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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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1. when HIV patient develop pcp?
When cd4 count falls below 200. 2p in pcp =200
Vaccine titer >10mU/ml
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Upper lobes; any fibrosis in this area suggestive of latent TB

2. hypertriglyceridemia in HIV
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
Do EBV antibody test
HIV viral load

3. thrombocytopenia in HIV
ELISA; initial visit - 6 - 12 and 24 weeks;
Similar pathophysiology as ITP - tx zidovudine
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Non pregnant premanopausal - elderly - dm - sci - chronic foley

4. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Oropharyngeal secretions; hence named as kissing disease
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.
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

5. Tx of choice for human bites
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
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
Ampicillin-sublactam; most bites contain eikenella

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

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7. When to tx asymptomatic bacteriurea >100 -000?
Viral load and CD4 count
Pregnacy - urologic procedure - hip arthoplastu
6-12 weeks
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

8. what if monospot test is neg in IM?
Clostridium perfringens after penetrative injuries/wounds
Do EBV antibody test
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.

9. How often viral load is monitored after 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.
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
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

10. What is fatal consequence of RMSF?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
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

11. What are the subjective /objective measure of encephalopathy?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
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

12. How to dx lyme arthritis?
ELISA and western blot of synovial fluid.
6-12 weeks
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Immune mediated; circulating IgG and IgM to penicillin derivatives

13. systolic HTN in elderly
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Vaccine titer >10mU/ml
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
If a sample is ELISA positive - it is tested fro western blot for confirmation

14. what parameters increases risk of neurosyphilis in HIV patient
Postcoital voiding - increased intake of cranberry juice
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.
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Others lesions are ring enhancing and have mass effect while PML don't

15. how im is transmitted?
Td every 10 years - tdap once before 65 and after 65
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
ELISA; initial visit - 6 - 12 and 24 weeks;
Oropharyngeal secretions; hence named as kissing disease

16. What is used for prophylaxis against meningo..meningitis?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Either TB or aspergillosis
Rifampin600mg q12. or cipro
Upper lobes; any fibrosis in this area suggestive of latent TB

17. How to tx pseudomonas?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

18. when not to give INH therapy if ppd positive and patient asyptomatic
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Pt who have been treated before for latent TB
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
PML; focal neurological deficit like MM; no specific tx; regress with HAART

19. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Bronchoalveolar washing and transbronchial biopsy
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Others lesions are ring enhancing and have mass effect while PML don't

20. What is the classic signs of nec fasc?
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
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
Immune mediated; circulating IgG and IgM to penicillin derivatives
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

21. How to dx IM?
Voriconazol. mycetoma-surgical removal
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

22. infiltrate in upper lobe of lung?
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
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.
Either TB or aspergillosis
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

23. when we see echym gangrenosum?
High risk 19-64; 1-2 dose - above 65; one dose
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Vaccine titer >10mU/ml
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

24. How long we tx chronic prostatis?
6-12 weeks
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Monospot test which screen heteropile ab that agglutinate horse rbc

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

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26. What is the criteria for Spontaneous bact peritonitis
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

27. How to tx TSS?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

28. When to give abx to prevent recurrent uti
Pregnacy - urologic procedure - hip arthoplastu
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
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

29. after exposure of HIV when antibody testing is performed?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Within 6 months viral load will be <50
ELISA; initial visit - 6 - 12 and 24 weeks;

30. How to dx IM?
Monospot test which screen heteropile ab that agglutinate horse rbc
ELISA; initial visit - 6 - 12 and 24 weeks;
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Every 3-4 hours to determine appropritate time to start HAART

31. What is lag time to develop lyme arthritis after exposure to vector
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
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

32. can HIV transmitted through human bite?
Need lumbar puncture to relieve pressure; they have high opening pressure >350
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol

33. hypertension in children
ELISA; initial visit - 6 - 12 and 24 weeks;
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

34. HIV patient having fat deposition on back of neck and abdomen - like cushing
Blastomycosis
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Rifampin600mg q12. or cipro
Others lesions are ring enhancing and have mass effect while PML don't

35. How to tx pcp?
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Pegylated interferon and lamivudine

36. How often HIV postiive patients CD4 count needs to be evaluated?
Every 3-4 hours to determine appropritate time to start HAART
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
ELISA and western blot of synovial fluid.

37. What is difference between uti relapse versus recurrence?
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Clostridium perfringens after penetrative injuries/wounds
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
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

38. How long abx is given in pseudomonas infection?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
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.
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

39. 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
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Pegylated interferon and lamivudine
Mainly clinical - epidemiological and seasonal setting

40. pathophysiology of toxic shock syndrom?
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
<500 copies/ml
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Need lumbar puncture to relieve pressure; they have high opening pressure >350

41. What is tetanus - diptheria - pertusis recommendation?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Td every 10 years - tdap once before 65 and after 65
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Pegylated interferon and lamivudine

42. How to confirm dx if pcp?
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Bronchoalveolar washing and transbronchial biopsy
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
PML; focal neurological deficit like MM; no specific tx; regress with HAART

43. after recent exposure - negative ELISA - How to confirm?
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
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
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
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

44. When to give prophylaxis against MAC
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
High risk 19-64; 1-2 dose - above 65; one dose
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

45. When to tx influenza with antiviral therapy?
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
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
Cd4 count
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

46. rifampin
Similar pathophysiology as ITP - tx zidovudine
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Postcoital voiding - increased intake of cranberry juice

47. causative organisms of uti
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
<500 copies/ml
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Upper lobes; any fibrosis in this area suggestive of latent TB

48. What is tx for herpes zoster
Immune mediated; circulating IgG and IgM to penicillin derivatives
Bronchoalveolar washing and transbronchial biopsy
Acyclovir
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

49. dame that has already occurred
ELISA; initial visit - 6 - 12 and 24 weeks;
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Cd4 count

50. How to confirm chlamydia infection?
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
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Pregnacy - urologic procedure - hip arthoplastu
HIV viral load

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USMLE Step3 Infectious Disease

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