S1B5 - Diphtheroids Flashcards
What populations of people are most susceptible to Listeria monocytogenes infection? (hint: what innate defense would make someone susceptible)
People deficient in cell-mediated immunity such as pregnant women, neonates, the elderly, and AIDS patients have ineffective phagocytosis and are most susceptible.
What are the treatment options for diphtheria?
Treatment includes penicillin or erythromycin for local colonization, antitoxin for toxin neutralization, and DTaP booster to prevent recolonization.
Cystine-tellurite agar is used to culture what organism? How will they appear when plated on this media?
Culture of C. diphtheriae on cystine-tellurite agar will reveal black colonies.
The following findings are identifications of what bacteria?
- Frequent exposure to animal handling/processing
- A gram positive rod
- Skin biopsy: usually negative as the bugs are in deep tissue
- Grow slowly on comon media
Identification of E. rhusiopathiae
- Frequent exposure to animal handling/processing
- A gram positive rod
- Skin biopsy: usually negative as the bugs are in deep tissue
- Grow slowly on comon media
L. monocytogenes can survive both intracellularly (in macrophages, neutrophils) and extracellularly.
L. monocytogenes penetrates the GI mucosa and invades phagocytes, growing intracellularly.
People deficient in cell-mediated immunity such as pregnant women, neonates, the elderly, and AIDS patients have ineffective phagocytosis and are most susceptible.
A) Congenital bony deformities
B) Neonatal pneumonia
C) Cirrhosis
D) Early-onset sepsis
E) Anemia
Early-onset sepsis
Answer Explanation
Vaginal/uterine transmission of Listeria monocytogenes from the mother to infant during birth results in granulomatosis infantisepticum, which usually manifests as either early-onset sepsis or neonatal meningitis.
What is the name of what is in the picture and description? What is the likely cause?
That is erysipeloid, most likely caused by Erysipelothrix rhusiopathiae infection.
Which molecular mechanism plays a pathogenic role in diphtheria?
A) ADP-ribosylation of elongation factor 2
B) Adenylate syclase stimulation
C) Inhibition of tRNA translocation from E site to P site
D) ADP-ribosylation of G proteins
E) MHC-II binding
ADP-ribosylation of elongation factor 2
Answer Explanation
Attach ADP-ribosyl groups to host cell proteins are a key molecular mechanism for toxins in diphtheria, cholera, E. coli diarrhea, and whooping cough. In diphtheria this occurs at EF-2, preventing tRNA translocation from the A site to the P site. In cholera, this occurs at G proteins which stimulate adenylyl cyclase, upregulating chloride ion secretion into the gut and downregulating sodium ion absorption in the gut. The E. coli heat-labile toxin ADP-ribosylates adenylate cyclase, also causing watery diarrhea. TSST-1 protein (S. aureus) binds to MHC-II and causes polyclonal T-cell activation, leading to toxic shock.
Does Listeria monocytogenes reside intracellularly, extracellulary, or both?
L. monocytogenes can survive both intracellularly (in macrophages, neutrophils) and extracellularly.
Which is an accurate description of Listeria monocytogenes?
A) Gram positive rods
B) Gram positive cocci
C) Gram negative rods
D) Gram negative cocci
E) Coccobacillus that does not gram stain
Gram positive rods
Answer Explanation
Listeria are gram-positive rods.
What vaccine against diphtheria is used for patients:
- Under 7 years of age?
- Older than 7 years of age?
DTaP (diphtheria, tetanus, acellular pertussis) vaccine is administered prior to 7 years of age.
Tdap vaccine can be given to persons older than 7.
(The two products differ in dose, and the upper case letters in DTaP indicate a higher antigen quantity.)
Corynebacterium diphtheria infection is suspected in a patient with pharyngeal pseudomembranes. What medium should wound cultures be grown on to confirm this suspicion?
A) Tellurite agar
B) Chocolate agar
C) Blood agar
D) Thayer-Martin agar
E) MacConkey agar
What is the mechanism of action of the Corynebacterium diphtheriae toxin?
C. diphtheriae synthesizes an AB exotoxin from an encoded bacteriophage (beta-phage) that catalyzes ADP-ribosylation of EF-2, inhibiting EF-2 and thereby preventing tRNA translocation from ribosomal A-sites to P-sites.
Why is cell-mediated immunity important for protection against Listeria monocytogenes infection?
L. monocytogenes can spread cell-to-cell without exposure to antibodies, complement, and neutrophils making cell-mediated immunity important.
What is the bacteria with the following epidemiology?
- Veterinary pathogen( particularly swine & turkey); rare in US.
- Aquired through scratches/punture wounds
- Occupational exposure (butchers, verterinarians)
That is the epidemiology of erysipelothrix rhusiopathiae.
Which patient population is advised to avoid consuming unpasteurized dairy products because of potential infection by gram-positive rods?
A) Poorly controlled diabetics
B) HIV+ patients
C) Pregnant women
D) Neonates
E) Geriatric population
Pregnant women
Answer Explanation
Listeria monocytogenes is associated with unpasteurized milk/soft cheeses, deli meats/hot dogs, raw vegetables. If a pregnant woman becomes bacteremic, the vagina/uterus can be colonized and Listeria can cause 3rd trimester amnionitis, spontaneous abortions, stillbirths, preterm labor. Infections can occur in immunocompromised patients as well, but not all HIV+ patients are clinically immunocompromised, especially if they adhere to an effective HAART regimen.
How can Corynebacterium diphtheriae appear under microscopy?
C. diphtheriae has a “Chinese letter” appearance under microscopy.
What are two neural effects from chronic infection with Corynebacterium diphtheriae?
Progressive deterioration of myelin sheaths in the central and peripheral nervous system can cause blurry vision and pharyngeal/diaphragmatic paralysis.
What is the treatment of choice for Listeria monocytogenes infection?
Treatment of L. monocytogenes infection includes ampicillin or penicillin G. Trimethoprim-sufamethoxazole (TMP-SMX) can be given as an alternative for penicillin-allergic patients.
How is Corynebacterium diphtheriae transmitted? Where does it colonize?
C. diphtheriae is transmitted via respiratory droplets and colonize the nasopharynx.
What are the systemic effects of the Corynebacterium diphtheriae toxin?
This toxin results in cardiac (arrhythmia and myocarditis) and nervous (cranial and peripheral nerve palsy) effects.
What is the most likely bacterial cause of this?
Acne vulgaris is associated with:
- Proprionibacterium acnes
- Adolescence
- Androgens
- Obstruction of pores by exfoliated skin or personal care products
- Family history
At what temperatures can Listeria monocytogenes uniquely grow, and how does this affect foodborne transmission?
L. monocytogenes can grow at refrigerated temperatures, allowing survival in refrigerated food such as poorly pasteurized milk/cheeses, deli meats, and raw vegetables.
The following is a description of what bacteria?
- A gram-positive rod, a normal human skin flora
- Grows well in humid conditions
- Infects inter-trigonous regions (axilla, anogenital)
- Invades upper 1/3rd of stratum corneum
- Causes a chronic superficial infection (erythrasma)
Corynebacterium minutissimum
- A gram-positive rod, a normal human skin flora
- Grows well in humid conditions
- Infects inter-trigonous regions (axilla, anogenital)
- Invades upper 1/3rd of stratum corneum
- Causes a chronic superficial infection (erythrasma)
What kind of motility does listeria monocytogenes show in an agar medium?
Listeria monocytogenes shows need-to-end tumbling motility in liquid medium, and umbrella motility in agar medium.
How does Listeria monocytogenes spread cell to cell without exposure to the extracellular environment?
L. monocytogenes spreads from cell to cell without exposing itself to an extracellular environment using an actin-based cellular contractile mechanism (actin rocket).
What is granulomatosis infantisepticum?
Granulomatosis infantisepticum is a placental transmission of L. monocytogenes to the infant, causing early-onset sepsis and formulation of granulomas throughout the body including the presence of a rash.
Which is an accurate characterization of the diphtheriae toxin?
A) ATP-ribosylating exotoxin
B) Complement scavenging exotoxin
C) ADP-ribosylating endotoxin
D) ATP-ribosylating endotoxin
E) ADP-ribosylating exotoxin
ADP-ribosylating exotoxin
Answer Explanation
The diphtheriae toxin adds an ADP-ribosyl group to elongation factor 2. It is an exotoxin (secreted by the bacterium).
How do patients with Corynebacterium diphtheriae typically present? What are the late (if untreated) complications?
Patients with diphtheria typically present with
- Grayish-white pseudomembranes in oropharynx that can lead to suffocation
- Cervical lymphadenopathy (“Bull’s neck”)
- Myocarditis if left untreated
In pregnant women, what are the potential complications of listeriosis?
Bacteremia during pregnancy can lead to:
- 3rd trimester amnionitis
- Preterm labor
- Spontaneous abortions
- Stillbirths
What is the only gram-positive organism with endotoxin?
L. monocytogenes is the only gram-positive organism with endotoxin.
What antibiotic can be added for synergy in select Listeria monocytogenes infections?
Gentamicin can be added to ampicillin for synergy in cases of Listeria meningitis, endocarditis, or in immunocompromised patients.
What type of motility does Listeria monocytogenes exhibit on light microscopy?
L. monocytogenes exhibits tumbling motility extracellularly on light microscopy.
Describe the morphology, gram stain, catalase ability, hemolysis on blood agar, and spore-forming capability Listeria monocytogenes?
Listeria monocytogenes is a non-spore forming beta-hemolytic, catalase-positive gram-positive bacillus.
What are the two common clinical presentations of Listeria monocytogenes infection?
Patients with L. monocytogenes infection typically present with signs of meningitis and bacteremia.
What is the morphology, gram staining, oxygen requirement, sporeforming/non-sporeforming of Corynebacterium diphtheriae?
Corynebacterium diphtheriae is an aerobic, non-sporeforming gram-positive bacillus.
What toxin does Listeria monocytogenes contain and what is its function?
L. monocytogenes contains listeriolysin O bacterial toxin, which allows digestion of the phagosome and for L. monocytogenes to freely infect the target cell.
