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

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2. aspergillosis
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
Voriconazol. mycetoma-surgical removal
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Immune mediated; circulating IgG and IgM to penicillin derivatives

3. When not to tx asymptomatic bacteriura?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Pegylated interferon and lamivudine

4. Tx of choice for human bites
Ampicillin-sublactam; most bites contain eikenella
Oropharyngeal secretions; hence named as kissing disease
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
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx

5. which heart valve is closer to ventricular conduction system/
Aortic valve; endocardiits of AR p/w AV block and LBBB
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
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

6. When to give prophylaxis against MAC
Voriconazol. mycetoma-surgical removal
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.
ELISA and western blot of synovial fluid.
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

7. when we see echym gangrenosum?
Bronchoalveolar washing and transbronchial biopsy
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

8. How to confirm chlamydia infection?
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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

9. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
HBIG hep B immunoglobulin

10. how HAART therapy affects HIV viral loads?
Within 6 months viral load will be <50
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Oropharyngeal secretions; hence named as kissing disease
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

11. What is the pathophysiology of Meningococcal meningitis?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Reddish orange discoloration of urine - feces - sweat - tears - sputum
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

12. How to tx pcp?
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Acyclovir
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

13. rifampin
Postcoital voiding - increased intake of cranberry juice
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Reddish orange discoloration of urine - feces - sweat - tears - sputum
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

14. How often viral load is monitored after HAART?
Every 3-4 hours to determine appropritate time to start HAART
If a sample is ELISA positive - it is tested fro western blot for confirmation
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
<5000 copies/ml

15. clinical manifestation of mucomycosis
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
6-12 weeks
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved

16. damae that is about to occur?
Mainly clinical - epidemiological and seasonal setting
HIV viral load
Upper lobes; any fibrosis in this area suggestive of latent TB
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

17. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
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
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
Bronchoalveolar washing and transbronchial biopsy

18. antibiotic with good prostate penetration?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
When cd4 count falls below 200. 2p in pcp =200
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

19. What is tetanus - diptheria - pertusis recommendation?
Every 3-4 hours to determine appropritate time to start HAART
Td every 10 years - tdap once before 65 and after 65
Acyclovir
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

20. how CMV presents in immunocompromised patients
Voriconazol. mycetoma-surgical removal
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
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
Blastomycosis

21. What is the Tx of cryptococcal meninngitis
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

22. What is used for prophylaxis against meningo..meningitis?
Rifampin600mg q12. or cipro
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

23. How to dx bacterial meningitis from CSF study?

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24. worsening of TB after starting HAART in HIV
PML; focal neurological deficit like MM; no specific tx; regress with HAART
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Pregnacy - urologic procedure - hip arthoplastu

25. What is difference between uti relapse versus recurrence?
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
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

26. foot infections in DM
Monospot test which screen heteropile ab that agglutinate horse rbc
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

27. patient with diagnosed case of cryptococcal meningitis p/w severe headache and vomiting
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Postcoital voiding - increased intake of cranberry juice
Within 6 months viral load will be <50

28. How to differentiate different types of necrotizing fascitis?
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Within 6 months viral load will be <50
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
Oropharyngeal secretions; hence named as kissing disease

29. How long we tx chronic prostatis?
6-12 weeks
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
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

30. How to differentiate gonococcal and nongonoccal urethritis?
Pregnacy - urologic procedure - hip arthoplastu
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
Bronchoalveolar washing and transbronchial biopsy
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.

31. What is fatal consequence of RMSF?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Similar pathophysiology as ITP - tx zidovudine

32. when not to give INH therapy if ppd positive and patient asyptomatic
Cd4 count
Pt who have been treated before for latent TB
Do EBV antibody test
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine

33. What are the behavioral interventions decrease the risk of UTI
6-12 weeks
Every 3-4 hours to determine appropritate time to start HAART
Postcoital voiding - increased intake of cranberry juice
Immune mediated; circulating IgG and IgM to penicillin derivatives

34. 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
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
<500 copies/ml
Viral load and CD4 count

35. What is the indication of corticosteroid in pcp 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
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Upper lobes; any fibrosis in this area suggestive of latent TB
AA gradient >35 or Po2 <70

36. thrombocytopenia in HIV
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
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
When cd4 count falls below 200. 2p in pcp =200

37. When to tx influenza with antiviral therapy?
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
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
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

38. What is the prognosis of lyme arthritis?
Bronchoalveolar washing and transbronchial biopsy
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
Viral load and CD4 count
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV

39. How to give postexposure prophylaxis for HIV
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
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

40. How to dx cryptococal meninggits
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ

41. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Non pregnant premanopausal - elderly - dm - sci - chronic foley
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Reddish orange discoloration of urine - feces - sweat - tears - sputum

42. pneumococcal vaccine indication?
High risk 19-64; 1-2 dose - above 65; one dose
Similar pathophysiology as ITP - tx zidovudine
Acyclovir
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma

43. what would be viral load after 2-4m of HAART?
<500 copies/ml
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
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

44. systolic HTN in elderly
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
Bronchoalveolar washing and transbronchial biopsy
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
If a sample is ELISA positive - it is tested fro western blot for confirmation

45. How to tx IM?
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Monospot test which screen heteropile ab that agglutinate horse rbc
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

46. 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
PML; focal neurological deficit like MM; no specific tx; regress with HAART
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Pegylated interferon and lamivudine

47. acute febrile reaction develops after starting penicilin tx to syphilis 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.
Acyclovir
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

48. How to tx TSS?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
6-12 weeks
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Doesn't exceed more than 15 mm and size significantly decreases after 15 years

49. INH
HIV viral load
Ampicillin-sublactam; most bites contain eikenella
Aortic valve; endocardiits of AR p/w AV block and LBBB
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50

50. What is lag time to develop lyme arthritis after exposure to vector
Pegylated interferon and lamivudine
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole