JH IM Board Review - Infectious Disease V Flashcards
1
Q
Leprosy - Basic info:
A
- Caused by M.leprae.
- Prevalence highest in South America, Africa, Asia.
- Rare indigenous leprosy in the USA in Louisiana, Texas, Hawaii.
2
Q
Leprosy - CP:
A
Predominantly affects skin, nerves, and upper airways.
==> Broad spectrum of disease to include tuberculoid, borderline, lepromatous forms.
3
Q
Tuberculoid form:
A
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.
4
Q
Lepromatous form:
A
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.
5
Q
Leprosy - Dx and evaluation:
A
Dx based on clinical presentation + skin bx (demonstration of AFB and histology).
==> M.leprae does NOT grow in culture.
6
Q
Leprosy - Tuberculoid form (paucibacillary), skin smear negative, with 5 or fewer skin lesions - Tx:
A
DAPSONE + RIF DAILY FOR 12 MONTHS.
7
Q
Leprosy - Lepromatous (multibacillary), skin-smear positive, with more than 5 skin lesions - Tx:
A
DAPSONE + RIF + CLOFAZIMINE DAILY FOR 2 YEARS.
8
Q
Leprosy - WHO recommends:
A
Shorter Tx durations (6 and 12 months, respectively) and LESS frequent dosing, largely because of resource limitations.
9
Q
Nontuberculous bacteria - Rapid growers:
A
Visible growth within 7 dys in culture:
- M.fortuitum.
- M.chelonae.
- M.abscessus.
10
Q
Nontuberculous bacteria - Slow growers:
A
Visible growth requires greater than 7 days in culture.
- M.kansasii.
- M.avium intracellulare.
- M.marinum.
11
Q
NTB mycobacteria - CP:
A
- 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.
12
Q
NTB - Prevention in HIV:
A
In patients with HIV infection with CD4 <50:
==> Azithro 1200mg ONCE WEEKLY should be given to prevent MAC.
13
Q
Infectious diarrhea - What percentage seeks medical care?
A
In the US only a minority (approx. 10%) of those affected seek medical care.
14
Q
Approach to the patient with infectious diarrhea - CP - Acute diarrhea:
A
At least 3 episodes of liquid stool in a 24h period.
==> Symptoms typically last <14days.
15
Q
Persistent diarrhea:
A
Duration of 14 days to 1 month.
16
Q
Chronic diarrhea:
A
Duration exceeds 1 month.
17
Q
Clinical classification of acute diarrhea:
A
- 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.
18
Q
Infectious diarrhea - Dx and evaluation - Hx:
A
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.
19
Q
Infectious diarrhea - PEx:
A
Should include:
- Evaluation of fever.
- Hydration status.
- Abdominal tenderness.
20
Q
Infectious diarrhea - Lab:
A
- Typically UNNECESSARY, unless inflammatory diarrhea is suspected or the patient is unstable or immunocompromised.
- Fecal leukocytes ==> Se and Sp is variable and imperfect.
21
Q
Infectious diarrhea - Stool culture:
A
Indicated ONLY IF patient is clinically ill, immunocompromised, and/or Hx or presence of fecal leukocytes suggests an inflammatory process.
22
Q
Infectious diarrhea - Occult blood cards:
A
Positive may indicate inflammatory diarrhea.
23
Q
Ova and parasites:
A
Reserve for persistent diarrhea (>14days) or high risk individuals (eg travel history or immunocompromised).
==> DO NOT ORDER ROUTINELY.
24
Q
Persistent and chronic diarrhea should be evaluated by …?
A
BOTH STOOL CULTURE + OVA/PARASITE exam.
25
Any etiology of acute diarrhea can cause ...?
Persistent diarrheal illnesses.
26
Approach to a patient with infectious diarrhea - Tx:
1. Hydration ==> Cornerstone of therapy for all patients, oral usually sufficient.
2. Diet ==> Avoid caffeine, dairy products, and sorbitol. (transient lactase def may occur).
3. Antidiarrheal medications.
4. Abx.
27
Antidiarrheal medications:
1. Loperamide.
2. Bismuth.
3. Diphenoxylate.
28
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).
29
Bismuth:
Moderately effective but inconvenient.
==> May darken tongue and stools/ Must consider potential tox caused by salicylate component.
30
Diphenoxylate:
Has central opiate effects and is linked to induction of TOXIC MEGACOLON.
31
Abx:
Use is CONTROVERSIAL ==> Data are weak that abx universally affect course of illness.
32
Abx in non inflammatory diarrhea:
RARELY indicated unless the patient is unstable or at high risk (eg immunocompressed, recent travel, older adult).
