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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 characteristic for dx of rocky mountain spotted fever?
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
High risk 19-64; 1-2 dose - above 65; one dose
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

2. how HAART therapy affects HIV viral loads?
Within 6 months viral load will be <50
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Non pregnant premanopausal - elderly - dm - sci - chronic foley

3. where TB normally affects
ELISA; initial visit - 6 - 12 and 24 weeks;
Upper lobes; any fibrosis in this area suggestive of latent TB
Within 6 months viral load will be <50
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

4. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Do EBV antibody test
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
When cd4 count falls below 200. 2p in pcp =200
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.

5. What is fatal consequence of RMSF?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Rifampin600mg q12. or cipro
Either TB or aspergillosis
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

6. foot infections in DM
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
AA gradient >35 or Po2 <70
Postcoital voiding - increased intake of cranberry juice
Reddish orange discoloration of urine - feces - sweat - tears - sputum

7. When to tx asymptomatic bacteriurea >100 -000?
Pregnacy - urologic procedure - hip arthoplastu
Immune mediated; circulating IgG and IgM to penicillin derivatives
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
Upper lobes; any fibrosis in this area suggestive of latent TB

8. How to confirm chlamydia infection?
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

9. How to dx cryptococal meninggits
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
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.
Non pregnant premanopausal - elderly - dm - sci - chronic foley

10. antibiotic with good prostate penetration?
<5000 copies/ml
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
High risk 19-64; 1-2 dose - above 65; one dose

11. which heart valve is closer to ventricular conduction system/
Aortic valve; endocardiits of AR p/w AV block and LBBB
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
ELISA and western blot of synovial fluid.

12. What is the Tx of STD uretheritis?
Pt who have been treated before for latent TB
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
Others lesions are ring enhancing and have mass effect while PML don't
Non pregnant premanopausal - elderly - dm - sci - chronic foley

13. When to tx influenza with antiviral therapy?
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
Upper lobes; any fibrosis in this area suggestive of latent TB
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

14. dame that has already occurred
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Upper lobes; any fibrosis in this area suggestive of latent TB
Cd4 count
Pt who have been treated before for latent TB

15. How long abx is given in pseudomonas infection?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Reddish orange discoloration of urine - feces - sweat - tears - sputum

16. wisconsin - missisipi - ohio
Blastomycosis
Acyclovir
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

17. What is the classic signs of nec fasc?
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
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
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
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

18. rifampin
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
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
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

19. How to give postexposure prophylaxis for HIV
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
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

20. What is the Tx of cryptococcal meninngitis
Others lesions are ring enhancing and have mass effect while PML don't
Immune mediated; circulating IgG and IgM to penicillin derivatives
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.
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

21. What is lag time to develop lyme arthritis after exposure to vector
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
6-12 weeks
Clostridium perfringens after penetrative injuries/wounds
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

22. How to tx TSS?
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
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
<5000 copies/ml
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

23. When not to tx asymptomatic bacteriura?
Ampicillin-sublactam; most bites contain eikenella
Pt who have been treated before for latent TB
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Blastomycosis

24. what if monospot test is neg in IM?
Viral load and CD4 count
Bronchoalveolar washing and transbronchial biopsy
Do EBV antibody test
Upper lobes; any fibrosis in this area suggestive of latent TB

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

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26. How to dx adequate response to HBV vaccine
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Rifampin600mg q12. or cipro
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Vaccine titer >10mU/ml

27. clinical manifestation of mucomycosis
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
<5000 copies/ml
Within 6 months viral load will be <50
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

28. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
Acyclovir
Bronchoalveolar washing and transbronchial biopsy
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Need lumbar puncture to relieve pressure; they have high opening pressure >350

29. when western blot is done for HIV testing
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Need lumbar puncture to relieve pressure; they have high opening pressure >350
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
If a sample is ELISA positive - it is tested fro western blot for confirmation

30. infiltrate in upper lobe of lung?
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Either TB or aspergillosis
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

31. after recent exposure - negative ELISA - How to confirm?
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

32. How to dx progressive multifocal leukoencephalopathy
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
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
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Voriconazol. mycetoma-surgical removal

33. HIV patient having fat deposition on back of neck and abdomen - like cushing
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

34. hypertriglyceridemia in HIV
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
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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. aspergillosis
Mainly clinical - epidemiological and seasonal setting
Every 3-4 hours to determine appropritate time to start HAART
Voriconazol. mycetoma-surgical removal
<500 copies/ml

36. causative organisms of uti
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
HBIG hep B immunoglobulin
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
ELISA; initial visit - 6 - 12 and 24 weeks;

37. 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
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
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
Pt who have been treated before for latent TB

38. how im is transmitted?
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Oropharyngeal secretions; hence named as kissing disease
Viral load and CD4 count

39. after exposure of HIV when antibody testing is performed?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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
Postcoital voiding - increased intake of cranberry juice
ELISA; initial visit - 6 - 12 and 24 weeks;

40. thrombocytopenia in HIV
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Pt who have been treated before for latent TB
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Similar pathophysiology as ITP - tx zidovudine

41. reddish colored papules with central umbilication in HIV or immunocompromised patient
High risk 19-64; 1-2 dose - above 65; one dose
Clostridium perfringens after penetrative injuries/wounds
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
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

42. pathophysiology of toxic shock syndrom?
Cd4 count
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

43. INH
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Similar pathophysiology as ITP - tx zidovudine
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;

44. chshould we tx IM with abx (ampicilin) if throat cx is positive?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
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
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

45. How long we tx chronic prostatis?
When cd4 count falls below 200. 2p in pcp =200
6-12 weeks
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

46. What is tx for herpes zoster
Others lesions are ring enhancing and have mass effect while PML don't
Acyclovir
Within 6 months viral load will be <50
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

47. when not to give INH therapy if ppd positive and patient asyptomatic
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
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Pt who have been treated before for latent TB
Blastomycosis

48. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
HBIG hep B immunoglobulin
Pegylated interferon and lamivudine

49. how CMV presents in immunocompromised patients
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Others lesions are ring enhancing and have mass effect while PML don't
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

50. What is used for prophylaxis against meningo..meningitis?
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Immune mediated; circulating IgG and IgM to penicillin derivatives