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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. what would be viral load after 4 weeks
<5000 copies/ml
Either TB or aspergillosis
Acyclovir
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

2. acute onset +rusty sputum
AA gradient >35 or Po2 <70
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
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.
If a sample is ELISA positive - it is tested fro western blot for confirmation

3. hypertension in children
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
ELISA and western blot of synovial fluid.
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

4. How long abx is given in pseudomonas infection?
Similar pathophysiology as ITP - tx zidovudine
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Either TB or aspergillosis

5. reddish colored papules with central umbilication in HIV or immunocompromised patient
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
If a sample is ELISA positive - it is tested fro western blot for confirmation
Rifampin600mg q12. or cipro
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

6. where TB normally affects
Upper lobes; any fibrosis in this area suggestive of latent TB
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Do EBV antibody test
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

7. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Within 6 months viral load will be <50

8. acute febrile reaction develops after starting penicilin tx to syphilis patient
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Clostridium perfringens after penetrative injuries/wounds
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

9. low grade fever - maculopapular rash - lymphadenopathy
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Ampicillin-sublactam; most bites contain eikenella
Pegylated interferon and lamivudine
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

10. What is fatal consequence of RMSF?
Mainly clinical - epidemiological and seasonal setting
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

11. How to tx chronic hep B
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Pegylated interferon and lamivudine
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

12. Tx of choice for human bites
Ampicillin-sublactam; most bites contain eikenella
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
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

13. aspergillosis
ELISA and western blot of synovial fluid.
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) -
Voriconazol. mycetoma-surgical removal

14. worsening of TB after starting HAART in HIV
Within 6 months viral load will be <50
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

15. 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.
Ampicillin-sublactam; most bites contain eikenella
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
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

16. What is used for prophylaxis against meningo..meningitis?
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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Rifampin600mg q12. or cipro

17. How often HIV postiive patients CD4 count needs to be evaluated?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Every 3-4 hours to determine appropritate time to start HAART
Within 6 months viral load will be <50
Upper lobes; any fibrosis in this area suggestive of latent TB

18. How to dx lyme arthritis?
Mainly clinical - epidemiological and seasonal setting
Oropharyngeal secretions; hence named as kissing disease
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
ELISA and western blot of synovial fluid.

19. when western blot is done for HIV testing
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
If a sample is ELISA positive - it is tested fro western blot for confirmation
Need lumbar puncture to relieve pressure; they have high opening pressure >350
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

20. How to dx adequate response to HBV vaccine
Vaccine titer >10mU/ml
Viral load and CD4 count
ELISA and western blot of synovial fluid.
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

21. INH
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 -
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Need lumbar puncture to relieve pressure; they have high opening pressure >350

22. How to confirm chlamydia infection?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Need lumbar puncture to relieve pressure; they have high opening pressure >350

23. pneumococcal vaccine indication?
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
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
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

24. clinical manifestation of mucomycosis
Upper lobes; any fibrosis in this area suggestive of latent TB
Clostridium perfringens after penetrative injuries/wounds
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
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

25. what parameters increases risk of neurosyphilis in HIV patient
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.
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
If a sample is ELISA positive - it is tested fro western blot for confirmation

26. thrombocytopenia in HIV
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Similar pathophysiology as ITP - tx zidovudine

27. pathophysiology of toxic shock syndrom?
Blastomycosis
Cd4 count
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
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

28. What is the indication of corticosteroid in pcp infection?
Upper lobes; any fibrosis in this area suggestive of latent TB
AA gradient >35 or Po2 <70
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Td every 10 years - tdap once before 65 and after 65

29. What is the prognosis of lyme arthritis?
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Do EBV antibody test
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

30. infiltrate in upper lobe of lung?
Voriconazol. mycetoma-surgical removal
Blastomycosis
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Either TB or aspergillosis

31. How to tx TSS?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

32. How to differentiate gonococcal and nongonoccal urethritis?
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
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
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Every 3-4 hours to determine appropritate time to start HAART

33. What are the behavioral interventions decrease the risk of UTI
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
Non pregnant premanopausal - elderly - dm - sci - chronic foley
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

34. What is the classic signs of nec fasc?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Similar pathophysiology as ITP - tx zidovudine
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
6-12 weeks

35. What are indicators for progression of HIV
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Viral load and CD4 count
Pegylated interferon and lamivudine

36. What is the criteria for Spontaneous bact peritonitis
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
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.
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
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

37. When to tx asymptomatic bacteriurea >100 -000?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Postcoital voiding - increased intake of cranberry juice
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Pregnacy - urologic procedure - hip arthoplastu

38. How to differentiate different types of necrotizing fascitis?
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
6-12 weeks
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
HBIG hep B immunoglobulin

39. How long we tx chronic prostatis?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
PML; focal neurological deficit like MM; no specific tx; regress with HAART
6-12 weeks

40. What are the subjective /objective measure of encephalopathy?
Immune mediated; circulating IgG and IgM to penicillin derivatives
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Td every 10 years - tdap once before 65 and after 65

41. how CMV presents in immunocompromised patients
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.
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Vaccine titer >10mU/ml
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

42. when we see echym gangrenosum?
Blastomycosis
Oropharyngeal secretions; hence named as kissing disease
Every 3-4 hours to determine appropritate time to start HAART
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

43. What is the Tx of STD uretheritis?
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
HIV viral load
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
6-12 weeks

44. How to tx pcp?
Td every 10 years - tdap once before 65 and after 65
Voriconazol. mycetoma-surgical removal
Within 6 months viral load will be <50
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

45. How to tx pseudomonas?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
<500 copies/ml
Do EBV antibody test
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

46. What is the mch of ampicillin induced rash in IM
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Immune mediated; circulating IgG and IgM to penicillin derivatives
Do EBV antibody test
Either TB or aspergillosis

47. How often viral load is monitored after HAART?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

48. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
Voriconazol. mycetoma-surgical removal
Within 6 months viral load will be <50
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Need lumbar puncture to relieve pressure; they have high opening pressure >350

49. foot infections in DM
HIV viral load
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Ampicillin-sublactam; most bites contain eikenella
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

50. chshould we tx IM with abx (ampicilin) if throat cx is positive?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles