Four weeks after assisting in several calf deliveries, a farmer develops fever, weakness, muscle aches, and sweats. The fever rises in the afternoon and falls during the night. Brucella abortus is isolated. Which one of the three Brucella species is a possible bioterrorism agent and is best described by one of the following?
Correct Answer: Typically infects cattle, requires 5% to 10% carbon dioxide for growth, and is inhibited by the dye thionine
Description: All the organisms are short, ovoid, gram-negative rods. For the most part, they are nutritionally fastidious and require blood or blood products for growth. These and related organisms are unique among bacteria in that, though they have an animal reservoir, they can be transmitted to humans. Humans become infected by a variety of routes, including ingestion of contaminated animal products (B. abortus in cattle), direct contact with contaminated animal material or with infected animals themselves (Y. enterocolitica and B. bronchiseptica in dogs), and animal bites (P. multocida in many different animals). The laboratory differentiation of these microbes may be difficult and must rely on a number of parameters, including biochemical and serologic reactions, development of specific antibody response in affected persons, and epidemiologic evidence of infection.Yersinia enterocolitica are motile at 77degC (25degC) and nonmotile at 98.6degF (37degC). They are found in the intestinal tract of animals and cause a variety of clinical syndromes in humans. Transmission to humans probably occurs via animal fecal contamination of food, drink, or fomites.The brucellae are obligate parasites of animals and humans and are located intracellularly. Brucella abortus is typically found in cattle. Brucellosis (undulant fever) has an acute bacteremic phase followed by a chronic stage that may last years and involve many tissues. Brucella abortus requires CO2 for growth and is most often isolated from blood and bone marrow. Species differentiation is due to dye (thionine) sensitivity.Bordetella bronchiseptica causes diseases in animals (kennel cough in dogs) and occasionally respiratory disease and bacteremia in humans.Bordetella requires enriched medium (Bordet-Gengou) and is strongly urease-positive.Pasteurella multocida occurs worldwide in the respiratory and GI tracts of many domestic and wild animals. It is the most common organism in human wounds inflicted by cat and dog bites. It is one of the common causes of hemorrhagic septicemia in rabbits, rats, horses, sheep, fowl, cats, and swine. It can affect many systems in humans, as well as bite wounds.
Category:
Microbiology
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