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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. How to dx?
Mainly clinical - epidemiological and seasonal setting
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Ampicillin-sublactam; most bites contain eikenella

2. How to dx bacterial meningitis from CSF study?

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3. gas gangrene
Blastomycosis
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Clostridium perfringens after penetrative injuries/wounds

4. how im is transmitted?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Blastomycosis
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Oropharyngeal secretions; hence named as kissing disease

5. aspergillosis
Voriconazol. mycetoma-surgical removal
Blastomycosis
High risk 19-64; 1-2 dose - above 65; one dose
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

6. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
High risk 19-64; 1-2 dose - above 65; one dose
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
PML; focal neurological deficit like MM; no specific tx; regress with HAART

7. infiltrate in upper lobe of lung?
<5000 copies/ml
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
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Either TB or aspergillosis

8. What is characteristic for dx of rocky mountain spotted fever?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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
Need lumbar puncture to relieve pressure; they have high opening pressure >350

9. What is tetanus - diptheria - pertusis recommendation?
Vaccine titer >10mU/ml
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
6-12 weeks
Td every 10 years - tdap once before 65 and after 65

10. clinical manifestation of mucomycosis
Others lesions are ring enhancing and have mass effect while PML don't
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
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. What is the prognosis of lyme arthritis?
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

12. what parameters increases risk of neurosyphilis in HIV patient
Cd4 count
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
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

13. How to dx lyme arthritis?
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
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
ELISA and western blot of synovial fluid.

14. INH
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
Ampicillin-sublactam; most bites contain eikenella
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

15. which heart valve is closer to ventricular conduction system/
Aortic valve; endocardiits of AR p/w AV block and LBBB
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.
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Blastomycosis

16. What is the Tx of cryptococcal meninngitis
AA gradient >35 or Po2 <70
Postcoital voiding - increased intake of cranberry juice
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

17. How to tx pseudomonas?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

18. What is lag time to develop lyme arthritis after exposure to vector
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
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

19. What are the subjective /objective measure of encephalopathy?
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
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
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

20. acute onset +rusty sputum
When cd4 count falls below 200. 2p in pcp =200
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
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

21. When to give abx to prevent recurrent uti
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
Immune mediated; circulating IgG and IgM to penicillin derivatives
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Ampicillin-sublactam; most bites contain eikenella

22. How long abx is given in pseudomonas infection?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Pt who have been treated before for latent TB
Immune mediated; circulating IgG and IgM to penicillin derivatives

23. 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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Do EBV antibody test
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

24. dame that has already occurred
Cd4 count
High risk 19-64; 1-2 dose - above 65; one dose
Postcoital voiding - increased intake of cranberry juice
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

25. when not to give INH therapy if ppd positive and patient asyptomatic
6-12 weeks
Pt who have been treated before for latent TB
Oropharyngeal secretions; hence named as kissing disease
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

26. how CMV presents in immunocompromised patients
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

27. How long we tx chronic prostatis?
6-12 weeks
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.
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
When cd4 count falls below 200. 2p in pcp =200

28. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Do EBV antibody test
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

29. INH
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
<5000 copies/ml
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

30. How to tx IM?
Mainly clinical - epidemiological and seasonal setting
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
<5000 copies/ml

31. HIV patient having fat deposition on back of neck and abdomen - like cushing
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Pt who have been treated before for latent TB
When cd4 count falls below 200. 2p in pcp =200

32. What is tx for herpes zoster
Either TB or aspergillosis
ELISA; initial visit - 6 - 12 and 24 weeks;
Acyclovir
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

33. How to tx TSS?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Non pregnant premanopausal - elderly - dm - sci - chronic foley
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.
Similar pathophysiology as ITP - tx zidovudine

34. How to differentiate gonococcal and nongonoccal urethritis?
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
Postcoital voiding - increased intake of cranberry juice
<500 copies/ml
Viral load and CD4 count

35. reddish colored papules with central umbilication in HIV or immunocompromised patient
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
Vaccine titer >10mU/ml
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Immune mediated; circulating IgG and IgM to penicillin derivatives

36. What is the Tx of STD uretheritis?
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
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
AA gradient >35 or Po2 <70
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

37. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
<500 copies/ml
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
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

38. How to dx progressive multifocal leukoencephalopathy
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

39. When not to tx asymptomatic bacteriura?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Non pregnant premanopausal - elderly - dm - sci - chronic foley

40. what if monospot test is neg in IM?
Do EBV antibody test
Similar pathophysiology as ITP - tx zidovudine
Ampicillin-sublactam; most bites contain eikenella
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

41. when western blot is done for HIV testing
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
If a sample is ELISA positive - it is tested fro western blot for confirmation
HBIG hep B immunoglobulin
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

42. How to dx adequate response to HBV vaccine
Vaccine titer >10mU/ml
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

43. drugs work well on hypertriglyceridia?
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
ELISA; initial visit - 6 - 12 and 24 weeks;
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

44. pathophysiology of toxic shock syndrom?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Oropharyngeal secretions; hence named as kissing disease
ELISA and western blot of synovial fluid.

45. can HIV transmitted through human bite?
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Similar pathophysiology as ITP - tx zidovudine
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

46. rifampin
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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
Ampicillin-sublactam; most bites contain eikenella

47. What is the mch of ampicillin induced rash in IM
AA gradient >35 or Po2 <70
HBIG hep B immunoglobulin
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Immune mediated; circulating IgG and IgM to penicillin derivatives

48. thrombocytopenia in HIV
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
<500 copies/ml
Similar pathophysiology as ITP - tx zidovudine
Oropharyngeal secretions; hence named as kissing disease

49. How often viral load is monitored after HAART?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

50. causative organisms of uti
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Acyclovir
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Oropharyngeal secretions; hence named as kissing disease