A patient of oral surgery department has developed a purulent complication. Bacteriological analysis of the wound discharge allowed to isolate a culture producing a blue-and-green pigment. Which of the listed microorganisms may be a causative agent of the infection?

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas aeruginosa. Pseudomonas aeruginosa is known for producing a blue-green pigment called pyocyanin, which is characteristic of its colonies. This bacterium is commonly associated with purulent infections, especially in immunocompromised patients. Proteus vulgaris (B) is not typically associated with blue-green pigment production. Bacillus subtilis (C) is not a common pathogen in wound infections. Klebsiella pneumoniae (D) does not produce blue-green pigment and is more commonly associated with respiratory infections. Therefore, based on the clinical presentation and pigment production, Pseudomonas aeruginosa is the most likely causative agent in this case.

Correct Answer: A

Rationale: The correct answer is A: Tetanus. Tetanus is caused by the bacterium Clostridium tetani, which produces a neurotoxin leading to muscle stiffness, including trismus (restricted mouth opening). The patient's history of a stab wound increases the likelihood of tetanus infection due to the spores entering the body through the wound. Incorrect Choices: B: Brucellosis does not typically present with trismus and is more commonly associated with fever, joint pain, and fatigue. C: Whooping cough presents with severe coughing fits but does not cause trismus. D: Wound anaerobic infection may cause localized symptoms at the wound site but is less likely to cause trismus compared to tetanus.

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.

Correct Answer: D

Rationale: The correct answer is D, "All of the above," because all three bacteria (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) can cause urinary tract infections. E. coli is the most common causative agent of UTIs, followed by Staphylococcus aureus and occasionally Pseudomonas aeruginosa. Each of these bacteria has different virulence factors that enable them to infect the urinary tract. Therefore, it is important to consider all three options when diagnosing and treating UTIs. Choices A, B, and C are incorrect because each of those bacteria can individually cause UTIs, so the correct answer is D, as it encompasses all the possible causative agents.

Correct Answer: D

Rationale: The correct answer is D: Pulmonary tuberculosis. The presence of red bacilli stained with Ziehl-Nielsen method indicates acid-fast bacteria, which are characteristic of Mycobacterium tuberculosis, the causative agent of tuberculosis. The size and appearance of the bacilli described match those of M. tuberculosis. Chronic pneumonia, along with the specific staining pattern, strongly suggests tuberculosis as the likely diagnosis. Explanation for other choices: A: Pneumococcal pneumonia is caused by Streptococcus pneumoniae, which would not show red bacilli on Ziehl-Nielsen staining. B: Pulmonary actinomycosis is caused by Actinomyces species, not acid-fast bacteria like M. tuberculosis. C: Pulmonary candidiasis is caused by Candida species, which are fungi and do not appear as red bacilli on staining.

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: A

Rationale: The correct answer is A: Clostridium botulinum. This bacterium is responsible for causing botulism due to its production of botulinum toxin, which is one of the most potent neurotoxins known. Clostridium botulinum thrives in anaerobic conditions like improperly canned foods. Staphylococcus aureus (B), Bacillus anthracis (C), and Pseudomonas aeruginosa (D) do not produce the botulinum toxin and are not associated with botulism. Staphylococcus aureus is known for causing food poisoning, Bacillus anthracis for anthrax, and Pseudomonas aeruginosa for various infections, but not botulism.

Correct Answer: D

Rationale: The correct answer is D because all of the symptoms mentioned (short period of depression, nausea, restlessness) can be early signs of rabies. Rabies typically presents with a variety of non-specific symptoms in the early stages, including behavioral changes such as depression and restlessness, as well as gastrointestinal symptoms like nausea. Therefore, it is important to consider the combination of these symptoms collectively rather than individually when suspecting rabies. Choices A, B, and C alone may not definitively indicate rabies, but when seen together, they should raise suspicion and prompt further evaluation and testing for rabies.