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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 confirm chlamydia infection?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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
Immune mediated; circulating IgG and IgM to penicillin derivatives
Pregnacy - urologic procedure - hip arthoplastu

2. can HIV transmitted through human bite?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
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
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

3. What is the Tx of cryptococcal meninngitis
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
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.

4. low grade fever - maculopapular rash - lymphadenopathy
Within 6 months viral load will be <50
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Mainly clinical - epidemiological and seasonal setting

5. after recent exposure - negative ELISA - How to confirm?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
ELISA and western blot of synovial fluid.
Clostridium perfringens after penetrative injuries/wounds

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

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7. What is used for prophylaxis against meningo..meningitis?
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Rifampin600mg q12. or cipro
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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.

8. How often viral load is monitored after HAART?
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
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

9. How long we tx chronic prostatis?
Every 3-4 hours to determine appropritate time to start HAART
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
Similar pathophysiology as ITP - tx zidovudine
6-12 weeks

10. INH
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Mainly clinical - epidemiological and seasonal setting
<5000 copies/ml

11. damae that is about to occur?
HIV viral load
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

12. What is the Tx of STD uretheritis?
Others lesions are ring enhancing and have mass effect while PML don't
Mainly clinical - epidemiological and seasonal setting
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
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

13. What is tetanus - diptheria - pertusis recommendation?
Td every 10 years - tdap once before 65 and after 65
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Similar pathophysiology as ITP - tx zidovudine
Mainly clinical - epidemiological and seasonal setting

14. acute onset +rusty sputum
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Bronchoalveolar washing and transbronchial biopsy
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Pt who have been treated before for latent TB

15. When to tx asymptomatic bacteriurea >100 -000?
Pregnacy - urologic procedure - hip arthoplastu
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

16. How to give postexposure prophylaxis for HIV
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Blastomycosis
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

17. systolic HTN in elderly
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
HIV viral load

18. How to dx progressive multifocal leukoencephalopathy
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
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
AA gradient >35 or Po2 <70
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

19. after exposure of HIV when antibody testing is performed?
ELISA; initial visit - 6 - 12 and 24 weeks;
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

20. How to tx TSS?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Non pregnant premanopausal - elderly - dm - sci - chronic foley
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
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

21. How often HIV postiive patients CD4 count needs to be evaluated?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Either TB or aspergillosis
Every 3-4 hours to determine appropritate time to start 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

22. How long abx is given in pseudomonas infection?
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

23. wisconsin - missisipi - ohio
Similar pathophysiology as ITP - tx zidovudine
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Blastomycosis
Rifampin600mg q12. or cipro

24. What is the prognosis of lyme arthritis?
ELISA; initial visit - 6 - 12 and 24 weeks;
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Monospot test which screen heteropile ab that agglutinate horse rbc
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

25. which heart valve is closer to ventricular conduction system/
Pegylated interferon and lamivudine
Aortic valve; endocardiits of AR p/w AV block and LBBB
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

26. How to differentiate gonococcal and nongonoccal urethritis?
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
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
If a sample is ELISA positive - it is tested fro western blot for confirmation
Bronchoalveolar washing and transbronchial biopsy

27. hypertension in children
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Postcoital voiding - increased intake of cranberry juice
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

28. thrombocytopenia in HIV
Upper lobes; any fibrosis in this area suggestive of latent TB
Bronchoalveolar washing and transbronchial biopsy
Similar pathophysiology as ITP - tx zidovudine
Pt who have been treated before for latent TB

29. rifampin
Reddish orange discoloration of urine - feces - sweat - tears - sputum
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
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
<5000 copies/ml

30. pneumococcal vaccine indication?
High risk 19-64; 1-2 dose - above 65; one dose
Oropharyngeal secretions; hence named as kissing disease
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
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

31. acute febrile reaction develops after starting penicilin tx to syphilis patient
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
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
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

32. What are the behavioral interventions decrease the risk of UTI
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Postcoital voiding - increased intake of cranberry juice
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
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

33. hypertriglyceridemia in HIV
Blastomycosis
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Aortic valve; endocardiits of AR p/w AV block and LBBB
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

34. 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.
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Immune mediated; circulating IgG and IgM to penicillin derivatives
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

35. what parameters increases risk of neurosyphilis in HIV patient
Pt who have been treated before for latent TB
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.
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

36. what would be viral load after 2-4m of HAART?
Within 6 months viral load will be <50
Upper lobes; any fibrosis in this area suggestive of latent TB
Others lesions are ring enhancing and have mass effect while PML don't
<500 copies/ml

37. foot infections in DM
If a sample is ELISA positive - it is tested fro western blot for confirmation
Pt who have been treated before for latent TB
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Reddish orange discoloration of urine - feces - sweat - tears - sputum

38. How to tx pcp?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Bronchoalveolar washing and transbronchial biopsy
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

39. What are the subjective /objective measure of encephalopathy?
High risk 19-64; 1-2 dose - above 65; one dose
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
HIV viral load
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

40. how HAART therapy affects HIV viral loads?
Within 6 months viral load will be <50
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

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

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42. how im is transmitted?
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Oropharyngeal secretions; hence named as kissing disease
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Immune mediated; circulating IgG and IgM to penicillin derivatives

43. what if monospot test is neg in IM?
Do EBV antibody test
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
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

44. antibiotic with good prostate penetration?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
<500 copies/ml
Blastomycosis
Others lesions are ring enhancing and have mass effect while PML don't

45. How to tx pseudomonas?
Clostridium perfringens after penetrative injuries/wounds
Bronchoalveolar washing and transbronchial biopsy
Do EBV antibody test
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

46. What is the mch of ampicillin induced rash in IM
Immune mediated; circulating IgG and IgM to penicillin derivatives
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.
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

47. What is lag time to develop lyme arthritis after exposure to vector
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
ELISA; initial visit - 6 - 12 and 24 weeks;
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Reddish orange discoloration of urine - feces - sweat - tears - sputum

48. what would be viral load after 4 weeks
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Mainly clinical - epidemiological and seasonal setting
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
<5000 copies/ml

49. When to give abx to prevent recurrent uti
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
If a sample is ELISA positive - it is tested fro western blot for confirmation
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

50. What is difference between uti relapse versus recurrence?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Do EBV antibody test
Pregnacy - urologic procedure - hip arthoplastu
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