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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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This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. low grade fever - maculopapular rash - lymphadenopathy
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
Others lesions are ring enhancing and have mass effect while PML don't
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
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.

2. foot infections in DM
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Reddish orange discoloration of urine - feces - sweat - tears - sputum
HBIG hep B immunoglobulin
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

3. What is the indication of corticosteroid in pcp infection?
AA gradient >35 or Po2 <70
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
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
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

4. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

5. acute febrile reaction develops after starting penicilin tx to syphilis patient
Blastomycosis
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Postcoital voiding - increased intake of cranberry juice
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

6. What is the mch of ampicillin induced rash in IM
Immune mediated; circulating IgG and IgM to penicillin derivatives
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

7. what parameters increases risk of neurosyphilis in HIV patient
Do EBV antibody test
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.
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
ELISA; initial visit - 6 - 12 and 24 weeks;

8. What is the prognosis of lyme arthritis?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

9. how CMV presents in immunocompromised patients
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Oropharyngeal secretions; hence named as kissing disease

10. How to dx cryptococal meninggits
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Ampicillin-sublactam; most bites contain eikenella
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

11. antibiotic with good prostate penetration?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

12. how HAART therapy affects HIV viral loads?
Within 6 months viral load will be <50
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
Monospot test which screen heteropile ab that agglutinate horse rbc

13. What is characteristic for dx of rocky mountain spotted fever?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

14. pneumococcal vaccine indication?
HIV viral load
<500 copies/ml
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
High risk 19-64; 1-2 dose - above 65; one dose

15. When to tx influenza with antiviral therapy?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
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
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

16. Tx of choice for human bites
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Ampicillin-sublactam; most bites contain eikenella

17. what if monospot test is neg in IM?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
ELISA and western blot of synovial fluid.
Do EBV antibody test
If a sample is ELISA positive - it is tested fro western blot for confirmation

18. wisconsin - missisipi - ohio
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Blastomycosis
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
<500 copies/ml

19. after exposure of HIV when antibody testing is performed?
ELISA; initial visit - 6 - 12 and 24 weeks;
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
High risk 19-64; 1-2 dose - above 65; one dose
Upper lobes; any fibrosis in this area suggestive of latent TB

20. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
Upper lobes; any fibrosis in this area suggestive of latent TB
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
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.
HBIG hep B immunoglobulin

21. How to differentiate different types of necrotizing fascitis?
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.
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
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
Pregnacy - urologic procedure - hip arthoplastu

22. when we see echym gangrenosum?
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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

23. What are the behavioral interventions decrease the risk of UTI
Postcoital voiding - increased intake of cranberry juice
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Monospot test which screen heteropile ab that agglutinate horse rbc
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

24. gas gangrene
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Clostridium perfringens after penetrative injuries/wounds
AA gradient >35 or Po2 <70
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

25. What is the Tx of cryptococcal meninngitis
Clostridium perfringens after penetrative injuries/wounds
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Aortic valve; endocardiits of AR p/w AV block and LBBB
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

26. When to tx asymptomatic bacteriurea >100 -000?
If a sample is ELISA positive - it is tested fro western blot for confirmation
<500 copies/ml
Immune mediated; circulating IgG and IgM to penicillin derivatives
Pregnacy - urologic procedure - hip arthoplastu

27. What is the pathophysiology of Meningococcal meningitis?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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
If a sample is ELISA positive - it is tested fro western blot for confirmation

28. When not to tx asymptomatic bacteriura?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Upper lobes; any fibrosis in this area suggestive of latent TB
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

29. What is lag time to develop lyme arthritis after exposure to vector
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Vaccine titer >10mU/ml
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

30. where TB normally affects
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Upper lobes; any fibrosis in this area suggestive of latent TB
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Pregnacy - urologic procedure - hip arthoplastu

31. INH
If a sample is ELISA positive - it is tested fro western blot for confirmation
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

32. How to dx?
Acyclovir
Mainly clinical - epidemiological and seasonal setting
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Every 3-4 hours to determine appropritate time to start HAART

33. what would be viral load after 4 weeks
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Others lesions are ring enhancing and have mass effect while PML don't
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
<5000 copies/ml

34. How to dx bacterial meningitis from CSF study?

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35. How to dx progressive multifocal leukoencephalopathy
Postcoital voiding - increased intake of cranberry juice
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
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

36. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Monospot test which screen heteropile ab that agglutinate horse rbc
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
HIV viral load
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

37. How to tx pcp?
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

38. reddish colored papules with central umbilication in HIV or immunocompromised patient
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Others lesions are ring enhancing and have mass effect while PML don't
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

39. pathophysiology of toxic shock syndrom?
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
6-12 weeks

40. systolic HTN in elderly
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Oropharyngeal secretions; hence named as kissing disease
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
HBIG hep B immunoglobulin

41. damae that is about to occur?
Viral load and CD4 count
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
HBIG hep B immunoglobulin
HIV viral load

42. What is tetanus - diptheria - pertusis recommendation?
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
Immune mediated; circulating IgG and IgM to penicillin derivatives
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Td every 10 years - tdap once before 65 and after 65

43. How to dx IM?
HIV viral load
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Vaccine titer >10mU/ml
Monospot test which screen heteropile ab that agglutinate horse rbc

44. How to dx adequate response to HBV vaccine
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Vaccine titer >10mU/ml
Viral load and CD4 count

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

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46. What is the classic signs of nec fasc?
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
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
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

47. which heart valve is closer to ventricular conduction system/
Aortic valve; endocardiits of AR p/w AV block and LBBB
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Ampicillin-sublactam; most bites contain eikenella
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

48. How to confirm dx if pcp?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Bronchoalveolar washing and transbronchial biopsy
Every 3-4 hours to determine appropritate time to start HAART
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

49. rifampin
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Clostridium perfringens after penetrative injuries/wounds
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
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.

50. dame that has already occurred
Cd4 count
Blastomycosis
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
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w