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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 to differentiate gonococcal and nongonoccal urethritis?
HBIG hep B immunoglobulin
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 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Postcoital voiding - increased intake of cranberry juice

2. How to dx IM?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
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
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

3. What is the classic signs of nec fasc?
Classic triad: fever - pharyngitis - postauricular lymaphdenopahty - caused by EBV
ELISA and western blot of synovial fluid.
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
Monospot test which screen heteropile ab that agglutinate horse rbc

4. after exposure of HIV when antibody testing is performed?
ELISA; initial visit - 6 - 12 and 24 weeks;
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
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses

5. How to dx progressive multifocal leukoencephalopathy
ELISA and western blot of synovial fluid.
Voriconazol. mycetoma-surgical removal
Immunocompromised patient ? dec vision - weakness/tingling of extremities or other neurological symptoms - MRI nonenhancing lesion in parietooccipital region
Bed rest - NSAID - avoid contact sports; if patient develop SOB due to pharyngeal edema - give corticosteroid

6. can HIV transmitted through human bite?
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Reddish orange discoloration of urine - feces - sweat - tears - sputum

7. worsening of TB after starting HAART in HIV
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Voriconazol. mycetoma-surgical removal
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
Acyclovir

8. How to confirm dx if pcp?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Bronchoalveolar washing and transbronchial biopsy
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate

9. What is tx for herpes zoster
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
<500 copies/ml
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Acyclovir

10. When to give prophylaxis against MAC
Pt who have been treated before for latent TB
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)

11. after bone marrow transplant - patient develop headache - fever - cought and chest pain. What is dx?
Postcoital voiding - increased intake of cranberry juice
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes

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

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13. pneumococcal vaccine indication?
HBIG hep B immunoglobulin
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
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

14. What are the behavioral interventions decrease the risk of UTI
Either TB or aspergillosis
Postcoital voiding - increased intake of cranberry juice
Rifampin600mg q12. or cipro
Ampicillin-sublactam; most bites contain eikenella

15. causative organisms of uti
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
<500 copies/ml
Ampicillin-sublactam; most bites contain eikenella
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

16. What are indicators for progression of HIV
Postcoital voiding - increased intake of cranberry juice
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Td every 10 years - tdap once before 65 and after 65
Viral load and CD4 count

17. INH
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
<5000 copies/ml
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >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

18. How long we tx chronic prostatis?
If a sample is ELISA positive - it is tested fro western blot for confirmation
6-12 weeks
Pt who have been treated before for latent TB
Td every 10 years - tdap once before 65 and after 65

19. dame that has already occurred
Non pregnant premanopausal - elderly - dm - sci - chronic foley
Cd4 count
Vaccine titer >10mU/ml
Upper lobes; any fibrosis in this area suggestive of latent TB

20. INH
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Throat cx of positive of GAS means bacteria are colonized bur not infected in IM. tx with ampi can trigger maculopaular rash
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
AA gradient >35 or Po2 <70

21. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Harrt ---rapid improvement of immune function---increased inflammatory reaction--worsening of clinical symptoms; self limiting....needs no tx
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Immune mediated; circulating IgG and IgM to penicillin derivatives
PML; focal neurological deficit like MM; no specific tx; regress with HAART

22. acute onset +rusty sputum
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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
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

23. acute febrile reaction develops after starting penicilin tx to syphilis patient
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV

24. Tx of choice for human bites
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Ampicillin-sublactam; most bites contain eikenella
Pegylated interferon and lamivudine
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

25. What is lag time to develop lyme arthritis after exposure to vector
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Aortic valve; endocardiits of AR p/w AV block and LBBB

26. which heart valve is closer to ventricular conduction system/
AA gradient >35 or Po2 <70
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
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Aortic valve; endocardiits of AR p/w AV block and LBBB

27. HIV patient having fat deposition on back of neck and abdomen - like cushing
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
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

28. How to dx adequate response to HBV vaccine
Vaccine titer >10mU/ml
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
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
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

29. gas gangrene
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Clostridium perfringens after penetrative injuries/wounds
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

30. How to give postexposure prophylaxis for HIV
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
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

31. hypertension in children
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
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
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

32. What is difference between uti relapse versus recurrence?
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
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Acyclovir

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
Acyclovir
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin

34. What is the pathophysiology of Meningococcal meningitis?
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges

35. When not to tx asymptomatic bacteriura?
Non pregnant premanopausal - elderly - dm - sci - chronic foley
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
If a sample is ELISA positive - it is tested fro western blot for confirmation
ELISA; initial visit - 6 - 12 and 24 weeks;

36. how im is transmitted?
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 E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
Oropharyngeal secretions; hence named as kissing disease

37. How often viral load is monitored after HAART?
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Pregnacy - urologic procedure - hip arthoplastu
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months

38. thrombocytopenia in HIV
High risk 19-64; 1-2 dose - above 65; one dose
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
<500 copies/ml
Similar pathophysiology as ITP - tx zidovudine

39. 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
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.
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.

40. How to dx?
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Monospot test which screen heteropile ab that agglutinate horse rbc
Mainly clinical - epidemiological and seasonal setting
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

41. foot infections in DM
Need lumbar puncture to relieve pressure; they have high opening pressure >350
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

42. How to tx pcp?
Acyclovir
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
Reddish orange discoloration of urine - feces - sweat - tears - sputum
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

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

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

45. How to differentiate different types of necrotizing fascitis?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
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
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
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

46. How often HIV postiive patients CD4 count needs to be evaluated?
High risk 19-64; 1-2 dose - above 65; one dose
Similar pathophysiology as ITP - tx zidovudine
Every 3-4 hours to determine appropritate time to start HAART
Reddish orange discoloration of urine - feces - sweat - tears - sputum

47. When to give abx to prevent recurrent uti
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
Pegylated interferon and lamivudine
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

48. How to confirm chlamydia infection?
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
Either TB or aspergillosis
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole

49. how CMV presents in immunocompromised patients
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits
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
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Massive (even 20L/day) fluid resuscitaiton which may clear toxin

50. How to dx cryptococal meninggits
Upper lobes; any fibrosis in this area suggestive of latent TB
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Vaccine titer >10mU/ml
Similar pathophysiology as ITP - tx zidovudine