Infectious Disease

Question 1

Botulism
Path:
Pt:
Dx:
Tx:

Answer 1

Path: Clostridium botulinum
Inhibits acetylcholine release at presynaptic receptors

Infant-> ingesting of honey or corn syrup contaminated with spores

Adults-> Ingestion of preformed toxin in canned/smoked/vacuum-packed foods

Wounds-> traumatic injury w/ soil contamination or IVDU

Dx:
12-36 hrs post injection (6-8 hours if <1yr)
8 D’s: diplopia, dilated fixed pupils, dry mouth, dysphagia, dysarthria (difficult form/pronounce words), dysphonia (hoarseness), descending decreased muscle strength
N/V, CN palies
“Floppy baby syndrome”-> lethargy, weakness, flaccid paralysis weak cry, failure to thrive

Tx:
Contact CDC, supportive care, resp monitoring
Antitoxin:
>1yr old: equine serum heptavalent botulism antitoxin
<1yr old: human-derived botulism immune globulin
Abx:
-None for food borne type (may worsen disease via toxin release from bacteria lysis)
-For wounds:
1st:Penicillin G
metronidazole, clindamycin

Question 2

Candidiasis
Path:
Clinical manifestations, Pt, Tx

Answer 2

Path: Candida albicans

Clinical Manifestations:

Esophagitis
Pt: substernal odynophagia (painful swallowing), GERD, epigastric pain, N/V, +/-thrush
Endoscopy: white linear plaques/erosions
Tx: PO fluconazole

Oral thrush
Pt: friable white plaques +/- leave erythema or bleed if scraped
Tx: nystatin-> swish and swallow
Clotrimazole troches

Vaginal candidiasis
Pt: Vulvar pruritus, burning, vaginal discharge (white, curd like)
Tx: Miconazole, clotrimazole
Fluconazole weekly if persistent vaginitis

Intertrigo
Pt:
cutaneous infection MC in moist, macerated areas
Pruritic rash beefy red erythema w/ distinct, scalloped borders and satellite lesions
Tx: clotrimazole typical, keep area dry

Fungemia, endocarditis
Pt: immune compromised, +/- indwelling catheter
Tx: IV amphotericin B, caspofungin if severe
+/- IV fluconazole if mild

Dx: 
Potassium hydroxide (KOH) smear: buying yeast and pseudohyphae

Question 3

Chlamydia 
Path:
Clinical manifestations:
Dx:
Tx:

Answer 3

Path: Chlamydia trachomatis-> MC bacterial STD in US

Clinical Manifestations:

Urethritis
Purulent or mucopurulent discharge, pruritus, dysuria, dyspareunia, hematuria
Up to 40% asx (esp. men!)

Pelvic inflammatory disease (PID)
Abdominal pain, cervical motion tenderness

Reactive arthritis (Reiter’s syndrome)
urethritis, uveitis, arthritis
+HLA-B27

Lymphogranuloma venereum
genital/rectal lesion w/ softening, suppuration an lymphadenopathy

Dx:

• Nucleic acid amplification- test of choice for both gonorrhea and chlamydia (vaginal swab or first-catch urine)
• Genetic probe methods, culture, antigen detection

Tx:
Azithromycin 1gram x1 dose
Doxycycline 100mg BID x10 days
Retest in 3w to ensure clearance of organism
Also treat for gonorrhea-> ceftriaxone 250mg IM

Question 4

Cholera 
Path:
Pt:
Dx:
Tx:

Answer 4

Path: Vibrio cholerae
Incubation 11-72hrs
Fecal-oral
Contaminated water

Pt:
Explosive rice-water diarrhea
Fever (rare), vomiting, abdominal pain
Dehydration!!!

Dx:
Stool culture
Dark field microscopy -> mobile organisms

Tx:
Supportive; fluid replacement
Moderate-severe: fluoroquinolones, macrolides, tetracyclines
Doxycycline, ciprofloxacin
Azithromycin for children and pregnant women

Question 5

MRSA Abx coverage

Answer 5

Oral:
-SMX-TMP
-minocycline
-doxycycline
-clindamycin
-linezolid
IV:
-vancomycin
-daptomycin
-ceftaroline (also vanc resistance)

Question 6

Anaerobic abx coverage

Answer 6

-metronidazole
-augmentin
-clindamycin
-pip/tazo
Carbapenems: -> imipenem/cilastatin, meropenem, doripenem ertapenem

Question 7

Atypicals: Path and abx coverage

Answer 7

Path: mycoplasma, chlamydia, legionella

Doxycycline
Azithromycin
Levofloxacin
Ciprofloxacin

Question 8

Pseudomonas abx coverage

Answer 8

FQ-> cipro, levo, ofloxacin

AG-> tobi, amikacin, gent, streptomycin

Carbapenems-> imipenem/cilastatin, meropenem, doripenem
Aztreonam

BL->Pip/tazo, Cefepime, ceftazidime

Question 9

HIV with CD4 count 200 - 500

At risk infections and tx

Answer 9

TB
Tx:
1st line: Isoniazid if latent
2nd line: Rifampin

Kaposi Sarcoma
Thrush
Lymphoma
Zoster

Question 10

HIV with CD4 count = 200

At risk infections and tx

Answer 10

Pneumocystis (PCP)
Tx:
1st line: SMZ-TMP
2nd line: Dapson, Atovaquone, Pentamidine (aerosolized)

Question 11

HIV with CD4 count = 150

At risk infections and tx

Answer 11

Histoplasmosis
Tx:
1st line: Itraconazole
2nd line: Amphotericin B

Question 12

HIV with CD4 count = 100

At risk infections and tx

Answer 12

Toxoplasmosis
Tx:
1st line: TMP-SMX
2nd line: Dapsone + Pyrimethamine + Folic Acid

Cryptococcus
Tx:
1st line: fluconazole
2nd line: amphotericin B

Question 13

HIV with CD4 count = 50

At risk infections and tx

Answer 13

MAC
Tx:
1st line:
Azithromycin
Clarithromycin
2nd line:
Rifabutin-> must obtain CXR prior to use to r/o active TB

CMV retinitis
Tx:
1st line: Valganciclovir 450mg/day
2nd line: Ganciclovir + Foscarnet

Question 14

HIV

dx:

Answer 14

ELISA (screening test) 
If reactive the test is confirmed by Western Blot 
Usually becomes reactive within 3-6m
5% seroconvert in 7 days
50% in 20 days
>95% in 90 days 

Rapid testing: blood or saliva

Western Blot: confirmatory test

Question 15

Lyme disease
Path:
Pt:
Dx:
Tx:

Answer 15

Path: north west US, tick
Borrelia burgdorferi

Pt: erythema migrans (target lesion), b sx, GI

Dx: clx
ELISA followed by western blot

Tx: doxy, amoxil

ppx: doxy

Question 16

Rocky Mountain Spotted Fever
Path:
Pt:
Dx:
Tx:

Answer 16

Path: wood/dog tick borne illness-> Rickettsia rickettsii
MC south-central/southeastern US
Incubation from tick bite 2d-2w

Pt: Blanching, erythematous macular rash first on wrists/ankles-> palms/soles characteristic & spreading centrally over 2-3 days
fever/chills, myalgias, arthralgias, HAs, N/V, lethargy, seizures

Dx: Clx (don’t wait for serologies)- fever, rash, hx of tick bite
Serologies IgM and IgG abs
CSF: low glucose and pleocytosis

Tx:
Doxycycline (even in children) x5-14 days (dental staining not as likely with short course)
Chloramphenicol 2nd time; tx of choice in pregnancy