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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. What is the Tx of cryptococcal meninngitis
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.
6-12 weeks
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

2. clinical manifestation of mucomycosis
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
ELISA and western blot of synovial fluid.
Reddish orange discoloration of urine - feces - sweat - tears - sputum

3. when we see echym gangrenosum?
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
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
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Need lumbar puncture to relieve pressure; they have high opening pressure >350

4. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Immune mediated; circulating IgG and IgM to penicillin derivatives
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Monospot test which screen heteropile ab that agglutinate horse rbc
Do EBV antibody test

5. INH
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
If a sample is ELISA positive - it is tested fro western blot for confirmation
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

6. What are the subjective /objective measure of encephalopathy?
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
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

7. How to tx pseudomonas?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Voriconazol. mycetoma-surgical removal
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

8. when not to give INH therapy if ppd positive and patient asyptomatic
Monospot test which screen heteropile ab that agglutinate horse rbc
When cd4 count falls below 200. 2p in pcp =200
Pt who have been treated before for latent TB
<5000 copies/ml

9. hypertriglyceridemia in HIV
Aortic valve; endocardiits of AR p/w AV block and LBBB
Oropharyngeal secretions; hence named as kissing disease
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Do EBV antibody test

10. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Ampicillin-sublactam; most bites contain eikenella
High risk 19-64; 1-2 dose - above 65; one dose
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Bronchoalveolar washing and transbronchial biopsy

11. When to give abx to prevent recurrent uti
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.
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
Mainly clinical - epidemiological and seasonal setting

12. hypertension in children
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

13. low grade fever - maculopapular rash - lymphadenopathy
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

14. What is tx for herpes zoster
Acyclovir
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
If a sample is ELISA positive - it is tested fro western blot for confirmation
Td every 10 years - tdap once before 65 and after 65

15. How to dx cryptococal meninggits
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Acyclovir
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Within 6 months viral load will be <50

16. How to differentiate different types of necrotizing fascitis?
ELISA; initial visit - 6 - 12 and 24 weeks;
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
Voriconazol. mycetoma-surgical removal
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

17. What is the classic signs of nec fasc?
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
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
If a sample is ELISA positive - it is tested fro western blot for confirmation
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

18. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Oropharyngeal secretions; hence named as kissing disease
When cd4 count falls below 200. 2p in pcp =200
Voriconazol. mycetoma-surgical removal
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

19. where TB normally affects
Bronchoalveolar washing and transbronchial biopsy
Upper lobes; any fibrosis in this area suggestive of latent TB
Others lesions are ring enhancing and have mass effect while PML don't
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

20. acute onset +rusty sputum
Blastomycosis
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

21. How long abx is given in pseudomonas infection?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
High risk 19-64; 1-2 dose - above 65; one dose
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

22. pneumococcal vaccine indication?
High risk 19-64; 1-2 dose - above 65; one dose
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

23. how im is transmitted?
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Oropharyngeal secretions; hence named as kissing disease
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Pregnacy - urologic procedure - hip arthoplastu

24. foot infections in DM
Immune mediated; circulating IgG and IgM to penicillin derivatives
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
If a sample is ELISA positive - it is tested fro western blot for confirmation
Clostridium perfringens after penetrative injuries/wounds

25. What is tetanus - diptheria - pertusis recommendation?
Immune mediated; circulating IgG and IgM to penicillin derivatives
Td every 10 years - tdap once before 65 and after 65
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Bronchoalveolar washing and transbronchial biopsy

26. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Bronchoalveolar washing and transbronchial biopsy
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

27. how HAART therapy affects HIV viral loads?
AA gradient >35 or Po2 <70
Within 6 months viral load will be <50
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

28. How to give postexposure prophylaxis for HIV
Either TB or aspergillosis
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Postcoital voiding - increased intake of cranberry juice
Cd4 count

29. What is difference between uti relapse versus recurrence?
Rifampin600mg q12. or cipro
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
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

30. What are indicators for progression of HIV
When cd4 count falls below 200. 2p in pcp =200
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Every 3-4 hours to determine appropritate time to start HAART
Viral load and CD4 count

31. 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
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
Reddish orange discoloration of urine - feces - sweat - tears - sputum
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

32. How to dx bacterial meningitis from CSF study?

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33. How to dx lyme arthritis?
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Bronchoalveolar washing and transbronchial biopsy
Monospot test which screen heteropile ab that agglutinate horse rbc
ELISA and western blot of synovial fluid.

34. When not to tx asymptomatic bacteriura?
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Non pregnant premanopausal - elderly - dm - sci - chronic foley
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Aortic valve; endocardiits of AR p/w AV block and LBBB

35. What are the behavioral interventions decrease the risk of UTI
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Postcoital voiding - increased intake of cranberry juice
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

36. which heart valve is closer to ventricular conduction system/
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Aortic valve; endocardiits of AR p/w AV block and LBBB
Reddish orange discoloration of urine - feces - sweat - tears - sputum

37. systolic HTN in elderly
Aortic valve; endocardiits of AR p/w AV block and LBBB
AA gradient >35 or Po2 <70
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
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

38. When to give prophylaxis against MAC
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
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

39. How to dx adequate response to HBV vaccine
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Vaccine titer >10mU/ml
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

40. after exposure of HIV when antibody testing is performed?
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
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
ELISA; initial visit - 6 - 12 and 24 weeks;

41. what parameters increases risk of neurosyphilis in HIV patient
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
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

42. acute febrile reaction develops after starting penicilin tx to syphilis patient
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Postcoital voiding - increased intake of cranberry juice
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

43. When to tx asymptomatic bacteriurea >100 -000?
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Pregnacy - urologic procedure - hip arthoplastu
Ampicillin-sublactam; most bites contain eikenella
Do EBV antibody test

44. infiltrate in upper lobe of lung?
Monospot test which screen heteropile ab that agglutinate horse rbc
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Either TB or aspergillosis
Similar pathophysiology as ITP - tx zidovudine

45. rifampin
Immune mediated; circulating IgG and IgM to penicillin derivatives
Monospot test which screen heteropile ab that agglutinate horse rbc
Aortic valve; endocardiits of AR p/w AV block and LBBB
Reddish orange discoloration of urine - feces - sweat - tears - sputum

46. damae that is about to occur?
HIV viral load
Do EBV antibody test
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Upper lobes; any fibrosis in this area suggestive of latent TB

47. dame that has already occurred
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Cd4 count
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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

48. How to tx TSS?
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
<5000 copies/ml

49. HIV patient having fat deposition on back of neck and abdomen - like cushing
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
PML; focal neurological deficit like MM; no specific tx; regress with HAART
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Postcoital voiding - increased intake of cranberry juice

50. gas gangrene
6-12 weeks
Clostridium perfringens after penetrative injuries/wounds
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Upper lobes; any fibrosis in this area suggestive of latent TB