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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. hypertension in children
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

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

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3. What is the pathophysiology of Meningococcal meningitis?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Rifampin600mg q12. or cipro
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

4. when not to give INH therapy if ppd positive and patient asyptomatic
Pt who have been treated before for latent TB
ELISA; initial visit - 6 - 12 and 24 weeks;
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

5. How to confirm chlamydia infection?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

6. worsening of TB after starting HAART in HIV
ELISA; initial visit - 6 - 12 and 24 weeks;
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

7. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
Blastomycosis
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
HBIG hep B immunoglobulin
Voriconazol. mycetoma-surgical removal

8. infiltrate in upper lobe of lung?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Immune mediated; circulating IgG and IgM to penicillin derivatives
HBIG hep B immunoglobulin
Either TB or aspergillosis

9. What are the subjective /objective measure of encephalopathy?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
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
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

10. What is the criteria for Spontaneous bact peritonitis
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Do EBV antibody test
If a sample is ELISA positive - it is tested fro western blot for confirmation

11. How to tx TSS?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
PML; focal neurological deficit like MM; no specific tx; regress with HAART
When cd4 count falls below 200. 2p in pcp =200

12. Tx of choice for human bites
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Ampicillin-sublactam; most bites contain eikenella
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

13. low grade fever - maculopapular rash - lymphadenopathy
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

14. When to tx asymptomatic bacteriurea >100 -000?
Clostridium perfringens after penetrative injuries/wounds
Pregnacy - urologic procedure - hip arthoplastu
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
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.

15. What is characteristic for dx of rocky mountain spotted fever?
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
If a sample is ELISA positive - it is tested fro western blot for confirmation
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

16. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Every 3-4 hours to determine appropritate time to start HAART
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
ELISA; initial visit - 6 - 12 and 24 weeks;

17. How to give postexposure prophylaxis for HIV
Cd4 count
Clostridium perfringens after penetrative injuries/wounds
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Oropharyngeal secretions; hence named as kissing disease

18. aspergillosis
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
AA gradient >35 or Po2 <70
Either TB or aspergillosis
Voriconazol. mycetoma-surgical removal

19. How often viral load is monitored after HAART?
Acyclovir
6-12 weeks
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

20. when HIV patient develop pcp?
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
6-12 weeks
Cd4 count
When cd4 count falls below 200. 2p in pcp =200

21. thrombocytopenia in HIV
Cd4 count
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Similar pathophysiology as ITP - tx zidovudine
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

22. How to tx pseudomonas?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Within 6 months viral load will be <50
HIV viral load
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

23. INH
AA gradient >35 or Po2 <70
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
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.
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

24. after recent exposure - negative ELISA - How to confirm?
HIV viral load
Mainly clinical - epidemiological and seasonal setting
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

25. How to dx IM?
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Similar pathophysiology as ITP - tx zidovudine
<5000 copies/ml
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

26. How to differentiate gonococcal and nongonoccal urethritis?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
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

27. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Either TB or aspergillosis
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Non pregnant premanopausal - elderly - dm - sci - chronic foley

28. which heart valve is closer to ventricular conduction system/
Pt who have been treated before for latent TB
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Aortic valve; endocardiits of AR p/w AV block and LBBB

29. How to tx IM?
Clostridium perfringens after penetrative injuries/wounds
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
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
<500 copies/ml

30. What is the prognosis of lyme arthritis?
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Blastomycosis
High risk 19-64; 1-2 dose - above 65; one dose

31. How to dx IM?
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
When cd4 count falls below 200. 2p in pcp =200
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Monospot test which screen heteropile ab that agglutinate horse rbc

32. what would be viral load after 4 weeks
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Do EBV antibody test
Voriconazol. mycetoma-surgical removal
<5000 copies/ml

33. damae that is about to occur?
HIV viral load
When cd4 count falls below 200. 2p in pcp =200
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

34. What is difference between uti relapse versus recurrence?
Aortic valve; endocardiits of AR p/w AV block and LBBB
Acyclovir
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
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

35. What is fatal consequence of RMSF?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Td every 10 years - tdap once before 65 and after 65

36. What are indicators for progression of HIV
Clostridium perfringens after penetrative injuries/wounds
Viral load and CD4 count
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

37. 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.
Others lesions are ring enhancing and have mass effect while PML don't
Acyclovir
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

38. antibiotic with good prostate penetration?
Acyclovir
If a sample is ELISA positive - it is tested fro western blot for confirmation
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

39. how HAART therapy affects HIV viral loads?
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
ELISA; initial visit - 6 - 12 and 24 weeks;
Within 6 months viral load will be <50

40. causative organisms of uti
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
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

41. What are the behavioral interventions decrease the risk of UTI
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Others lesions are ring enhancing and have mass effect while PML don't
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Postcoital voiding - increased intake of cranberry juice

42. How to dx adequate response to HBV vaccine
Vaccine titer >10mU/ml
Viral load and CD4 count
Do EBV antibody test
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

43. pathophysiology of toxic shock syndrom?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
6-12 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
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

44. What is the indication of corticosteroid in pcp infection?
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
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
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.

45. how im is transmitted?
Others lesions are ring enhancing and have mass effect while PML don't
Oropharyngeal secretions; hence named as kissing disease
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

46. When to give prophylaxis against MAC
Pt who have been treated before for latent TB
Pegylated interferon and lamivudine
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 RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

47. can HIV transmitted through human bite?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

48. systolic HTN in elderly
Pegylated interferon and lamivudine
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

49. when western blot is done for HIV testing
PML; focal neurological deficit like MM; no specific tx; regress with HAART
If a sample is ELISA positive - it is tested fro western blot for confirmation
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

50. How to dx cryptococal meninggits
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
ELISA; initial visit - 6 - 12 and 24 weeks;
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Non pregnant premanopausal - elderly - dm - sci - chronic foley