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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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1. What is the Tx of cryptococcal meninngitis
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
High risk 19-64; 1-2 dose - above 65; one dose
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

2. How long abx is given in pseudomonas infection?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Pegylated interferon and lamivudine

3. 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.
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Others lesions are ring enhancing and have mass effect while PML don't

4. How to dx lyme arthritis?
ELISA and western blot of synovial fluid.
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
ELISA; initial visit - 6 - 12 and 24 weeks;
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

5. after exposure of HIV when antibody testing is performed?
Immune mediated; circulating IgG and IgM to penicillin derivatives
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
ELISA; initial visit - 6 - 12 and 24 weeks;
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

6. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Acyclovir
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Oropharyngeal secretions; hence named as kissing disease
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

7. What is difference between uti relapse versus recurrence?
HIV viral load
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
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Td every 10 years - tdap once before 65 and after 65

8. 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
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Pegylated interferon and lamivudine
High risk 19-64; 1-2 dose - above 65; one dose

9. worsening of TB after starting HAART in HIV
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
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Similar pathophysiology as ITP - tx zidovudine

10. What is tx for herpes zoster
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Blastomycosis
Acyclovir

11. can HIV transmitted through human bite?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
ELISA; initial visit - 6 - 12 and 24 weeks;
Mainly clinical - epidemiological and seasonal setting
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

12. Tx of choice for human bites
Every 3-4 hours to determine appropritate time to start HAART
Ampicillin-sublactam; most bites contain eikenella
Vaccine titer >10mU/ml
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. causative organisms of uti
Others lesions are ring enhancing and have mass effect while PML don't
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
If a sample is ELISA positive - it is tested fro western blot for confirmation

14. What is used for prophylaxis against meningo..meningitis?
AA gradient >35 or Po2 <70
Rifampin600mg q12. or cipro
ELISA and western blot of synovial fluid.
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

15. How to dx?
Td every 10 years - tdap once before 65 and after 65
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Upper lobes; any fibrosis in this area suggestive of latent TB
Mainly clinical - epidemiological and seasonal setting

16. What are the behavioral interventions decrease the risk of UTI
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Postcoital voiding - increased intake of cranberry juice
PML; focal neurological deficit like MM; no specific tx; regress with HAART

17. How to dx IM?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

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

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19. How often viral load is monitored after HAART?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Aortic valve; endocardiits of AR p/w AV block and LBBB
Need lumbar puncture to relieve pressure; they have high opening pressure >350
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

20. HIV patient having fat deposition on back of neck and abdomen - like cushing
High risk 19-64; 1-2 dose - above 65; one dose
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

21. reddish colored papules with central umbilication in HIV or immunocompromised patient
Reddish orange discoloration of urine - feces - sweat - tears - sputum
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
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

22. hypertriglyceridemia in HIV
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
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

23. How to differentiate different types of necrotizing fascitis?
Monospot test which screen heteropile ab that agglutinate horse rbc
Others lesions are ring enhancing and have mass effect while PML don't
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
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

24. low grade fever - maculopapular rash - lymphadenopathy
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
Reddish orange discoloration of urine - feces - sweat - tears - sputum
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

25. damae that is about to occur?
HIV viral load
Immune mediated; circulating IgG and IgM to penicillin derivatives
Either TB or aspergillosis
Postcoital voiding - increased intake of cranberry juice

26. What is the indication of corticosteroid in pcp infection?
AA gradient >35 or Po2 <70
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
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

27. systolic HTN in elderly
<5000 copies/ml
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

28. when HIV patient develop pcp?
High risk 19-64; 1-2 dose - above 65; one dose
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
When cd4 count falls below 200. 2p in pcp =200

29. where TB normally affects
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
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
Upper lobes; any fibrosis in this area suggestive of latent TB

30. 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
Oropharyngeal secretions; hence named as kissing disease
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
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

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

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32. What are the subjective /objective measure of encephalopathy?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
ELISA; initial visit - 6 - 12 and 24 weeks;
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

33. what would be viral load after 2-4m of HAART?
<500 copies/ml
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

34. 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
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

35. How to confirm dx if pcp?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Bronchoalveolar washing and transbronchial biopsy
Rifampin600mg q12. or cipro

36. How to tx chronic hep B
Aortic valve; endocardiits of AR p/w AV block and LBBB
Every 3-4 hours to determine appropritate time to start HAART
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Pegylated interferon and lamivudine

37. acute febrile reaction develops after starting penicilin tx to syphilis patient
High risk 19-64; 1-2 dose - above 65; one dose
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
HIV viral load

38. How to confirm chlamydia infection?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

39. What are indicators for progression of HIV
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Viral load and CD4 count
Immune mediated; circulating IgG and IgM to penicillin derivatives

40. infiltrate in upper lobe of lung?
Td every 10 years - tdap once before 65 and after 65
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Either TB or aspergillosis
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

41. What is tetanus - diptheria - pertusis recommendation?
Pegylated interferon and lamivudine
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
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
Td every 10 years - tdap once before 65 and after 65

42. pneumococcal vaccine indication?
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
High risk 19-64; 1-2 dose - above 65; one dose
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

43. foot infections in DM
Pegylated interferon and lamivudine
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Every 3-4 hours to determine appropritate time to start HAART
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

44. when western blot is done for HIV testing
HIV viral load
If a sample is ELISA positive - it is tested fro western blot for confirmation
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Vaccine titer >10mU/ml

45. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
<500 copies/ml
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

46. aspergillosis
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
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
Voriconazol. mycetoma-surgical removal
When cd4 count falls below 200. 2p in pcp =200

47. acute onset +rusty sputum
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Cd4 count
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

48. What is the classic signs of nec fasc?
Rifampin600mg q12. or cipro
High risk 19-64; 1-2 dose - above 65; one dose
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
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

49. how im is transmitted?
Monospot test which screen heteropile ab that agglutinate horse rbc
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Aortic valve; endocardiits of AR p/w AV block and LBBB
Oropharyngeal secretions; hence named as kissing disease

50. What is the pathophysiology of Meningococcal meningitis?
AA gradient >35 or Po2 <70
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
<500 copies/ml