33
Abx - Most guidelines recommend ...?
Empirical use of FQ in inflammatory diarrhea.
==> Azithro is 2nd choice in clinically ill patients.
34
Abx for V.cholerae, Shigella , and Giardia spp:
Should ALWAYS be treated with abx.
35
Abx for mild-to-moderate nontyphoidal Salmonella or Campylobacter:
Typically DO NOT require abx in stable, immunocompetent individuals.
36
Abx for STEC:
STEC DOES NOT require abx.
37
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).
38
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.
39
Classification of acute diarrhea - Noninflammatory - Organisms:
1. Noroviruses.
2. Rotavirus.
3. Enterotoxinogenic E.coli.
4. C.perfringens.
5. V.cholera.
6. G.lamblia.
7. Cryptosporidium.
40
Classification of acute diarrhea - Inflammatory - Organisms:
1. Salmo/Shigella.
2. Campylo.
3. STEC (O157 and non-O157).
4. EIEC.
5. C.diff.
6. Yersinia, Vibrio parahaemolyticus and ENTAMOEBA.
41
Potential reportable food-borne diseases - Bacteria:
Botulism, brucellosis, cholera, STEC.
+ Campylo, salmo (incl. typhoid fever), Shigella, Giardia, Listeria, Yersinia.
42
Potential reportable food-borne diseases - Viruses:
Hep A and Noro.
43
Potential reportable food-borne diseases - Parasites:
Cryptosporidiosis, cyclosporiasis, trichinosis.
44
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.
45
Noro diarrhea:
1. F/O, food-borne, airborne, and fomite transmission common as a result of LOW INOCULUM required for disease.
2. Incubation period is usually 24-48h.
3. Noninflammatory diarrhea with/without vomiting ==> Approx. 80% have both.
4. Low-grade fever in approx. 50%.
5. Tx is supportive.
46
Rotavirus diarrhea:
Sporadic outbreaks in children - Much less common in adults.
1. F/O transmission.
2. Vomiting, low fever, transient lactase def can be present.
3. May last >1WEEK.
4. Tx supportive.
47
Hep A diarrhea:
1. Rare cause of food-borne disease.
2. LONG incubation period (15-50 days).
3. Transmission ==> Shellfish, raw produce, and foods contaminated after handling by infected people.
4. Jaundice, abd pain, fever, elevated LFTs.
5. Dx ==> Anti-HAV IgM.
6. Tx is supportive/ Contacts not previously vaccinated against HAV may be given Ig.
48
Infectious diarrhea - Parasitic pathogens:
1. Giardia.
2. Cryptosporidium.
3. Cyclospora cayetanensis.
4. Entamoeba.
5. Trichinella spiralis.
49
Giardiasis:
1. Common cause of persistent or chronic diarrhea.
2. Watery diarrhea, but steatorrhea/malabsorption can arise.
3. Bloating and nausea are common.
50
Giardia - Major source:
Drinking water (often well water); person-to-person spread occurs.
51
Giardia - Tx:
Usually responds to Tx with MNZ.
52
Giardia - Dx:
Stool EIA.
53
Cryptosporidium:
Regionally variable, but can be similar in incidence to Giardia.
54
Cryptosporidium - Source:
WATER, but can be transmitted through person-to-person, F/O routes.
55
Cryptosporidiosis:
Usually self-limited in normal host but can cause persistent or chronic diarrhea.
==> If CD4<150 often a chronic illness.
56
Cryptosporidiosis - Symptoms:
Variable, but can cause large-volume losses or malabsorption - May be relapsing.
==> Abd pain, fever, vomiting can occur.
57
Cryptosporidiosis - Dx:
1. Stool oocysts can be detected by modified acid-fast stain.
2. On histopathology, life-cycle forms can be detected in the brush border of the intestinal mucosa.
3. Cryptosporidium stool EIA available for Dx.
58
Cryptosporidiosis in HIV - Tx:
HAART.
==> Nitazoxanide available for Tx of persistent and/or severe disease.
59
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
60
Cyclospora cayetanensis - Tx:
TMP-SMX.
61
Cyclospora cayetanensis - Dx:
Stool oocysts are also acid-fast but TWICE the size of Cryptosporidium.
62
Entamoeba histolytica:
Inflammatory process, often chronic, with bloody diarrhea and lower abdominal pain (similar to Shigella).
==> Can cause extraintestinal disease, especially liver abscess.
63
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.
64
E.histolytica - Tx:
MNZ.
