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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
Similar pathophysiology as ITP - tx zidovudine
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
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
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

2. acute onset +rusty sputum
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
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

3. When not to tx asymptomatic bacteriura?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
AA gradient >35 or Po2 <70
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

4. How to tx chronic hep B
<5000 copies/ml
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Pegylated interferon and lamivudine
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

5. INH
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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
Rifampin600mg q12. or cipro
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

6. How to tx pcp?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
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
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

7. What is lag time to develop lyme arthritis after exposure to vector
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
When cd4 count falls below 200. 2p in pcp =200
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

8. How to dx cryptococal meninggits
<500 copies/ml
Vaccine titer >10mU/ml
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

9. after exposure of HIV when antibody testing is performed?
ELISA; initial visit - 6 - 12 and 24 weeks;
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

10. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

11. What is the criteria for Spontaneous bact peritonitis
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

12. How to tx IM?
Rifampin600mg q12. or cipro
Either TB or aspergillosis
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

13. drugs work well on hypertriglyceridia?
Td every 10 years - tdap once before 65 and after 65
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
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

14. How to confirm chlamydia infection?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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) -
Either TB or aspergillosis

15. How to tx TSS?
<500 copies/ml
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Cd4 count
When cd4 count falls below 200. 2p in pcp =200

16. acute febrile reaction develops after starting penicilin tx to syphilis patient
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

17. HIV patient having fat deposition on back of neck and abdomen - like cushing
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
<500 copies/ml
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

18. how HAART therapy affects HIV viral loads?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Monospot test which screen heteropile ab that agglutinate horse rbc
Within 6 months viral load will be <50
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

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

20. How to dx lyme arthritis?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
<500 copies/ml
ELISA and western blot of synovial fluid.

21. systolic HTN in elderly
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Vaccine titer >10mU/ml
ELISA and western blot of synovial fluid.
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

22. What is fatal consequence of RMSF?
<5000 copies/ml
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

23. damae that is about to occur?
HIV viral load
Rifampin600mg q12. or cipro
Similar pathophysiology as ITP - tx zidovudine
Oropharyngeal secretions; hence named as kissing disease

24. pathophysiology of toxic shock syndrom?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Acyclovir
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Clostridium perfringens after penetrative injuries/wounds

25. 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
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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
6-12 weeks

26. causative organisms of uti
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
ELISA and western blot of synovial fluid.
Every 3-4 hours to determine appropritate time to start HAART
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

27. foot infections in DM
Mainly clinical - epidemiological and seasonal setting
Upper lobes; any fibrosis in this area suggestive of latent TB
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

28. pneumococcal vaccine indication?
Mainly clinical - epidemiological and seasonal setting
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
Pegylated interferon and lamivudine

29. aspergillosis
Vaccine titer >10mU/ml
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Voriconazol. mycetoma-surgical removal
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

30. INH
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
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

31. when western blot is done for HIV testing
If a sample is ELISA positive - it is tested fro western blot for confirmation
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Mainly clinical - epidemiological and seasonal setting

32. how CMV presents in immunocompromised patients
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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

33. gas gangrene
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Clostridium perfringens after penetrative injuries/wounds
<500 copies/ml
Others lesions are ring enhancing and have mass effect while PML don't

34. infiltrate in upper lobe of lung?
Either TB or aspergillosis
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

35. dame that has already occurred
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Oropharyngeal secretions; hence named as kissing disease
Cd4 count

36. 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.
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
6-12 weeks
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

37. how im is transmitted?
Oropharyngeal secretions; hence named as kissing disease
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
AA gradient >35 or Po2 <70
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

38. clinical manifestation of mucomycosis
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
If a sample is ELISA positive - it is tested fro western blot for confirmation
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

39. hypertension in children
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
If a sample is ELISA positive - it is tested fro western blot for confirmation
Pt who have been treated before for latent TB
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

40. What is tx for herpes zoster
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Pt who have been treated before for latent TB
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Acyclovir

41. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
<500 copies/ml
Postcoital voiding - increased intake of cranberry juice
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
HIV viral load

42. what would be viral load after 4 weeks
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
<5000 copies/ml
HBIG hep B immunoglobulin

43. What is used for prophylaxis against meningo..meningitis?
Rifampin600mg q12. or cipro
Td every 10 years - tdap once before 65 and after 65
Similar pathophysiology as ITP - tx zidovudine
AA gradient >35 or Po2 <70

44. what would be viral load after 2-4m of HAART?
<500 copies/ml
Either TB or aspergillosis
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

45. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
HBIG hep B immunoglobulin
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Pt who have been treated before for latent TB

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

47. 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
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
ELISA and western blot of synovial fluid.
Clostridium perfringens after penetrative injuries/wounds

48. when not to give INH therapy if ppd positive and patient asyptomatic
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Oropharyngeal secretions; hence named as kissing disease
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Pt who have been treated before for latent TB

49. How to dx bacterial meningitis from CSF study?

50. How to confirm dx if pcp?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Bronchoalveolar washing and transbronchial biopsy
Either TB or aspergillosis