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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. systolic HTN in elderly
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.

2. What is the classic signs of nec fasc?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
Immune mediated; circulating IgG and IgM to penicillin derivatives
Non pregnant premanopausal - elderly - dm - sci - chronic foley
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

3. What is the Tx of STD uretheritis?
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
AA gradient >35 or Po2 <70
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
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.

4. INH
Vitamin B6 antagonist - can cause peripheral neuropathy if not give with b6
Every 3-4 hours to determine appropritate time to start HAART
6-12 weeks
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

5. what parameters increases risk of neurosyphilis in HIV 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.
Blastomycosis
Jarish-Herxheimer reaction; immunologica reaction due to rupture of sprochetes
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.

6. What is the pathophysiology of Meningococcal meningitis?
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease
N meningitidis colonize in nasopharynx; cause mucosal invasion - systemic bacterimia and seeding in the meninges
Either TB or aspergillosis
<5000 copies/ml

7. what would be viral load after 4 weeks
Quinoloes (cipro/levo) cure rate 70% - TMP-SMZ
ELISA and western blot of synovial fluid.
<5000 copies/ml
Pt who have been treated before for latent TB

8. low grade fever - maculopapular rash - lymphadenopathy
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Reddish orange discoloration of urine - feces - sweat - tears - sputum

9. What are the subjective /objective measure of encephalopathy?
Acyclovir
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
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

10. clinical manifestation of mucomycosis
Hepatotoxitcity incidence 2.6% - commonly seen in alcoholic - liver disease - >50
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
HIV viral load
Immune mediated; circulating IgG and IgM to penicillin derivatives

11. thrombocytopenia in HIV
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Similar pathophysiology as ITP - tx zidovudine
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles

12. rifampin
Viral load and CD4 count
Reddish orange discoloration of urine - feces - sweat - tears - sputum
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -
Rifampin600mg q12. or cipro

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

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14. drugs work well on hypertriglyceridia?
Do EBV antibody test
Within 6 months viral load will be <50
Gemfibrozil and other fibrate drugs; statin and niacin also work not as good as fibrate drugs like gemfibrozil
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads

15. hypertension in children
Rifampin600mg q12. or cipro
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
Aortic valve; endocardiits of AR p/w AV block and LBBB
Ampicillin-sublactam; most bites contain eikenella

16. What is difference between uti relapse versus recurrence?
Blastomycosis
Acyclovir
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
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

17. How to dx?
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
ELISA and western blot of synovial fluid.
Mainly clinical - epidemiological and seasonal setting

18. How often viral load is monitored after HAART?
At first 4 weeks - then 8-12weks; remeasusing every 2m until viral load is undetectatable. then every 3 months
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Within 72hrs of unprotected sex with HIV pos person - give two nucleosidase inhibitors (eg. zidovudin - lamivudein - tenofovir -) X4w
Pregnacy - urologic procedure - hip arthoplastu

19. How to differentiate gonococcal and nongonoccal urethritis?
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
Every 3-4 hours to determine appropritate time to start HAART
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
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

20. How to confirm dx if pcp?
Fever - facial swelling - nasal discha - maxilary pain and tenderness - headache - present in DKA - caused by zygomycetes tx surgical debridement and intranasal amphotericin
Pegylated interferon and lamivudine
Bronchoalveolar washing and transbronchial biopsy
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)

21. acute onset +rusty sputum
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx
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

22. What is tetanus - diptheria - pertusis recommendation?
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
ELISA and western blot of synovial fluid.
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Td every 10 years - tdap once before 65 and after 65

23. What is lag time to develop lyme arthritis after exposure to vector
Tampoon in nostril/vagina. think t for t - staph release exotoxin --activation of t cells directly--release of massive cytokines.
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
HIV viral load
Upper lobes; any fibrosis in this area suggestive of latent TB

24. oligodendrocyte with intranuclear inclusion and demyelination in HIV patient
Upper lobes; any fibrosis in this area suggestive of latent TB
Monospot test which screen heteropile ab that agglutinate horse rbc
Ampicillin-sublactam; most bites contain eikenella
PML; focal neurological deficit like MM; no specific tx; regress with HAART

25. what would be viral load after 2-4m of HAART?
<500 copies/ml
If a sample is ELISA positive - it is tested fro western blot for confirmation
Postcoital voiding - increased intake of cranberry juice
Oropharyngeal secretions; hence named as kissing disease

26. after exposure of HIV when antibody testing is performed?
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
Most common; fibromuscular dysplasia - Rt renal artery more common - angiography string of beads
ELISA; initial visit - 6 - 12 and 24 weeks;
Due to decrease elasticity of arterial wall; only systolic - diastolic normal - wide pulse pressure

27. How to confirm chlamydia infection?
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
4 months; characterized by knee joint effusion-large amount - joint stiffness - pain
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
ELISA; initial visit - 6 - 12 and 24 weeks;

28. What is characteristic for dx of rocky mountain spotted fever?
<500 copies/ml
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
High risk 19-64; 1-2 dose - above 65; one dose
Tx with amoxicillin or ceftriaxone. 90% are disease free after one year after tx

29. What is used for prophylaxis against meningo..meningitis?
6-12 weeks
Rifampin600mg q12. or cipro
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)

