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USMLE Step3 Infectious Disease

Subjects : health-sciences, usmle-step-3

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1. How to tx TSS?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
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
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Monospot test which screen heteropile ab that agglutinate horse rbc

2. reddish colored papules with central umbilication in HIV or immunocompromised patient
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.
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
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
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. systolic HTN in elderly
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
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
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

4. When to give abx to prevent recurrent uti
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
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
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

5. When not to tx asymptomatic bacteriura?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Postcoital voiding - increased intake of cranberry juice
Cd4 count

6. What is the indication of corticosteroid in pcp infection?
AA gradient >35 or Po2 <70
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
Td every 10 years - tdap once before 65 and after 65
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

7. How to differentiate different types of necrotizing fascitis?
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
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
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

8. What is the mch of ampicillin induced rash in IM
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Postcoital voiding - increased intake of cranberry juice
Voriconazol. mycetoma-surgical removal
Immune mediated; circulating IgG and IgM to penicillin derivatives

9. How to dx IM?
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
Rifampin600mg q12. or cipro
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
<500 copies/ml

10. How to dx IM?
Upper lobes; any fibrosis in this area suggestive of latent TB
Monospot test which screen heteropile ab that agglutinate horse rbc
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Acyclovir

11. what would be viral load after 4 weeks
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
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
<5000 copies/ml
PML; focal neurological deficit like MM; no specific tx; regress with HAART

12. Tx of choice for human bites
Pt who have been treated before for latent TB
Ampicillin-sublactam; most bites contain eikenella
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

13. acute febrile reaction develops after starting penicilin tx to syphilis patient
Aortic valve; endocardiits of AR p/w AV block and LBBB
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
<500 copies/ml
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

14. What is used for prophylaxis against meningo..meningitis?
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Rifampin600mg q12. or cipro
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

15. What is difference between uti relapse versus recurrence?
Blastomycosis
Every 3-4 hours to determine appropritate time to start HAART
When cd4 count falls below 200. 2p in pcp =200
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

16. acute onset +rusty sputum
ELISA; initial visit - 6 - 12 and 24 weeks;
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

17. causative organisms of uti
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Every 3-4 hours to determine appropritate time to start HAART
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

18. How to dx?
<500 copies/ml
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
Mainly clinical - epidemiological and seasonal setting
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

19. aspergillosis
<5000 copies/ml
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Voriconazol. mycetoma-surgical removal
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

20. What are the subjective /objective measure of encephalopathy?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

21. what parameters increases risk of neurosyphilis in HIV patient
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
PML; focal neurological deficit like MM; no specific tx; regress with HAART
AA gradient >35 or Po2 <70
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.

22. when HIV patient develop pcp?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Pregnacy - urologic procedure - hip arthoplastu
When cd4 count falls below 200. 2p in pcp =200
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

23. How to tx chronic hep B
ELISA and western blot of synovial fluid.
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Pegylated interferon and lamivudine

24. thrombocytopenia in HIV
Similar pathophysiology as ITP - tx zidovudine
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
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

25. 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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

26. What is tetanus - diptheria - pertusis recommendation?
PML; focal neurological deficit like MM; no specific tx; regress with 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
Either TB or aspergillosis
Td every 10 years - tdap once before 65 and after 65

27. What is fatal consequence of RMSF?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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
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
High risk 19-64; 1-2 dose - above 65; one dose

28. wisconsin - missisipi - ohio
Blastomycosis
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.
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

29. INH
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
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Rifampin600mg q12. or cipro

30. How to dx bacterial meningitis from CSF study?

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31. How to confirm chlamydia infection?
Immune mediated; circulating IgG and IgM to penicillin derivatives
Td every 10 years - tdap once before 65 and after 65
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

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

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33. how HAART therapy affects HIV viral loads?
Acyclovir
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Within 6 months viral load will be <50

34. worsening of TB after starting HAART in HIV
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

35. dame that has already occurred
Ampicillin-sublactam; most bites contain eikenella
Others lesions are ring enhancing and have mass effect while PML don't
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
Cd4 count

36. What is tx for herpes zoster
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.
When cd4 count falls below 200. 2p in pcp =200
Immune mediated; circulating IgG and IgM to penicillin derivatives
Acyclovir

37. 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
Aortic valve; endocardiits of AR p/w AV block and LBBB
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Every 3-4 hours to determine appropritate time to start HAART

38. How to dx lyme arthritis?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
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
ELISA and western blot of synovial fluid.
Need lumbar puncture to relieve pressure; they have high opening pressure >350

39. after exposure of HIV when antibody testing is performed?
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.
ELISA; initial visit - 6 - 12 and 24 weeks;
Within 6 months viral load will be <50
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

40. What is the prognosis of lyme arthritis?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Vaccine titer >10mU/ml
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Ampicillin-sublactam; most bites contain eikenella

41. damae that is about to occur?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Cd4 count
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
HIV viral load

42. How to dx progressive multifocal leukoencephalopathy
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Do EBV antibody test
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

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

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44. 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
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

45. How to confirm dx if pcp?
Bronchoalveolar washing and transbronchial biopsy
ELISA; initial visit - 6 - 12 and 24 weeks;
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Need lumbar puncture to relieve pressure; they have high opening pressure >350

46. antibiotic with good prostate penetration?
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Blastomycosis
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Immune mediated; circulating IgG and IgM to penicillin derivatives

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
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
Similar pathophysiology as ITP - tx zidovudine

48. How long abx is given in pseudomonas infection?
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
Clostridium perfringens after penetrative injuries/wounds
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

49. what if monospot test is neg in IM?
Do EBV antibody test
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
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

50. rifampin
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Do EBV antibody test
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

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USMLE Step3 Infectious Disease

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