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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 to give abx to prevent recurrent uti
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
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Bronchoalveolar washing and transbronchial biopsy
Pregnacy - urologic procedure - hip arthoplastu

2. What is the Tx of cryptococcal meninngitis
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
Viral load and CD4 count
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

3. INH
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
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
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

4. dame that has already occurred
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Cd4 count
Reddish orange discoloration of urine - feces - sweat - tears - sputum

5. reddish colored papules with central umbilication in HIV or immunocompromised patient
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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
Oropharyngeal secretions; hence named as kissing disease
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

6. INH
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
ELISA; initial visit - 6 - 12 and 24 weeks;

7. What is fatal consequence of RMSF?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Ampicillin-sublactam; most bites contain eikenella
Upper lobes; any fibrosis in this area suggestive of latent TB
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

8. 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.
Clostridium perfringens after penetrative injuries/wounds
Acyclovir
Either TB or aspergillosis

9. rifampin
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Similar pathophysiology as ITP - tx zidovudine
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Reddish orange discoloration of urine - feces - sweat - tears - sputum

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

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11. What is the prognosis of lyme arthritis?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Rifampin600mg q12. or cipro
Similar pathophysiology as ITP - tx zidovudine

12. What is the criteria for Spontaneous bact peritonitis
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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

13. 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.
Cd4 count
6-12 weeks
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

14. damae that is about to occur?
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
HIV viral load
Similar pathophysiology as ITP - tx zidovudine

15. acute febrile reaction develops after starting penicilin tx to syphilis patient
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
<5000 copies/ml

16. where TB normally affects
Upper lobes; any fibrosis in this area suggestive of latent TB
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Within 6 months viral load will be <50

17. low grade fever - maculopapular rash - lymphadenopathy
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Pregnacy - urologic procedure - hip arthoplastu
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
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

18. How to tx IM?
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Clostridium perfringens after penetrative injuries/wounds
<500 copies/ml

19. How long abx is given in pseudomonas infection?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Postcoital voiding - increased intake of cranberry juice
Oropharyngeal secretions; hence named as kissing disease

20. What is the indication of corticosteroid in pcp infection?
Vaccine titer >10mU/ml
AA gradient >35 or Po2 <70
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
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

21. How to dx IM?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Pregnacy - urologic procedure - hip arthoplastu
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

22. worsening of TB after starting HAART in HIV
Acyclovir
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

23. acute onset +rusty sputum
Either TB or aspergillosis
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

24. gas gangrene
AA gradient >35 or Po2 <70
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Clostridium perfringens after penetrative injuries/wounds
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

25. systolic HTN in elderly
Pt who have been treated before for latent TB
Bronchoalveolar washing and transbronchial biopsy
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
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

26. When to give prophylaxis against MAC
Blastomycosis
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
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
Either TB or aspergillosis

27. How often viral load is monitored after HAART?
Bronchoalveolar washing and transbronchial biopsy
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

28. hypertriglyceridemia in HIV
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
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

29. when HIV patient develop pcp?
Ampicillin-sublactam; most bites contain eikenella
Pregnacy - urologic procedure - hip arthoplastu
Bronchoalveolar washing and transbronchial biopsy
When cd4 count falls below 200. 2p in pcp =200

30. 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
Pregnacy - urologic procedure - hip arthoplastu
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
Vaccine titer >10mU/ml

31. what would be viral load after 2-4m of HAART?
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
HIV viral load
<500 copies/ml
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

32. HIV patient having fat deposition on back of neck and abdomen - like cushing
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Acyclovir
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
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

33. How to tx chronic hep B
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Every 3-4 hours to determine appropritate time to start HAART
Pegylated interferon and lamivudine
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

34. How to confirm chlamydia infection?
6-12 weeks
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Postcoital voiding - increased intake of cranberry juice
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

35. How to dx?
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Immune mediated; circulating IgG and IgM to penicillin derivatives
Mainly clinical - epidemiological and seasonal setting

36. How to dx IM?
Similar pathophysiology as ITP - tx zidovudine
AA gradient >35 or Po2 <70
Either TB or aspergillosis
Monospot test which screen heteropile ab that agglutinate horse rbc

37. How to give postexposure prophylaxis for HIV
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Pregnacy - urologic procedure - hip arthoplastu
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Others lesions are ring enhancing and have mass effect while PML don't

38. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
AA gradient >35 or Po2 <70

39. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
<5000 copies/ml
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

40. How to dx lyme arthritis?
Bronchoalveolar washing and transbronchial biopsy
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
ELISA and western blot of synovial fluid.
HBIG hep B immunoglobulin

41. What is the mch of ampicillin induced rash in IM
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Immune mediated; circulating IgG and IgM to penicillin derivatives
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

42. antibiotic with good prostate penetration?
Either TB or aspergillosis
High risk 19-64; 1-2 dose - above 65; one dose
<5000 copies/ml
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

43. Tx of choice for human bites
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Acyclovir
Ampicillin-sublactam; most bites contain eikenella

44. How to dx cryptococal meninggits
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Within 6 months viral load will be <50
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Blastomycosis

45. How to differentiate different types of necrotizing fascitis?
Acyclovir
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
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

46. How long we tx chronic prostatis?
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
When cd4 count falls below 200. 2p in pcp =200
6-12 weeks
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

47. 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.
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
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

48. What are the subjective /objective measure of encephalopathy?
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
Either TB or aspergillosis
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

49. What is characteristic for dx of rocky mountain spotted fever?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
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
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

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

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