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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 tx IM?
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
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
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

2. How to confirm chlamydia infection?
Pegylated interferon and lamivudine
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Pt who have been treated before for latent TB
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

3. where TB normally affects
Vaccine titer >10mU/ml
Upper lobes; any fibrosis in this area suggestive of latent TB
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Need lumbar puncture to relieve pressure; they have high opening pressure >350

4. INH
Within 6 months viral load will be <50
<5000 copies/ml
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Ampicillin-sublactam; most bites contain eikenella

5. What is the Tx of STD uretheritis?
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
Acyclovir
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
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

6. 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
ELISA; initial visit - 6 - 12 and 24 weeks;
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

7. How to tx pseudomonas?
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
Mainly clinical - epidemiological and seasonal setting
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

8. How to confirm dx if pcp?
Bronchoalveolar washing and transbronchial biopsy
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
AA gradient >35 or Po2 <70

9. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
HBIG hep B immunoglobulin
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Either TB or aspergillosis
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

10. after recent exposure - negative ELISA - How to confirm?
Blastomycosis
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

11. How to give postexposure prophylaxis for HIV
Cd4 count
HBIG hep B immunoglobulin
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

12. What is the pathophysiology of Meningococcal meningitis?
Within 6 months viral load will be <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
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

13. What are the subjective /objective measure of encephalopathy?
ELISA and western blot of synovial fluid.
6-12 weeks
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Non pregnant premanopausal - elderly - dm - sci - chronic foley

14. What is fatal consequence of RMSF?
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
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.
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

15. When to give abx to prevent recurrent uti
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
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

16. chshould we tx IM with abx (ampicilin) if throat cx is positive?
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
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Immune mediated; circulating IgG and IgM to penicillin derivatives

17. infiltrate in upper lobe of lung?
HBIG hep B immunoglobulin
Either TB or aspergillosis
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

18. how im is transmitted?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Oropharyngeal secretions; hence named as kissing disease
Blastomycosis
Viral load and CD4 count

19. How to dx adequate response to HBV vaccine
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Monospot test which screen heteropile ab that agglutinate horse rbc
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Vaccine titer >10mU/ml

20. worsening of TB after starting HAART in HIV
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Oropharyngeal secretions; hence named as kissing disease
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

21. 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
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
ELISA and western blot of synovial fluid.
Ampicillin-sublactam; most bites contain eikenella

22. What is the prognosis of lyme arthritis?
When cd4 count falls below 200. 2p in pcp =200
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Upper lobes; any fibrosis in this area suggestive of latent TB
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

23. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Upper lobes; any fibrosis in this area suggestive of latent TB
Ampicillin-sublactam; most bites contain eikenella

24. when not to give INH therapy if ppd positive and patient asyptomatic
Pt who have been treated before for latent TB
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
ELISA and western blot of synovial fluid.
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

25. systolic HTN in elderly
<5000 copies/ml
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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

26. can HIV transmitted through human bite?
Upper lobes; any fibrosis in this area suggestive of latent TB
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

27. How long we tx chronic prostatis?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
6-12 weeks
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

28. How to dx cryptococal meninggits
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
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
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

29. when HIV patient develop pcp?
Mainly clinical - epidemiological and seasonal setting
Either TB or aspergillosis
Acyclovir
When cd4 count falls below 200. 2p in pcp =200

30. What is tetanus - diptheria - pertusis recommendation?
ELISA and western blot of synovial fluid.
Td every 10 years - tdap once before 65 and after 65
Pt who have been treated before for latent TB
Rifampin600mg q12. or cipro

31. What is difference between uti relapse versus recurrence?
Clostridium perfringens after penetrative injuries/wounds
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
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

32. What is the Tx of cryptococcal meninngitis
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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

33. how HAART therapy affects HIV viral loads?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Within 6 months viral load will be <50
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
HBIG hep B immunoglobulin

34. When not to tx asymptomatic bacteriura?
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Postcoital voiding - increased intake of cranberry juice
If a sample is ELISA positive - it is tested fro western blot for confirmation
Non pregnant premanopausal - elderly - dm - sci - chronic foley

35. acute onset +rusty sputum
High risk 19-64; 1-2 dose - above 65; one dose
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Monospot test which screen heteropile ab that agglutinate horse rbc
Pt who have been treated before for latent TB

36. What is used for prophylaxis against meningo..meningitis?
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Rifampin600mg q12. or cipro
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
ELISA and western blot of synovial fluid.

37. reddish colored papules with central umbilication in HIV or immunocompromised patient
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
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
Reddish orange discoloration of urine - feces - sweat - tears - sputum

38. low grade fever - maculopapular rash - lymphadenopathy
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Aortic valve; endocardiits of AR p/w AV block and LBBB
Pt who have been treated before for latent TB
Viral load and CD4 count

39. dame that has already occurred
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Cd4 count
<5000 copies/ml
Mainly clinical - epidemiological and seasonal setting

40. How to dx bacterial meningitis from CSF study?

41. damae that is about to occur?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
HIV viral load
Similar pathophysiology as ITP - tx zidovudine
<500 copies/ml

42. which heart valve is closer to ventricular conduction system/
<500 copies/ml
Td every 10 years - tdap once before 65 and after 65
Aortic valve; endocardiits of AR p/w AV block and LBBB
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

43. When to tx asymptomatic bacteriurea >100 -000?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Pregnacy - urologic procedure - hip arthoplastu
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
Vaccine titer >10mU/ml

44. What is tx for herpes zoster
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
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Acyclovir
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

45. after exposure of HIV when antibody testing is performed?
ELISA; initial visit - 6 - 12 and 24 weeks;
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to 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
Clostridium perfringens after penetrative injuries/wounds

46. foot infections in DM
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
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Voriconazol. mycetoma-surgical removal
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

47. hypertension in children
HIV viral load
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

48. aspergillosis
Vaccine titer >10mU/ml
Voriconazol. mycetoma-surgical removal
Cd4 count
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

49. What is the mch of ampicillin induced rash in IM
Vaccine titer >10mU/ml
Immune mediated; circulating IgG and IgM to penicillin derivatives
If a sample is ELISA positive - it is tested fro western blot for confirmation
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

50. thrombocytopenia in HIV
ELISA; initial visit - 6 - 12 and 24 weeks;
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Similar pathophysiology as ITP - tx zidovudine
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer