JH IM Board Review - Infectious Disease V Flashcards
Leprosy - Basic info:
- Caused by M.leprae.
- Prevalence highest in South America, Africa, Asia.
- Rare indigenous leprosy in the USA in Louisiana, Texas, Hawaii.
Leprosy - CP:
Predominantly affects skin, nerves, and upper airways.
==> Broad spectrum of disease to include tuberculoid, borderline, lepromatous forms.
Tuberculoid form:
PAUCIBACILLARY:
==> One or few asymmetrical anesthetic skin macules.
==> Nerve involvement (classically Ulnar nerve at elbow) may be severe.
==> Bx of skin, nerves show few or no bacteria.
Lepromatous form:
MULTIBACILLARY:
==> Symmetrical skin nodules and plaques on cool areas of body.
- Affected tissues laden with mycobacteria.
- Upper resp. tract involvement common, manifest by nasal congestion.
- Epistaxis.
- Cartilage erosion/collapse (saddle-nose deformity).
- Peripheral neuropathy occurs LATE in the disease course.
Leprosy - Dx and evaluation:
Dx based on clinical presentation + skin bx (demonstration of AFB and histology).
==> M.leprae does NOT grow in culture.
Leprosy - Tuberculoid form (paucibacillary), skin smear negative, with 5 or fewer skin lesions - Tx:
DAPSONE + RIF DAILY FOR 12 MONTHS.
Leprosy - Lepromatous (multibacillary), skin-smear positive, with more than 5 skin lesions - Tx:
DAPSONE + RIF + CLOFAZIMINE DAILY FOR 2 YEARS.
Leprosy - WHO recommends:
Shorter Tx durations (6 and 12 months, respectively) and LESS frequent dosing, largely because of resource limitations.
Nontuberculous bacteria - Rapid growers:
Visible growth within 7 dys in culture:
- M.fortuitum.
- M.chelonae.
- M.abscessus.
Nontuberculous bacteria - Slow growers:
Visible growth requires greater than 7 days in culture.
- M.kansasii.
- M.avium intracellulare.
- M.marinum.
NTB mycobacteria - CP:
- Isolation of NTM from clinical specimen may result from contamination (eg from tap water)/ Colonization in absence of NTM disease, or NTM DISEASE.
- IMMUNOSUPPRESSION = Risk factor.
NTB - Prevention in HIV:
In patients with HIV infection with CD4 <50:
==> Azithro 1200mg ONCE WEEKLY should be given to prevent MAC.
Infectious diarrhea - What percentage seeks medical care?
In the US only a minority (approx. 10%) of those affected seek medical care.
Approach to the patient with infectious diarrhea - CP - Acute diarrhea:
At least 3 episodes of liquid stool in a 24h period.
==> Symptoms typically last <14days.
Persistent diarrhea:
Duration of 14 days to 1 month.
Chronic diarrhea:
Duration exceeds 1 month.
Clinical classification of acute diarrhea:
- Non inflammatory ==> Large-volume watery stools without blood. Fecal inflammatory cells can be seen, but frank pus is absent.
- Inflammatory ==> Frequent, small-volume stools containing blood or pus. Fever and abdominal pain may be present.
==> CLINICAL OVERLAP does occur, such that common causes of inflammatory diarrhea appear to be noninflammatory diarrhea clinically.
Infectious diarrhea - Dx and evaluation - Hx:
Hx should focus:
- Duration of symptoms.
- Features of stool (hematochezia, volume).
- Associated symptoms (fever, abdominal pain, tenesmus).
- Previous abx use.
- Immune status.
- Travel Hx.
- Exposure to children.
- Risk for food-borne illness.
==> May be able to determine whether or not diarrhea is inflammatory by Hx ALONE.
Infectious diarrhea - PEx:
Should include:
- Evaluation of fever.
- Hydration status.
- Abdominal tenderness.
Infectious diarrhea - Lab:
- Typically UNNECESSARY, unless inflammatory diarrhea is suspected or the patient is unstable or immunocompromised.
- Fecal leukocytes ==> Se and Sp is variable and imperfect.
Infectious diarrhea - Stool culture:
Indicated ONLY IF patient is clinically ill, immunocompromised, and/or Hx or presence of fecal leukocytes suggests an inflammatory process.
Infectious diarrhea - Occult blood cards:
Positive may indicate inflammatory diarrhea.
Ova and parasites:
Reserve for persistent diarrhea (>14days) or high risk individuals (eg travel history or immunocompromised).
==> DO NOT ORDER ROUTINELY.
Persistent and chronic diarrhea should be evaluated by …?
BOTH STOOL CULTURE + OVA/PARASITE exam.
Any etiology of acute diarrhea can cause …?
Persistent diarrheal illnesses.
Approach to a patient with infectious diarrhea - Tx:
- Hydration ==> Cornerstone of therapy for all patients, oral usually sufficient.
- Diet ==> Avoid caffeine, dairy products, and sorbitol. (transient lactase def may occur).
- Antidiarrheal medications.
- Abx.
Antidiarrheal medications:
- Loperamide.
- Bismuth.
- Diphenoxylate.
Antidiarrheal medications - Loperamide:
Delays passage through the intestine.
==> CONTRA in infl. diarrheas because of concern for decr. clearance of toxin or organism (particularly for Shiga toxin-producing E.coli [STEC] and C.diff).
Bismuth:
Moderately effective but inconvenient.
==> May darken tongue and stools/ Must consider potential tox caused by salicylate component.
Diphenoxylate:
Has central opiate effects and is linked to induction of TOXIC MEGACOLON.
Abx:
Use is CONTROVERSIAL ==> Data are weak that abx universally affect course of illness.
Abx in non inflammatory diarrhea:
RARELY indicated unless the patient is unstable or at high risk (eg immunocompressed, recent travel, older adult).
Abx - Most guidelines recommend …?
Empirical use of FQ in inflammatory diarrhea.
==> Azithro is 2nd choice in clinically ill patients.
Abx for V.cholerae, Shigella , and Giardia spp:
Should ALWAYS be treated with abx.
Abx for mild-to-moderate nontyphoidal Salmonella or Campylobacter:
Typically DO NOT require abx in stable, immunocompetent individuals.
Abx for STEC:
STEC DOES NOT require abx.
Food-borne illness - Source of food (if known) can be important in identifying a particular causative organism:
Shellfish ==> V.cholerae, V.parahaemolyticus.
Poultry and eggs ==> Campylo, Salmo spp.
Meat ==> C.perfringens, Salmo, STEC.
Dairy ==> Salmo, STEC, Yersinia.
Prepared protein-rich foods ==> Staph (ingestion of preformed toxin).
Deli foods ==> Listeria (causes bacteremia and meningitis).
Timing of illness (incubation period) may be helpful:
1-6h ==> Staph and B.cereus.
8-16h ==> C.perfringens and B.cereus.
16-72h ==> C.jejuni, Salmonella, Shigella, E.coli (Incl. STEC), Yersinia, Vibrio.
Days to >1month ==> Listeria.
Classification of acute diarrhea - Noninflammatory - Organisms:
- Noroviruses.
- Rotavirus.
- Enterotoxinogenic E.coli.
- C.perfringens.
- V.cholera.
- G.lamblia.
- Cryptosporidium.
Classification of acute diarrhea - Inflammatory - Organisms:
- Salmo/Shigella.
- Campylo.
- STEC (O157 and non-O157).
- EIEC.
- C.diff.
- Yersinia, Vibrio parahaemolyticus and ENTAMOEBA.