25- Listeria and Erysipelothrix Flashcards
How is listeria transmitted?
Transmission of Listeria is believed to be primarily in soil and decaying vegetable matter
Large outbreaks have been associated with contaminated food usually peaks in the warmer months of the years.
Focal epidemics and sporadic cases have been associated with listeriosis have been associated with consumption of contaminated milk, soft cheese, undercooked meat and poultry, unwashed raw vegetables, and cabbage.
Listeria can grow in a wide range of pH and in cold temperatures; foods with small number of organisms can become grossly contaminated during prolonged refrigeration.
Disease can occur if the food is uncooked or inadequately cooked (e.g. microwaved beef or turkey franks) before consumption.
Which populations are problematic to listeria infections?
Neonates, elderly, pregnant women, patients with severe defects in cell-mediated immunity (e.g. transplants, lymphomas, acquired immune deficiency syndrome [AIDS])
When does the early-onset disease occur for neonates?
Early-onset disease is acquired transplacentally in utero and can result in abortion, stillbirth, and premature birth.
What is Granulomatosis infantiseptica?
Granulomatosis infantiseptica is a severe form of listeriosis characterized by the formation of disseminated abscesses and granulomas in multiple organs and a high mortality rate unless treated promptly which is acquired transplacentally in utero.
When does the late-onset disease occur for neonates?
Late onset disease is acquired at or soon after birth and occurs 2 to 3 weeks after birth in the form of meningitis or meningoencephalitis with septicemia.
What type of media is used for listeria?
Capable of growth at 4 degree Celsius and in high salt concentrations.
What is special about the hemolysis pattern of listeria?
Beta hemolysis can serve to distinguish Listeria from morphologically similar bacteria; however hemolysis is generally weak or may not be observed initially. Hemolysis is enhanced though if grown next to beta-hemolytic S. aureus which enhances hemolysis and is known as a positive CAMP test.
Erysipelothrix-morphology
Erysipelothrix, more so E. rhusiopathiae as it is responsible for human disease, are gram-positive, non-spore-forming, slender, pleomorphic rods that distribute worldwide in wild and domestic animals
Erysipelothrix- media
Erysipelothrix are microaerophilic, preferring a reduced oxygen atmosphere Grow well on blood and chocolate agar incubated in 5%-10% carbon dioxide. Small grayish, alpha-hemolytic colonies that are observed after 2 to 3 days of incubation
Erysipelothrix- virulence factors
Produce neuraminidase that is believed to be important for attachment and penetration into epithelial cells and a polysaccharide capsule protects the bacteria against phagocytosis.
Erysipelothrix- epidemiology
Disease in humans is zoonotic and is primarily occupational. Butchers, meat processors, farmers, poultry workers, fish handlers, and veterinarians are at greatest risks.
Cutaneous infections typically develop after the organism is inoculated subcutaneously through an abrasion or puncture wound during the handling of contaminated animal products or soil.
What is zoonosis?
Zoonosis is defined as any infectious disease that can be transmitted from non-human animals to humans or vice versa.
What are the 2 diseases of Erysipelothrix?
localized skin infection (erysipeloid) and a septecemic form
How long is the Erysipeloid incubation period?
Th skin infection 2-7 days after the trauma occurs
What are the erysipeloid clinical features?
Lesions most commonly present on the fingers or hands and appear violaceous with a raised edge. It spreads peripherally as the discoloration in the central area fades.
The painful lesion is pruritic, and the patient experiences a burning or throbbing sensation.
Suppuration is uncommon, a feature distinguishing erysipeloid from streptococcal erysipelas.
