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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
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Within 6 months viral load will be <50
Reddish orange discoloration of urine - feces - sweat - tears - sputum

2. acute onset +rusty sputum
High risk 19-64; 1-2 dose - above 65; one dose
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
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

3. How to tx pseudomonas?
Pt who have been treated before for latent TB
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Mainly clinical - epidemiological and seasonal setting
<5000 copies/ml

4. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
When cd4 count falls below 200. 2p in pcp =200
6-12 weeks
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Need lumbar puncture to relieve pressure; they have high opening pressure >350

5. acute febrile reaction develops after starting penicilin tx to syphilis patient
Aortic valve; endocardiits of AR p/w AV block and LBBB
ELISA and western blot of synovial fluid.
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

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

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7. When not to tx asymptomatic bacteriura?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Oropharyngeal secretions; hence named as kissing disease
Cd4 count

8. worsening of TB after starting HAART in HIV
Blastomycosis
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
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

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

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10. after exposure of HIV when antibody testing is performed?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
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; initial visit - 6 - 12 and 24 weeks;

11. How long abx is given in pseudomonas infection?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
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
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

12. can HIV transmitted through human bite?
Pregnacy - urologic procedure - hip arthoplastu
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Need lumbar puncture to relieve pressure; they have high opening pressure >350
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

13. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
6-12 weeks
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

14. 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
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Td every 10 years - tdap once before 65 and after 65
Non pregnant premanopausal - elderly - dm - sci - chronic foley

15. how im is transmitted?
Monospot test which screen heteropile ab that agglutinate horse rbc
Oropharyngeal secretions; hence named as kissing disease
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Immune mediated; circulating IgG and IgM to penicillin derivatives

16. How to dx IM?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
When cd4 count falls below 200. 2p in pcp =200
Rifampin600mg q12. or cipro
Monospot test which screen heteropile ab that agglutinate horse rbc

17. What is the Tx of STD uretheritis?
Postcoital voiding - increased intake of cranberry juice
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
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
PML; focal neurological deficit like MM; no specific tx; regress with HAART

18. How often HIV postiive patients CD4 count needs to be evaluated?
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
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
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Every 3-4 hours to determine appropritate time to start HAART

19. How to tx IM?
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
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
Postcoital voiding - increased intake of cranberry juice
Cd4 count

20. What are the subjective /objective measure of encephalopathy?
AA gradient >35 or Po2 <70
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Postcoital voiding - increased intake of cranberry juice
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. What is tx for herpes zoster
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
<5000 copies/ml
Acyclovir

22. When to give abx to prevent recurrent uti
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
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
Immune mediated; circulating IgG and IgM to penicillin derivatives
Every 3-4 hours to determine appropritate time to start HAART

23. What is lag time to develop lyme arthritis after exposure to vector
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Need lumbar puncture to relieve pressure; they have high opening pressure >350
When cd4 count falls below 200. 2p in pcp =200
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

24. what if monospot test is neg in IM?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Do EBV antibody test
<5000 copies/ml
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

25. What is the indication of corticosteroid in pcp infection?
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
Mainly clinical - epidemiological and seasonal setting
Td every 10 years - tdap once before 65 and after 65

26. How to dx lyme arthritis?
Pegylated interferon and lamivudine
6-12 weeks
ELISA and western blot of synovial fluid.
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

27. How to confirm dx if pcp?
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Bronchoalveolar washing and transbronchial biopsy
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

28. What is characteristic for dx of rocky mountain spotted fever?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
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

29. reddish colored papules with central umbilication in HIV or immunocompromised patient
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
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
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

30. pathophysiology of toxic shock syndrom?
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.
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
If a sample is ELISA positive - it is tested fro western blot for confirmation
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

31. 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
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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.

32. pneumococcal vaccine indication?
High risk 19-64; 1-2 dose - above 65; one dose
Td every 10 years - tdap once before 65 and after 65
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
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

33. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Bronchoalveolar washing and transbronchial biopsy
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

34. 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
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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

35. What is used for prophylaxis against meningo..meningitis?
Rifampin600mg q12. or cipro
Immune mediated; circulating IgG and IgM to penicillin derivatives
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 months; characterized by knee joint effusion-large amount - joint stiffness - pain

36. 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
Bronchoalveolar washing and transbronchial biopsy
Aortic valve; endocardiits of AR p/w AV block and LBBB
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

37. How to differentiate different types of necrotizing fascitis?
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
Monospot test which screen heteropile ab that agglutinate horse rbc
Clostridium perfringens after penetrative injuries/wounds
Blastomycosis

38. gas gangrene
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
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
Clostridium perfringens after penetrative injuries/wounds
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

39. infiltrate in upper lobe of lung?
<500 copies/ml
Either TB or aspergillosis
Clostridium perfringens after penetrative injuries/wounds
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

40. How to dx adequate response to HBV vaccine
Upper lobes; any fibrosis in this area suggestive of latent TB
Monospot test which screen heteropile ab that agglutinate horse rbc
Others lesions are ring enhancing and have mass effect while PML don't
Vaccine titer >10mU/ml

41. How to tx TSS?
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Rifampin600mg q12. or cipro
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

42. hypertension in children
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

43. How to tx pcp?
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Others lesions are ring enhancing and have mass effect while PML don't
Postcoital voiding - increased intake of cranberry juice
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

44. INH
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Rifampin600mg q12. or cipro

45. How to dx cryptococal meninggits
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
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
Voriconazol. mycetoma-surgical removal
Postcoital voiding - increased intake of cranberry juice

46. How to confirm chlamydia infection?
Either TB or aspergillosis
Monospot test which screen heteropile ab that agglutinate horse rbc
Aortic valve; endocardiits of AR p/w AV block and LBBB
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

47. How to dx IM?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Acyclovir

48. thrombocytopenia in HIV
Mainly clinical - epidemiological and seasonal setting
Similar pathophysiology as ITP - tx zidovudine
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
<500 copies/ml

49. after recent exposure - negative ELISA - How to confirm?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
High risk 19-64; 1-2 dose - above 65; one dose
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

50. How to dx?
Others lesions are ring enhancing and have mass effect while PML don't
Pegylated interferon and lamivudine
When cd4 count falls below 200. 2p in pcp =200
Mainly clinical - epidemiological and seasonal setting