==> Attention to elimination of tissue and fecal cyst forms is important.
65
T.spiralis:
Diarrhea, vomiting, abd pain, myalgias, fever, + PERIORBITAL EDEMA.
66
T.spiralis diarrhea occurs when?
DAYS TO WEEKS after ingestion of raw or undercooked meat (eg pork, bear, moose).
67
T.spiralis - Cardiac involvement:
NOT common - But can lead to myocarditis with life-threatening arrhythmias.
68
T.spiralis - What CBC is usually seen?
EOSINOPHILIA.
69
T.spiralis - Tx:
Supportive for mild cases.
==> Mebendazole/Albendazole is used for more severe cases.
==> Prednisone is added if inflammation is severe.
70
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.
71
HIV patients can develop diarrhea ...?
SECONDARY TO HAART Tx.
72
HIV patients - Common diarrheal infections:
1. C.diff ==> Leading cause.
2. Cryptosporidium ==> MC PROTOZOAL cause.
3. CMV ==> MCC of viral colonic disease in HIV.
4. MAC.
5. Microsporidium.
6. Isospora belli.
7. HSV.
73
CMV colitis in AIDS:
1. CD4 <50.
2. Variable presentation can range from mild diarrhea to acute abdomen.
3. Bx is REQUIRED for Dx ==> "Owl's eye" nucleus with basophilic intranuclear inclusion surrounded by clear halo.
74
MAC diarrhea in HIV:
1. CD4 <50.
2. Small/Large bowel ==> Mucosa can appear NORMAL on colono.
3. May present as abdominal pain, lymphadenopathy, prominent liver/spleen.
75
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.
76
MAC diarrhea in HIV patients - Tx:
Combination therapy is important.
==> Tx with clarithro + ethambutol +/- rifabutin.
77
Microsporidium diarrhea in HIV patients:
1. Obligate intracellular pathogen.
2. CD4 <100.
3. Chronic diarrhea.
78
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.
79
Isospora belli diarrhea in HIV patients:
1. Endemic to tropical areas; rare in the USA.
2. Dx by ova/parasite exam or Bx.
3. TMP-SMX.
80
Traveler's diarrhea:
CAUSE USUALLY NOT IDENTIFIED (MCC is ETEC).
==> Up to 80% are bacterial in origin.
81
Traveler's diarrhea - Abx:
Abx shorten illness to approx. 24-48h.
==> Without Tx lasts 4-7days.
==> FQ = Empiric abx of choice.
82
Traveler's diarrhea - Alternative abx to FQ:
Azithro ==> In Southeast Asia where FQ-RESISTANT C.jejuni is a common cause of traveler's diarrhea.
83
Traveler's diarrhea - Patients should be advised to avoid ...?
1. Tap water.
2. Ice.
3. Unpeeled or raw fruits and vegetables.
4. Undercooked meats in low-resource countries.
84
Traveler's diarrhea - Prophylaxis:
TMP-SMX considered only for high-risk patients.
85
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.
86
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.
87
Rates of C.diff disease presenting from the community have increased:
1. Most have health care or abx exposure.
2. Specific risk groups of concern include:
==> Peripartum women with young infants, children 1-5, and patients with IBD.
3. Patients >65 are at increased risk for severe disease.
88
C.diff - CP - Severe disease is defined by:
1. Fever.
2. Low albumin.
3. Renal insufficiency.
4. WBC >15000.
5. +/- colon wall thickening on abd CT.
89
C.diff - Fever occurs ...?
IN ONLY 10-15% of C.diff patients but, if present, is a sign of severe disease.
90
C.diff disease symptoms can range from ...?
Mild, loose, or watery bowel movements to acute severe colitis with leukocytosis and abd pain.
91
C.diff - When do the symptoms occur?
Can be delayed up to 4-8 weeks after abx exposure.
92
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.
93
C.diff - Which toxins?
Most cases involve toxins A and B, and less frequently, toxin B alone.
94
What should be avoided until C.diff-associated disease is excluded?
ANTIPERISTALTIC AGENTS.
95
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.
96
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.
97
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.
98
Relapse rate of C.diff?
20-25%.
99
Tx of C.diff relapses:
1. Initial relapses of mild diseases ==>MNZ if WBC <15K and Serum Cr not rising.
2. Otherwise ==> Oral vanco.
100
Method of Tx of pts with more than one relapse is controversial:
1. Prolonged, tapered tx with vanco most often used.
2. Do not use mnz for fear of cumulative neurotox.
3. Sequential tx with vanco followed by rifaximin or fidaxomicin may be useful for recurrences.
101
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.
