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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. when not to give INH therapy if ppd positive and patient asyptomatic
Within 6 months viral load will be <50
Bronchoalveolar washing and transbronchial biopsy
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
Pt who have been treated before for latent TB

2. What is the Tx of STD uretheritis?
Monospot test which screen heteropile ab that agglutinate horse rbc
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
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

3. 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.
AA gradient >35 or Po2 <70
HIV viral load
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

4. How to dx bacterial meningitis from CSF study?

5. antibiotic with good prostate penetration?
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 syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
6-12 weeks
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

6. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Vaccine titer >10mU/ml
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Upper lobes; any fibrosis in this area suggestive of latent TB

7. acute febrile reaction develops after starting penicilin tx to syphilis patient
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
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
Td every 10 years - tdap once before 65 and after 65

8. How often HIV postiive patients CD4 count needs to be evaluated?
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Cd4 count
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Every 3-4 hours to determine appropritate time to start HAART

9. How long abx is given in pseudomonas infection?
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
<5000 copies/ml
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

10. What are the subjective /objective measure of encephalopathy?
Upper lobes; any fibrosis in this area suggestive of latent TB
Do EBV antibody test
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

11. What is the mch of ampicillin induced rash in IM
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
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
Postcoital voiding - increased intake of cranberry juice

12. How to differentiate gonococcal and nongonoccal urethritis?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
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
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
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

13. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
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
Give nystatin suspension or clotrimazol with an oral antifungal eg. 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

14. wisconsin - missisipi - ohio
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Blastomycosis
Similar pathophysiology as ITP - tx zidovudine

15. How to tx pseudomonas?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
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
Immune mediated; circulating IgG and IgM to penicillin derivatives

16. after recent exposure - negative ELISA - How to confirm?
Vaccine titer >10mU/ml
Mainly clinical - epidemiological and seasonal setting
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

17. What is fatal consequence of RMSF?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

18. 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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
AA gradient >35 or Po2 <70
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

19. How to dx cryptococal meninggits
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
PML; focal neurological deficit like MM; no specific tx; regress with HAART
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
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

20. What is used for prophylaxis against meningo..meningitis?
Rifampin600mg q12. or cipro
<5000 copies/ml
Pt who have been treated before for latent TB
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

21. when we see echym gangrenosum?
If a sample is ELISA positive - it is tested fro western blot for confirmation
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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

22. How to tx TSS?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Others lesions are ring enhancing and have mass effect while PML don't
Viral load and CD4 count
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

23. can HIV transmitted through human bite?
Others lesions are ring enhancing and have mass effect while PML don't
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
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

24. How to dx?
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Mainly clinical - epidemiological and seasonal setting
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Aortic valve; endocardiits of AR p/w AV block and LBBB

25. What is tetanus - diptheria - pertusis recommendation?
Pegylated interferon and lamivudine
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
Td every 10 years - tdap once before 65 and after 65
HBIG hep B immunoglobulin

26. How to tx IM?
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
<500 copies/ml
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
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

27. HIV patient having fat deposition on back of neck and abdomen - like cushing
AA gradient >35 or Po2 <70
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Aortic valve; endocardiits of AR p/w AV block and LBBB
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

28. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Need lumbar puncture to relieve pressure; they have high opening pressure >350
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

29. pathophysiology of toxic shock syndrom?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
When cd4 count falls below 200. 2p in pcp =200
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

30. How often viral load is monitored after HAART?
Bronchoalveolar washing and transbronchial biopsy
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Either TB or aspergillosis

31. pneumococcal vaccine indication?
High risk 19-64; 1-2 dose - above 65; one dose
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

32. What is the prognosis of lyme arthritis?
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
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
AA gradient >35 or Po2 <70

33. How to tx pcp?
When cd4 count falls below 200. 2p in pcp =200
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

34. How to give postexposure prophylaxis for HIV
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
Cd4 count
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

35. thrombocytopenia in HIV
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
Similar pathophysiology as ITP - tx zidovudine
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 lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

36. How to dx progressive multifocal leukoencephalopathy
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Similar pathophysiology as ITP - tx zidovudine

37. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Ampicillin-sublactam; most bites contain eikenella
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.

38. what parameters increases risk of neurosyphilis in HIV patient
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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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.
Vaccine titer >10mU/ml

39. where TB normally affects
AA gradient >35 or Po2 <70
Cd4 count
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Upper lobes; any fibrosis in this area suggestive of latent TB

40. What is the pathophysiology of Meningococcal meningitis?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Within 6 months viral load will be <50

41. drugs work well on hypertriglyceridia?
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

42. gas gangrene
<500 copies/ml
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Clostridium perfringens after penetrative injuries/wounds
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

43. hypertriglyceridemia in HIV
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
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.

44. what if monospot test is neg in IM?
Do EBV antibody test
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

45. How to dx IM?
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Do EBV antibody test
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
Monospot test which screen heteropile ab that agglutinate horse rbc

46. What is tx for herpes zoster
<500 copies/ml
<5000 copies/ml
Pregnacy - urologic procedure - hip arthoplastu
Acyclovir

47. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
HBIG hep B immunoglobulin
Every 3-4 hours to determine appropritate time to start HAART
HIV viral load
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

48. How to tx chronic hep B
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Pegylated interferon and lamivudine
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Similar pathophysiology as ITP - tx zidovudine

49. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
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
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

50. What is lag time to develop lyme arthritis after exposure to vector
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
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine