A 52 year old female goes to her health care provider complaining of fever, head

Question

A 52 year old female goes to her health care provider complaining of fever, headache, and arthralgia lasting about a week. She also has some abdominal pain, vomiting, diarrhea, and has experienced weight loss and fatigue lasting for approximately one month. Microbiologic and biochemical testing shows small gram negative non-motile coccobacilli which grow as small grey non-hemolytic colonies on blood agar plates. The bacterium is urease, catalase and oxidase positive. MR-VP and indole tests are negative, and the bacterium does not produce acid when metabolizing carbohydrates. Public health investigators interview the patient and find out she has worked on a farm with sheep. goats, and pigs. She also reports drinking unpasteurized milk. What is the pathogen causing the woman's illness? EXPLAIN your reasoning. Name a virulence factor related to this pathogen. This pathogen is from a large genus. What characteristics did you use to determine Q1. Q2. the species? Q4. How did the patient become exposed to this pathogen? Yes/No and Q5. why? If the IDso is between 10 to 100 organisms, is this a virulent pathogen? Q6. Select two "terms" that were addressed in Unit 3 and describe how they relate to this pathogen. (Hint... there are multiple terms that apply, so just pick two and tell me how they relate)

Explanation / Answer

1. A woman is diagnosed with fever, headache, arthralgia and also experiencing abdominal pain, vomiting and diarrhea, fatigue and weight loss lasting since a month. The microbiological examination revealed that the microorganism is gram negative nonmotile coccobacilli. This organism produces nonhemolytic grey colored colonies are blood agar. Basing on these characteristics, the microorganism is identified as Brucella miltensis. This organism causes a chronic disease.

2. Brucella does not contain regular virulence factor such as capsule, lipopolysaccharide, pili, fimbriae, exotoxin or endotoxin etc. The virulence of this organism depends on its ability of survival and replication in specific types of cells in host. It is an facultative intracellular pathogen and it controls the maturation of its vacuole avoiding innate immune responses in host. This means it infects phagocytes and escape lysis.

3. The identification chracteristics of B. miltensis are gram negative nonmotile coccobacilli. This organism produces nonhemolytic grey colored colonies are blood agar. The biochemical tests reveal that the organism is positive for catalase, urease and oixidase. Negative for MR- VP and indole tests. The bacterium does not produce acid on fermentation of carbohydrates.

4. The patient works with farm animals like sheep, goats and pigs. The patient consumed unpasteurized milk. The pathogen spreads through animals and animal products (esp. sheep and goats). The principal reservoir is goat and pathogen is acquired by consumption of infected unpasteurized milk and cheese.

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