GRAM POSITIVE RODS. PART 5 Flashcards
Clostridium difficile
What percentage of healthy adults have C. difficile in their fecal flora?
C. difficile occurs in the fecal flora of 1–4% of healthy adults.
What percentage of children during the first year of life have C. difficile in their fecal flora?
In children during the first year of life, C. difficile is found in 30–50% of cases.
How does C. difficile become established in the gut of hospitalized patients?
The organism requires diminution of normal gut flora, which occurs due to the activity of various antimicrobial agents. This allows C. difficile to become established in the gut of hospitalized patients.
What are the consequences of C. difficile once it is established in the gut?
Once established, C. difficile elaborates one or more toxins, leading to antibiotic-associated diarrhea or potentially life-threatening inflammation of the colon.
What is the term used when the surface of the inflamed bowel is overlaid with a “pseudomembrane”?
When the surface of the inflamed bowel is overlaid with a “pseudomembrane” composed of necrotic debris, white blood cells, and fibrin, the disease is referred to as pseudomembranous colitis.
How is C. difficile transmitted
C. difficile is transmitted by the fecal-oral route.
What role do the hands of hospital personnel play in the transmission of C. difficile?
The hands of hospital personnel serve as important intermediaries in the transmission of C. difficile
How do antibiotics contribute to the pathogenesis of C. difficile infection?
Antibiotics suppress drug-sensitive members of the normal flora, which allows C. difficile to multiply and produce exotoxins A and B.
What are the main effects of exotoxin B produced by C. difficile?
Exotoxin B causes depolymerization of actin, resulting in a loss of cytoskeletal integrity, apoptosis (cell death), and ultimately death of the enterocytes (cells lining the intestine).
Which specific antibiotics are associated with frequent cases of pseudomembranous colitis caused by C. difficile?
Clindamycin
Aminopenicillins
Cephalosporins
what are the clinical manifestations of C. deficile
1.Includes fever, diarrhea, and spasmodic abdominal pains
2.The diarrhea is usually not bloody, and neutrophils are found in the stool in about
half of the cases.
3. The pseudomembranes are visualized by sigmoidoscopy.
4. Toxic megacolon can occur, and surgical resection of the colon may be necessary.
5. Pseudomembranous colitis can be distinguished from the transient diarrhea that
occurs as a side effect of many oral antibiotics by testing for the presence of the
toxin in the stool.
What are the steps involved in the laboratory diagnosis of C. difficile?
Culturing the pathogen from patient stool.
Detecting the cytotoxin in bacteria-free stool filtrates.
How is the cytotoxin detected in the laboratory?
The cytotoxin is detected based on a cytopathic effect (CPE) observed in cell cultures. After neutralization with an antiserum, the CPE is no longer observed.
What are the two types of tests commonly used to detect the exotoxins produced by C. difficile?
ELISA (Enzyme-Linked Immunosorbent Assay): This test uses known antibodies to the exotoxins. It provides rapid results but is less sensitive.
Cytotoxicity test: In this test, human cells in culture are exposed to the exotoxin in the stool filtrate, and the death of the cells is observed. This test is more sensitive and specific but requires 24 to 48 hours of incubation time
Is there any additional test used to detect the presence of the toxin gene DNA?
Yes, in addition to tests that detect the toxin itself, a PCR (Polymerase Chain Reaction) assay is used to detect the presence of the toxin gene DNA.
