When a pathogen spreads from the original site to other tissues or organs it is called a(n) __________ infection.

Correct Answer: B

Rationale: The correct answer is B: focal. When a pathogen spreads from the original site to other tissues or organs, it is considered a focal infection. This term specifically refers to an infection that is localized to a specific area but can spread to other parts of the body. A: Local infection refers to an infection that is confined to a specific area without spreading to other tissues or organs. C: Natural is not a term commonly used to describe the spread of pathogens within the body. D: Acute refers to the rapid onset of a disease but does not specifically address the spread of pathogens from one site to another. In summary, the term "focal" best describes the scenario provided in the question, making it the correct answer.

Correct Answer: D

Rationale: The correct answer is D because antigenic shift is a major change in the influenza virus where genetic material from different influenza viruses mix to create a new subtype. This is a large-scale change that results in a novel virus with a different antigenic composition. Option A and B are incorrect because antigenic shift does involve the exchange of genetic information between animal and human influenza A viruses, and it does occur when animal or avian influenza viruses of type A directly pass into the human population. Option C is incorrect because antigenic shift is not related to the recirculation of a previously circulating influenza strain.

Correct Answer: B

Rationale: The correct answer is B: Salmonellosis. The description of microorganisms resembling a tennis racket indicates the presence of Salmonella typhi, which causes salmonellosis. Salmonella bacteria can appear like tennis rackets under a microscope due to their flagella. Botulism (A) is caused by Clostridium botulinum, which does not resemble a tennis racket. Cholera (C) is caused by Vibrio cholerae, which appears as curved rods under the microscope. Dysentery (D) is usually caused by bacteria like Shigella or Entamoeba histolytica, which do not resemble tennis rackets.

Correct Answer: A

Rationale: Rationale: Bacillus cereus is associated with food intoxication due to its ability to produce toxins that cause gastrointestinal symptoms. B. subtilis is not known to cause food intoxication. B. anthracis causes anthrax, not food intoxication. Option D is incorrect as not all Bacillus species cause food intoxication.

Correct Answer: D

Rationale: The correct answer is D: Gram-negative coccobacillus. Francisella tularensis is a Gram-negative coccobacillus because it has a unique shape that is between a coccus (spherical) and a bacillus (rod-shaped) and it stains pink/red in the Gram staining process. It is important to note that it is not a coccus (choice B) or a Gram-positive bacterium (choice A). Choice C is too general and does not specify the coccobacillus shape of F. tularensis. So, the correct answer is D due to its specific characteristics as a Gram-negative coccobacillus.

Correct Answer: B

Rationale: The correct answer is B: Thermophiles. Thermophiles are bacteria that can survive in extreme temperatures, typically between 45°C to 80°C. This ability is due to their unique enzymes and cell membrane structures that are adapted to high temperatures. Escherichia coli (A) is a common bacterium found in the human gut and does not thrive in extreme temperatures. Clostridium tetani (C) is a bacterium that causes tetanus and prefers moderate temperatures. Salmonella enterica (D) is a pathogenic bacterium that does not thrive in extreme temperatures. Therefore, Thermophiles are the only bacteria on the list known for surviving in extreme temperatures.

Correct Answer: D

Rationale: The correct answer is D because fungi do not form flagella. Fungi reproduce sexually and asexually (A) through spores, have a cell wall (B) made of chitin, and are mostly aerobic or facultative anaerobes (C). Flagella are structures found in some protozoa and bacteria, not in fungi. Therefore, option D is the only statement that is not true about fungi.

Correct Answer: B

Rationale: The correct answer is B because the AST reaction, or anti-streptolysin titer, is used in the diagnostic of post-streptococcal sequelae, such as rheumatic fever and glomerulonephritis. This test measures the level of antibodies produced by the body in response to Streptolysin O, a toxin produced by Group A Streptococcus bacteria. It helps in identifying if a patient has had a recent Streptococcus infection that could lead to these complications. A: Incorrect. The AST reaction does not require urine samples, but rather blood samples. C: Incorrect. The AST reaction specifically targets antibodies produced in response to Group A Streptococcus. D: Incorrect. The AST reaction does not directly identify isolated streptococci but rather measures the body's immune response to Streptolysin O.

Correct Answer: B

Rationale: The correct answer is B: focal. When a pathogen spreads from the original site to other tissues or organs, it is considered a focal infection. This term specifically refers to an infection that is localized to a specific area but can spread to other parts of the body. A: Local infection refers to an infection that is confined to a specific area without spreading to other tissues or organs. C: Natural is not a term commonly used to describe the spread of pathogens within the body. D: Acute refers to the rapid onset of a disease but does not specifically address the spread of pathogens from one site to another. In summary, the term "focal" best describes the scenario provided in the question, making it the correct answer.