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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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1. How to differentiate gonococcal and nongonoccal urethritis?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
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

2. What is the criteria for Spontaneous bact peritonitis
Pegylated interferon and lamivudine
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.
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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

3. How to differentiate different types of necrotizing fascitis?
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
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
Monospot test which screen heteropile ab that agglutinate horse rbc
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

4. How to give postexposure prophylaxis for HIV
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Pregnacy - urologic procedure - hip arthoplastu
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

5. How to dx IM?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Vaccine titer >10mU/ml
Cd4 count
Monospot test which screen heteropile ab that agglutinate horse rbc

6. When to tx asymptomatic bacteriurea >100 -000?
Aortic valve; endocardiits of AR p/w AV block and LBBB
Pregnacy - urologic procedure - hip arthoplastu
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
ELISA and western blot of synovial fluid.

7. How long we tx chronic prostatis?
Within 6 months viral load will be <50
6-12 weeks
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

8. How to confirm dx if pcp?
Similar pathophysiology as ITP - tx zidovudine
HBIG hep B immunoglobulin
Others lesions are ring enhancing and have mass effect while PML don't
Bronchoalveolar washing and transbronchial biopsy

9. How long abx is given in pseudomonas infection?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
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
Acyclovir
Pt who have been treated before for latent TB

10. What is characteristic for dx of rocky mountain spotted fever?
Postcoital voiding - increased intake of cranberry juice
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

11. What is tx for herpes zoster
ELISA and western blot of synovial fluid.
Acyclovir
Cd4 count
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

12. after recent exposure - negative ELISA - How to confirm?
HBIG hep B immunoglobulin
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
When cd4 count falls below 200. 2p in pcp =200
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

13. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Pregnacy - urologic procedure - hip arthoplastu
Oropharyngeal secretions; hence named as kissing disease
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

14. INH
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >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.
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

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

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16. What are indicators for progression of HIV
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.
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Viral load and CD4 count

17. low grade fever - maculopapular rash - lymphadenopathy
Every 3-4 hours to determine appropritate time to start HAART
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
AA gradient >35 or Po2 <70
Non pregnant premanopausal - elderly - dm - sci - chronic foley

18. What is the indication of corticosteroid in pcp infection?
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
AA gradient >35 or Po2 <70
Clostridium perfringens after penetrative injuries/wounds

19. clinical manifestation of mucomycosis
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
High risk 19-64; 1-2 dose - above 65; one dose

20. wisconsin - missisipi - ohio
Blastomycosis
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Td every 10 years - tdap once before 65 and after 65

21. when not to give INH therapy if ppd positive and patient asyptomatic
Pt who have been treated before for latent TB
Clostridium perfringens after penetrative injuries/wounds
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

22. when we see echym gangrenosum?
Within 6 months viral load will be <50
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Voriconazol. mycetoma-surgical removal

23. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
HBIG hep B immunoglobulin
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

24. How to dx cryptococal meninggits
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Blastomycosis
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
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

25. What is the prognosis of lyme arthritis?
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
HIV viral load
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

26. How to dx adequate response to HBV vaccine
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Vaccine titer >10mU/ml
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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

27. How to tx TSS?
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
Others lesions are ring enhancing and have mass effect while PML don't
Mainly clinical - epidemiological and seasonal setting
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

28. acute onset +rusty sputum
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Monospot test which screen heteropile ab that agglutinate horse rbc

29. acute febrile reaction develops after starting penicilin tx to syphilis patient
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
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.

30. What is fatal consequence of RMSF?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

31. rifampin
PML; focal neurological deficit like MM; no specific tx; regress with HAART
ELISA; initial visit - 6 - 12 and 24 weeks;
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

32. What is the pathophysiology of Meningococcal meningitis?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Cd4 count

33. How often HIV postiive patients CD4 count needs to be evaluated?
Every 3-4 hours to determine appropritate time to start HAART
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
If a sample is ELISA positive - it is tested fro western blot for confirmation
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

34. antibiotic with good prostate penetration?
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.
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
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

35. When not to tx asymptomatic bacteriura?
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Bronchoalveolar washing and transbronchial biopsy
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Clostridium perfringens after penetrative injuries/wounds

36. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Bronchoalveolar washing and transbronchial biopsy
<5000 copies/ml
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

37. damae that is about to occur?
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
HIV viral load
Similar pathophysiology as ITP - tx zidovudine
Blastomycosis

38. What are the subjective /objective measure of encephalopathy?
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
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

39. where TB normally affects
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
Similar pathophysiology as ITP - tx zidovudine
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
Upper lobes; any fibrosis in this area suggestive of latent TB

40. when western blot is done for HIV testing
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
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
If a sample is ELISA positive - it is tested fro western blot for confirmation

41. causative organisms of uti
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
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
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

42. How to dx lyme arthritis?
ELISA and western blot of synovial fluid.
ELISA; initial visit - 6 - 12 and 24 weeks;
<500 copies/ml
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

43. dame that has already occurred
Cd4 count
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

44. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
AA gradient >35 or Po2 <70
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
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
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

45. hypertension in children
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
Every 3-4 hours to determine appropritate time to start HAART
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

46. thrombocytopenia in HIV
Upper lobes; any fibrosis in this area suggestive of latent TB
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
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

47. INH
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
When cd4 count falls below 200. 2p in pcp =200
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

48. what if monospot test is neg in IM?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Do EBV antibody test
6-12 weeks
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

49. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Rifampin600mg q12. or cipro
Voriconazol. mycetoma-surgical removal
Vaccine titer >10mU/ml
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

50. What is the mch of ampicillin induced rash in IM
Immune mediated; circulating IgG and IgM to penicillin derivatives
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
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w