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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. when not to give INH therapy if ppd positive and patient asyptomatic
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
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
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Pt who have been treated before for latent TB

2. pneumococcal vaccine indication?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
High risk 19-64; 1-2 dose - above 65; one dose

3. after exposure of HIV when antibody testing is performed?
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; initial visit - 6 - 12 and 24 weeks;
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
HBIG hep B immunoglobulin

4. How often viral load is monitored after HAART?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Within 6 months viral load will be <50
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Need lumbar puncture to relieve pressure; they have high opening pressure >350

5. when HIV patient develop pcp?
When cd4 count falls below 200. 2p in pcp =200
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
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
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

6. How often HIV postiive patients CD4 count needs to be evaluated?
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
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
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

7. What is tx for herpes zoster
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Acyclovir
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

8. When to give abx to prevent recurrent uti
Postcoital voiding - increased intake of cranberry juice
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
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
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

9. What is the criteria for Spontaneous bact peritonitis
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Oropharyngeal secretions; hence named as kissing disease
6-12 weeks
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

10. How to give postexposure prophylaxis for HIV
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Viral load and CD4 count
Postcoital voiding - increased intake of cranberry juice
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

11. What are the behavioral interventions decrease the risk of UTI
Postcoital voiding - increased intake of cranberry juice
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
6-12 weeks
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

12. what would be viral load after 4 weeks
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
<5000 copies/ml
Ampicillin-sublactam; most bites contain eikenella
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

13. foot infections in DM
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
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
<5000 copies/ml

14. What is the mch of ampicillin induced rash in IM
Immune mediated; circulating IgG and IgM to penicillin derivatives
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
ELISA and western blot of synovial fluid.

15. What is the pathophysiology of Meningococcal meningitis?
Others lesions are ring enhancing and have mass effect while PML don't
Every 3-4 hours to determine appropritate time to start HAART
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
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

16. damae that is about to occur?
Voriconazol. mycetoma-surgical removal
Bronchoalveolar washing and transbronchial biopsy
HIV viral load
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

17. hypertension in children
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

18. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Pregnacy - urologic procedure - hip arthoplastu
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
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

19. How to dx IM?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Monospot test which screen heteropile ab that agglutinate horse rbc
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

20. clinical manifestation of mucomycosis
Viral load and CD4 count
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
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
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

21. how HAART therapy affects HIV viral loads?
Within 6 months viral load will be <50
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
When cd4 count falls below 200. 2p in pcp =200
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

22. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
HIV viral load

23. wisconsin - missisipi - ohio
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
ELISA; initial visit - 6 - 12 and 24 weeks;
Blastomycosis
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

24. antibiotic with good prostate penetration?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

25. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
6-12 weeks
Similar pathophysiology as ITP - tx zidovudine
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
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

26. how im is transmitted?
Oropharyngeal secretions; hence named as kissing disease
Bronchoalveolar washing and transbronchial biopsy
Within 6 months viral load will be <50
Clostridium perfringens after penetrative injuries/wounds

27. where TB normally affects
HIV viral load
Blastomycosis
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Upper lobes; any fibrosis in this area suggestive of latent TB

28. How long we tx chronic prostatis?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
6-12 weeks

29. How to dx lyme arthritis?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
<500 copies/ml
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
ELISA and western blot of synovial fluid.

30. How to confirm dx if pcp?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Bronchoalveolar washing and transbronchial biopsy
Aortic valve; endocardiits of AR p/w AV block and LBBB

31. How to tx pcp?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Mainly clinical - epidemiological and seasonal setting
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

32. What is characteristic for dx of rocky mountain spotted fever?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Ampicillin-sublactam; most bites contain eikenella
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

33. hypertriglyceridemia in HIV
Td every 10 years - tdap once before 65 and after 65
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Pegylated interferon and lamivudine
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

34. after recent exposure - negative ELISA - How to confirm?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
High risk 19-64; 1-2 dose - above 65; one dose

35. When to tx influenza with antiviral therapy?
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Voriconazol. mycetoma-surgical removal
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
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

36. Tx of choice for human bites
Ampicillin-sublactam; most bites contain eikenella
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Td every 10 years - tdap once before 65 and after 65
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

37. causative organisms of uti
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Rifampin600mg q12. or cipro

38. When to tx asymptomatic bacteriurea >100 -000?
Blastomycosis
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Pregnacy - urologic procedure - hip arthoplastu
Non pregnant premanopausal - elderly - dm - sci - chronic foley

39. How to confirm chlamydia infection?
Oropharyngeal secretions; hence named as kissing disease
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

40. How to dx cryptococal meninggits
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
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
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

41. reddish colored papules with central umbilication in HIV or immunocompromised patient
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
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Aortic valve; endocardiits of AR p/w AV block and LBBB
AA gradient >35 or Po2 <70

42. When to give prophylaxis against MAC
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Acyclovir
Reddish orange discoloration of urine - feces - sweat - tears - sputum

43. what if monospot test is neg in IM?
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Do EBV antibody test

44. what would be viral load after 2-4m of HAART?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Monospot test which screen heteropile ab that agglutinate horse rbc
<500 copies/ml
Mainly clinical - epidemiological and seasonal setting

45. when we see echym gangrenosum?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit 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
Td every 10 years - tdap once before 65 and after 65

46. INH
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
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

47. How to differentiate gonococcal and nongonoccal urethritis?
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
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
Immune mediated; circulating IgG and IgM to penicillin derivatives

48. How long abx is given in pseudomonas infection?
AA gradient >35 or Po2 <70
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Cd4 count
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

49. What are indicators for progression of HIV
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Viral load and CD4 count
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Postcoital voiding - increased intake of cranberry juice

50. dame that has already occurred
Do EBV antibody test
Monospot test which screen heteropile ab that agglutinate horse rbc
<500 copies/ml
Cd4 count