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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. antibiotic with good prostate penetration?
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
6-12 weeks
<5000 copies/ml
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

2. after recent exposure - negative ELISA - How to confirm?
Ampicillin-sublactam; most bites contain eikenella
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

3. foot infections in DM
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
ELISA and western blot of synovial fluid.
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Rifampin600mg q12. or cipro

4. How to confirm dx if pcp?
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
AA gradient >35 or Po2 <70
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
Bronchoalveolar washing and transbronchial biopsy

5. causative organisms of uti
Upper lobes; any fibrosis in this area suggestive of latent TB
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep

6. damae that is about to occur?
Pregnacy - urologic procedure - hip arthoplastu
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
HIV viral load
Oropharyngeal secretions; hence named as kissing disease

7. thrombocytopenia in HIV
Rifampin600mg q12. or cipro
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Similar pathophysiology as ITP - tx zidovudine
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

8. acute onset +rusty sputum
Do EBV antibody test
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Every 3-4 hours to determine appropritate time to start HAART

9. How long abx is given in pseudomonas infection?
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
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
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
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

10. hypertriglyceridemia in HIV
Either TB or aspergillosis
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Monospot test which screen heteropile ab that agglutinate horse rbc
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

11. When to tx asymptomatic bacteriurea >100 -000?
Pt who have been treated before for latent TB
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
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.

12. how HAART therapy affects HIV viral loads?
Within 6 months viral load will be <50
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 E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region

13. 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
Viral load and CD4 count
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
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.

14. when western blot is done for HIV testing
If a sample is ELISA positive - it is tested fro western blot for confirmation
HBIG hep B immunoglobulin
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
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

15. What is the Tx of cryptococcal meninngitis
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
HIV viral load

16. how im is transmitted?
Mainly clinical - epidemiological and seasonal setting
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
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Oropharyngeal secretions; hence named as kissing disease

17. what would be viral load after 2-4m of HAART?
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
Upper lobes; any fibrosis in this area suggestive of latent TB
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
<500 copies/ml

18. How to confirm chlamydia infection?
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Blastomycosis
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

19. acute febrile reaction develops after starting penicilin tx to syphilis patient
Others lesions are ring enhancing and have mass effect while PML don't
Mainly clinical - epidemiological and seasonal setting
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

20. low grade fever - maculopapular rash - lymphadenopathy
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Either TB or aspergillosis
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

21. What are the behavioral interventions decrease the risk of UTI
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
Pregnacy - urologic procedure - hip arthoplastu
Postcoital voiding - increased intake of cranberry juice

22. patient is taking inhaled corticosteroid for asthma - now p/w oral candidiasis
Need lumbar puncture to relieve pressure; they have high opening pressure >350
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
Oropharyngeal secretions; hence named as kissing disease

23. when HIV patient develop pcp?
When cd4 count falls below 200. 2p in pcp =200
Ampicillin-sublactam; most bites contain eikenella
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
Mainly clinical - epidemiological and seasonal setting

24. after exposure of HIV when antibody testing is performed?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
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
ELISA; initial visit - 6 - 12 and 24 weeks;

25. where TB normally affects
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Upper lobes; any fibrosis in this area suggestive of latent TB
Immune mediated; circulating IgG and IgM to penicillin derivatives
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

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

27. How to dx adequate response to HBV vaccine
Vaccine titer >10mU/ml
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Similar pathophysiology as ITP - tx zidovudine

28. aspergillosis
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Voriconazol. mycetoma-surgical removal
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

29. how CMV presents in immunocompromised patients
Upper lobes; any fibrosis in this area suggestive of latent TB
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
High risk 19-64; 1-2 dose - above 65; one dose

30. What is difference between uti relapse versus recurrence?
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
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
Non pregnant premanopausal - elderly - dm - sci - chronic foley

31. when not to give INH therapy if ppd positive and patient asyptomatic
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Voriconazol. mycetoma-surgical removal
Either TB or aspergillosis
Pt who have been treated before for latent TB

32. How to differentiate gonococcal and nongonoccal urethritis?
<5000 copies/ml
Pegylated interferon and lamivudine
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

33. INH
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Clostridium perfringens after penetrative injuries/wounds
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

34. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
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
<5000 copies/ml

35. chshould we tx IM with abx (ampicilin) if throat cx is positive?
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
<500 copies/ml
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash

36. Tx of choice for human bites
Cd4 count
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Ampicillin-sublactam; most bites contain eikenella

37. INH
Similar pathophysiology as ITP - tx zidovudine
Do EBV antibody test
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

38. What is the pathophysiology of Meningococcal meningitis?
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.
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

39. How to tx pcp?
Pegylated interferon and lamivudine
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
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

40. clinical manifestation of mucomycosis
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Mainly clinical - epidemiological and seasonal setting
Blastomycosis

41. How to dx IM?
Monospot test which screen heteropile ab that agglutinate horse rbc
Either TB or aspergillosis
Cd4 count
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

42. When to give abx to prevent recurrent uti
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
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
Td every 10 years - tdap once before 65 and after 65

43. when we see echym gangrenosum?
Bronchoalveolar washing and transbronchial biopsy
Postcoital voiding - increased intake of cranberry juice
Pegylated interferon and lamivudine
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

44. 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
Bronchoalveolar washing and transbronchial biopsy
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6

45. How to give postexposure prophylaxis for HIV
HIV viral load
<500 copies/ml
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

46. What is fatal consequence of RMSF?
Similar pathophysiology as ITP - tx zidovudine
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle

47. wisconsin - missisipi - ohio
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
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
Blastomycosis
HIV viral load

48. 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
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Blastomycosis
High risk 19-64; 1-2 dose - above 65; one dose

49. can HIV transmitted through human bite?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

50. When to give prophylaxis against MAC
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Rifampin600mg q12. or cipro
<5000 copies/ml
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