. aspergillosis
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
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Voriconazol. mycetoma-surgical removal
Non pregnant premanopausal - elderly - dm - sci - chronic foley

45. What is used for prophylaxis against meningo..meningitis?
Acyclovir
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Rifampin600mg q12. or cipro
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

46. when not to give INH therapy if ppd positive and patient asyptomatic
Postcoital voiding - increased intake of cranberry juice
Pregnacy - urologic procedure - hip arthoplastu
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Pt who have been treated before for latent TB

47. what would be viral load after 4 weeks
<5000 copies/ml
Oropharyngeal secretions; hence named as kissing disease
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

48. damae that is about to occur?
HIV viral load
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Voriconazol. mycetoma-surgical removal
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

49. What is tx for herpes zoster
Acyclovir
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Pegylated interferon and lamivudine

50. How to dx bacterial meningitis from CSF study?

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