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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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1. How often HIV postiive patients CD4 count needs to be evaluated?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Every 3-4 hours to determine appropritate time to start HAART
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

2. Tx of choice for human bites
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Ampicillin-sublactam; most bites contain eikenella
HIV viral load
Postcoital voiding - increased intake of cranberry juice

3. 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.
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

4. How long we tx chronic prostatis?
Similar pathophysiology as ITP - tx zidovudine
6-12 weeks
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Immune mediated; circulating IgG and IgM to penicillin derivatives

5. What is the criteria for Spontaneous bact peritonitis
Postcoital voiding - increased intake of cranberry juice
Others lesions are ring enhancing and have mass effect while PML don't
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
If a sample is ELISA positive - it is tested fro western blot for confirmation

6. acute febrile reaction develops after starting penicilin tx to syphilis patient
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
HBIG hep B immunoglobulin
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Non pregnant premanopausal - elderly - dm - sci - chronic foley

7. What is tx for herpes zoster
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Acyclovir
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

8. What is the pathophysiology of Meningococcal meningitis?
Similar pathophysiology as ITP - tx zidovudine
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
AA gradient >35 or Po2 <70

9. aspergillosis
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Voriconazol. mycetoma-surgical removal
AA gradient >35 or Po2 <70
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

10. How to tx TSS?
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Aortic valve; endocardiits of AR p/w AV block and LBBB
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

11. antibiotic with good prostate penetration?
Pegylated interferon and lamivudine
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Reddish orange discoloration of urine - feces - sweat - tears - sputum

12. what would be viral load after 4 weeks
<5000 copies/ml
<500 copies/ml
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Viral load and CD4 count

13. When not to tx asymptomatic bacteriura?
Aortic valve; endocardiits of AR p/w AV block and LBBB
HBIG hep B immunoglobulin
Acyclovir
Non pregnant premanopausal - elderly - dm - sci - chronic foley

14. How to give postexposure prophylaxis for HIV
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
ELISA; initial visit - 6 - 12 and 24 weeks;
HIV viral load

15. What is characteristic for dx of rocky mountain spotted fever?
Monospot test which screen heteropile ab that agglutinate horse rbc
6-12 weeks
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Bronchoalveolar washing and transbronchial biopsy

16. what parameters increases risk of neurosyphilis in HIV patient
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.
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
ELISA; initial visit - 6 - 12 and 24 weeks;
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

17. How to dx adequate response to HBV vaccine
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Vaccine titer >10mU/ml

18. What is lag time to develop lyme arthritis after exposure to vector
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

19. hypertriglyceridemia in HIV
Oropharyngeal secretions; hence named as kissing disease
Do EBV antibody test
When cd4 count falls below 200. 2p in pcp =200
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

20. What is tetanus - diptheria - pertusis recommendation?
Td every 10 years - tdap once before 65 and after 65
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Pregnacy - urologic procedure - hip arthoplastu
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

21. after recent exposure - negative ELISA - How to confirm?
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
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
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

22. How to dx IM?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Monospot test which screen heteropile ab that agglutinate horse rbc
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
Blastomycosis

23. thrombocytopenia in HIV
Similar pathophysiology as ITP - tx zidovudine
Upper lobes; any fibrosis in this area suggestive of latent TB
Mainly clinical - epidemiological and seasonal setting
Within 6 months viral load will be <50

24. after exposure of HIV when antibody testing is performed?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Rifampin600mg q12. or cipro
ELISA; initial visit - 6 - 12 and 24 weeks;
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

25. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Postcoital voiding - increased intake of cranberry juice

26. How to tx IM?
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
Others lesions are ring enhancing and have mass effect while PML don't
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

27. How often viral load is monitored after HAART?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
<5000 copies/ml
Bronchoalveolar washing and transbronchial biopsy

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

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29. What is fatal consequence of RMSF?
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
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
Either TB or aspergillosis
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

30. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Viral load and CD4 count
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

31. What is the prognosis of lyme arthritis?
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
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.
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

32. reddish colored papules with central umbilication in HIV or immunocompromised patient
When cd4 count falls below 200. 2p in pcp =200
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
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

33. 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
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Aortic valve; endocardiits of AR p/w AV block and LBBB
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

34. when HIV patient develop pcp?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
When cd4 count falls below 200. 2p in pcp =200

35. How to differentiate different types of necrotizing fascitis?
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Viral load and CD4 count
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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

36. INH
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Others lesions are ring enhancing and have mass effect while PML don't
Clostridium perfringens after penetrative injuries/wounds

37. What is the indication of corticosteroid in pcp infection?
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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

38. can HIV transmitted through human bite?
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
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
HBIG hep B immunoglobulin

39. How to dx lyme arthritis?
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
ELISA and western blot of synovial fluid.
Non pregnant premanopausal - elderly - dm - sci - chronic foley

40. When to tx influenza with antiviral therapy?
Do EBV antibody test
Acyclovir
Ampicillin-sublactam; most bites contain eikenella
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

41. How to confirm dx if pcp?
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Bronchoalveolar washing and transbronchial biopsy
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
If a sample is ELISA positive - it is tested fro western blot for confirmation

42. how HAART therapy affects HIV viral loads?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Monospot test which screen heteropile ab that agglutinate horse rbc
Blastomycosis
Within 6 months viral load will be <50

43. What are the behavioral interventions decrease the risk of UTI
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Non pregnant premanopausal - elderly - dm - sci - chronic foley
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Postcoital voiding - increased intake of cranberry juice

44. gas gangrene
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
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Clostridium perfringens after penetrative injuries/wounds

45. when not to give INH therapy if ppd positive and patient asyptomatic
Every 3-4 hours to determine appropritate time to start HAART
Pt who have been treated before for latent TB
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

46. HIV patient having fat deposition on back of neck and abdomen - like cushing
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Ampicillin-sublactam; most bites contain eikenella

47. When to give prophylaxis against MAC
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
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
Clostridium perfringens after penetrative injuries/wounds

48. when we see echym gangrenosum?
Need lumbar puncture to relieve pressure; they have high opening pressure >350
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
Monospot test which screen heteropile ab that agglutinate horse rbc

49. dame that has already occurred
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
Cd4 count
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

50. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
Non pregnant premanopausal - elderly - dm - sci - chronic foley
AA gradient >35 or Po2 <70
Monospot test which screen heteropile ab that agglutinate horse rbc
Need lumbar puncture to relieve pressure; they have high opening pressure >350