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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. worsening of TB after starting HAART in HIV
If a sample is ELISA positive - it is tested fro western blot for confirmation
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Blastomycosis
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

2. What is tetanus - diptheria - pertusis recommendation?
Td every 10 years - tdap once before 65 and after 65
Oropharyngeal secretions; hence named as kissing disease
Mainly clinical - epidemiological and seasonal setting
If a sample is ELISA positive - it is tested fro western blot for confirmation

3. How long abx is given in pseudomonas infection?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
HBIG hep B immunoglobulin
<5000 copies/ml
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

4. How to dx adequate response to HBV vaccine
Do EBV antibody test
Vaccine titer >10mU/ml
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.
Ampicillin-sublactam; most bites contain eikenella

5. What is characteristic for dx of rocky mountain spotted fever?
Oropharyngeal secretions; hence named as kissing disease
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
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
<5000 copies/ml

6. How to dx lyme arthritis?
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
ELISA and western blot of synovial fluid.
Postcoital voiding - increased intake of cranberry juice
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

7. gas gangrene
Clostridium perfringens after penetrative injuries/wounds
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
ELISA and western blot of synovial fluid.
Voriconazol. mycetoma-surgical removal

8. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Immune mediated; circulating IgG and IgM to penicillin derivatives
Reddish orange discoloration of urine - feces - sweat - tears - sputum

9. How to tx IM?
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
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
<500 copies/ml
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

10. How to dx IM?
HIV viral load
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
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Monospot test which screen heteropile ab that agglutinate horse rbc

11. how im is transmitted?
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Within 6 months viral load will be <50
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Oropharyngeal secretions; hence named as kissing disease

12. How to dx progressive multifocal leukoencephalopathy
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
6-12 weeks
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Immune mediated; circulating IgG and IgM to penicillin derivatives

13. How to tx pseudomonas?
Clostridium perfringens after penetrative injuries/wounds
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

14. How to confirm chlamydia infection?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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
When cd4 count falls below 200. 2p in pcp =200

15. after exposure of HIV when antibody testing is performed?
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
ELISA; initial visit - 6 - 12 and 24 weeks;

16. 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.
Similar pathophysiology as ITP - tx zidovudine
Pt who have been treated before for latent TB
Td every 10 years - tdap once before 65 and after 65

17. What are the behavioral interventions decrease the risk of UTI
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Postcoital voiding - increased intake of cranberry juice
Oropharyngeal secretions; hence named as kissing disease

18. pneumococcal vaccine indication?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Either TB or aspergillosis
High risk 19-64; 1-2 dose - above 65; one dose

19. wisconsin - missisipi - ohio
Monospot test which screen heteropile ab that agglutinate horse rbc
Blastomycosis
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Aortic valve; endocardiits of AR p/w AV block and LBBB

20. Tx of choice for human bites
Td every 10 years - tdap once before 65 and after 65
Ampicillin-sublactam; most bites contain eikenella
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

21. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Pegylated interferon and lamivudine
Need lumbar puncture to relieve pressure; they have high opening pressure >350
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

22. INH
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
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;

23. aspergillosis
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Bronchoalveolar washing and transbronchial biopsy
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Voriconazol. mycetoma-surgical removal

24. HIV patient having fat deposition on back of neck and abdomen - like cushing
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Postcoital voiding - increased intake of cranberry juice
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

25. hypertension in children
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Pt who have been treated before for latent TB
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

26. INH
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

27. what would be viral load after 2-4m of HAART?
HBIG hep B immunoglobulin
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
<500 copies/ml
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

28. How often viral load is monitored after HAART?
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
Upper lobes; any fibrosis in this area suggestive of latent TB
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

29. 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
Clostridium perfringens after penetrative injuries/wounds
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Mainly clinical - epidemiological and seasonal setting

30. How to dx bacterial meningitis from CSF study?

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31. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Others lesions are ring enhancing and have mass effect while PML don't
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Reddish orange discoloration of urine - feces - sweat - tears - sputum

32. What is the mch of ampicillin induced rash in IM
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.
Clostridium perfringens after penetrative injuries/wounds
Immune mediated; circulating IgG and IgM to penicillin derivatives
Pegylated interferon and lamivudine

33. which heart valve is closer to ventricular conduction system/
Pegylated interferon and lamivudine
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
High risk 19-64; 1-2 dose - above 65; one dose
Aortic valve; endocardiits of AR p/w AV block and LBBB

34. What are the subjective /objective measure of encephalopathy?
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
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

35. What is difference between uti relapse versus recurrence?
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

36. How to tx chronic hep B
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Pegylated interferon and lamivudine
Monospot test which screen heteropile ab that agglutinate horse rbc
High risk 19-64; 1-2 dose - above 65; one dose

37. When to give prophylaxis against MAC
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Aortic valve; endocardiits of AR p/w AV block and LBBB
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Blastomycosis

38. how CMV presents in immunocompromised patients
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

39. pathophysiology of toxic shock syndrom?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Mainly clinical - epidemiological and seasonal setting

40. rifampin
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
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
Pegylated interferon and lamivudine
Reddish orange discoloration of urine - feces - sweat - tears - sputum

41. What is the indication of corticosteroid in pcp infection?
AA gradient >35 or Po2 <70
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
HBIG hep B immunoglobulin

42. damae that is about to occur?
HIV viral load
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

43. dame that has already occurred
Cd4 count
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Immune mediated; circulating IgG and IgM to penicillin derivatives

44. How to tx pcp?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

45. drugs work well on hypertriglyceridia?
Cd4 count
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

46. antibiotic with good prostate penetration?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Immune mediated; circulating IgG and IgM to penicillin derivatives
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
High risk 19-64; 1-2 dose - above 65; one dose

47. where TB normally affects
When cd4 count falls below 200. 2p in pcp =200
Upper lobes; any fibrosis in this area suggestive of latent TB
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

48. can HIV transmitted through human bite?
If a sample is ELISA positive - it is tested fro western blot for confirmation
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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

49. What is used for prophylaxis against meningo..meningitis?
Voriconazol. mycetoma-surgical removal
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
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Rifampin600mg q12. or cipro

50. How to differentiate different types of necrotizing fascitis?
HBIG hep B immunoglobulin
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
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