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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 fatal consequence of RMSF?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

2. how CMV presents in immunocompromised patients
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Need lumbar puncture to relieve pressure; they have high opening pressure >350
PML; focal neurological deficit like MM; no specific tx; regress with HAART

3. rifampin
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.
High risk 19-64; 1-2 dose - above 65; one dose
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
Reddish orange discoloration of urine - feces - sweat - tears - sputum

4. What is the criteria for Spontaneous bact peritonitis
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

5. How to dx cryptococal meninggits
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
HBIG hep B immunoglobulin
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

6. after recent exposure - negative ELISA - How to confirm?
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.
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Postcoital voiding - increased intake of cranberry juice

7. hypertension in children
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
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 viral load
Do EBV antibody test

8. How often HIV postiive patients CD4 count needs to be evaluated?
Every 3-4 hours to determine appropritate time to start HAART
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
Reddish orange discoloration of urine - feces - sweat - tears - sputum

9. How to dx?
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
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
Mainly clinical - epidemiological and seasonal setting
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

10. thrombocytopenia in HIV
Others lesions are ring enhancing and have mass effect while PML don't
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Similar pathophysiology as ITP - tx zidovudine

11. which heart valve is closer to ventricular conduction system/
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
Aortic valve; endocardiits of AR p/w AV block and LBBB
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

12. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
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
HBIG hep B immunoglobulin
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Clostridium perfringens after penetrative injuries/wounds

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

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14. hypertriglyceridemia in HIV
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
6-12 weeks
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

15. antibiotic with good prostate penetration?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

16. How to tx chronic hep B
Others lesions are ring enhancing and have mass effect while PML don't
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Pegylated interferon and lamivudine
Do EBV antibody test

17. INH
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Postcoital voiding - increased intake of cranberry juice
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

18. what would be viral load after 2-4m of HAART?
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
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
<500 copies/ml
Similar pathophysiology as ITP - tx zidovudine

19. How to differentiate different types of necrotizing fascitis?
Upper lobes; any fibrosis in this area suggestive of latent TB
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
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

20. causative organisms of uti
Vaccine titer >10mU/ml
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
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

21. How to dx adequate response to HBV vaccine
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Vaccine titer >10mU/ml
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

22. dame that has already occurred
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
Rifampin600mg q12. or cipro
Cd4 count
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

23. 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
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Td every 10 years - tdap once before 65 and after 65
Within 6 months viral load will be <50

24. How to tx IM?
When cd4 count falls below 200. 2p in pcp =200
Pt who have been treated before for latent TB
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
High risk 19-64; 1-2 dose - above 65; one dose

25. Tx of choice for human bites
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Ampicillin-sublactam; most bites contain eikenella

26. How to dx bacterial meningitis from CSF study?

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27. How to tx TSS?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
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
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
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

28. How to dx IM?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Immune mediated; circulating IgG and IgM to penicillin derivatives
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

29. where TB normally affects
Mainly clinical - epidemiological and seasonal setting
Upper lobes; any fibrosis in this area suggestive of latent TB
Postcoital voiding - increased intake of cranberry juice
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

30. When to tx asymptomatic bacteriurea >100 -000?
Pregnacy - urologic procedure - hip arthoplastu
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
<500 copies/ml
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

31. INH
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Postcoital voiding - increased intake of cranberry juice
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
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

32. 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
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
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
If a sample is ELISA positive - it is tested fro western blot for confirmation

33. How long abx is given in pseudomonas infection?
ELISA; initial visit - 6 - 12 and 24 weeks;
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
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

34. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

35. when HIV patient develop pcp?
When cd4 count falls below 200. 2p in pcp =200
Pregnacy - urologic procedure - hip arthoplastu
Pt who have been treated before for latent TB
Oropharyngeal secretions; hence named as kissing disease

36. low grade fever - maculopapular rash - lymphadenopathy
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
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

37. 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
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Cd4 count
HBIG hep B immunoglobulin

38. acute onset +rusty sputum
Do EBV antibody test
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
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

39. How long we tx chronic prostatis?
6-12 weeks
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
PML; focal neurological deficit like MM; no specific tx; regress with HAART
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

40. How to dx IM?
Ampicillin-sublactam; most bites contain eikenella
Monospot test which screen heteropile ab that agglutinate horse rbc
6-12 weeks
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

41. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Either TB or aspergillosis
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

42. What is the indication of corticosteroid in pcp infection?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Similar pathophysiology as ITP - tx zidovudine
PML; focal neurological deficit like MM; no specific tx; regress with HAART
AA gradient >35 or Po2 <70

43. What is the mch of ampicillin induced rash in IM
Viral load and CD4 count
Immune mediated; circulating IgG and IgM to penicillin derivatives
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

44. How to tx pseudomonas?
ELISA; initial visit - 6 - 12 and 24 weeks;
AA gradient >35 or Po2 <70
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
6-12 weeks

45. What is the classic signs of nec fasc?
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
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
Rifampin600mg q12. or cipro

46. HIV patient having fat deposition on back of neck and abdomen - like cushing
If a sample is ELISA positive - it is tested fro western blot for confirmation
Pregnacy - urologic procedure - hip arthoplastu
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

47. acute febrile reaction develops after starting penicilin tx to syphilis patient
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Vaccine titer >10mU/ml
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
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.

48. How to differentiate gonococcal and nongonoccal urethritis?
If a sample is ELISA positive - it is tested fro western blot for confirmation
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
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 and western blot of synovial fluid.

49. when not to give INH therapy if ppd positive and patient asyptomatic
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
Pt who have been treated before for latent TB
PML; focal neurological deficit like MM; no specific tx; regress with HAART

50. what if monospot test is neg in IM?
Ampicillin-sublactam; most bites contain eikenella
Td every 10 years - tdap once before 65 and after 65
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Do EBV antibody test