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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. acute febrile reaction develops after starting penicilin tx to syphilis patient
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
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.
Cd4 count
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

2. HIV patient having fat deposition on back of neck and abdomen - like cushing
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Monospot test which screen heteropile ab that agglutinate horse rbc
Bronchoalveolar washing and transbronchial biopsy
Non pregnant premanopausal - elderly - dm - sci - chronic foley

3. How to tx TSS?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Pegylated interferon and lamivudine
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

4. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Aortic valve; endocardiits of AR p/w AV block and LBBB
Pregnacy - urologic procedure - hip arthoplastu
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

5. pneumococcal vaccine indication?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Td every 10 years - tdap once before 65 and after 65
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
High risk 19-64; 1-2 dose - above 65; one dose

6. When to tx influenza with antiviral therapy?
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
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
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

7. how HAART therapy affects HIV viral loads?
Within 6 months viral load will be <50
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
Either TB or aspergillosis

8. What is the indication of corticosteroid in pcp infection?
AA gradient >35 or Po2 <70
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
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
If a sample is ELISA positive - it is tested fro western blot for confirmation

9. What is lag time to develop lyme arthritis after exposure to vector
<500 copies/ml
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
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
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

10. causative organisms of uti
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
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
Pegylated interferon and lamivudine
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

11. What is the prognosis of lyme arthritis?
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
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
Need lumbar puncture to relieve pressure; they have high opening pressure >350

12. How to tx IM?
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
ELISA and western blot of synovial fluid.

13. 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
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

14. foot infections in DM
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Every 3-4 hours to determine appropritate time to start HAART
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

15. which heart valve is closer to ventricular conduction system/
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.
Aortic valve; endocardiits of AR p/w AV block and LBBB
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

16. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
Postcoital voiding - increased intake of cranberry juice
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.
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
Need lumbar puncture to relieve pressure; they have high opening pressure >350

17. When not to tx asymptomatic bacteriura?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Bronchoalveolar washing and transbronchial biopsy
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Oropharyngeal secretions; hence named as kissing disease

18. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Postcoital voiding - increased intake of cranberry juice
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

19. INH
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
HBIG hep B immunoglobulin
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Bronchoalveolar washing and transbronchial biopsy

20. What is fatal consequence of RMSF?
Clostridium perfringens after penetrative injuries/wounds
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
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

21. What is the Tx of STD uretheritis?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
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
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

22. How to tx pcp?
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Ampicillin-sublactam; most bites contain eikenella
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 the Tx of cryptococcal meninngitis
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Pegylated interferon and lamivudine

24. What are the subjective /objective measure of encephalopathy?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Similar pathophysiology as ITP - tx zidovudine
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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

25. after recent exposure - negative ELISA - How to confirm?
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Either TB or aspergillosis
Aortic valve; endocardiits of AR p/w AV block and LBBB
Non pregnant premanopausal - elderly - dm - sci - chronic foley

26. infiltrate in upper lobe of lung?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Acyclovir
Either TB or aspergillosis
Similar pathophysiology as ITP - tx zidovudine

27. When to give abx to prevent recurrent uti
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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
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
ELISA and western blot of synovial fluid.

28. What is the pathophysiology of Meningococcal meningitis?
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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Acyclovir

29. after exposure of HIV when antibody testing is performed?
Every 3-4 hours to determine appropritate time to start HAART
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
ELISA; initial visit - 6 - 12 and 24 weeks;
Cd4 count

30. How to dx?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Mainly clinical - epidemiological and seasonal setting
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

31. How to dx lyme arthritis?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
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
Every 3-4 hours to determine appropritate time to start HAART
ELISA and western blot of synovial fluid.

32. How long we tx chronic prostatis?
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
6-12 weeks
Do EBV antibody test
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

33. 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
Immune mediated; circulating IgG and IgM to penicillin derivatives
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

34. thrombocytopenia in HIV
Bronchoalveolar washing and transbronchial biopsy
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
Similar pathophysiology as ITP - tx zidovudine

35. damae that is about to occur?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Rifampin600mg q12. or cipro
Td every 10 years - tdap once before 65 and after 65
HIV viral load

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

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37. How to dx adequate response to HBV vaccine
Vaccine titer >10mU/ml
Within 6 months viral load will be <50
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Clostridium perfringens after penetrative injuries/wounds

38. How to dx IM?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
6-12 weeks

39. How to confirm dx if pcp?
Bronchoalveolar washing and transbronchial biopsy
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

40. worsening of TB after starting HAART in HIV
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
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
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

41. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
6-12 weeks
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

42. How to differentiate different types of necrotizing fascitis?
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
PML; focal neurological deficit like MM; no specific tx; regress with HAART
ELISA and western blot of synovial fluid.
Rifampin600mg q12. or cipro

43. How often HIV postiive patients CD4 count needs to be evaluated?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Immune mediated; circulating IgG and IgM to penicillin derivatives
Every 3-4 hours to determine appropritate time to start HAART

44. What is tx for herpes zoster
Viral load and CD4 count
Acyclovir
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)

45. gas gangrene
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Pregnacy - urologic procedure - hip arthoplastu
Upper lobes; any fibrosis in this area suggestive of latent TB
Clostridium perfringens after penetrative injuries/wounds

46. what if monospot test is neg in IM?
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Mainly clinical - epidemiological and seasonal setting
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Do EBV antibody test

47. what would be viral load after 2-4m of HAART?
Mainly clinical - epidemiological and seasonal setting
<500 copies/ml
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
Blastomycosis

48. dame that has already occurred
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Cd4 count
Bronchoalveolar washing and transbronchial biopsy

49. rifampin
6-12 weeks
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
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

50. What is difference between uti relapse versus recurrence?
Pt who have been treated before for latent TB
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
Others lesions are ring enhancing and have mass effect while PML don't
Upper lobes; any fibrosis in this area suggestive of latent TB