Polyclonal antibodies can respond to multiple antigens:

Correct Answer: A

Rationale: Polyclonal antibodies are produced by different B cells, each recognizing a different epitope on an antigen. Therefore, they can respond to multiple antigens. This diversity in recognition allows polyclonal antibodies to bind to various targets, making option A true. Options B, C, and D are incorrect as they do not accurately reflect the nature of polyclonal antibodies' ability to recognize multiple antigens.

Correct Answer: A

Rationale: The correct answer is A: Capnophilic. Brucella requires a CO2 enriched atmosphere for cultivation, making it capnophilic. This is because Brucella is a microaerophilic bacterium that thrives in low oxygen conditions and elevated CO2 levels. Choice B (Facultative anaerobic) and D (Obligate aerobic) are incorrect as Brucella does not grow well under aerobic conditions. Choice C (Obligate anaerobic) is also incorrect as Brucella can grow in the presence of oxygen, although it prefers low oxygen environments.

Correct Answer: C

Rationale: The correct answer is C: green monkeys. The Marburg virus was first identified in 1967 in Marburg and Frankfurt, Germany, after outbreaks in lab workers exposed to infected African green monkeys. These monkeys were imported from Uganda. The virus is believed to be originally endemic in certain species of African bats and is transmitted to humans through contact with infected animals. Choice A, laboratory rats, is incorrect as the virus did not originate from rats. Choice B, birds, and Choice D, wild turkeys, are also incorrect as there is no evidence linking these animals to the transmission of the Marburg virus.

Correct Answer: A

Rationale: The correct answer is A because the cytoplasmic membrane in bacteria is primarily composed of phospholipids, glycerol, and glycolipids. Phospholipids form the basic structure of the membrane, with glycerol serving as the backbone and glycolipids present on the outer surface. Lipopolysaccharides (choice B) are primarily found in the outer membrane of Gram-negative bacteria, not the cytoplasmic membrane. Choice C is incorrect because peptidoglycan is a component of the bacterial cell wall, not the cytoplasmic membrane. Choice D is incorrect as the cytoplasmic membrane in bacteria is indeed composed of phospholipids, glycerol, and glycolipids.

Correct Answer: A

Rationale: Step 1: Pear-shaped protozoa with two nuclei, four pairs of flagella, two axostyles, and a ventral adhesive disc match the characteristics of Giardia lamblia. Step 2: Giardia lamblia is commonly found in the duodenum and causes giardiasis. Step 3: Lamblia is the correct answer as it specifically matches all the described characteristics. Summary: B, Toxoplasma, is incorrect as it does not match the described features. C, Leishmania, does not have the specific characteristics mentioned. D, Intestinal trichomonad, does not match the detailed descriptions given.

Correct Answer: A

Rationale: Neisseria gonorrhoeae is the correct answer because it is the specific bacterium responsible for causing gonorrhea. It is a sexually transmitted infection that primarily affects the genital tract. Neisseria gonorrhoeae is transmitted through sexual contact and can lead to symptoms such as painful urination, discharge, and pelvic pain. Chlamydia trachomatis (Choice B) is another sexually transmitted bacterium, but it causes chlamydia, not gonorrhea. Mycobacterium tuberculosis (Choice C) is responsible for tuberculosis, a different infectious disease that primarily affects the lungs. Treponema pallidum (Choice D) causes syphilis, another sexually transmitted infection that presents with distinct symptoms from gonorrhea. Therefore, Neisseria gonorrhoeae is the correct choice for causing gonorrhea due to its specific association with this particular infection.

Correct Answer: B

Rationale: The correct answer is B: Pseudomonas aeruginosa. This bacterium is important for controlling air quality as it can degrade a wide range of organic compounds present in the air, helping to maintain a clean and healthy environment. Alpha and beta-hemolytic streptococci (Choice A) are not typically associated with air quality control. E. coli (Choice C) and Salmonella spp. (Choice D) are more commonly found in water and food sources, not air, making them incorrect choices for this question. Pseudomonas aeruginosa's ability to break down organic matter in the air makes it the most suitable option for maintaining sanitary air quality.

Correct Answer: C

Rationale: The correct answer is C: Salmonella. This bacterium should be handled in a Biosafety Level 2 facility due to its potential to cause disease in humans. Salmonella is a pathogenic bacterium that can cause foodborne illnesses and infections. Handling it in a Biosafety Level 2 facility ensures proper containment and protection of personnel. A: Micrococcus luteus and B: Bacillus subtilis are common environmental bacteria that do not pose significant risks to human health, so they can be safely handled in lower biosafety levels. D: Staphylococcus epidermidis is a common skin commensal bacterium that is generally not considered highly pathogenic, so it does not require Biosafety Level 2 containment.

Correct Answer: D

Rationale: The correct answer is D, chemotherapy combined with surgical therapy. Actinomycosis is a bacterial infection that requires a combination of antibiotics to target the bacteria and surgery to remove abscesses or infected tissues. Antibiotics alone may not penetrate abscesses effectively. Waiting for self-clearance can lead to complications. Surgical treatment alone may not eradicate the infection entirely. Therefore, the most effective therapeutic plan is to combine chemotherapy to treat the infection systemically and surgery to remove localized infections.