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.
Potential reportable food-borne diseases - Bacteria:
Botulism, brucellosis, cholera, STEC.
+ Campylo, salmo (incl. typhoid fever), Shigella, Giardia, Listeria, Yersinia.
Potential reportable food-borne diseases - Viruses:
Hep A and Noro.
Potential reportable food-borne diseases - Parasites:
Cryptosporidiosis, cyclosporiasis, trichinosis.
Infectious diarrhea - Common pathogens:
50% are viruses. Usually the cause is never identified.
NOROVIRUS is the MC identified viral cause of endemic and epidemic diarrhea in ADULTS.
Noro diarrhea:
- F/O, food-borne, airborne, and fomite transmission common as a result of LOW INOCULUM required for disease.
- Incubation period is usually 24-48h.
- Noninflammatory diarrhea with/without vomiting ==> Approx. 80% have both.
- Low-grade fever in approx. 50%.
- Tx is supportive.
Rotavirus diarrhea:
Sporadic outbreaks in children - Much less common in adults.
- F/O transmission.
- Vomiting, low fever, transient lactase def can be present.
- May last >1WEEK.
- Tx supportive.
Hep A diarrhea:
- Rare cause of food-borne disease.
- LONG incubation period (15-50 days).
- Transmission ==> Shellfish, raw produce, and foods contaminated after handling by infected people.
- Jaundice, abd pain, fever, elevated LFTs.
- Dx ==> Anti-HAV IgM.
- Tx is supportive/ Contacts not previously vaccinated against HAV may be given Ig.
Infectious diarrhea - Parasitic pathogens:
- Giardia.
- Cryptosporidium.
- Cyclospora cayetanensis.
- Entamoeba.
- Trichinella spiralis.
Giardiasis:
- Common cause of persistent or chronic diarrhea.
- Watery diarrhea, but steatorrhea/malabsorption can arise.
- Bloating and nausea are common.
Giardia - Major source:
Drinking water (often well water); person-to-person spread occurs.
Giardia - Tx:
Usually responds to Tx with MNZ.
Giardia - Dx:
Stool EIA.
Cryptosporidium:
Regionally variable, but can be similar in incidence to Giardia.
Cryptosporidium - Source:
WATER, but can be transmitted through person-to-person, F/O routes.
Cryptosporidiosis:
Usually self-limited in normal host but can cause persistent or chronic diarrhea.
==> If CD4<150 often a chronic illness.
Cryptosporidiosis - Symptoms:
Variable, but can cause large-volume losses or malabsorption - May be relapsing.
==> Abd pain, fever, vomiting can occur.
Cryptosporidiosis - Dx:
- Stool oocysts can be detected by modified acid-fast stain.
- On histopathology, life-cycle forms can be detected in the brush border of the intestinal mucosa.
- Cryptosporidium stool EIA available for Dx.
Cryptosporidiosis in HIV - Tx:
HAART.
==> Nitazoxanide available for Tx of persistent and/or severe disease.
Cyclospora cayetanensis - Diarrhea:
More commonly seen in HIV, but can infect immunocompetent hosts ==> Outbreaks associated with imported raspberries, salad greens, cilantro.
==> Symptoms similar to cryptosporidium
Cyclospora cayetanensis - Tx:
TMP-SMX.
Cyclospora cayetanensis - Dx:
Stool oocysts are also acid-fast but TWICE the size of Cryptosporidium.
Entamoeba histolytica:
Inflammatory process, often chronic, with bloody diarrhea and lower abdominal pain (similar to Shigella).
==> Can cause extraintestinal disease, especially liver abscess.
E.histolytica - Dx:
Examine stool for cysts or trophozoites.
==> Morphologically indistinguishable from NON pathogenic E.dispar or E.moshkovskii strains.
==> Antigen detection for serum/stool are available.
E.histolytica - Tx:
MNZ.
==> Attention to elimination of tissue and fecal cyst forms is important.
T.spiralis:
Diarrhea, vomiting, abd pain, myalgias, fever, + PERIORBITAL EDEMA.
T.spiralis diarrhea occurs when?
DAYS TO WEEKS after ingestion of raw or undercooked meat (eg pork, bear, moose).
T.spiralis - Cardiac involvement:
NOT common - But can lead to myocarditis with life-threatening arrhythmias.
T.spiralis - What CBC is usually seen?
EOSINOPHILIA.
T.spiralis - Tx:
Supportive for mild cases.
==> Mebendazole/Albendazole is used for more severe cases.
==> Prednisone is added if inflammation is severe.
HIV patients:
CD4 <200 is a major risk factor for persistent/chronic infectious diarrhea.
==> In addition to directed antimicrobial Tx, HAART is required to resolve peristent or chronic diarrhea caused by opportunistic infections.
HIV patients can develop diarrhea …?
SECONDARY TO HAART Tx.
HIV patients - Common diarrheal infections:
- C.diff ==> Leading cause.
- Cryptosporidium ==> MC PROTOZOAL cause.
- CMV ==> MCC of viral colonic disease in HIV.
- MAC.
- Microsporidium.
- Isospora belli.
- HSV.
CMV colitis in AIDS:
- CD4 <50.
