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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 to give postexposure prophylaxis to patient who received vaccine but titer inadequate
Monospot test which screen heteropile ab that agglutinate horse rbc
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
HBIG hep B immunoglobulin

2. What are the subjective /objective measure of encephalopathy?
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.
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Need lumbar puncture to relieve pressure; they have high opening pressure >350

3. What is the Tx of cryptococcal meninngitis
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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

4. What is the mch of ampicillin induced rash in IM
Immune mediated; circulating IgG and IgM to penicillin derivatives
Monospot test which screen heteropile ab that agglutinate horse rbc
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

5. When to give prophylaxis against MAC
ELISA; initial visit - 6 - 12 and 24 weeks;
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

6. gas gangrene
HIV viral load
When cd4 count falls below 200. 2p in pcp =200
Clostridium perfringens after penetrative injuries/wounds
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

7. drugs work well on hypertriglyceridia?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Mainly clinical - epidemiological and seasonal setting
Upper lobes; any fibrosis in this area suggestive of latent TB
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

8. How to dx IM?
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
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
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

9. after exposure of HIV when antibody testing is performed?
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
ELISA; initial visit - 6 - 12 and 24 weeks;
Every 3-4 hours to determine appropritate time to start HAART

10. How to differentiate different types of necrotizing fascitis?
When cd4 count falls below 200. 2p in pcp =200
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
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
6-12 weeks

11. What is the criteria for Spontaneous bact peritonitis
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
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
Do EBV antibody test
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

12. How long abx is given in pseudomonas infection?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Bronchoalveolar washing and transbronchial biopsy
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

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

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14. How to confirm dx if pcp?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Bronchoalveolar washing and transbronchial biopsy
Cd4 count
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

15. infiltrate in upper lobe of lung?
Upper lobes; any fibrosis in this area suggestive of latent TB
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Either TB or aspergillosis
PML; focal neurological deficit like MM; no specific tx; regress with HAART

16. How to tx pcp?
Others lesions are ring enhancing and have mass effect while PML don't
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Either TB or aspergillosis

17. can HIV transmitted through human bite?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Mainly clinical - epidemiological and seasonal setting
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

18. reddish colored papules with central umbilication in HIV or immunocompromised patient
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
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
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

19. When to tx asymptomatic bacteriurea >100 -000?
Pregnacy - urologic procedure - hip arthoplastu
Monospot test which screen heteropile ab that agglutinate horse rbc
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
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

20. How to differentiate gonococcal and nongonoccal urethritis?
Pt who have been treated before for latent TB
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
Others lesions are ring enhancing and have mass effect while PML don't
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

21. hypertension in children
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Td every 10 years - tdap once before 65 and after 65

22. How often HIV postiive patients CD4 count needs to be evaluated?
Rifampin600mg q12. or cipro
Every 3-4 hours to determine appropritate time to start HAART
Ampicillin-sublactam; most bites contain eikenella
Acyclovir

23. What is tx for herpes zoster
Pegylated interferon and lamivudine
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
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

24. How to dx IM?
Monospot test which screen heteropile ab that agglutinate horse rbc
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Mainly clinical - epidemiological and seasonal setting
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

25. INH
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

26. How to dx cryptococal meninggits
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

27. How to dx lyme arthritis?
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
ELISA and western blot of synovial fluid.
Upper lobes; any fibrosis in this area suggestive of latent TB
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

28. where TB normally affects
Upper lobes; any fibrosis in this area suggestive of latent TB
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

29. What is the prognosis of lyme arthritis?
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Aortic valve; endocardiits of AR p/w AV block and LBBB
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

30. What are indicators for progression of HIV
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Viral load and CD4 count
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
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

31. What is difference between uti relapse versus recurrence?
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
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 patient is older >65 - pregnant - cardiac of pulmonary disease; patient without above risks are treated when they come within 48 hours of symptom onset
Need lumbar puncture to relieve pressure; they have high opening pressure >350

32. wisconsin - missisipi - ohio
Blastomycosis
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
<500 copies/ml

33. aspergillosis
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.
Voriconazol. mycetoma-surgical removal
Ampicillin-sublactam; most bites contain eikenella
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

34. What is the Tx of STD uretheritis?
Monospot test which screen heteropile ab that agglutinate horse rbc
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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

35. 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
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Within 6 months viral load will be <50
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

36. when western blot is done for HIV testing
If a sample is ELISA positive - it is tested fro western blot for confirmation
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
ELISA and western blot of synovial fluid.

37. how HAART therapy affects HIV viral loads?
Pt who have been treated before for latent TB
Others lesions are ring enhancing and have mass effect while PML don't
Within 6 months viral load will be <50
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

38. when not to give INH therapy if ppd positive and patient asyptomatic
Pt who have been treated before for latent TB
Do EBV antibody test
Others lesions are ring enhancing and have mass effect while PML don't
Non pregnant premanopausal - elderly - dm - sci - chronic foley

39. How to dx?
Mainly clinical - epidemiological and seasonal setting
HIV viral load
ELISA; initial visit - 6 - 12 and 24 weeks;
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

40. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Immune mediated; circulating IgG and IgM to penicillin derivatives
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

41. What is the indication of corticosteroid in pcp infection?
If a sample is ELISA positive - it is tested fro western blot for confirmation
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
AA gradient >35 or Po2 <70

42. systolic HTN in elderly
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
Acyclovir
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

43. acute onset +rusty sputum
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

44. acute febrile reaction develops after starting penicilin tx to syphilis patient
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
ELISA; initial visit - 6 - 12 and 24 weeks;
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

45. How to dx bacterial meningitis from CSF study?

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46. foot infections in DM
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
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

47. When not to tx asymptomatic bacteriura?
Acyclovir
Similar pathophysiology as ITP - tx zidovudine
When cd4 count falls below 200. 2p in pcp =200
Non pregnant premanopausal - elderly - dm - sci - chronic foley

48. what would be viral load after 2-4m of HAART?
<500 copies/ml
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Pregnacy - urologic procedure - hip arthoplastu
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

49. after recent exposure - negative ELISA - How to confirm?
HBIG hep B immunoglobulin
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
ELISA and western blot of synovial fluid.
Blastomycosis

50. What is the pathophysiology of Meningococcal meningitis?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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
Immune mediated; circulating IgG and IgM to penicillin derivatives
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