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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. Tx of choice for human bites
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
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.
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

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

3. How to differentiate gonococcal and nongonoccal urethritis?
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.
Mainly clinical - epidemiological and seasonal setting
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

4. How often HIV postiive patients CD4 count needs to be evaluated?
Every 3-4 hours to determine appropritate time to start HAART
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
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

5. How to confirm dx if pcp?
Ampicillin-sublactam; most bites contain eikenella
Postcoital voiding - increased intake of cranberry juice
<5000 copies/ml
Bronchoalveolar washing and transbronchial biopsy

6. What is fatal consequence of RMSF?
Every 3-4 hours to determine appropritate time to start HAART
<5000 copies/ml
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

7. infiltrate in upper lobe of lung?
HBIG hep B immunoglobulin
Either TB or aspergillosis
<500 copies/ml
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

8. What is the mch of ampicillin induced rash in IM
Immune mediated; circulating IgG and IgM to penicillin derivatives
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

9. thrombocytopenia in HIV
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Similar pathophysiology as ITP - tx zidovudine

10. What is lag time to develop lyme arthritis after exposure to vector
Pt who have been treated before for latent TB
Within 6 months viral load will be <50
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

11. What is tx for herpes zoster
AA gradient >35 or Po2 <70
Acyclovir
ELISA and western blot of synovial fluid.
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

12. drugs work well on hypertriglyceridia?
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
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
HIV viral load

13. HIV patient having fat deposition on back of neck and abdomen - like cushing
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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
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

14. When to give abx to prevent recurrent uti
ELISA and western blot of synovial fluid.
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
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

15. where TB normally affects
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
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
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
Upper lobes; any fibrosis in this area suggestive of latent TB

16. rifampin
HBIG hep B immunoglobulin
Do EBV antibody test
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Aortic valve; endocardiits of AR p/w AV block and LBBB

17. how HAART therapy affects HIV viral loads?
Within 6 months viral load will be <50
Acyclovir
Viral load and CD4 count
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

18. What is the indication of corticosteroid in pcp infection?
AA gradient >35 or Po2 <70
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

19. clinical manifestation of mucomycosis
Aortic valve; endocardiits of AR p/w AV block and LBBB
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
AA gradient >35 or Po2 <70
Either TB or aspergillosis

20. after exposure of HIV when antibody testing is performed?
If a sample is ELISA positive - it is tested fro western blot for confirmation
ELISA and western blot of synovial fluid.
ELISA; initial visit - 6 - 12 and 24 weeks;
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

21. How to dx adequate response to HBV vaccine
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Vaccine titer >10mU/ml
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

22. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
Reddish orange discoloration of urine - feces - sweat - tears - sputum
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Monospot test which screen heteropile ab that agglutinate horse rbc
Need lumbar puncture to relieve pressure; they have high opening pressure >350

23. pneumococcal vaccine indication?
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
High risk 19-64; 1-2 dose - above 65; one dose
When cd4 count falls below 200. 2p in pcp =200

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

25. What are the behavioral interventions decrease the risk of UTI
Bronchoalveolar washing and transbronchial biopsy
Pegylated interferon and lamivudine
ELISA; initial visit - 6 - 12 and 24 weeks;
Postcoital voiding - increased intake of cranberry juice

26. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
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
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

27. systolic HTN in elderly
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

28. hypertriglyceridemia in 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
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

29. How to tx TSS?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
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
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

30. what would be viral load after 2-4m of HAART?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Every 3-4 hours to determine appropritate time to start HAART
AA gradient >35 or Po2 <70
<500 copies/ml

31. acute onset +rusty sputum
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
HBIG hep B immunoglobulin
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

32. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

33. what if monospot test is neg in IM?
Rifampin600mg q12. or cipro
Do EBV antibody test
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Mainly clinical - epidemiological and seasonal setting

34. dame that has already occurred
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Cd4 count
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
ELISA and western blot of synovial fluid.

35. INH
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Postcoital voiding - increased intake of cranberry juice
Similar pathophysiology as ITP - tx zidovudine

36. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
HBIG hep B immunoglobulin
ELISA; initial visit - 6 - 12 and 24 weeks;
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Viral load and CD4 count

37. what parameters increases risk of neurosyphilis in HIV patient
Vaccine titer >10mU/ml
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;

38. worsening of TB after starting HAART in HIV
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Immune mediated; circulating IgG and IgM to penicillin derivatives
Aortic valve; endocardiits of AR p/w AV block and LBBB
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

39. How to dx IM?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Non pregnant premanopausal - elderly - dm - sci - chronic foley
6-12 weeks

40. how im is transmitted?
Rifampin600mg q12. or cipro
Similar pathophysiology as ITP - tx zidovudine
Oropharyngeal secretions; hence named as kissing disease
<500 copies/ml

41. What is the Tx of cryptococcal meninngitis
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
6-12 weeks

42. How to tx IM?
Others lesions are ring enhancing and have mass effect while PML don't
<5000 copies/ml
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

43. When to tx influenza with antiviral therapy?
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
Ampicillin-sublactam; most bites contain eikenella
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
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

44. What is the classic signs of nec fasc?
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.
Oropharyngeal secretions; hence named as kissing disease
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

45. How to dx bacterial meningitis from CSF study?

46. What is difference between uti relapse versus recurrence?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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
Others lesions are ring enhancing and have mass effect while PML don't
Pegylated interferon and lamivudine

47. How to dx progressive multifocal leukoencephalopathy
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
<5000 copies/ml
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

48. damae that is about to occur?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
HIV viral load
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

49. What is characteristic for dx of rocky mountain spotted fever?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Clostridium perfringens after penetrative injuries/wounds
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

50. What is used for prophylaxis against meningo..meningitis?
<500 copies/ml
Pt who have been treated before for latent TB
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Rifampin600mg q12. or cipro