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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. What is characteristic for dx of rocky mountain spotted fever?
Cd4 count
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
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

2. What is tx for herpes zoster
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
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
Acyclovir

3. What are indicators for progression of HIV
Viral load and CD4 count
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
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

4. pathophysiology of toxic shock syndrom?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

5. How to tx IM?
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
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
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
If a sample is ELISA positive - it is tested fro western blot for confirmation

6. 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
<5000 copies/ml
Upper lobes; any fibrosis in this area suggestive of latent TB
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

7. hypertriglyceridemia in HIV
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
HBIG hep B immunoglobulin
AA gradient >35 or Po2 <70
Ampicillin-sublactam; most bites contain eikenella

8. what would be viral load after 4 weeks
<5000 copies/ml
Postcoital voiding - increased intake of cranberry juice
Oropharyngeal secretions; hence named as kissing disease
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w

9. INH
HIV viral load
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

10. How to confirm dx if pcp?
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Bronchoalveolar washing and transbronchial biopsy
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Viral load and CD4 count

11. pneumococcal vaccine indication?
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
High risk 19-64; 1-2 dose - above 65; one dose
When cd4 count falls below 200. 2p in pcp =200

12. What is tetanus - diptheria - pertusis recommendation?
HBIG hep B immunoglobulin
Td every 10 years - tdap once before 65 and after 65
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Acyclovir

13. foot infections in DM
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Pregnacy - urologic procedure - hip arthoplastu
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.
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

14. What are the subjective /objective measure of encephalopathy?
ELISA; initial visit - 6 - 12 and 24 weeks;
AA gradient >35 or Po2 <70
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

15. causative organisms of uti
<5000 copies/ml
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Oropharyngeal secretions; hence named as kissing disease
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

16. 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
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
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.
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

17. When to tx influenza with antiviral therapy?
Acyclovir
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
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
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

18. What is the indication of corticosteroid in pcp infection?
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Cd4 count
AA gradient >35 or Po2 <70
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil

19. How to dx lyme arthritis?
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
ELISA and western blot of synovial fluid.
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

20. INH
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

21. what parameters increases risk of neurosyphilis in HIV patient
High risk 19-64; 1-2 dose - above 65; one dose
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.
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

22. How to tx pseudomonas?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Acyclovir
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

23. What is the criteria for Spontaneous bact peritonitis
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
If a sample is ELISA positive - it is tested fro western blot for confirmation
Aortic valve; endocardiits of AR p/w AV block and LBBB
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

24. When not to tx asymptomatic bacteriura?
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
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

25. what if monospot test is neg in IM?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
Do EBV antibody test
ELISA; initial visit - 6 - 12 and 24 weeks;

26. What is lag time to develop lyme arthritis after exposure to vector
ELISA and western blot of synovial fluid.
When cd4 count falls below 200. 2p in pcp =200
Pt who have been treated before for latent TB
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain

27. How to differentiate gonococcal and nongonoccal urethritis?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
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
Immune mediated; circulating IgG and IgM to penicillin derivatives

28. when not to give INH therapy if ppd positive and patient asyptomatic
Bronchoalveolar washing and transbronchial biopsy
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Pt who have been treated before for latent TB
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

29. What is the pathophysiology of Meningococcal meningitis?
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Oropharyngeal secretions; hence named as kissing disease

30. What is the prognosis of lyme arthritis?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
ELISA and western blot of synovial fluid.

31. drugs work well on hypertriglyceridia?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
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

32. What is the classic signs of nec fasc?
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
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
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

33. What is the Tx of STD uretheritis?
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
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Ampicillin-sublactam; most bites contain eikenella
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.

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

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35. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Within 6 months viral load will be <50
HBIG hep B immunoglobulin
Pregnacy - urologic procedure - hip arthoplastu

36. How to tx TSS?
Others lesions are ring enhancing and have mass effect while PML don't
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
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
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

37. What is used for prophylaxis against meningo..meningitis?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Rifampin600mg q12. or cipro
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

38. after recent exposure - negative ELISA - How to confirm?
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Do EBV antibody test
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

39. after exposure of HIV when antibody testing is performed?
ELISA; initial visit - 6 - 12 and 24 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
High risk 19-64; 1-2 dose - above 65; one dose
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

40. rifampin
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Monospot test which screen heteropile ab that agglutinate horse rbc
Reddish orange discoloration of urine - feces - sweat - tears - sputum

41. how im is transmitted?
AA gradient >35 or Po2 <70
Ampicillin-sublactam; most bites contain eikenella
Either TB or aspergillosis
Oropharyngeal secretions; hence named as kissing disease

42. How to dx adequate response to HBV vaccine
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Vaccine titer >10mU/ml
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

43. 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
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
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
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

44. antibiotic with good prostate penetration?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
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 lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

45. 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.
Aortic valve; endocardiits of AR p/w AV block and LBBB
Voriconazol. mycetoma-surgical removal
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

46. When to give abx to prevent recurrent uti
Voriconazol. mycetoma-surgical removal
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Others lesions are ring enhancing and have mass effect while PML don't
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

47. which heart valve is closer to ventricular conduction system/
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
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
Aortic valve; endocardiits of AR p/w AV block and LBBB

48. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
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
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Mainly clinical - epidemiological and seasonal setting

49. dame that has already occurred
Td every 10 years - tdap once before 65 and after 65
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Clostridium perfringens after penetrative injuries/wounds
Cd4 count

50. How to dx IM?
Viral load and CD4 count
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Others lesions are ring enhancing and have mass effect while PML don't