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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. which heart valve is closer to ventricular conduction system/
Aortic valve; endocardiits of AR p/w AV block and LBBB
Either TB or aspergillosis
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Need lumbar puncture to relieve pressure; they have high opening pressure >350

2. How to dx cryptococal meninggits
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Aortic valve; endocardiits of AR p/w AV block and LBBB
Similar pathophysiology as ITP - tx zidovudine

3. What is the mch of ampicillin induced rash in IM
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Immune mediated; circulating IgG and IgM to penicillin derivatives
When cd4 count falls below 200. 2p in pcp =200

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

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5. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Upper lobes; any fibrosis in this area suggestive of latent TB
PML; focal neurological deficit like MM; no specific tx; regress with HAART
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

6. INH
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Pegylated interferon and lamivudine
Within 6 months viral load will be <50
Need lumbar puncture to relieve pressure; they have high opening pressure >350

7. When to give abx to prevent recurrent uti
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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
Clostridium perfringens after penetrative injuries/wounds
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

8. How to differentiate gonococcal and nongonoccal urethritis?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Cd4 count
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
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

9. What is the indication of corticosteroid in pcp infection?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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
AA gradient >35 or Po2 <70

10. when western blot is done for HIV testing
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 viral load
If a sample is ELISA positive - it is tested fro western blot for confirmation
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

11. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Do EBV antibody test
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
AA gradient >35 or Po2 <70
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

12. foot infections in DM
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
When cd4 count falls below 200. 2p in pcp =200
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

13. acute febrile reaction develops after starting penicilin tx to syphilis patient
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
HIV viral load

14. What is tetanus - diptheria - pertusis recommendation?
Viral load and CD4 count
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Td every 10 years - tdap once before 65 and after 65

15. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
<500 copies/ml
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

16. what if monospot test is neg in IM?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Do EBV antibody test
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

17. When not to tx asymptomatic bacteriura?
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Vaccine titer >10mU/ml
6-12 weeks

18. reddish colored papules with central umbilication in HIV or immunocompromised patient
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Non pregnant premanopausal - elderly - dm - sci - chronic foley
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

19. pathophysiology of toxic shock syndrom?
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
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

20. low grade fever - maculopapular rash - lymphadenopathy
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
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Cd4 count

21. what would be viral load after 4 weeks
<5000 copies/ml
Others lesions are ring enhancing and have mass effect while PML don't
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

22. dame that has already occurred
Cd4 count
Monospot test which screen heteropile ab that agglutinate horse rbc
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
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

23. What is the prognosis of lyme arthritis?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

24. how CMV presents in immunocompromised patients
Pregnacy - urologic procedure - hip arthoplastu
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Non pregnant premanopausal - elderly - dm - sci - chronic foley

25. How to tx chronic hep B
Upper lobes; any fibrosis in this area suggestive of latent TB
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Pegylated interferon and lamivudine
Reddish orange discoloration of urine - feces - sweat - tears - sputum

26. gas gangrene
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Clostridium perfringens after penetrative injuries/wounds
Monospot test which screen heteropile ab that agglutinate horse rbc

27. What is characteristic for dx of rocky mountain spotted fever?
6-12 weeks
Bronchoalveolar washing and transbronchial biopsy
Blastomycosis
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

28. causative organisms of uti
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
AA gradient >35 or Po2 <70
Ampicillin-sublactam; most bites contain eikenella

29. How to dx IM?
Postcoital voiding - increased intake of cranberry juice
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Monospot test which screen heteropile ab that agglutinate horse rbc

30. thrombocytopenia in HIV
ELISA and western blot of synovial fluid.
Similar pathophysiology as ITP - tx zidovudine
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Acyclovir

31. How to give postexposure prophylaxis for HIV
Upper lobes; any fibrosis in this area suggestive of latent TB
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

32. how HAART therapy affects HIV viral loads?
Voriconazol. mycetoma-surgical removal
Within 6 months viral load will be <50
Monospot test which screen heteropile ab that agglutinate horse rbc
Bronchoalveolar washing and transbronchial biopsy

33. When to give prophylaxis against MAC
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
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Clostridium perfringens after penetrative injuries/wounds

34. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Others lesions are ring enhancing and have mass effect while PML don't
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Non pregnant premanopausal - elderly - dm - sci - chronic foley

35. How to tx TSS?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
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.
Postcoital voiding - increased intake of cranberry juice

36. What is fatal consequence of RMSF?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
High risk 19-64; 1-2 dose - above 65; one dose
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

37. when HIV patient develop pcp?
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) -
When cd4 count falls below 200. 2p in pcp =200
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

38. where TB normally affects
Upper lobes; any fibrosis in this area suggestive of latent TB
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
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

39. What is used for prophylaxis against meningo..meningitis?
Mainly clinical - epidemiological and seasonal setting
Rifampin600mg q12. or cipro
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

40. drugs work well on hypertriglyceridia?
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

41. when not to give INH therapy if ppd positive and patient asyptomatic
High risk 19-64; 1-2 dose - above 65; one dose
Pt who have been treated before for latent TB
Acyclovir
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

42. What is the pathophysiology of Meningococcal meningitis?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Pt who have been treated before for latent TB
Either TB or aspergillosis

43. rifampin
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
Td every 10 years - tdap once before 65 and after 65
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

44. can HIV transmitted through human bite?
AA gradient >35 or Po2 <70
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
6-12 weeks
Others lesions are ring enhancing and have mass effect while PML don't

45. What is the Tx of cryptococcal meninngitis
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

46. What is the classic signs of nec fasc?
ELISA; initial visit - 6 - 12 and 24 weeks;
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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
Similar pathophysiology as ITP - tx zidovudine

47. acute onset +rusty sputum
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Aortic valve; endocardiits of AR p/w AV block and LBBB
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

48. antibiotic with good prostate penetration?
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
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
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

49. What is lag time to develop lyme arthritis after exposure to vector
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
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Postcoital voiding - increased intake of cranberry juice

50. infiltrate in upper lobe of lung?
Upper lobes; any fibrosis in this area suggestive of latent TB
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Either TB or aspergillosis