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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. thrombocytopenia in HIV
Similar pathophysiology as ITP - tx zidovudine
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
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
HIV viral load

2. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
HBIG hep B immunoglobulin
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Others lesions are ring enhancing and have mass effect while PML don't
Viral load and CD4 count

3. 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.
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
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

4. What are the subjective /objective measure of encephalopathy?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
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
<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

5. How to confirm chlamydia infection?
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Pt who have been treated before for latent TB
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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

6. How to dx lyme arthritis?
ELISA and western blot of synovial fluid.
Either TB or aspergillosis
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

7. How to dx progressive multifocal leukoencephalopathy
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

8. How to confirm dx if pcp?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Blastomycosis
Bronchoalveolar washing and transbronchial biopsy
Viral load and CD4 count

9. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Upper lobes; any fibrosis in this area suggestive of latent TB
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Others lesions are ring enhancing and have mass effect while PML don't

10. What is tx for herpes zoster
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Acyclovir

11. acute febrile reaction develops after starting penicilin tx to syphilis patient
Mainly clinical - epidemiological and seasonal setting
Rifampin600mg q12. or cipro
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

12. worsening of TB after starting HAART in HIV
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Rifampin600mg q12. or cipro
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

13. What is used for prophylaxis against meningo..meningitis?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Rifampin600mg q12. or cipro
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

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

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15. how im is transmitted?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
HBIG hep B immunoglobulin
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Oropharyngeal secretions; hence named as kissing disease

16. How to dx?
Mainly clinical - epidemiological and seasonal setting
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Others lesions are ring enhancing and have mass effect while PML don't
Immune mediated; circulating IgG and IgM to penicillin derivatives

17. wisconsin - missisipi - ohio
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Blastomycosis
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

18. HIV patient having fat deposition on back of neck and abdomen - like cushing
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.
<500 copies/ml
If a sample is ELISA positive - it is tested fro western blot for confirmation
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

19. What is the mch of ampicillin induced rash in IM
Immune mediated; circulating IgG and IgM to penicillin derivatives
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Reddish orange discoloration of urine - feces - sweat - tears - sputum
AA gradient >35 or Po2 <70

20. INH
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Similar pathophysiology as ITP - tx zidovudine

21. What is the pathophysiology of Meningococcal meningitis?
Blastomycosis
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
6-12 weeks
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

22. rifampin
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.
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Bronchoalveolar washing and transbronchial biopsy
Reddish orange discoloration of urine - feces - sweat - tears - sputum

23. after recent exposure - negative ELISA - How to confirm?
Others lesions are ring enhancing and have mass effect while PML don't
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
AA gradient >35 or Po2 <70

24. What is lag time to develop lyme arthritis after exposure to vector
PML; focal neurological deficit like MM; no specific tx; regress with HAART
HIV viral load
Oropharyngeal secretions; hence named as kissing disease
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

25. How often viral load is monitored after HAART?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
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
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

26. aspergillosis
Voriconazol. mycetoma-surgical removal
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

27. How often HIV postiive patients CD4 count needs to be evaluated?
Blastomycosis
Immune mediated; circulating IgG and IgM to penicillin derivatives
Every 3-4 hours to determine appropritate time to start HAART
HIV viral load

28. How to tx IM?
ELISA and western blot of synovial fluid.
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
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

29. what if monospot test is neg in IM?
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Do EBV antibody test
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

30. How to give postexposure prophylaxis for HIV
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
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
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

31. gas gangrene
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) -
Clostridium perfringens after penetrative injuries/wounds
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

32. pathophysiology of toxic shock syndrom?
Voriconazol. mycetoma-surgical removal
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

33. How to dx bacterial meningitis from CSF study?

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34. When not to tx asymptomatic bacteriura?
Others lesions are ring enhancing and have mass effect while PML don't
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
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
Non pregnant premanopausal - elderly - dm - sci - chronic foley

35. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Cd4 count
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Rifampin600mg q12. or cipro

36. When to tx asymptomatic bacteriurea >100 -000?
Pregnacy - urologic procedure - hip arthoplastu
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Pegylated interferon and lamivudine
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

37. What are the behavioral interventions decrease the risk of UTI
Postcoital voiding - increased intake of cranberry juice
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

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

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39. How to tx TSS?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Vaccine titer >10mU/ml
Viral load and CD4 count
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

40. What is the Tx of cryptococcal meninngitis
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
HIV viral load

41. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Cd4 count

42. When to give abx to prevent recurrent uti
Oropharyngeal secretions; hence named as kissing disease
Td every 10 years - tdap once before 65 and after 65
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
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

43. INH
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Within 6 months viral load will be <50
When cd4 count falls below 200. 2p in pcp =200
Mainly clinical - epidemiological and seasonal setting

44. infiltrate in upper lobe of lung?
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Pt who have been treated before for latent TB
Either TB or aspergillosis

45. damae that is about to occur?
HIV viral load
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Ampicillin-sublactam; most bites contain eikenella
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

46. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
PML; focal neurological deficit like MM; no specific tx; regress with HAART

47. When to give prophylaxis against MAC
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

48. hypertension in children
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
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

49. How to dx IM?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
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
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Mainly clinical - epidemiological and seasonal setting

50. 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
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
ELISA; initial visit - 6 - 12 and 24 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