A wound smear revealed Gram-negative rods producing blue-green pigment. The bacteria had a fruity odor. What is the causative agent?

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas aeruginosa. Pseudomonas aeruginosa is known to produce a blue-green pigment called pyocyanin, which is characteristic of the organism. Additionally, it has a distinct fruity odor due to the production of certain volatile compounds. Escherichia coli (B) does not produce blue-green pigment or have a fruity odor. Klebsiella pneumoniae (C) and Proteus mirabilis (D) also do not exhibit these specific characteristics associated with Pseudomonas aeruginosa.

Correct Answer: C

Rationale: Granulomatosis infantiseptica is commonly caused by Listeria monocytogenes, a bacterium known to infect newborns. It can lead to granulomatous lesions in various organs. Staphylococcus aureus and Mycobacterium tuberculosis are not typical causes of this condition in infants. Choice D is incorrect as it suggests all listed bacteria are responsible, which is not accurate. Therefore, the correct answer is C as Listeria monocytogenes is the specific pathogen associated with granulomatosis infantiseptica.

Correct Answer: B

Rationale: Rationale: 1. The grain-like sediment indicates a precipitation reaction. 2. Precipitins are antibodies that cause precipitation reactions. 3. In serological diagnostics, precipitation reactions are used to detect specific antibodies. 4. Therefore, the reaction revealed in this scenario is due to the presence of precipitins. Summary: A: Bacteriolysins - These antibodies cause bacterial lysis, not precipitation. C: Antitoxins - These antibodies neutralize toxins, not involved in precipitation reactions. D: Opsonins - These antibodies enhance phagocytosis, not related to precipitation reactions.

Correct Answer: B

Rationale: The correct answer is B because there are two types of herpes simplex virus: HSV-1 and HSV-2. HSV-1 typically causes oral herpes, while HSV-2 usually causes genital herpes. Choice A is incorrect because there is more than one type. Choices C and D are also incorrect as there are only two types of herpes simplex virus known to infect humans.

Correct Answer: A

Rationale: Step 1: The patient's symptoms align with tetanus infection, such as muscle spasms and fever. Step 2: Tetanus is caused by Clostridium tetani bacteria found in soil. Step 3: The wound from tilling soil provides an entry point for the bacteria. Step 4: Delayed seeking medical attention increases the risk of tetanus development. Step 5: Tetanus toxin affects the nervous system, leading to muscle stiffness and spasms. Summary: Choice A is correct due to symptom alignment, bacterial source, wound type, delayed treatment, and specific neurological effects. Choices B, C, and D lack these specific connections to the given scenario.

Correct Answer: C

Rationale: The correct answer is C because disinfectants are non-selective and can harm a wide range of microbial cells. Disinfectants work by disrupting cell membranes, proteins, and nucleic acids, affecting both harmful and beneficial microorganisms. Choices A and B are incorrect because disinfectants are designed to be potent and non-selective. Choice D is incorrect because the effects of disinfectants are often permanent and irreversible on microbial cells.

Correct Answer: A

Rationale: Rationale: The correct answer is A: Syphilis. Spiral microorganisms with pointed ends are characteristic of Treponema pallidum, the causative agent of syphilis. This bacterium is known for its corkscrew shape. Other choices are incorrect because Leptospirosis, Lyme disease, and Relapsing fever are caused by different pathogens and do not exhibit spiral microorganisms on blood smears. Syphilis should be suspected in the presence of these specific spiral microorganisms.

Correct Answer: C

Rationale: The correct answer is C: Helicobacter pylori. This bacterium is a well-known cause of peptic ulcers due to its ability to survive in the acidic environment of the stomach and produce enzymes that weaken the protective mucous layer of the stomach lining. Treponema pallidum (choice A) causes syphilis, Vibrio cholerae (choice B) causes cholera, and Escherichia coli (choice D) can cause various infections but is not a common cause of peptic ulcers. Therefore, Helicobacter pylori is the correct answer as it is specifically associated with peptic ulcer formation.

Correct Answer: A

Rationale: The correct answer is A because most bacteria can grow in both the presence and absence of oxygen. Some bacteria are aerobic and require oxygen for growth, while others are anaerobic and can grow in the absence of oxygen. Choice B is incorrect because not all bacteria grow in the absence of oxygen. Choice C is incorrect because not all bacteria are microaerophiles, which are bacteria that require a low level of oxygen for growth. Choice D is incorrect because most bacteria exhibit flexibility in their oxygen requirements.