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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. acute febrile reaction develops after starting penicilin tx to syphilis patient
Clostridium perfringens after penetrative injuries/wounds
Blastomycosis
<500 copies/ml
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

2. What is used for prophylaxis against meningo..meningitis?
Rifampin600mg q12. or cipro
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
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

3. How to dx bacterial meningitis from CSF study?

4. How to differentiate different types of necrotizing fascitis?
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
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

5. antibiotic with good prostate penetration?
Upper lobes; any fibrosis in this area suggestive of latent TB
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
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
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

6. How to tx chronic hep B
Upper lobes; any fibrosis in this area suggestive of latent TB
High risk 19-64; 1-2 dose - above 65; one dose
Pegylated interferon and lamivudine
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

7. How to differentiate gonococcal and nongonoccal urethritis?
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Do EBV antibody test
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
Pt who have been treated before for latent TB

8. How to dx progressive multifocal leukoencephalopathy
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
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
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

9. How to dx?
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
Mainly clinical - epidemiological and seasonal setting
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

10. 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
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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

11. Tx of choice for human bites
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Ampicillin-sublactam; most bites contain eikenella
Blastomycosis
Clostridium perfringens after penetrative injuries/wounds

12. worsening of TB after starting HAART in HIV
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
When cd4 count falls below 200. 2p in pcp =200

13. How to tx pseudomonas?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

14. how im is transmitted?
HIV viral load
Pregnacy - urologic procedure - hip arthoplastu
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

15. INH
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Ampicillin-sublactam; most bites contain eikenella
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

16. What is the criteria for Spontaneous bact peritonitis
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Td every 10 years - tdap once before 65 and after 65

17. When to tx influenza with antiviral therapy?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
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

18. how CMV presents in immunocompromised patients
Cd4 count
Rifampin600mg q12. or cipro
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

19. 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
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
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
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

20. HIV patient having fat deposition on back of neck and abdomen - like cushing
Postcoital voiding - increased intake of cranberry juice
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
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

21. when HIV patient develop pcp?
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Either TB or aspergillosis
When cd4 count falls below 200. 2p in pcp =200
Postcoital voiding - increased intake of cranberry juice

22. hypertriglyceridemia in HIV
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Monospot test which screen heteropile ab that agglutinate horse rbc
Vaccine titer >10mU/ml

23. thrombocytopenia in HIV
HBIG hep B immunoglobulin
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
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
Similar pathophysiology as ITP - tx zidovudine

24. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
HBIG hep B immunoglobulin
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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

25. rifampin
Voriconazol. mycetoma-surgical removal
Mainly clinical - epidemiological and seasonal setting
Reddish orange discoloration of urine - feces - sweat - tears - sputum
HBIG hep B immunoglobulin

26. How to give postexposure prophylaxis for HIV
When cd4 count falls below 200. 2p in pcp =200
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
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

27. dame that has already occurred
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Cd4 count

28. gas gangrene
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
When cd4 count falls below 200. 2p in pcp =200
Acyclovir
Clostridium perfringens after penetrative injuries/wounds

29. How often HIV postiive patients CD4 count needs to be evaluated?
Rifampin600mg q12. or cipro
Every 3-4 hours to determine appropritate time to start HAART
Pegylated interferon and lamivudine
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

30. How to dx cryptococal meninggits
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
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
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

31. where TB normally affects
Immune mediated; circulating IgG and IgM to penicillin derivatives
Pt who have been treated before for latent TB
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.
Upper lobes; any fibrosis in this area suggestive of latent TB

32. when western blot is done for HIV testing
If a sample is ELISA positive - it is tested fro western blot for confirmation
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
When cd4 count falls below 200. 2p in pcp =200
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

33. What is fatal consequence of RMSF?
<500 copies/ml
Acyclovir
Need lumbar puncture to relieve pressure; they have high opening pressure >350
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

34. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Blastomycosis
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

35. when we see echym gangrenosum?
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Viral load and CD4 count
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

36. low grade fever - maculopapular rash - lymphadenopathy
ELISA and western blot of synovial fluid.
Aortic valve; endocardiits of AR p/w AV block and LBBB
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Mainly clinical - epidemiological and seasonal setting

37. When to give prophylaxis against MAC
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Bronchoalveolar washing and transbronchial biopsy
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
When cd4 count falls below 200. 2p in pcp =200

38. aspergillosis
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Voriconazol. mycetoma-surgical removal
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

39. can HIV transmitted through human bite?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

40. What is characteristic for dx of rocky mountain spotted fever?
Others lesions are ring enhancing and have mass effect while PML don't
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
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

41. pathophysiology of toxic shock syndrom?
Cd4 count
Either TB or aspergillosis
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

42. acute onset +rusty sputum
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Vaccine titer >10mU/ml
Rifampin600mg q12. or cipro

43. What is the Tx of STD uretheritis?
Monospot test which screen heteropile ab that agglutinate horse rbc
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
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
High risk 19-64; 1-2 dose - above 65; one dose

44. What is the mch of ampicillin induced rash in IM
Blastomycosis
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Immune mediated; circulating IgG and IgM to penicillin derivatives
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

45. after recent exposure - negative ELISA - How to confirm?
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
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
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.

46. How long abx is given in pseudomonas infection?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Need lumbar puncture to relieve pressure; they have high opening pressure >350
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
<5000 copies/ml

47. What is lag time to develop lyme arthritis after exposure to vector
High risk 19-64; 1-2 dose - above 65; one dose
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

48. How to tx TSS?
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
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
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Oropharyngeal secretions; hence named as kissing disease

49. what would be viral load after 2-4m of HAART?
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
<500 copies/ml
Either TB or aspergillosis
Monospot test which screen heteropile ab that agglutinate horse rbc

50. damae that is about to occur?
HIV viral load
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 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