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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 IM?
ELISA; initial visit - 6 - 12 and 24 weeks;
Monospot test which screen heteropile ab that agglutinate horse rbc
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Clostridium perfringens after penetrative injuries/wounds

2. What is the pathophysiology of Meningococcal meningitis?
Pegylated interferon and lamivudine
PML; focal neurological deficit like MM; no specific tx; regress with HAART
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

3. how CMV presents in immunocompromised patients
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
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

4. How to dx progressive multifocal leukoencephalopathy
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
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
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
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

5. acute febrile reaction develops after starting penicilin tx to syphilis patient
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Viral load and CD4 count
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

6. where TB normally affects
When cd4 count falls below 200. 2p in pcp =200
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.
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Upper lobes; any fibrosis in this area suggestive of latent TB

7. dame that has already occurred
Cd4 count
Rifampin600mg q12. or cipro
6-12 weeks
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

8. When not to tx asymptomatic bacteriura?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

9. how im is transmitted?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
HBIG hep B immunoglobulin
Oropharyngeal secretions; hence named as kissing disease
Similar pathophysiology as ITP - tx zidovudine

10. INH
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Upper lobes; any fibrosis in this area suggestive of latent TB
Vaccine titer >10mU/ml
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

11. How to dx bacterial meningitis from CSF study?

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

13. What is tetanus - diptheria - pertusis recommendation?
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
Td every 10 years - tdap once before 65 and after 65
Pregnacy - urologic procedure - hip arthoplastu

14. What is difference between uti relapse versus recurrence?
<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
Bronchoalveolar washing and transbronchial biopsy
Similar pathophysiology as ITP - tx zidovudine

15. what would be viral load after 2-4m of HAART?
Rifampin600mg q12. or cipro
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
<500 copies/ml
Td every 10 years - tdap once before 65 and after 65

16. What is the indication of corticosteroid in pcp infection?
Monospot test which screen heteropile ab that agglutinate horse rbc
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
AA gradient >35 or Po2 <70

17. What are the subjective /objective measure of encephalopathy?
High risk 19-64; 1-2 dose - above 65; one dose
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Viral load and CD4 count
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

18. causative organisms of uti
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
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
Immune mediated; circulating IgG and IgM to penicillin derivatives

19. aspergillosis
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
Voriconazol. mycetoma-surgical removal
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Within 6 months viral load will be <50

20. which heart valve is closer to ventricular conduction system/
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Bronchoalveolar washing and transbronchial biopsy
Monospot test which screen heteropile ab that agglutinate horse rbc
Aortic valve; endocardiits of AR p/w AV block and LBBB

21. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Monospot test which screen heteropile ab that agglutinate horse rbc
Pregnacy - urologic procedure - hip arthoplastu
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

22. HIV patient having fat deposition on back of neck and abdomen - like cushing
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Within 6 months viral load will be <50
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

23. What is used for prophylaxis against meningo..meningitis?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Rifampin600mg q12. or cipro
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Ampicillin-sublactam; most bites contain eikenella

24. How often viral load is monitored after HAART?
6-12 weeks
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

25. How often HIV postiive patients CD4 count needs to be evaluated?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Every 3-4 hours to determine appropritate time to start HAART

26. pneumococcal vaccine indication?
Upper lobes; any fibrosis in this area suggestive of latent TB
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
High risk 19-64; 1-2 dose - above 65; one dose
If a sample is ELISA positive - it is tested fro western blot for confirmation

27. How to confirm dx if pcp?
Acyclovir
Bronchoalveolar washing and transbronchial biopsy
Pt who have been treated before for latent TB
Ampicillin-sublactam; most bites contain eikenella

28. wisconsin - missisipi - ohio
Bronchoalveolar washing and transbronchial biopsy
Pt who have been treated before for latent TB
Blastomycosis
Do EBV antibody test

29. What is characteristic for dx of rocky mountain spotted fever?
Either TB or aspergillosis
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

30. when HIV patient develop pcp?
Pegylated interferon and lamivudine
When cd4 count falls below 200. 2p in pcp =200
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

31. How to differentiate gonococcal and nongonoccal urethritis?
Viral load and CD4 count
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
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
High risk 19-64; 1-2 dose - above 65; one dose

32. what parameters increases risk of neurosyphilis in HIV patient
HBIG hep B immunoglobulin
Within 6 months viral load will be <50
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.
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

33. What is lag time to develop lyme arthritis after exposure to vector
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
High risk 19-64; 1-2 dose - above 65; one dose
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
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

34. How to differentiate different types of necrotizing fascitis?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
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
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.
Pegylated interferon and lamivudine

35. What is the prognosis of lyme arthritis?
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Blastomycosis
Monospot test which screen heteropile ab that agglutinate horse rbc

36. worsening of TB after starting HAART in HIV
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Either TB or aspergillosis
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

37. 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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Upper lobes; any fibrosis in this area suggestive of latent TB
ELISA and western blot of synovial fluid.

38. rifampin
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Bronchoalveolar washing and transbronchial biopsy
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Similar pathophysiology as ITP - tx zidovudine

39. after recent exposure - negative ELISA - How to confirm?
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

40. What is tx for herpes zoster
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Acyclovir
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Pregnacy - urologic procedure - hip arthoplastu

41. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
When cd4 count falls below 200. 2p in pcp =200
HBIG hep B immunoglobulin
Similar pathophysiology as ITP - tx zidovudine
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

42. gas gangrene
Rifampin600mg q12. or cipro
Clostridium perfringens after penetrative injuries/wounds
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

43. How to tx pseudomonas?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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

44. when not to give INH therapy if ppd positive and patient asyptomatic
Ampicillin-sublactam; most bites contain eikenella
Pt who have been treated before for latent TB
High risk 19-64; 1-2 dose - above 65; one dose
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

45. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
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.
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Acyclovir

46. low grade fever - maculopapular rash - lymphadenopathy
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Aortic valve; endocardiits of AR p/w AV block and LBBB
Td every 10 years - tdap once before 65 and after 65

47. 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
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
ELISA; initial visit - 6 - 12 and 24 weeks;

48. 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
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Either TB or aspergillosis

49. What is the criteria for Spontaneous bact peritonitis
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Voriconazol. mycetoma-surgical removal
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

50. antibiotic with good prostate penetration?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w