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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 im is transmitted?
Oropharyngeal secretions; hence named as kissing disease
Aortic valve; endocardiits of AR p/w AV block and LBBB
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

2. When to give abx to prevent recurrent uti
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
AA gradient >35 or Po2 <70
Pegylated interferon and lamivudine
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

3. thrombocytopenia in HIV
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
Similar pathophysiology as ITP - tx zidovudine
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

4. INH
Blastomycosis
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Clostridium perfringens after penetrative injuries/wounds
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

5. How to tx pseudomonas?
Pegylated interferon and lamivudine
Every 3-4 hours to determine appropritate time to start HAART
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

6. how HAART therapy affects HIV viral loads?
Within 6 months viral load will be <50
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
AA gradient >35 or Po2 <70
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

7. How to tx TSS?
High risk 19-64; 1-2 dose - above 65; one dose
Cd4 count
Pt who have been treated before for latent TB
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

8. what would be viral load after 4 weeks
Acyclovir
<5000 copies/ml
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Cd4 count

9. How to dx progressive multifocal leukoencephalopathy
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Non pregnant premanopausal - elderly - dm - sci - chronic foley

10. INH
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
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

11. What is difference between uti relapse versus recurrence?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
<500 copies/ml
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
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

12. What is used for prophylaxis against meningo..meningitis?
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.
Every 3-4 hours to determine appropritate time to start HAART
Rifampin600mg q12. or cipro

13. 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.
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

14. When to tx asymptomatic bacteriurea >100 -000?
When cd4 count falls below 200. 2p in pcp =200
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Oropharyngeal secretions; hence named as kissing disease
Pregnacy - urologic procedure - hip arthoplastu

15. 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
Cd4 count
Rifampin600mg q12. or cipro
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. What is the indication of corticosteroid in pcp infection?
Postcoital voiding - increased intake of cranberry juice
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
AA gradient >35 or Po2 <70

17. HIV patient having fat deposition on back of neck and abdomen - like cushing
When cd4 count falls below 200. 2p in pcp =200
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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

18. wisconsin - missisipi - ohio
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Ampicillin-sublactam; most bites contain eikenella
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
Blastomycosis

19. How to tx IM?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
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

20. 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
Pt who have been treated before for latent TB
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

21. Tx of choice for human bites
Vaccine titer >10mU/ml
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
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
Ampicillin-sublactam; most bites contain eikenella

22. when not to give INH therapy if ppd positive and patient asyptomatic
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Pt who have been treated before for latent TB
Rifampin600mg q12. or cipro

23. How to dx bacterial meningitis from CSF study?

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24. How to differentiate different types of necrotizing fascitis?
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
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
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
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

25. What is fatal consequence of RMSF?
HBIG hep B immunoglobulin
Pt who have been treated before for latent TB
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Within 6 months viral load will be <50

26. How long we tx chronic prostatis?
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
If a sample is ELISA positive - it is tested fro western blot for confirmation
6-12 weeks
Monospot test which screen heteropile ab that agglutinate horse rbc

27. When to tx influenza with antiviral therapy?
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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
HBIG hep B immunoglobulin

28. reddish colored papules with central umbilication in HIV or immunocompromised patient
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
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
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

29. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Immune mediated; circulating IgG and IgM to penicillin derivatives
<5000 copies/ml
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
PML; focal neurological deficit like MM; no specific tx; regress with HAART

30. How to tx pcp?
Ampicillin-sublactam; most bites contain eikenella
Within 6 months viral load will be <50
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
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

31. causative organisms of uti
Within 6 months viral load will be <50
Immune mediated; circulating IgG and IgM to penicillin derivatives
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

32. How long abx is given in pseudomonas infection?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Vaccine titer >10mU/ml
Need lumbar puncture to relieve pressure; they have high opening pressure >350
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

33. how CMV presents in immunocompromised patients
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
ELISA and western blot of synovial fluid.
Bronchoalveolar washing and transbronchial biopsy

34. foot infections in DM
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

35. What is characteristic for dx of rocky mountain spotted fever?
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Monospot test which screen heteropile ab that agglutinate horse rbc
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

36. systolic HTN in elderly
AA gradient >35 or Po2 <70
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
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
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

37. When not to tx asymptomatic bacteriura?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Pregnacy - urologic procedure - hip arthoplastu

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

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39. How to dx IM?
Monospot test which screen heteropile ab that agglutinate horse rbc
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

40. What is the criteria for Spontaneous bact peritonitis
Do EBV antibody test
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
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

41. What is the prognosis of lyme arthritis?
Immune mediated; circulating IgG and IgM to penicillin derivatives
HBIG hep B immunoglobulin
Postcoital voiding - increased intake of cranberry juice
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

42. How to confirm chlamydia infection?
Either TB or aspergillosis
Acyclovir
Mainly clinical - epidemiological and seasonal setting
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

43. How to give postexposure prophylaxis for HIV
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Ampicillin-sublactam; most bites contain eikenella
Rifampin600mg q12. or cipro

44. How to confirm dx if pcp?
Blastomycosis
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
Bronchoalveolar washing and transbronchial biopsy
6-12 weeks

45. 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
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
High risk 19-64; 1-2 dose - above 65; one dose
Similar pathophysiology as ITP - tx zidovudine

46. How to dx?
Mainly clinical - epidemiological and seasonal setting
Every 3-4 hours to determine appropritate time to start HAART
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
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

47. pathophysiology of toxic shock syndrom?
Blastomycosis
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Rifampin600mg q12. or cipro
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

48. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
HBIG hep B immunoglobulin
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
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Need lumbar puncture to relieve pressure; they have high opening pressure >350

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

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50. what if monospot test is neg in IM?
Do EBV antibody test
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Within 6 months viral load will be <50
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose