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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. when not to give INH therapy if ppd positive and patient asyptomatic
Pt who have been treated before for latent TB
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
PML; focal neurological deficit like MM; no specific tx; regress with HAART

2. 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
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

3. Tx of choice for human bites
Bronchoalveolar washing and transbronchial biopsy
Ampicillin-sublactam; most bites contain eikenella
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

4. What is characteristic for dx of rocky mountain spotted fever?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Immune mediated; circulating IgG and IgM to penicillin derivatives
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

5. How to give postexposure prophylaxis for HIV
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
ELISA and western blot of synovial fluid.
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

6. which heart valve is closer to ventricular conduction system/
Aortic valve; endocardiits of AR p/w AV block and LBBB
Td every 10 years - tdap once before 65 and after 65
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

7. How often HIV postiive patients CD4 count needs to be evaluated?
If a sample is ELISA positive - it is tested fro western blot for confirmation
Every 3-4 hours to determine appropritate time to start HAART
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
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

8. What is fatal consequence of RMSF?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Oropharyngeal secretions; hence named as kissing disease
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Immune mediated; circulating IgG and IgM to penicillin derivatives

9. How to tx chronic hep B
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Viral load and CD4 count
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Pegylated interferon and lamivudine

10. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
If a sample is ELISA positive - it is tested fro western blot for confirmation
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

11. What is the pathophysiology of Meningococcal meningitis?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
ELISA and western blot of synovial fluid.
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

12. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
HBIG hep B immunoglobulin
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
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
6-12 weeks

13. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
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
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

14. what if monospot test is neg in IM?
Do EBV antibody test
Vaccine titer >10mU/ml
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
High risk 19-64; 1-2 dose - above 65; one dose

15. How to tx pcp?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Vaccine titer >10mU/ml
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

16. How to dx IM?
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Others lesions are ring enhancing and have mass effect while PML don't
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Monospot test which screen heteropile ab that agglutinate horse rbc

17. how HAART therapy affects HIV viral loads?
<500 copies/ml
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Within 6 months viral load will be <50
Either TB or aspergillosis

18. rifampin
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
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

19. where TB normally affects
Upper lobes; any fibrosis in this area suggestive of latent TB
Mainly clinical - epidemiological and seasonal setting
Blastomycosis
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

20. low grade fever - maculopapular rash - lymphadenopathy
Oropharyngeal secretions; hence named as kissing disease
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
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
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

21. How often viral load is monitored after HAART?
ELISA and western blot of synovial fluid.
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Pegylated interferon and lamivudine
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

22. reddish colored papules with central umbilication in HIV or immunocompromised patient
Vaccine titer >10mU/ml
If a sample is ELISA positive - it is tested fro western blot for confirmation
Others lesions are ring enhancing and have mass effect while PML don't
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

23. when we see echym gangrenosum?
ELISA and western blot of synovial fluid.
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
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
Do EBV antibody test

24. 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.
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
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

25. after recent exposure - negative ELISA - How to confirm?
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
If a sample is ELISA positive - it is tested fro western blot for confirmation
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

26. when HIV patient develop pcp?
When cd4 count falls below 200. 2p in pcp =200
Postcoital voiding - increased intake of cranberry juice
Aortic valve; endocardiits of AR p/w AV block and LBBB
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

27. What are indicators for progression of HIV
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Ampicillin-sublactam; most bites contain eikenella
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Viral load and CD4 count

28. How to tx pseudomonas?
ELISA and western blot of synovial fluid.
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

29. What is the prognosis of lyme arthritis?
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
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
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

30. 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
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Monospot test which screen heteropile ab that agglutinate horse rbc
Need lumbar puncture to relieve pressure; they have high opening pressure >350

31. What is lag time to develop lyme arthritis after exposure to vector
Voriconazol. mycetoma-surgical removal
Immune mediated; circulating IgG and IgM to penicillin derivatives
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
ELISA; initial visit - 6 - 12 and 24 weeks;

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

33. drugs work well on hypertriglyceridia?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
ELISA and western blot of synovial fluid.
Non pregnant premanopausal - elderly - dm - sci - chronic foley

34. how im is transmitted?
Oropharyngeal secretions; hence named as kissing disease
HIV viral load
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

35. When to tx asymptomatic bacteriurea >100 -000?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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 present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Pregnacy - urologic procedure - hip arthoplastu

36. How to differentiate gonococcal and nongonoccal urethritis?
Cd4 count
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
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
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

37. when western blot is done for HIV testing
Blastomycosis
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
If a sample is ELISA positive - it is tested fro western blot for confirmation
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

38. 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
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Ampicillin-sublactam; most bites contain eikenella
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

39. What is difference between uti relapse versus recurrence?
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Vaccine titer >10mU/ml
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

40. hypertension in children
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

41. How to dx cryptococal meninggits
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

42. What is the Tx of STD uretheritis?
Voriconazol. mycetoma-surgical removal
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Need lumbar puncture to relieve pressure; they have high opening pressure >350
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

43. infiltrate in upper lobe of lung?
Either TB or aspergillosis
Oropharyngeal secretions; hence named as kissing disease
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Pt who have been treated before for latent TB

44. What is used for prophylaxis against meningo..meningitis?
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Rifampin600mg q12. or cipro
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

45. pathophysiology of toxic shock syndrom?
Cd4 count
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

46. antibiotic with good prostate penetration?
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Rifampin600mg q12. or cipro
Cd4 count
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

47. How to dx bacterial meningitis from CSF study?

48. How to dx lyme arthritis?
Monospot test which screen heteropile ab that agglutinate horse rbc
High risk 19-64; 1-2 dose - above 65; one dose
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
ELISA and western blot of synovial fluid.

49. systolic HTN in elderly
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.
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

50. When not to tx asymptomatic bacteriura?
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Aortic valve; endocardiits of AR p/w AV block and LBBB
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Viral load and CD4 count