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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. pathophysiology of toxic shock syndrom?
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
HIV viral load
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

2. can HIV transmitted through human bite?
Bronchoalveolar washing and transbronchial biopsy
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Pegylated interferon and lamivudine

3. aspergillosis
Vaccine titer >10mU/ml
<5000 copies/ml
ELISA and western blot of synovial fluid.
Voriconazol. mycetoma-surgical removal

4. What are indicators for progression of HIV
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
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Viral load and CD4 count
HBIG hep B immunoglobulin

5. what would be viral load after 2-4m of HAART?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
<500 copies/ml
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

6. 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
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
Within 6 months viral load will be <50

7. How to dx cryptococal meninggits
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Pregnacy - urologic procedure - hip arthoplastu

8. where TB normally affects
6-12 weeks
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
Do EBV antibody test
Upper lobes; any fibrosis in this area suggestive of latent TB

9. INH
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Clostridium perfringens after penetrative injuries/wounds
Do EBV antibody test
Ampicillin-sublactam; most bites contain eikenella

10. which heart valve is closer to ventricular conduction system/
Aortic valve; endocardiits of AR p/w AV block and LBBB
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
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
PML; focal neurological deficit like MM; no specific tx; regress with HAART

11. how CMV presents in immunocompromised patients
When cd4 count falls below 200. 2p in pcp =200
<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
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

12. antibiotic with good prostate penetration?
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

13. What is used for prophylaxis against meningo..meningitis?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Rifampin600mg q12. or cipro
Mainly clinical - epidemiological and seasonal setting
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

14. causative organisms of uti
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Mainly clinical - epidemiological and seasonal setting
Immune mediated; circulating IgG and IgM to penicillin derivatives
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

15. when HIV patient develop pcp?
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Monospot test which screen heteropile ab that agglutinate horse rbc
When cd4 count falls below 200. 2p in pcp =200
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

16. reddish colored papules with central umbilication in HIV or immunocompromised patient
If a sample is ELISA positive - it is tested fro western blot for confirmation
HIV viral load
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

17. What is lag time to develop lyme arthritis after exposure to vector
Either TB or aspergillosis
ELISA and western blot of synovial fluid.
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Postcoital voiding - increased intake of cranberry juice

18. How often HIV postiive patients CD4 count needs to be evaluated?
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Every 3-4 hours to determine appropritate time to start HAART

19. How to dx IM?
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
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
Postcoital voiding - increased intake of cranberry juice

20. What are the behavioral interventions decrease the risk of UTI
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Postcoital voiding - increased intake of cranberry juice
Oropharyngeal secretions; hence named as kissing disease

21. When to tx asymptomatic bacteriurea >100 -000?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
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
Pregnacy - urologic procedure - hip arthoplastu
Blastomycosis

22. what parameters increases risk of neurosyphilis in HIV patient
Bronchoalveolar washing and transbronchial biopsy
Need lumbar puncture to relieve pressure; they have high opening pressure >350
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.
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

23. What is tx for herpes zoster
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Aortic valve; endocardiits of AR p/w AV block and LBBB
Acyclovir
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

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

25. after recent exposure - negative ELISA - How to confirm?
Oropharyngeal secretions; hence named as kissing disease
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Need lumbar puncture to relieve pressure; they have high opening pressure >350
HIV viral load

26. Tx of choice for human bites
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Ampicillin-sublactam; most bites contain eikenella
AA gradient >35 or Po2 <70
Pegylated interferon and lamivudine

27. How to dx adequate response to HBV vaccine
Td every 10 years - tdap once before 65 and after 65
Vaccine titer >10mU/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
Immune mediated; circulating IgG and IgM to penicillin derivatives

28. When to give abx to prevent recurrent uti
PML; focal neurological deficit like MM; no specific tx; regress with HAART
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
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

29. What is difference between uti relapse versus recurrence?
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Do EBV antibody test
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
<5000 copies/ml

30. what if monospot test is neg in IM?
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
Immune mediated; circulating IgG and IgM to penicillin derivatives
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Do EBV antibody test

31. What are the subjective /objective measure of encephalopathy?
If a sample is ELISA positive - it is tested fro western blot for confirmation
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Clostridium perfringens after penetrative injuries/wounds

32. What is the Tx of cryptococcal meninngitis
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
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
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

33. gas gangrene
Every 3-4 hours to determine appropritate time to start HAART
Td every 10 years - tdap once before 65 and after 65
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Clostridium perfringens after penetrative injuries/wounds

34. foot infections in DM
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

35. When not to tx asymptomatic bacteriura?
Mainly clinical - epidemiological and seasonal setting
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

36. 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
Mainly clinical - epidemiological and seasonal setting
When cd4 count falls below 200. 2p in pcp =200
AA gradient >35 or Po2 <70

37. What is the criteria for Spontaneous bact peritonitis
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
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
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

38. pneumococcal vaccine indication?
Aortic valve; endocardiits of AR p/w AV block and LBBB
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
High risk 19-64; 1-2 dose - above 65; one dose
Every 3-4 hours to determine appropritate time to start HAART

39. How to dx lyme arthritis?
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
ELISA and western blot of synovial fluid.
Immune mediated; circulating IgG and IgM to penicillin derivatives

40. What is the prognosis of lyme arthritis?
<5000 copies/ml
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Oropharyngeal secretions; hence named as kissing disease

41. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
<500 copies/ml
HIV viral load
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Either TB or aspergillosis

42. drugs work well on hypertriglyceridia?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
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
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

43. How to differentiate gonococcal and nongonoccal urethritis?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
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
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
Clostridium perfringens after penetrative injuries/wounds

44. What is the mch of ampicillin induced rash in IM
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Immune mediated; circulating IgG and IgM to penicillin derivatives
Pt who have been treated before for latent TB
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

45. How often viral load is monitored after HAART?
Rifampin600mg q12. or cipro
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Ampicillin-sublactam; most bites contain eikenella
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

46. how im is transmitted?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Clostridium perfringens after penetrative injuries/wounds
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
Oropharyngeal secretions; hence named as kissing disease

47. infiltrate in upper lobe of lung?
Either TB or aspergillosis
Blastomycosis
ELISA and western blot of synovial fluid.
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

48. How to dx progressive multifocal leukoencephalopathy
AA gradient >35 or Po2 <70
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

49. dame that has already occurred
Cd4 count
<500 copies/ml
Within 6 months viral load will be <50
Need lumbar puncture to relieve pressure; they have high opening pressure >350

50. low grade fever - maculopapular rash - lymphadenopathy
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
6-12 weeks
Pregnacy - urologic procedure - hip arthoplastu
HBIG hep B immunoglobulin