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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 HAART therapy affects HIV viral loads?
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
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Within 6 months viral load will be <50
Ampicillin-sublactam; most bites contain eikenella

2. HIV patient having fat deposition on back of neck and abdomen - like cushing
<500 copies/ml
Postcoital voiding - increased intake of cranberry juice
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

3. How often HIV postiive patients CD4 count needs to be evaluated?
Ampicillin-sublactam; most bites contain eikenella
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Every 3-4 hours to determine appropritate time to start HAART
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

4. How long abx is given in pseudomonas infection?
Vaccine titer >10mU/ml
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

5. What is used for prophylaxis against meningo..meningitis?
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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Rifampin600mg q12. or cipro

6. what would be viral load after 2-4m of HAART?
Do EBV antibody test
Aortic valve; endocardiits of AR p/w AV block and LBBB
<500 copies/ml
Non pregnant premanopausal - elderly - dm - sci - chronic foley

7. How to dx progressive multifocal leukoencephalopathy
Do EBV antibody test
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

8. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
Pt who have been treated before for latent TB
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
HBIG hep B immunoglobulin
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

9. How to tx pseudomonas?
Immune mediated; circulating IgG and IgM to penicillin derivatives
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

10. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Rifampin600mg q12. or cipro
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
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

11. How to dx cryptococal meninggits
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Mainly clinical - epidemiological and seasonal setting
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

12. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Either TB or aspergillosis
ELISA; initial visit - 6 - 12 and 24 weeks;

13. reddish colored papules with central umbilication in HIV or immunocompromised patient
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
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

14. pathophysiology of toxic shock syndrom?
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Voriconazol. mycetoma-surgical removal
AA gradient >35 or Po2 <70

15. How to dx IM?
Monospot test which screen heteropile ab that agglutinate horse rbc
Aortic valve; endocardiits of AR p/w AV block and LBBB
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

16. acute febrile reaction develops after starting penicilin tx to syphilis patient
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)
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

17. gas gangrene
Clostridium perfringens after penetrative injuries/wounds
ELISA and western blot of synovial fluid.
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Cd4 count

18. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Mainly clinical - epidemiological and seasonal setting
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

19. What are indicators for progression of HIV
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Viral load and CD4 count
Need lumbar puncture to relieve pressure; they have high opening pressure >350

20. What is the prognosis of lyme arthritis?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Pegylated interferon and lamivudine
ELISA and western blot of synovial fluid.
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

21. How to tx pcp?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
HIV viral load
Every 3-4 hours to determine appropritate time to start HAART
<500 copies/ml

22. What is characteristic for dx of rocky mountain spotted fever?
ELISA and western blot of synovial fluid.
Non pregnant premanopausal - elderly - dm - sci - chronic foley
If a sample is ELISA positive - it is tested fro western blot for confirmation
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

23. hypertension in children
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
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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
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.

24. What is the indication of corticosteroid in pcp infection?
AA gradient >35 or Po2 <70
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Either TB or aspergillosis

25. What are the behavioral interventions decrease the risk of UTI
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Every 3-4 hours to determine appropritate time to start HAART
Postcoital voiding - increased intake of cranberry juice

26. What is difference between uti relapse versus recurrence?
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
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
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

27. infiltrate in upper lobe of lung?
Either TB or aspergillosis
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Pt who have been treated before for latent TB

28. What is the criteria for Spontaneous bact peritonitis
Voriconazol. mycetoma-surgical removal
Pt who have been treated before for latent TB
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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

29. hypertriglyceridemia in HIV
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
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

30. When to tx influenza with antiviral therapy?
When cd4 count falls below 200. 2p in pcp =200
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Voriconazol. mycetoma-surgical removal
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

31. When not to tx asymptomatic bacteriura?
Oropharyngeal secretions; hence named as kissing disease
Non pregnant premanopausal - elderly - dm - sci - chronic foley
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

32. systolic HTN in elderly
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Upper lobes; any fibrosis in this area suggestive of latent TB

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

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34. how im is transmitted?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to 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
Oropharyngeal secretions; hence named as kissing disease

35. How to dx bacterial meningitis from CSF study?

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36. thrombocytopenia in HIV
Similar pathophysiology as ITP - tx zidovudine
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
If a sample is ELISA positive - it is tested fro western blot for confirmation

37. after recent exposure - negative ELISA - How to confirm?
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
Cd4 count
Need lumbar puncture to relieve pressure; they have high opening pressure >350
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

38. can HIV transmitted through human bite?
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
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

39. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
Bronchoalveolar washing and transbronchial biopsy
Others lesions are ring enhancing and have mass effect while PML don't
Vaccine titer >10mU/ml
Need lumbar puncture to relieve pressure; they have high opening pressure >350

40. What is lag time to develop lyme arthritis after exposure to vector
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Clostridium perfringens after penetrative injuries/wounds
Viral load and CD4 count
Others lesions are ring enhancing and have mass effect while PML don't

41. dame that has already occurred
When cd4 count falls below 200. 2p in pcp =200
Non pregnant premanopausal - elderly - dm - sci - chronic foley
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Cd4 count

42. rifampin
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Cd4 count
Reddish orange discoloration of urine - feces - sweat - tears - sputum

43. What is fatal consequence of RMSF?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
When cd4 count falls below 200. 2p in pcp =200
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
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

44. 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
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
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. How to give postexposure prophylaxis for HIV
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
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
When cd4 count falls below 200. 2p in pcp =200

46. antibiotic with good prostate penetration?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Every 3-4 hours to determine appropritate time to start HAART

47. What is tetanus - diptheria - pertusis recommendation?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Td every 10 years - tdap once before 65 and after 65
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Rifampin600mg q12. or cipro

48. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
HIV viral load
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

49. aspergillosis
Every 3-4 hours to determine appropritate time to start HAART
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Voriconazol. mycetoma-surgical removal
Similar pathophysiology as ITP - tx zidovudine

50. How to tx chronic hep B
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
Pegylated interferon and lamivudine
Aortic valve; endocardiits of AR p/w AV block and LBBB
Pregnacy - urologic procedure - hip arthoplastu