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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
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Others lesions are ring enhancing and have mass effect while PML don't
Pregnacy - urologic procedure - hip arthoplastu
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

2. hypertension in children
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Clostridium perfringens after penetrative injuries/wounds

3. How to dx cryptococal meninggits
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

4. how HAART therapy affects HIV viral loads?
Within 6 months viral load will be <50
Immune mediated; circulating IgG and IgM to penicillin derivatives
Blastomycosis
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

5. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
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
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

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

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7. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Aortic valve; endocardiits of AR p/w AV block and LBBB
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Rifampin600mg q12. or cipro

8. hypertriglyceridemia in HIV
Monospot test which screen heteropile ab that agglutinate horse rbc
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
High risk 19-64; 1-2 dose - above 65; one dose
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

9. acute febrile reaction develops after starting penicilin tx to syphilis patient
ELISA; initial visit - 6 - 12 and 24 weeks;
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Immune mediated; circulating IgG and IgM to penicillin derivatives
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

10. pathophysiology of toxic shock syndrom?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Postcoital voiding - increased intake of cranberry juice
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Vaccine titer >10mU/ml

11. How to give postexposure prophylaxis for HIV
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
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
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

12. 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
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Voriconazol. mycetoma-surgical removal
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

13. low grade fever - maculopapular rash - lymphadenopathy
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Bronchoalveolar washing and transbronchial biopsy
Blastomycosis
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

14. after recent exposure - negative ELISA - How to confirm?
Immune mediated; circulating IgG and IgM to penicillin derivatives
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

15. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
PML; focal neurological deficit like MM; no specific tx; regress with HAART
ELISA and western blot of synovial fluid.
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
Mainly clinical - epidemiological and seasonal setting

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

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17. What are the subjective /objective measure of encephalopathy?
Bronchoalveolar washing and transbronchial biopsy
Cd4 count
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

18. How to dx adequate response to HBV vaccine
Vaccine titer >10mU/ml
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Immune mediated; circulating IgG and IgM to penicillin derivatives

19. What is the indication of corticosteroid in pcp infection?
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
AA gradient >35 or Po2 <70
Aortic valve; endocardiits of AR p/w AV block and LBBB
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

20. How to dx bacterial meningitis from CSF study?

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21. gas gangrene
Oropharyngeal secretions; hence named as kissing disease
When cd4 count falls below 200. 2p in pcp =200
Clostridium perfringens after penetrative injuries/wounds
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

22. How to differentiate gonococcal and nongonoccal urethritis?
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
Pt who have been treated before for latent TB
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

23. How to confirm dx if pcp?
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Bronchoalveolar washing and transbronchial biopsy
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

24. How to confirm chlamydia infection?
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
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
Within 6 months viral load will be <50

25. can HIV transmitted through human bite?
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
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

26. What is characteristic for dx of rocky mountain spotted fever?
ELISA and western blot of synovial fluid.
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Viral load and CD4 count

27. What is tetanus - diptheria - pertusis recommendation?
Td every 10 years - tdap once before 65 and after 65
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Oropharyngeal secretions; hence named as kissing disease
Rifampin600mg q12. or cipro

28. What is used for prophylaxis against meningo..meningitis?
<500 copies/ml
Rifampin600mg q12. or cipro
Others lesions are ring enhancing and have mass effect while PML don't
AA gradient >35 or Po2 <70

29. wisconsin - missisipi - ohio
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
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
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Blastomycosis

30. When to tx influenza with antiviral therapy?
Cd4 count
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
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. What is fatal consequence of RMSF?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Viral load and CD4 count
Need lumbar puncture to relieve pressure; they have high opening pressure >350

32. Tx of choice for human bites
Ampicillin-sublactam; most bites contain eikenella
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
6-12 weeks
Blastomycosis

33. What is tx for herpes zoster
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Acyclovir
Upper lobes; any fibrosis in this area suggestive of latent TB

34. rifampin
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

35. what would be viral load after 4 weeks
<5000 copies/ml
Vaccine titer >10mU/ml
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

36. where TB normally affects
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Upper lobes; any fibrosis in this area suggestive of latent TB
Pegylated interferon and lamivudine

37. How to tx chronic hep B
Pegylated interferon and lamivudine
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Postcoital voiding - increased intake of cranberry juice

38. What is the pathophysiology of Meningococcal meningitis?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
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
Cd4 count

39. after exposure of HIV when antibody testing is performed?
Clostridium perfringens after penetrative injuries/wounds
Blastomycosis
ELISA; initial visit - 6 - 12 and 24 weeks;
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

40. HIV patient having fat deposition on back of neck and abdomen - like cushing
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Ampicillin-sublactam; most bites contain eikenella

41. dame that has already occurred
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Cd4 count
Pt who have been treated before for latent TB

42. 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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
ELISA; initial visit - 6 - 12 and 24 weeks;
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

43. antibiotic with good prostate penetration?
ELISA and western blot of synovial fluid.
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

44. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
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
<500 copies/ml
HBIG hep B immunoglobulin

45. infiltrate in upper lobe of lung?
HBIG hep B immunoglobulin
Cd4 count
If a sample is ELISA positive - it is tested fro western blot for confirmation
Either TB or aspergillosis

46. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Pegylated interferon and lamivudine
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
6-12 weeks
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

47. How to dx IM?
Vaccine titer >10mU/ml
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
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

48. When not to tx asymptomatic bacteriura?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Pegylated interferon and lamivudine
Monospot test which screen heteropile ab that agglutinate horse rbc
Non pregnant premanopausal - elderly - dm - sci - chronic foley

49. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
HBIG hep B immunoglobulin
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

50. When to give abx to prevent recurrent uti
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
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
Blastomycosis
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