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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. after exposure of HIV when antibody testing is performed?
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
ELISA; initial visit - 6 - 12 and 24 weeks;
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Pregnacy - urologic procedure - hip arthoplastu

2. when we see echym gangrenosum?
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
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

3. reddish colored papules with central umbilication in HIV or immunocompromised patient
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
ELISA and western blot of synovial fluid.
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

4. When to give prophylaxis against MAC
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
HBIG hep B immunoglobulin
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
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

5. what parameters increases risk of neurosyphilis in HIV patient
Oropharyngeal secretions; hence named as kissing disease
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
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.
Acyclovir

6. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
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
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

7. causative organisms of uti
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Pegylated interferon and lamivudine
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.

8. after recent exposure - negative ELISA - How to confirm?
Clostridium perfringens after penetrative injuries/wounds
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 -
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

9. which heart valve is closer to ventricular conduction system/
Aortic valve; endocardiits of AR p/w AV block and LBBB
Need lumbar puncture to relieve pressure; they have high opening pressure >350
<500 copies/ml
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

10. wisconsin - missisipi - ohio
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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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

11. How to tx TSS?
Blastomycosis
Aortic valve; endocardiits of AR p/w AV block and LBBB
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

12. What is fatal consequence of RMSF?
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
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

13. HIV patient having fat deposition on back of neck and abdomen - like cushing
Every 3-4 hours to determine appropritate time to start HAART
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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

14. gas gangrene
Clostridium perfringens after penetrative injuries/wounds
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Voriconazol. mycetoma-surgical removal
Vaccine titer >10mU/ml

15. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Need lumbar puncture to relieve pressure; they have high opening pressure >350

16. Tx of choice for human bites
When cd4 count falls below 200. 2p in pcp =200
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Ampicillin-sublactam; most bites contain eikenella
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

17. What is the classic signs of nec fasc?
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
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
HBIG hep B immunoglobulin
Ampicillin-sublactam; most bites contain eikenella

18. What is the criteria for Spontaneous bact peritonitis
Pregnacy - urologic procedure - hip arthoplastu
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

19. What is the prognosis of lyme arthritis?
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Blastomycosis
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

20. How to dx adequate response to HBV vaccine
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Oropharyngeal secretions; hence named as kissing disease
Clostridium perfringens after penetrative injuries/wounds
Vaccine titer >10mU/ml

21. worsening of TB after starting HAART in HIV
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
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Every 3-4 hours to determine appropritate time to start HAART
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

22. What are the subjective /objective measure of encephalopathy?
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
Aortic valve; endocardiits of AR p/w AV block and LBBB
Either TB or aspergillosis
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

23. 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
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Mainly clinical - epidemiological and seasonal setting
Pegylated interferon and lamivudine

24. When not to tx asymptomatic bacteriura?
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
Aortic valve; endocardiits of AR p/w AV block and LBBB
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

25. acute onset +rusty sputum
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Pt who have been treated before for latent TB
Clostridium perfringens after penetrative injuries/wounds
Immune mediated; circulating IgG and IgM to penicillin derivatives

26. When to tx influenza with antiviral therapy?
Blastomycosis
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

27. systolic HTN in elderly
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Oropharyngeal secretions; hence named as kissing disease
6-12 weeks

28. How to tx pseudomonas?
High risk 19-64; 1-2 dose - above 65; one dose
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Reddish orange discoloration of urine - feces - sweat - tears - sputum

29. How to confirm dx if pcp?
Either TB or aspergillosis
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Bronchoalveolar washing and transbronchial biopsy
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

30. How long we tx chronic prostatis?
High risk 19-64; 1-2 dose - above 65; one dose
6-12 weeks
Td every 10 years - tdap once before 65 and after 65
HBIG hep B immunoglobulin

31. infiltrate in upper lobe of lung?
Td every 10 years - tdap once before 65 and after 65
Either TB or aspergillosis
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
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

32. How to tx chronic hep B
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Pegylated interferon and lamivudine

33. How long abx is given in pseudomonas infection?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
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

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

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

36. How to dx cryptococal meninggits
High risk 19-64; 1-2 dose - above 65; one dose
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
<5000 copies/ml

37. what would be viral load after 2-4m of HAART?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Pregnacy - urologic procedure - hip arthoplastu
Vaccine titer >10mU/ml
<500 copies/ml

38. When to tx asymptomatic bacteriurea >100 -000?
Acyclovir
Clostridium perfringens after penetrative injuries/wounds
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Pregnacy - urologic procedure - hip arthoplastu

39. hypertension in children
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Td every 10 years - tdap once before 65 and after 65

40. foot infections in DM
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Pregnacy - urologic procedure - hip arthoplastu
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

41. What are the behavioral interventions decrease the risk of UTI
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
Oropharyngeal secretions; hence named as kissing disease
Mainly clinical - epidemiological and seasonal setting
Postcoital voiding - increased intake of cranberry juice

42. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
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.

43. When to give abx to prevent recurrent uti
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
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

44. drugs work well on hypertriglyceridia?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Acyclovir
High risk 19-64; 1-2 dose - above 65; one dose
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

45. What is difference between uti relapse versus recurrence?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
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
Blastomycosis
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

46. 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.
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
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
Vaccine titer >10mU/ml

47. How to differentiate different types of necrotizing fascitis?
Blastomycosis
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
Bronchoalveolar washing and transbronchial biopsy
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

48. What is the mch of ampicillin induced rash in IM
<500 copies/ml
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Immune mediated; circulating IgG and IgM to penicillin derivatives
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

49. 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
HBIG hep B immunoglobulin
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

50. dame that has already occurred
Cd4 count
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
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles