Microscopy of a smear from a patient with foul-smelling diarrhea revealed large ciliated protozoa with a kidney-shaped macronucleus. What is the diagnosis?

Correct Answer: A

Rationale: The correct diagnosis is A: Balantidiasis. The presence of large ciliated protozoa with a kidney-shaped macronucleus is characteristic of Balantidium coli, the causative agent of balantidiasis. The ciliated trophozoites of Balantidium coli are unique compared to the other choices. Giardiasis is caused by Giardia lamblia, which has flagella and not cilia. Amoebiasis is caused by Entamoeba histolytica, which lacks cilia. Trichomoniasis is caused by Trichomonas vaginalis, which also lacks cilia. Therefore, based on the specific morphology described, the correct diagnosis is Balantidiasis.

Correct Answer: C

Rationale: The correct answer is C: heterotrophic. Fungi are heterotrophic organisms that obtain nutrients by absorbing organic compounds from their environment. They do not produce their own food through photosynthesis (option A: autotrophic) or chemosynthesis (option B: chemotrophic). Fungi also do not rely on light for energy (option D: phototrophic). Therefore, the correct choice is C as it accurately describes the nutritional mode of fungi.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pyogenes. This bacterium fits all the given characteristics: Gram-positive cocci arranged in chains, catalase-negative, and beta-hemolytic on blood agar. Streptococcus pyogenes is known for causing skin and soft tissue infections. Staphylococcus aureus (B) is catalase-positive and typically forms clusters, not chains. Enterococcus faecalis (C) is catalase-negative but not beta-hemolytic. Micrococcus luteus (D) is catalase-positive and not typically associated with wound infections.

Correct Answer: A

Rationale: The correct answer is A: Neutralization. In this scenario, the antibotulinic serum of types A, B, and E were introduced to neutralize the botulinum toxin in the test specimen. The serological reaction applied here involves the neutralization of the toxin by the specific antibodies present in the serum. This process prevents the toxin from causing harm to the mice. Summary of other choices: B: Precipitation - This involves the formation of insoluble complexes between antigen and antibody, not the specific neutralization seen in this case. C: Complement binding - This involves activation of the complement system leading to cell lysis, not the direct neutralization of toxin. D: Double immune diffusion - This technique is used to determine the presence of specific antibodies or antigens based on their diffusion patterns, not the neutralization of toxin as seen in this scenario.

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: Method of Moller. This method uses malachite green to stain bacterial spores due to their resistance to decolorization. The other choices, A, B, and D, are incorrect because Romanovski-Gymsa is used for staining blood smears, Ziehl-Nielsen is used for acid-fast bacteria, and Neisser is used for staining Neisseria species, not bacterial spores.

Correct Answer: B

Rationale: The correct answer is B: H antigen. Flagellar antigen is typically referred to as the H antigen in bacteria. Flagella are the whip-like structures used for movement in bacteria, and the H antigen is specifically associated with the flagella. The other choices (A: D antigen, C: K antigen, D: F antigen) are not related to flagella in bacteria and are commonly associated with other types of antigens in bacterial classification.

Correct Answer: A

Rationale: The correct answer is A: Cell wall. Mycoplasma species lack a cell wall, making them unique among bacteria. This is because they have a flexible cell membrane that provides structural support instead of a rigid cell wall. The absence of a cell wall allows them to be pleomorphic and gives them resistance to certain antibiotics targeting cell wall synthesis. Plasma membrane (B), DNA (C), and ribosomes (D) are present in Mycoplasma species, so they are not the correct answer.

Correct Answer: C

Rationale: The correct staining technique for staining sputum smears from a tuberculosis patient is Ziehl-Neelsen staining. This technique uses a carbol fuchsin stain that specifically stains acid-fast organisms like Mycobacterium tuberculosis. The steps involved include staining with carbol fuchsin, decolorizing with acid-alcohol, counterstaining with methylene blue, and then examining under a microscope. This staining method is crucial for detecting the acid-fast bacilli characteristic of tuberculosis. Explanation for incorrect choices: A: Gram staining is used to differentiate bacteria into Gram-positive and Gram-negative, not suitable for acid-fast organisms like Mycobacterium tuberculosis. B: Giemsa staining is used for detecting parasites and certain types of white blood cells, not specific for acid-fast bacteria. D: Burry staining is not a recognized staining technique in microbiology for staining acid-fast organisms.