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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. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
HIV viral load
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

2. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Blastomycosis
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

3. how im is transmitted?
Oropharyngeal secretions; hence named as kissing disease
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
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

4. where TB normally affects
Bronchoalveolar washing and transbronchial biopsy
Upper lobes; any fibrosis in this area suggestive of latent TB
Td every 10 years - tdap once before 65 and after 65
Monospot test which screen heteropile ab that agglutinate horse rbc

5. after recent exposure - negative ELISA - How to confirm?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Every 3-4 hours to determine appropritate time to start HAART
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
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

6. antibiotic with good prostate penetration?
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
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
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
AA gradient >35 or Po2 <70

7. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
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
Mainly clinical - epidemiological and seasonal setting

8. How to differentiate gonococcal and nongonoccal urethritis?
Within 6 months viral load will be <50
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 viral load
AA gradient >35 or Po2 <70

9. dame that has already occurred
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
Cd4 count
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

10. hypertriglyceridemia in HIV
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
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
Bronchoalveolar washing and transbronchial biopsy

11. How long we tx chronic prostatis?
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
6-12 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
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

12. reddish colored papules with central umbilication in HIV or immunocompromised patient
Ampicillin-sublactam; most bites contain eikenella
Pregnacy - urologic procedure - hip arthoplastu
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
Pt who have been treated before for latent TB

13. How to confirm dx if pcp?
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
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
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Bronchoalveolar washing and transbronchial biopsy

14. hypertension in children
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Mainly clinical - epidemiological and seasonal setting
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
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

15. What is the mch of ampicillin induced rash in IM
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
When cd4 count falls below 200. 2p in pcp =200
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Immune mediated; circulating IgG and IgM to penicillin derivatives

16. What is the Tx of STD uretheritis?
Monospot test which screen heteropile ab that agglutinate horse rbc
Need lumbar puncture to relieve pressure; they have high opening pressure >350
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
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

17. 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.
High risk 19-64; 1-2 dose - above 65; one dose
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

18. what if monospot test is neg in IM?
Do EBV antibody test
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

19. 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
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
ELISA and western blot of synovial fluid.

20. causative organisms of uti
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Need lumbar puncture to relieve pressure; they have high opening pressure >350
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

21. rifampin
Blastomycosis
Oropharyngeal secretions; hence named as kissing disease
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

22. What is the indication of corticosteroid in pcp infection?
AA gradient >35 or Po2 <70
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Voriconazol. mycetoma-surgical removal
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

23. What is the prognosis of lyme arthritis?
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Bronchoalveolar washing and transbronchial biopsy

24. What are indicators for progression of HIV
Viral load and CD4 count
Do EBV antibody test
Aortic valve; endocardiits of AR p/w AV block and LBBB
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

25. How to tx TSS?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Ampicillin-sublactam; most bites contain eikenella
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

26. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
HBIG hep B immunoglobulin
Postcoital voiding - increased intake of cranberry juice
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

27. how CMV presents in immunocompromised patients
AA gradient >35 or Po2 <70
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
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

28. How to dx progressive multifocal leukoencephalopathy
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
AA gradient >35 or Po2 <70
Oropharyngeal secretions; hence named as kissing disease
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

29. what would be viral load after 4 weeks
If a sample is ELISA positive - it is tested fro western blot for confirmation
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
<5000 copies/ml

30. What is the criteria for Spontaneous bact peritonitis
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Acyclovir
AA gradient >35 or Po2 <70

31. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Every 3-4 hours to determine appropritate time to start HAART
HBIG hep B immunoglobulin
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

32. What is lag time to develop lyme arthritis after exposure to vector
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Do EBV antibody test
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

33. How to confirm chlamydia infection?
Blastomycosis
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
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
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

34. pneumococcal vaccine indication?
High risk 19-64; 1-2 dose - above 65; one dose
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

35. What is characteristic for dx of rocky mountain spotted fever?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Acyclovir
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

36. How often HIV postiive patients CD4 count needs to be evaluated?
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
Every 3-4 hours to determine appropritate time to start HAART
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

37. When not to tx asymptomatic bacteriura?
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.
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Non pregnant premanopausal - elderly - dm - sci - chronic foley

38. What is difference between uti relapse versus recurrence?
Every 3-4 hours to determine appropritate time to start HAART
HBIG hep B immunoglobulin
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
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

39. clinical manifestation of mucomycosis
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
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
Pt who have been treated before for latent TB

40. 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
Ampicillin-sublactam; most bites contain eikenella
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

41. How to dx cryptococal meninggits
Need lumbar puncture to relieve pressure; they have high opening pressure >350
HBIG hep B immunoglobulin
Within 6 months viral load will be <50
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

42. How to dx adequate response to HBV vaccine
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Vaccine titer >10mU/ml
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

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

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44. HIV patient having fat deposition on back of neck and abdomen - like cushing
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Reddish orange discoloration of urine - feces - sweat - tears - sputum
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

45. Tx of choice for human bites
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Ampicillin-sublactam; most bites contain eikenella
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

46. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
6-12 weeks
Rifampin600mg q12. or cipro
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

47. when HIV patient develop pcp?
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
If a sample is ELISA positive - it is tested fro western blot for confirmation
When cd4 count falls below 200. 2p in pcp =200
Pegylated interferon and lamivudine

48. wisconsin - missisipi - ohio
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
Blastomycosis
AA gradient >35 or Po2 <70
Either TB or aspergillosis

49. How to dx bacterial meningitis from CSF study?

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50. What is used for prophylaxis against meningo..meningitis?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Rifampin600mg q12. or cipro
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
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