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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. rifampin
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
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Either TB or aspergillosis

2. What is the pathophysiology of Meningococcal meningitis?
Within 6 months viral load will be <50
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

3. can HIV transmitted through human bite?
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
Pt who have been treated before for latent TB
High risk 19-64; 1-2 dose - above 65; one dose
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

4. How to dx adequate response to HBV vaccine
Vaccine titer >10mU/ml
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

5. how CMV presents in immunocompromised patients
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Postcoital voiding - increased intake of cranberry juice

6. drugs work well on hypertriglyceridia?
ELISA; initial visit - 6 - 12 and 24 weeks;
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

7. How to dx IM?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Postcoital voiding - increased intake of cranberry juice
Monospot test which screen heteropile ab that agglutinate horse rbc
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

8. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Monospot test which screen heteropile ab that agglutinate horse rbc
Similar pathophysiology as ITP - tx zidovudine
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

9. systolic HTN in elderly
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
<500 copies/ml
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
<5000 copies/ml

10. What is the Tx of cryptococcal meninngitis
Mainly clinical - epidemiological and seasonal setting
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with 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
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

11. How to confirm chlamydia infection?
Bronchoalveolar washing and transbronchial biopsy
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
Monospot test which screen heteropile ab that agglutinate horse rbc

12. How to differentiate gonococcal and nongonoccal urethritis?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
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

13. When to tx influenza with antiviral therapy?
Oropharyngeal secretions; hence named as kissing disease
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Within 6 months viral load will be <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

14. after exposure of HIV when antibody testing is performed?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
ELISA; initial visit - 6 - 12 and 24 weeks;
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

15. when not to give INH therapy if ppd positive and patient asyptomatic
<5000 copies/ml
Pt who have been treated before for latent TB
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
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

16. which heart valve is closer to ventricular conduction system/
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
Aortic valve; endocardiits of AR p/w AV block and LBBB
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
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

17. When to give prophylaxis against MAC
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Need lumbar puncture to relieve pressure; they have high opening pressure >350
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

18. acute febrile reaction develops after starting penicilin tx to syphilis patient
Postcoital voiding - increased intake of cranberry juice
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
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

19. What is the classic signs of nec fasc?
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
<5000 copies/ml
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

20. wisconsin - missisipi - ohio
Blastomycosis
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Aortic valve; endocardiits of AR p/w AV block and LBBB
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

21. when we see echym gangrenosum?
Every 3-4 hours to determine appropritate time to start HAART
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
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
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

22. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Pt who have been treated before for latent TB
HBIG hep B immunoglobulin
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

23. 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
ELISA and western blot of synovial fluid.
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
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

24. When not to tx asymptomatic bacteriura?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Pegylated interferon and lamivudine
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

25. What is characteristic for dx of rocky mountain spotted fever?
Viral load and CD4 count
HBIG hep B immunoglobulin
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

26. low grade fever - maculopapular rash - lymphadenopathy
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Every 3-4 hours to determine appropritate time to start HAART
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
ELISA; initial visit - 6 - 12 and 24 weeks;

27. thrombocytopenia in HIV
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Similar pathophysiology as ITP - tx zidovudine
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
If a sample is ELISA positive - it is tested fro western blot for confirmation

28. How to tx pcp?
Pt who have been treated before for latent TB
When cd4 count falls below 200. 2p in pcp =200
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

29. What is tetanus - diptheria - pertusis recommendation?
Immune mediated; circulating IgG and IgM to penicillin derivatives
Td every 10 years - tdap once before 65 and after 65
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

30. How to tx chronic hep B
Pegylated interferon and lamivudine
Every 3-4 hours to determine appropritate time to start HAART
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
AA gradient >35 or Po2 <70

31. What is the prognosis of lyme arthritis?
ELISA and western blot of synovial fluid.
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

32. How often viral load is monitored after HAART?
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Acyclovir
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

33. what if monospot test is neg in IM?
When cd4 count falls below 200. 2p in pcp =200
<5000 copies/ml
Do EBV antibody test
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

34. How to dx progressive multifocal leukoencephalopathy
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
AA gradient >35 or Po2 <70
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

35. worsening of TB after starting HAART in HIV
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
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Every 3-4 hours to determine appropritate time to start HAART

36. gas gangrene
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Either TB or aspergillosis
6-12 weeks
Clostridium perfringens after penetrative injuries/wounds

37. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Do EBV antibody test
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Acyclovir
PML; focal neurological deficit like MM; no specific tx; regress with HAART

38. When to tx asymptomatic bacteriurea >100 -000?
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Pregnacy - urologic procedure - hip arthoplastu
ELISA; initial visit - 6 - 12 and 24 weeks;
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

39. How to dx bacterial meningitis from CSF study?

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40. when western blot is done for HIV testing
Cd4 count
ELISA and western blot of synovial fluid.
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
If a sample is ELISA positive - it is tested fro western blot for confirmation

41. How to dx lyme arthritis?
Acyclovir
ELISA and western blot of synovial fluid.
Non pregnant premanopausal - elderly - dm - sci - chronic foley
PML; focal neurological deficit like MM; no specific tx; regress with HAART

42. when HIV patient develop pcp?
Within 6 months viral load will be <50
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Non pregnant premanopausal - elderly - dm - sci - chronic foley
When cd4 count falls below 200. 2p in pcp =200

43. How to tx pseudomonas?
Cd4 count
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

44. 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.
If a sample is ELISA positive - it is tested fro western blot for confirmation
ELISA; initial visit - 6 - 12 and 24 weeks;
HIV viral load

45. damae that is about to occur?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
HIV viral load
Others lesions are ring enhancing and have mass effect while PML don't
Immune mediated; circulating IgG and IgM to penicillin derivatives

46. What is the Tx of STD uretheritis?
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
Bronchoalveolar washing and transbronchial biopsy
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Upper lobes; any fibrosis in this area suggestive of latent TB

47. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
HBIG hep B immunoglobulin
Mainly clinical - epidemiological and seasonal setting
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

48. How to dx?
Mainly clinical - epidemiological and seasonal setting
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Viral load and CD4 count
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

49. How to confirm dx if pcp?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Bronchoalveolar washing and transbronchial biopsy
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
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

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

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