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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. when we see echym gangrenosum?
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
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Pregnacy - urologic procedure - hip arthoplastu

2. where TB normally affects
Upper lobes; any fibrosis in this area suggestive of latent TB
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Cd4 count

3. pneumococcal vaccine indication?
High risk 19-64; 1-2 dose - above 65; one dose
Clostridium perfringens after penetrative injuries/wounds
Do EBV antibody test
Reddish orange discoloration of urine - feces - sweat - tears - sputum

4. can HIV transmitted through human bite?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
ELISA and western blot of synovial fluid.
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

5. What is the pathophysiology of Meningococcal meningitis?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Vaccine titer >10mU/ml
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

6. How to dx IM?
Monospot test which screen heteropile ab that agglutinate horse rbc
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Clostridium perfringens after penetrative injuries/wounds
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

7. When not to tx asymptomatic bacteriura?
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Non pregnant premanopausal - elderly - dm - sci - chronic foley
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
Need lumbar puncture to relieve pressure; they have high opening pressure >350

8. How to tx chronic hep B
AA gradient >35 or Po2 <70
Pegylated interferon and lamivudine
If a sample is ELISA positive - it is tested fro western blot for confirmation
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

9. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Mainly clinical - epidemiological and seasonal setting
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Similar pathophysiology as ITP - tx zidovudine

10. How to tx TSS?
ELISA and western blot of synovial fluid.
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Viral load and CD4 count

11. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

12. aspergillosis
AA gradient >35 or Po2 <70
Voriconazol. mycetoma-surgical removal
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

13. thrombocytopenia in HIV
Similar pathophysiology as ITP - tx zidovudine
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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.

14. rifampin
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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
Mainly clinical - epidemiological and seasonal setting

15. How to differentiate gonococcal and nongonoccal urethritis?
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
Ampicillin-sublactam; most bites contain eikenella
Non pregnant premanopausal - elderly - dm - sci - chronic foley
When cd4 count falls below 200. 2p in pcp =200

16. what parameters increases risk of neurosyphilis in HIV patient
Ampicillin-sublactam; most bites contain eikenella
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
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.

17. what would be viral load after 4 weeks
<5000 copies/ml
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
HIV viral load
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

18. How to dx?
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
HIV viral load
Voriconazol. mycetoma-surgical removal
Mainly clinical - epidemiological and seasonal setting

19. How to dx bacterial meningitis from CSF study?

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20. wisconsin - missisipi - ohio
Blastomycosis
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Td every 10 years - tdap once before 65 and after 65
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

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

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22. What is the criteria for Spontaneous bact peritonitis
When cd4 count falls below 200. 2p in pcp =200
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Postcoital voiding - increased intake of cranberry juice

23. When to tx influenza with antiviral therapy?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
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

24. What are the subjective /objective measure of encephalopathy?
Oropharyngeal secretions; hence named as kissing disease
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
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.
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

25. INH
Rifampin600mg q12. or cipro
<500 copies/ml
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

26. what if monospot test is neg in IM?
Do EBV antibody test
If a sample is ELISA positive - it is tested fro western blot for confirmation
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Within 6 months viral load will be <50

27. What is difference between uti relapse versus recurrence?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
ELISA and western blot of synovial fluid.
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
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

28. 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
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Upper lobes; any fibrosis in this area suggestive of latent TB

29. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
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
HBIG hep B immunoglobulin
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Within 6 months viral load will be <50

30. How long abx is given in pseudomonas infection?
Aortic valve; endocardiits of AR p/w AV block and LBBB
PML; focal neurological deficit like MM; no specific tx; regress with HAART
ELISA and western blot of synovial fluid.
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

31. systolic HTN in elderly
Monospot test which screen heteropile ab that agglutinate horse rbc
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Td every 10 years - tdap once before 65 and after 65
Acyclovir

32. What is tetanus - diptheria - pertusis recommendation?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Td every 10 years - tdap once before 65 and after 65

33. How to tx pseudomonas?
Viral load and CD4 count
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Postcoital voiding - increased intake of cranberry juice

34. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
Upper lobes; any fibrosis in this area suggestive of latent TB
Oropharyngeal secretions; hence named as kissing disease
6-12 weeks
Need lumbar puncture to relieve pressure; they have high opening pressure >350

35. clinical manifestation of mucomycosis
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
If a sample is ELISA positive - it is tested fro western blot for confirmation
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

36. What is the Tx of STD uretheritis?
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
Pt who have been treated before for latent TB
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

37. What is used for prophylaxis against meningo..meningitis?
6-12 weeks
Rifampin600mg q12. or cipro
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
High risk 19-64; 1-2 dose - above 65; one dose

38. infiltrate in upper lobe of lung?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Either TB or aspergillosis
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Reddish orange discoloration of urine - feces - sweat - tears - sputum

39. hypertriglyceridemia in HIV
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
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

40. What is characteristic for dx of rocky mountain spotted fever?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
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. How to dx progressive multifocal leukoencephalopathy
High risk 19-64; 1-2 dose - above 65; one dose
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
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

42. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
<5000 copies/ml
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
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

43. hypertension in children
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
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
Voriconazol. mycetoma-surgical removal

44. How to dx adequate response to HBV vaccine
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
ELISA; initial visit - 6 - 12 and 24 weeks;
Vaccine titer >10mU/ml
Postcoital voiding - increased intake of cranberry juice

45. after recent exposure - negative ELISA - How to confirm?
Rifampin600mg q12. or cipro
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Ampicillin-sublactam; most bites contain eikenella
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

46. 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
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
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
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

47. acute febrile reaction develops after starting penicilin tx to syphilis patient
HBIG hep B immunoglobulin
Every 3-4 hours to determine appropritate time to start HAART
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Blastomycosis

48. acute onset +rusty sputum
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

49. how CMV presents in immunocompromised patients
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Monospot test which screen heteropile ab that agglutinate horse rbc
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

50. worsening of TB after starting HAART in HIV
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months