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USMLE Step3 Infectious Disease

Subjects : health-sciences, usmle-step-3

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Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
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1. how CMV presents in immunocompromised patients
Vaccine titer >10mU/ml
Oropharyngeal secretions; hence named as kissing disease
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
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

2. How to dx IM?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Non pregnant premanopausal - elderly - dm - sci - chronic foley
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
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

3. What are the subjective /objective measure of encephalopathy?
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
ELISA and western blot of synovial fluid.
Every 3-4 hours to determine appropritate time to start HAART

4. where TB normally affects
Reddish orange discoloration of urine - feces - sweat - tears - sputum
AA gradient >35 or Po2 <70
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Upper lobes; any fibrosis in this area suggestive of latent TB

5. 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
HIV viral load
Acyclovir
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

6. after exposure of HIV when antibody testing is performed?
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)
ELISA; initial visit - 6 - 12 and 24 weeks;
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

7. damae that is about to occur?
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
HIV viral load
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

8. antibiotic with good prostate penetration?
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
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
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
Ampicillin-sublactam; most bites contain eikenella

9. What is the Tx of STD uretheritis?
Mainly clinical - epidemiological and seasonal setting
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
Monospot test which screen heteropile ab that agglutinate horse rbc
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

10. what parameters increases risk of neurosyphilis in HIV patient
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Mainly clinical - epidemiological and seasonal setting
Ampicillin-sublactam; most bites contain eikenella
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.

11. What is the classic signs of nec fasc?
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
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Pregnacy - urologic procedure - hip arthoplastu

12. pathophysiology of toxic shock syndrom?
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Every 3-4 hours to determine appropritate time to start HAART
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

13. can HIV transmitted through human bite?
<5000 copies/ml
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

14. What is the criteria for Spontaneous bact peritonitis
Do EBV antibody test
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

15. What are indicators for progression of 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
Viral load and CD4 count
Voriconazol. mycetoma-surgical removal
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

16. What is the mch of ampicillin induced rash in IM
Bronchoalveolar washing and transbronchial biopsy
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Immune mediated; circulating IgG and IgM to penicillin derivatives
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

17. What is the pathophysiology of Meningococcal meningitis?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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

18. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
If a sample is ELISA positive - it is tested fro western blot for confirmation
Similar pathophysiology as ITP - tx zidovudine
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Non pregnant premanopausal - elderly - dm - sci - chronic foley

19. rifampin
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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
Aortic valve; endocardiits of AR p/w AV block and LBBB

20. How to dx cryptococal meninggits
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
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 to tx pseudomonas?
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
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
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

22. what if monospot test is neg in IM?
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
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Do EBV antibody test
High risk 19-64; 1-2 dose - above 65; one dose

23. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
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.
Similar pathophysiology as ITP - tx zidovudine
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

24. When to tx asymptomatic bacteriurea >100 -000?
Monospot test which screen heteropile ab that agglutinate horse rbc
Pregnacy - urologic procedure - hip arthoplastu
6-12 weeks
AA gradient >35 or Po2 <70

25. When not to tx asymptomatic bacteriura?
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
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Non pregnant premanopausal - elderly - dm - sci - chronic foley
If a sample is ELISA positive - it is tested fro western blot for confirmation

26. How to confirm dx if pcp?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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
Bronchoalveolar washing and transbronchial biopsy
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

27. acute febrile reaction develops after starting penicilin tx to syphilis patient
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Bronchoalveolar washing and transbronchial biopsy
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

28. How to dx bacterial meningitis from CSF study?

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29. How often HIV postiive patients CD4 count needs to be evaluated?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Every 3-4 hours to determine appropritate time to start HAART
Do EBV antibody test

30. how im is transmitted?
Clostridium perfringens after penetrative injuries/wounds
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
ELISA; initial visit - 6 - 12 and 24 weeks;
Oropharyngeal secretions; hence named as kissing disease

31. causative organisms of uti
High risk 19-64; 1-2 dose - above 65; one dose
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
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

32. aspergillosis
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Mainly clinical - epidemiological and seasonal setting
Voriconazol. mycetoma-surgical removal
Within 6 months viral load will be <50

33. systolic HTN in elderly
Ampicillin-sublactam; most bites contain eikenella
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Every 3-4 hours to determine appropritate time to start HAART

34. after recent exposure - negative ELISA - How to confirm?
ELISA; initial visit - 6 - 12 and 24 weeks;
High risk 19-64; 1-2 dose - above 65; one dose
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
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.

35. How to dx?
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
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
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

36. How to differentiate different types of necrotizing fascitis?
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Clostridium perfringens after penetrative injuries/wounds
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 viral load

37. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Non pregnant premanopausal - elderly - dm - sci - chronic foley
HBIG hep B immunoglobulin

38. clinical manifestation of mucomycosis
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
ELISA and western blot of synovial fluid.
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Reddish orange discoloration of urine - feces - sweat - tears - sputum

39. How to tx IM?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Clostridium perfringens after penetrative injuries/wounds

40. drugs work well on hypertriglyceridia?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

41. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Cd4 count
Monospot test which screen heteropile ab that agglutinate horse rbc

42. 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
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Upper lobes; any fibrosis in this area suggestive of latent TB

43. How to tx chronic hep B
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Pegylated interferon and lamivudine
ELISA; initial visit - 6 - 12 and 24 weeks;
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

44. reddish colored papules with central umbilication in HIV or immunocompromised patient
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
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
Ampicillin-sublactam; most bites contain eikenella
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

45. What is tetanus - diptheria - pertusis recommendation?
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Td every 10 years - tdap once before 65 and after 65
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

46. what would be viral load after 2-4m of HAART?
Within 6 months viral load will be <50
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
<500 copies/ml
Pegylated interferon and lamivudine

47. What are the behavioral interventions decrease the risk of UTI
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Postcoital voiding - increased intake of cranberry juice

48. How to dx IM?
Monospot test which screen heteropile ab that agglutinate horse rbc
Acyclovir
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

49. What is the indication of corticosteroid in pcp infection?
6-12 weeks
AA gradient >35 or Po2 <70
ELISA; initial visit - 6 - 12 and 24 weeks;
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

50. 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.
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle