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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. How long we tx chronic prostatis?
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Oropharyngeal secretions; hence named as kissing disease
6-12 weeks
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

2. How to dx IM?
Cd4 count
Monospot test which screen heteropile ab that agglutinate horse rbc
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
Vaccine titer >10mU/ml

3. How to differentiate different types of necrotizing fascitis?
Immune mediated; circulating IgG and IgM to penicillin derivatives
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
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
Td every 10 years - tdap once before 65 and after 65

4. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
PML; focal neurological deficit like MM; no specific tx; regress with HAART
HBIG hep B immunoglobulin
ELISA and western blot of synovial fluid.

5. How to dx adequate response to HBV vaccine
PML; focal neurological deficit like MM; no specific tx; regress with 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.
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
Vaccine titer >10mU/ml

6. antibiotic with good prostate penetration?
Postcoital voiding - increased intake of cranberry juice
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
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

7. HIV patient having fat deposition on back of neck and abdomen - like cushing
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
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Immune mediated; circulating IgG and IgM to penicillin derivatives
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

8. What is used for prophylaxis against meningo..meningitis?
ELISA; initial visit - 6 - 12 and 24 weeks;
Every 3-4 hours to determine appropritate time to start HAART
HBIG hep B immunoglobulin
Rifampin600mg q12. or cipro

9. what would be viral load after 2-4m of HAART?
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
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
<500 copies/ml
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

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

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

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12. after exposure of HIV when antibody testing is performed?
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
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
ELISA; initial visit - 6 - 12 and 24 weeks;
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

13. pneumococcal vaccine indication?
Either TB or aspergillosis
HBIG hep B immunoglobulin
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
High risk 19-64; 1-2 dose - above 65; one dose

14. 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.
Similar pathophysiology as ITP - tx zidovudine
Others lesions are ring enhancing and have mass effect while PML don't
Need lumbar puncture to relieve pressure; they have high opening pressure >350

15. low grade fever - maculopapular rash - lymphadenopathy
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Pt who have been treated before for latent TB
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

16. How to dx IM?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Td every 10 years - tdap once before 65 and after 65
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

17. what parameters increases risk of neurosyphilis in HIV patient
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
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.
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
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

18. damae that is about to occur?
Immune mediated; circulating IgG and IgM to penicillin derivatives
Td every 10 years - tdap once before 65 and after 65
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
HIV viral load

19. How to confirm dx if pcp?
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
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
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

20. What is tetanus - diptheria - pertusis recommendation?
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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
Within 6 months viral load will be <50

21. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Cd4 count
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Pregnacy - urologic procedure - hip arthoplastu

22. How to dx progressive multifocal leukoencephalopathy
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
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
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

23. how HAART therapy affects HIV viral loads?
Within 6 months viral load will be <50
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Upper lobes; any fibrosis in this area suggestive of latent TB
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

24. How to tx TSS?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
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
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
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

25. When not to tx asymptomatic bacteriura?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Within 6 months viral load will be <50
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

26. drugs work well on hypertriglyceridia?
Voriconazol. mycetoma-surgical removal
Oropharyngeal secretions; hence named as kissing disease
Similar pathophysiology as ITP - tx zidovudine
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

27. Tx of choice for human bites
Immune mediated; circulating IgG and IgM to penicillin derivatives
Mainly clinical - epidemiological and seasonal setting
Vaccine titer >10mU/ml
Ampicillin-sublactam; most bites contain eikenella

28. What is the prognosis of lyme arthritis?
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
ELISA; initial visit - 6 - 12 and 24 weeks;

29. what if monospot test is neg in IM?
Aortic valve; endocardiits of AR p/w AV block and LBBB
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Do EBV antibody test
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

30. INH
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Oropharyngeal secretions; hence named as kissing disease

31. How to dx lyme arthritis?
Reddish orange discoloration of urine - feces - sweat - tears - sputum
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
ELISA and western blot of synovial fluid.

32. 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
Voriconazol. mycetoma-surgical removal
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
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

33. worsening of TB after starting HAART in HIV
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Pt who have been treated before for latent TB
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

34. thrombocytopenia in HIV
Similar pathophysiology as ITP - tx zidovudine
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

35. What is tx for herpes zoster
Acyclovir
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
HBIG hep B immunoglobulin
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

36. What is the Tx of STD uretheritis?
Aortic valve; endocardiits of AR p/w AV block and LBBB
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
Cd4 count
Oropharyngeal secretions; hence named as kissing disease

37. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Others lesions are ring enhancing and have mass effect while PML don't
Viral load and CD4 count
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

38. What is characteristic for dx of rocky mountain spotted fever?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
<500 copies/ml

39. What is the criteria for Spontaneous bact peritonitis
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)
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

40. gas gangrene
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
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
Clostridium perfringens after penetrative injuries/wounds

41. What is lag time to develop lyme arthritis after exposure to vector
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
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
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
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

42. when HIV patient develop pcp?
When cd4 count falls below 200. 2p in pcp =200
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

43. How often HIV postiive patients CD4 count needs to be evaluated?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Every 3-4 hours to determine appropritate time to start HAART
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
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

44. which heart valve is closer to ventricular conduction system/
HIV viral load
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Aortic valve; endocardiits of AR p/w AV block and LBBB
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

45. causative organisms of uti
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
<500 copies/ml

46. reddish colored papules with central umbilication in HIV or immunocompromised 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.
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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
Viral load and CD4 count

47. How to tx pcp?
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
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Clostridium perfringens after penetrative injuries/wounds
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

48. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Non pregnant premanopausal - elderly - dm - sci - chronic foley
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
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

49. How to tx pseudomonas?
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
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
6-12 weeks
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

50. systolic HTN in elderly
Immune mediated; circulating IgG and IgM to penicillin derivatives
Pegylated interferon and lamivudine
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)