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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.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

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. INH
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Pregnacy - urologic procedure - hip arthoplastu
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Blastomycosis

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
Clostridium perfringens after penetrative injuries/wounds
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

3. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Bronchoalveolar washing and transbronchial biopsy
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Ampicillin-sublactam; most bites contain eikenella

4. clinical manifestation of mucomycosis
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Pt who have been treated before for latent TB
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

5. when we see echym gangrenosum?
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Similar pathophysiology as ITP - tx zidovudine
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
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

6. low grade fever - maculopapular rash - lymphadenopathy
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
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
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

7. rifampin
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Pregnacy - urologic procedure - hip arthoplastu
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

8. What is tx for herpes zoster
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
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Acyclovir

9. acute onset +rusty sputum
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Need lumbar puncture to relieve pressure; they have high opening pressure >350
6-12 weeks

10. what would be viral load after 4 weeks
<5000 copies/ml
Bronchoalveolar washing and transbronchial biopsy
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Others lesions are ring enhancing and have mass effect while PML don't

11. how HAART therapy affects HIV viral loads?
AA gradient >35 or Po2 <70
Ampicillin-sublactam; most bites contain eikenella
Pegylated interferon and lamivudine
Within 6 months viral load will be <50

12. How often HIV postiive patients CD4 count needs to be evaluated?
Every 3-4 hours to determine appropritate time to start HAART
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Voriconazol. mycetoma-surgical removal
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

13. How to tx chronic hep B
Monospot test which screen heteropile ab that agglutinate horse rbc
Pegylated interferon and lamivudine
ELISA; initial visit - 6 - 12 and 24 weeks;
Mainly clinical - epidemiological and seasonal setting

14. What is the mch of ampicillin induced rash in IM
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
<5000 copies/ml
Immune mediated; circulating IgG and IgM to penicillin derivatives
Others lesions are ring enhancing and have mass effect while PML don't

15. How to tx pseudomonas?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Viral load and CD4 count
AA gradient >35 or Po2 <70

16. acute febrile reaction develops after starting penicilin tx to syphilis patient
Similar pathophysiology as ITP - tx zidovudine
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Postcoital voiding - increased intake of cranberry juice

17. reddish colored papules with central umbilication in HIV or immunocompromised patient
Immune mediated; circulating IgG and IgM to penicillin derivatives
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
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

18. What is characteristic for dx of rocky mountain spotted fever?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Bronchoalveolar washing and transbronchial biopsy
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Mainly clinical - epidemiological and seasonal setting

19. When to tx asymptomatic bacteriurea >100 -000?
Pregnacy - urologic procedure - hip arthoplastu
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
HBIG hep B immunoglobulin
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

20. When to tx influenza with antiviral therapy?
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
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
Clostridium perfringens after penetrative injuries/wounds

21. where TB normally affects
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Upper lobes; any fibrosis in this area suggestive of latent TB
HBIG hep B immunoglobulin
Pregnacy - urologic procedure - hip arthoplastu

22. how CMV presents in immunocompromised patients
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
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
Either TB or aspergillosis

23. can HIV transmitted through human bite?
Immune mediated; circulating IgG and IgM to penicillin derivatives
Need lumbar puncture to relieve pressure; they have high opening pressure >350
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. 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.
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
AA gradient >35 or Po2 <70

25. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Ampicillin-sublactam; most bites contain eikenella
HIV viral load

26. What is the classic signs of nec fasc?
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
Acyclovir
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
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

27. How to dx?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Mainly clinical - epidemiological and seasonal setting

28. pneumococcal vaccine indication?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
High risk 19-64; 1-2 dose - above 65; one dose
Either TB or aspergillosis

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

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30. What is used for prophylaxis against meningo..meningitis?
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Rifampin600mg q12. or cipro
Reddish orange discoloration of urine - feces - sweat - tears - sputum

31. thrombocytopenia in HIV
Similar pathophysiology as ITP - tx zidovudine
Blastomycosis
Cd4 count
<500 copies/ml

32. gas gangrene
Clostridium perfringens after penetrative injuries/wounds
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
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Similar pathophysiology as ITP - tx zidovudine

33. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Do EBV antibody test

34. after exposure of HIV when antibody testing is performed?
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
ELISA; initial visit - 6 - 12 and 24 weeks;
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

35. How to confirm dx if pcp?
Monospot test which screen heteropile ab that agglutinate horse rbc
Bronchoalveolar washing and transbronchial biopsy
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

36. How to tx IM?
Oropharyngeal secretions; hence named as kissing disease
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
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
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

37. INH
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Vaccine titer >10mU/ml
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Aortic valve; endocardiits of AR p/w AV block and LBBB

38. wisconsin - missisipi - ohio
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Blastomycosis

39. When to give prophylaxis against MAC
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
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
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
Others lesions are ring enhancing and have mass effect while PML don't

40. When to give abx to prevent recurrent uti
Within 6 months viral load will be <50
Vaccine titer >10mU/ml
Postcoital voiding - increased intake of cranberry juice
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

41. What is the pathophysiology of Meningococcal meningitis?
Pegylated interferon and lamivudine
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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

42. 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
6-12 weeks
Acyclovir
Td every 10 years - tdap once before 65 and after 65

43. systolic HTN in elderly
Within 6 months viral load will be <50
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
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

44. How to dx bacterial meningitis from CSF study?

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45. What is the indication of corticosteroid in pcp infection?
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
AA gradient >35 or Po2 <70
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

46. What is the prognosis of lyme arthritis?
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Pegylated interferon and lamivudine
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

47. How to tx pcp?
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
Upper lobes; any fibrosis in this area suggestive of latent TB
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

48. 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.
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
6-12 weeks
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

49. What is the Tx of STD uretheritis?
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Oropharyngeal secretions; hence named as kissing disease
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

50. worsening of TB after starting HAART in HIV
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50