- Variable presentation can range from mild diarrhea to acute abdomen.
- Bx is REQUIRED for Dx ==> “Owl’s eye” nucleus with basophilic intranuclear inclusion surrounded by clear halo.
MAC diarrhea in HIV:
- CD4 <50.
- Small/Large bowel ==> Mucosa can appear NORMAL on colono.
- May present as abdominal pain, lymphadenopathy, prominent liver/spleen.
MAC diarrhea in HIV - Dx:
Mycobacterial blood culture or tissue Bx.
==> Stool culture alone is NOT diagnostic and may represent colonization ==> Predictive of risk of disease over time.
MAC diarrhea in HIV patients - Tx:
Combination therapy is important.
==> Tx with clarithro + ethambutol +/- rifabutin.
Microsporidium diarrhea in HIV patients:
- Obligate intracellular pathogen.
- CD4 <100.
- Chronic diarrhea.
Microsporidium diarrhea in HIV - Dx:
Can visualize the organisms on small-bowel Bx or on fecal examination using special stains, such as fluorescence with calcofluor white.
Isospora belli diarrhea in HIV patients:
- Endemic to tropical areas; rare in the USA.
- Dx by ova/parasite exam or Bx.
- TMP-SMX.
Traveler’s diarrhea:
CAUSE USUALLY NOT IDENTIFIED (MCC is ETEC).
==> Up to 80% are bacterial in origin.
Traveler’s diarrhea - Abx:
Abx shorten illness to approx. 24-48h.
==> Without Tx lasts 4-7days.
==> FQ = Empiric abx of choice.
Traveler’s diarrhea - Alternative abx to FQ:
Azithro ==> In Southeast Asia where FQ-RESISTANT C.jejuni is a common cause of traveler’s diarrhea.
Traveler’s diarrhea - Patients should be advised to avoid …?
- Tap water.
- Ice.
- Unpeeled or raw fruits and vegetables.
- Undercooked meats in low-resource countries.
Traveler’s diarrhea - Prophylaxis:
TMP-SMX considered only for high-risk patients.
Abx-associated diarrhea:
Noninfectious diarrhea can occur in up to 20% of patients receiving certain abx (ampicillin, amoxil/clavulanate, cefixime, clindamycin).
==> Most cases of mild diarrhea caused by abx use is because of noninfectious causes.
C.diff:
ONLY 10-20% of cases of abx-associated diarrhea are caused by C.diff infection.
==> C.diff does, however, account for most cases of colitis caused by abx.
Rates of C.diff disease presenting from the community have increased:
- Most have health care or abx exposure.
- Specific risk groups of concern include:
==> Peripartum women with young infants, children 1-5, and patients with IBD.
- Patients >65 are at increased risk for severe disease.
C.diff - CP - Severe disease is defined by:
- Fever.
- Low albumin.
- Renal insufficiency.
- WBC >15000.
- +/- colon wall thickening on abd CT.
C.diff - Fever occurs …?
IN ONLY 10-15% of C.diff patients but, if present, is a sign of severe disease.
C.diff disease symptoms can range from …?
Mild, loose, or watery bowel movements to acute severe colitis with leukocytosis and abd pain.
C.diff - When do the symptoms occur?
Can be delayed up to 4-8 weeks after abx exposure.
C.diff - Dx:
Toxins in stool ==> PCR test of choice.
==> 1 negative PCR is often enough to r/o.
==> EIAs for C.diff toxins are suboptimal for Dx.
C.diff - Which toxins?
Most cases involve toxins A and B, and less frequently, toxin B alone.
What should be avoided until C.diff-associated disease is excluded?
ANTIPERISTALTIC AGENTS.
C.diff - Tx - Current guidelines are for 10-14 days of Tx with drug selection based on severity of disease - Initial episode, mild:
Oral MNZ, 500mg every 8h.
==> Some experts recommend oral vanco for ALL initial episodes.
C.diff - Tx - Current guidelines are for 10-14 days of Tx with drug selection based on severity of disease - Severe disease:
Start oral vanco 125mg/6h.
C.diff - Tx - Current guidelines are for 10-14 days of Tx with drug selection based on severity of disease - Initial episode, severe and complicated:
Oral vanco 500mg/6h + IV MNZ 500mg/8h.
==> IF COMPLETE ILEUS ==> Consider adding rectal instillation of vanco and surgical consult.
Relapse rate of C.diff?
20-25%.
Tx of C.diff relapses:
- Initial relapses of mild diseases ==>MNZ if WBC <15K and Serum Cr not rising.
- Otherwise ==> Oral vanco.
Method of Tx of pts with more than one relapse is controversial:
- Prolonged, tapered tx with vanco most often used.
- Do not use mnz for fear of cumulative neurotox.
- Sequential tx with vanco followed by rifaximin or fidaxomicin may be useful for recurrences.
Role of fidaxomicin:
Useful in patients with relapsing C.diff and in pts who cannot tolerate or do not respond to vanco.
==> For severe disease ==> IV MNZ, vanco by NGT or enema, and surgical consult. Consider IVIG (investigational).
==> Fecal transplantation may be an option for recurrent, severe disease.