30. How to tx TSS?
AA gradient >35 or Po2 <70
Mainly clinical - epidemiological and seasonal setting
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Give nystatin suspension or clotrimazol with an oral antifungal eg. fluconazol

31. When to tx asymptomatic bacteriurea >100 -000?
Pregnacy - urologic procedure - hip arthoplastu
If a sample is ELISA positive - it is tested fro western blot for confirmation
Rifampin600mg q12. or cipro
Upper lobes; any fibrosis in this area suggestive of latent TB

32. damae that is about to occur?
AMS - focal neurological signs - seizures - multiorgan dysfunction - death; tx; doxycycline; for pregnant give chloramphenicle
Td every 10 years - tdap once before 65 and after 65
HIV lipodystrophy; no correlation with viral load; p/w insulin resistance and dyslipidemia (inc cholesterol - dec HDL)
HIV viral load

33. What is the Tx of cryptococcal meninngitis
Start with amphotericin B and flucytosin for 2 weeks - if there is clinical improvement discontinue them and start with fluconazol
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
<5000 copies/ml
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -

34. What is the criteria for Spontaneous bact peritonitis
Voriconazol. mycetoma-surgical removal
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
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose

35. where TB normally affects
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
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
PML; focal neurological deficit like MM; no specific tx; regress with HAART

36. what if monospot test is neg in IM?
Similar pathophysiology as ITP - tx zidovudine
Vaccine titer >10mU/ml
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Do EBV antibody test

37. can HIV transmitted through human bite?
Reddish orange discoloration of urine - feces - sweat - tears - sputum
HIV present in very minimal quantities in human saliva. exposure/contact of saliva will never trasmit HIV
250 neutrophil/mm3 in peritoneal fluid - tx empiric abx; if tremor or other neuro sign give lactulose
CTP subjective; MELD objective; meld uses serum billirubin - inr and serum creatinin. meld used to determine 90 day mortality of liver diease

38. Do we need to give vaccine or immunoglobulin for rabies exposure in previously vaccinated person?
Viral load and CD4 count
Only vaccine. immunoglobuin not required. previously unvaccinated person will receive both.
Voriconazol. mycetoma-surgical removal
Clostridium perfringens after penetrative injuries/wounds

39. 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
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
If a sample is ELISA positive - it is tested fro western blot for confirmation
Within 6 months viral load will be <50

40. aspergillosis
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
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
Voriconazol. mycetoma-surgical removal
Fever of unknown orign - esophagiti - retinitis - diarrhoea - encephalits

41. What is the mch of ampicillin induced rash in IM
Immune mediated; circulating IgG and IgM to penicillin derivatives
Massive (even 20L/day) fluid resuscitaiton which may clear toxin
Aspergillosis. common in bone marrow transplants. typically involves lungs and sinuses
6-12 weeks

42. hypertriglyceridemia in HIV
PML; focal neurological deficit like MM; no specific tx; regress with HAART
Exacerbate by HAART; give statin - if triglyceride >500 - give a fibrate
Aortic valve; endocardiits of AR p/w AV block and LBBB
Voriconazol. mycetoma-surgical removal

43. How to tx pseudomonas?
Antipseudomonal penicillin (pipercillin) or cephalosporin (ceftazdidime/cefepime) and aminoglycoside (tobramycin/amikacin)
<5000 copies/ml
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Staph - GBS - proteus - pseudomona - e coli - candida - bacteroids; organisms isolated only from deep curettage of ulcer

44. wisconsin - missisipi - ohio
S. pneumonie. differentitate this from atypical pneumonia and pcp which are gradual onset - non productive cough -
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Chlamydia pcr - 88% sensitivity and 99% specificity; if negative think about MUT organims; mycoplasma - ureaplasma and trichomonas; tx MUT with metronidazole
Blastomycosis

45. How to dx cryptococal meninggits
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
Markedly elevated csf pressure >200 - inc protein - low glucose ; tx amphotericin and flucytosine
Leukocytosis >100 cells - dec glucose - inc protien - inc opening pressure; in viral there will be lymphocytosis - normal glucose (virus doesn't eat) -

46. When to give prophylaxis against MAC
2 weeks in neutropenic patients and 7-10 days after catheter removed/patient improved
Blastomycosis
For mac - we give azithromycin - mac has a for azithromycin; cd4 <50; remember CML designates for <50 c-cmv; m- mac - L-cns lymphoma
Pregnacy - urologic procedure - hip arthoplastu

47. How to dx lyme arthritis?
HIV syndrome or anti-retroviral syndrome; 2-3w after virus exposure. similar to IM.
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
ELISA and western blot of synovial fluid.
Oropharyngeal secretions; hence named as kissing disease

48. How to give postexposure prophylaxis to patient who received vaccine but titer inadequate
<500 copies/ml
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Trimethoprime-sulphamethoxazole if intolerant give pentamidine (cause pancreatitis p for p)
HBIG hep B immunoglobulin

49. How to dx bacterial meningitis from CSF study?

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50. causative organisms of uti
HIV RNA PCR assay; there may be small amount of virus that are not detectable in ELISA.
Most common E coli; less common; klebsiella - enterobacter - proteus - staph - groupd d strep
Doesn't exceed more than 15 mm and size significantly decreases after 15 years
Petechial rash developed 3-5th days of illness begins ankle or wrist and spread to palm/soles