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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 to dx lyme arthritis?
Others lesions are ring enhancing and have mass effect while PML don't
ELISA and western blot of synovial fluid.
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Mainly clinical - epidemiological and seasonal setting

2. What is lag time to develop lyme arthritis after exposure to vector
Immune mediated; circulating IgG and IgM to penicillin derivatives
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Clostridium perfringens after penetrative injuries/wounds
Others lesions are ring enhancing and have mass effect while PML don't

3. HIV patient having fat deposition on back of neck and abdomen - like cushing
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Pegylated interferon and lamivudine

4. wisconsin - missisipi - ohio
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Blastomycosis
Mainly clinical - epidemiological and seasonal setting

5. after exposure of HIV when antibody testing is performed?
ELISA and western blot of synovial fluid.
ELISA; initial visit - 6 - 12 and 24 weeks;
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
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

6. When not to tx asymptomatic bacteriura?
ELISA; initial visit - 6 - 12 and 24 weeks;
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Non pregnant premanopausal - elderly - dm - sci - chronic foley
HBIG hep B immunoglobulin

7. How to tx pseudomonas?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Vaccine titer >10mU/ml
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Viral load and CD4 count

8. How to confirm dx if pcp?
Bronchoalveolar washing and transbronchial biopsy
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
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

9. How long we tx chronic prostatis?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
6-12 weeks
<500 copies/ml

10. how HAART therapy affects HIV viral loads?
When cd4 count falls below 200. 2p in pcp =200
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Within 6 months viral load will be <50

11. What is the classic signs of nec fasc?
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
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
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. drugs work well on hypertriglyceridia?
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Do EBV antibody test
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

13. causative organisms of uti
Others lesions are ring enhancing and have mass effect while PML don't
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Cd4 count

14. how CMV presents in immunocompromised patients
6-12 weeks
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Rifampin600mg q12. or cipro
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

15. When to give abx to prevent recurrent uti
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
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

16. damae that is about to occur?
Clostridium perfringens after penetrative injuries/wounds
ELISA; initial visit - 6 - 12 and 24 weeks;
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
HIV viral load

17. after recent exposure - negative ELISA - How to confirm?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Cd4 count

18. acute febrile reaction develops after starting penicilin tx to syphilis patient
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Mainly clinical - epidemiological and seasonal setting
Cd4 count
<5000 copies/ml

19. which heart valve is closer to ventricular conduction system/
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Aortic valve; endocardiits of AR p/w AV block and LBBB
Oropharyngeal secretions; hence named as kissing disease

20. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
When cd4 count falls below 200. 2p in pcp =200
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Need lumbar puncture to relieve pressure; they have high opening pressure >350
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

21. What is the mch of ampicillin induced rash in IM
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
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Immune mediated; circulating IgG and IgM to penicillin derivatives
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

22. aspergillosis
High risk 19-64; 1-2 dose - above 65; one dose
Do EBV antibody test
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Voriconazol. mycetoma-surgical removal

23. How to confirm chlamydia infection?
Blastomycosis
<500 copies/ml
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

24. pathophysiology of toxic shock syndrom?
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
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

25. how im is transmitted?
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Oropharyngeal secretions; hence named as kissing disease

26. How to tx TSS?
Td every 10 years - tdap once before 65 and after 65
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

27. reddish colored papules with central umbilication in HIV or immunocompromised patient
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
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
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

28. thrombocytopenia in HIV
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Similar pathophysiology as ITP - tx zidovudine
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

29. Tx of choice for human bites
Ampicillin-sublactam; most bites contain eikenella
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Every 3-4 hours to determine appropritate time to start HAART
Upper lobes; any fibrosis in this area suggestive of latent TB

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

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31. 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
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
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
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

32. What is the Tx of cryptococcal meninngitis
Aortic valve; endocardiits of AR p/w AV block and LBBB
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
ELISA; initial visit - 6 - 12 and 24 weeks;

33. what if monospot test is neg in IM?
Acyclovir
Do EBV antibody test
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
HIV viral load

34. How to tx chronic hep B
Pegylated interferon and lamivudine
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Pt who have been treated before for latent TB
<500 copies/ml

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

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36. INH
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
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

37. What is the indication of corticosteroid in pcp infection?
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
AA gradient >35 or Po2 <70
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

38. When to tx asymptomatic bacteriurea >100 -000?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Pregnacy - urologic procedure - hip arthoplastu
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

39. How to dx progressive multifocal leukoencephalopathy
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Do EBV antibody test
If a sample is ELISA positive - it is tested fro western blot for confirmation
PML; focal neurological deficit like MM; no specific tx; regress with HAART

40. What are indicators for progression of HIV
Viral load and CD4 count
Td every 10 years - tdap once before 65 and after 65
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Clostridium perfringens after penetrative injuries/wounds

41. foot infections in DM
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Others lesions are ring enhancing and have mass effect while PML don't
Ampicillin-sublactam; most bites contain eikenella
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

42. How to dx IM?
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Monospot test which screen heteropile ab that agglutinate horse rbc
Pt who have been treated before for latent TB

43. What is fatal consequence of RMSF?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
If a sample is ELISA positive - it is tested fro western blot for confirmation
ELISA; initial visit - 6 - 12 and 24 weeks;
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

44. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Mainly clinical - epidemiological and seasonal setting
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

45. hypertriglyceridemia in HIV
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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

46. where TB normally affects
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
Pegylated interferon and lamivudine
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Upper lobes; any fibrosis in this area suggestive of latent TB

47. pneumococcal vaccine indication?
Blastomycosis
Every 3-4 hours to determine appropritate time to start HAART
High risk 19-64; 1-2 dose - above 65; one dose
<500 copies/ml

48. can HIV transmitted through human bite?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
HBIG hep B immunoglobulin
Similar pathophysiology as ITP - tx zidovudine

49. How to dx bacterial meningitis from CSF study?

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50. How to dx cryptococal meninggits
Monospot test which screen heteropile ab that agglutinate horse rbc
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
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Postcoital voiding - increased intake of cranberry juice