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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 often viral load is monitored after HAART?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
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

2. how HAART therapy affects HIV viral loads?
Aortic valve; endocardiits of AR p/w AV block and LBBB
Within 6 months viral load will be <50
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

3. How to differentiate gonococcal and nongonoccal urethritis?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
<5000 copies/ml
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

4. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
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
Others lesions are ring enhancing and have mass effect while PML don't
Need lumbar puncture to relieve pressure; they have high opening pressure >350

5. which heart valve is closer to ventricular conduction system/
Ampicillin-sublactam; most bites contain eikenella
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
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

6. rifampin
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

7. hypertension in children
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
High risk 19-64; 1-2 dose - above 65; one dose
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

8. How to tx pseudomonas?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
HIV viral load

9. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Blastomycosis
HBIG hep B immunoglobulin
Vaccine titer >10mU/ml

10. after exposure of HIV when antibody testing is performed?
Bronchoalveolar washing and transbronchial biopsy
ELISA; initial visit - 6 - 12 and 24 weeks;
If a sample is ELISA positive - it is tested fro western blot for confirmation
Rifampin600mg q12. or cipro

11. INH
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Viral load and CD4 count
Ampicillin-sublactam; most bites contain eikenella
Oropharyngeal secretions; hence named as kissing disease

12. How to give postexposure prophylaxis for HIV
Clostridium perfringens after penetrative injuries/wounds
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
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.
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

13. HIV patient having fat deposition on back of neck and abdomen - like cushing
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)
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Pt who have been treated before for latent TB

14. how CMV presents in immunocompromised patients
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Every 3-4 hours to determine appropritate time to start HAART

15. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
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
Upper lobes; any fibrosis in this area suggestive of latent TB

16. what if monospot test is neg in IM?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Do EBV antibody test
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
<500 copies/ml

17. What is used for prophylaxis against meningo..meningitis?
Viral load and CD4 count
Within 6 months viral load will be <50
Rifampin600mg q12. or cipro
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

18. How to tx pcp?
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Ampicillin-sublactam; most bites contain eikenella

19. How to dx?
Mainly clinical - epidemiological and seasonal setting
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Reddish orange discoloration of urine - feces - sweat - tears - sputum

20. INH
Td every 10 years - tdap once before 65 and after 65
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Reddish orange discoloration of urine - feces - sweat - tears - sputum

21. When to tx asymptomatic bacteriurea >100 -000?
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
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Pregnacy - urologic procedure - hip arthoplastu

22. foot infections in DM
Rifampin600mg q12. or cipro
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

23. How to dx adequate response to HBV vaccine
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Vaccine titer >10mU/ml
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
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. when not to give INH therapy if ppd positive and patient asyptomatic
Pt who have been treated before for latent TB
ELISA and western blot of synovial fluid.
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

25. How to confirm chlamydia infection?
Similar pathophysiology as ITP - tx zidovudine
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Viral load and CD4 count

26. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

27. dame that has already occurred
Cd4 count
Upper lobes; any fibrosis in this area suggestive of latent TB
HBIG hep B immunoglobulin
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

28. What is the mch of ampicillin induced rash in IM
Immune mediated; circulating IgG and IgM to penicillin derivatives
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
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
Within 6 months viral load will be <50

29. thrombocytopenia in HIV
Similar pathophysiology as ITP - tx zidovudine
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
HIV viral load
HBIG hep B immunoglobulin

30. What is fatal consequence of RMSF?
ELISA; initial visit - 6 - 12 and 24 weeks;
Pt who have been treated before for latent TB
Either TB or aspergillosis
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

31. acute onset +rusty sputum
Monospot test which screen heteropile ab that agglutinate horse rbc
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
ELISA; initial visit - 6 - 12 and 24 weeks;
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

32. after recent exposure - negative ELISA - How to confirm?
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
ELISA and western blot of synovial fluid.
Ampicillin-sublactam; most bites contain eikenella
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

33. How to dx lyme arthritis?
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
ELISA and western blot of synovial fluid.
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

34. How to dx IM?
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Immune mediated; circulating IgG and IgM to penicillin derivatives
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Viral load and CD4 count

35. How to confirm dx if pcp?
<5000 copies/ml
Bronchoalveolar washing and transbronchial biopsy
Monospot test which screen heteropile ab that agglutinate horse rbc
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

36. infiltrate in upper lobe of lung?
Pregnacy - urologic procedure - hip arthoplastu
Immune mediated; circulating IgG and IgM to penicillin derivatives
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Either TB or aspergillosis

37. What is the prognosis of lyme arthritis?
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Rifampin600mg q12. or cipro
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Need lumbar puncture to relieve pressure; they have high opening pressure >350

38. How often HIV postiive patients CD4 count needs to be evaluated?
Every 3-4 hours to determine appropritate time to start HAART
Others lesions are ring enhancing and have mass effect while PML don't
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
ELISA; initial visit - 6 - 12 and 24 weeks;

39. How to tx IM?
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

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

41. where TB normally affects
Pegylated interferon and lamivudine
High risk 19-64; 1-2 dose - above 65; one dose
Upper lobes; any fibrosis in this area suggestive of latent TB
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

42. What is difference between uti relapse versus recurrence?
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Within 6 months viral load will be <50
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
High risk 19-64; 1-2 dose - above 65; one dose

43. 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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
If a sample is ELISA positive - it is tested fro western blot for confirmation

44. 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
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Similar pathophysiology as ITP - tx zidovudine
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

45. What is tx for herpes zoster
Monospot test which screen heteropile ab that agglutinate horse rbc
<5000 copies/ml
6-12 weeks
Acyclovir

46. How long abx is given in pseudomonas infection?
<500 copies/ml
Aortic valve; endocardiits of AR p/w AV block and LBBB
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

47. when western blot is done for HIV testing
Every 3-4 hours to determine appropritate time to start HAART
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
If a sample is ELISA positive - it is tested fro western blot for confirmation
Clostridium perfringens after penetrative injuries/wounds

48. When to give prophylaxis against MAC
HIV viral load
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
ELISA and western blot of synovial fluid.
Upper lobes; any fibrosis in this area suggestive of latent TB

49. how im is transmitted?
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Oropharyngeal secretions; hence named as kissing disease
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Bronchoalveolar washing and transbronchial biopsy

50. How to dx IM?
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
High risk 19-64; 1-2 dose - above 65; one dose
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose