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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. can HIV transmitted through human bite?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Acyclovir
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Oropharyngeal secretions; hence named as kissing disease

2. How to dx IM?
Monospot test which screen heteropile ab that agglutinate horse rbc
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
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
Either TB or aspergillosis

3. How often HIV postiive patients CD4 count needs to be evaluated?
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
When cd4 count falls below 200. 2p in pcp =200
Immune mediated; circulating IgG and IgM to penicillin derivatives
Every 3-4 hours to determine appropritate time to start HAART

4. acute febrile reaction develops after starting penicilin tx to syphilis patient
If a sample is ELISA positive - it is tested fro western blot for confirmation
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

5. When to tx influenza with antiviral therapy?
Every 3-4 hours to determine appropritate time to start HAART
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
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
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

6. reddish colored papules with central umbilication in HIV or immunocompromised patient
Viral load and CD4 count
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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
Clostridium perfringens after penetrative injuries/wounds

7. How to dx cryptococal meninggits
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
HBIG hep B immunoglobulin

8. how im is transmitted?
Oropharyngeal secretions; hence named as kissing disease
HBIG hep B immunoglobulin
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

9. Tx of choice for human bites
HBIG hep B immunoglobulin
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Immune mediated; circulating IgG and IgM to penicillin derivatives
Ampicillin-sublactam; most bites contain eikenella

10. What is the criteria for Spontaneous bact peritonitis
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Voriconazol. mycetoma-surgical removal
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

11. which heart valve is closer to ventricular conduction system/
Bronchoalveolar washing and transbronchial biopsy
Cd4 count
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Aortic valve; endocardiits of AR p/w AV block and LBBB

12. What is the pathophysiology of Meningococcal meningitis?
Rifampin600mg q12. or cipro
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
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Pegylated interferon and lamivudine

13. How to dx IM?
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
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Voriconazol. mycetoma-surgical removal

14. after recent exposure - negative ELISA - How to confirm?
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
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Need lumbar puncture to relieve pressure; they have high opening pressure >350

15. foot infections in DM
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Rifampin600mg q12. or cipro
Ampicillin-sublactam; most bites contain eikenella
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

16. When to give prophylaxis against MAC
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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 of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

17. how HAART therapy affects HIV viral loads?
Td every 10 years - tdap once before 65 and after 65
Within 6 months viral load will be <50
When cd4 count falls below 200. 2p in pcp =200
Non pregnant premanopausal - elderly - dm - sci - chronic foley

18. How to dx bacterial meningitis from CSF study?

19. when western blot is done for HIV testing
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Do EBV antibody test
If a sample is ELISA positive - it is tested fro western blot for confirmation
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

20. How to dx lyme arthritis?
Bronchoalveolar washing and transbronchial biopsy
Oropharyngeal secretions; hence named as kissing disease
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
ELISA and western blot of synovial fluid.

21. what if monospot test is neg in IM?
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
Do EBV antibody test
Non pregnant premanopausal - elderly - dm - sci - chronic foley
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

22. What is used for prophylaxis against meningo..meningitis?
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
Rifampin600mg q12. or cipro
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
PML; focal neurological deficit like MM; no specific tx; regress with HAART

23. 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
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
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

24. INH
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Pegylated interferon and lamivudine
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

25. systolic HTN in elderly
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Either TB or aspergillosis
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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.

26. What is lag time to develop lyme arthritis after exposure to vector
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Non pregnant premanopausal - elderly - dm - sci - chronic foley
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
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

27. How to dx adequate response to HBV vaccine
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Vaccine titer >10mU/ml
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

28. 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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Blastomycosis
Pegylated interferon and lamivudine

29. hypertriglyceridemia in HIV
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Do EBV antibody test
HBIG hep B immunoglobulin
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

30. How to dx progressive multifocal leukoencephalopathy
Pegylated interferon and lamivudine
Do EBV antibody test
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

31. low grade fever - maculopapular rash - lymphadenopathy
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

32. What is the prognosis of lyme arthritis?
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Pregnacy - urologic procedure - hip arthoplastu
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Pt who have been treated before for latent TB

33. drugs work well on hypertriglyceridia?
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

34. What is the indication of corticosteroid in pcp infection?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
AA gradient >35 or Po2 <70
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

35. when we see echym gangrenosum?
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
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
ELISA; initial visit - 6 - 12 and 24 weeks;
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.

36. How to tx chronic hep B
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
Upper lobes; any fibrosis in this area suggestive of latent TB
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Pegylated interferon and lamivudine

37. dame that has already occurred
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Others lesions are ring enhancing and have mass effect while PML don't
Cd4 count
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

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

39. worsening of TB after starting HAART in HIV
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
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
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

40. How to tx pseudomonas?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Either TB or aspergillosis
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Viral load and CD4 count

41. infiltrate in upper lobe of lung?
Either TB or aspergillosis
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
<500 copies/ml
Need lumbar puncture to relieve pressure; they have high opening pressure >350

42. How long we tx chronic prostatis?
ELISA; initial visit - 6 - 12 and 24 weeks;
Bronchoalveolar washing and transbronchial biopsy
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
6-12 weeks

43. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
ELISA; initial visit - 6 - 12 and 24 weeks;
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
<500 copies/ml

44. What are the behavioral interventions decrease the risk of UTI
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Postcoital voiding - increased intake of cranberry juice
Either TB or aspergillosis
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

45. gas gangrene
Oropharyngeal secretions; hence named as kissing disease
Aortic valve; endocardiits of AR p/w AV block and LBBB
Clostridium perfringens after penetrative injuries/wounds
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

46. How to differentiate gonococcal and nongonoccal urethritis?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
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

47. antibiotic with good prostate penetration?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Td every 10 years - tdap once before 65 and after 65
High risk 19-64; 1-2 dose - above 65; one dose

48. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

49. aspergillosis
Voriconazol. mycetoma-surgical removal
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Pt who have been treated before for latent TB

50. When not to tx asymptomatic bacteriura?
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
Vaccine titer >10mU/ml
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Non pregnant premanopausal - elderly - dm - sci - chronic foley