Which one of the following statements about Campylobacter fetus is NOT CORRECT?

Correct Answer: A

Rationale: The correct answer is A: Gram-positive rod-shaped bacterium. Campylobacter fetus is actually a Gram-negative bacterium. This is because it has a thin peptidoglycan layer in its cell wall, which does not retain the crystal violet stain used in the Gram-staining technique. It appears red or pink under a microscope after counterstaining with safranin. Therefore, statement A is incorrect. B: Optimal temperature for cultivation 35-37C - Correct, as Campylobacter fetus thrives at this temperature range. C: Opportunistic pathogen causes infections usually in newborns, immunocompromised patients, and cancer - Correct, as Campylobacter fetus can cause infections in these populations. D: Fastidious, microaerophile - Correct, as Campylobacter fetus is fastidious and requires specific growth conditions, including low oxygen levels.

Correct Answer: C

Rationale: The correct answer is C. Bacterial spores are NOT used for cell division. Bacterial spores are dormant, resistant forms of bacteria that are formed in response to harsh environmental conditions. They are not involved in cell division but rather serve as a survival mechanism for the bacteria. A: They can deform the cell or not - This is true. Bacterial spores can deform the cell or not depending on the conditions. B: They can be terminal, subterminal, and central - This is true. Bacterial spores can be located at different positions within the bacterial cell. D: They are formed for 6-8h - This is incorrect. The formation of bacterial spores can take variable time periods depending on the species and environmental conditions.

Correct Answer: D

Rationale: The correct answer is D: Bacillus cereus. Bacillus intoxication is typically caused by Bacillus cereus, which is a common foodborne pathogen. This bacterium produces toxins that can lead to gastrointestinal illness when ingested. Bacillus subtilis (A) and Bacillus thuringiensis (B) are not known to cause intoxication in humans. Bacillus anthracis (C) causes anthrax, not intoxication. Therefore, Bacillus cereus is the correct choice for Bacillus intoxication.

Correct Answer: A

Rationale: The correct answer is A: Protein synthesis. Bacterial ribosomes are responsible for translating mRNA into proteins through a process called translation. This is a crucial step in gene expression, where amino acids are assembled into polypeptide chains. Choice B (DNA replication) is incorrect because ribosomes are not involved in DNA replication. Choice C (Flagella formation) is incorrect as ribosomes do not play a direct role in flagella formation. Choice D (Toxin production) is incorrect as ribosomes are not directly involved in producing toxins.

Correct Answer: C

Rationale: The Gram stain process involves staining bacterial cells with crystal violet and iodine, followed by decolorization and counterstaining. The primary differentiation is based on the cell wall structure, distinguishing bacteria into Gram-positive (retain purple color) and Gram-negative (lose purple color). This classification is crucial in microbiology for treatment decisions as it correlates with different antibiotic susceptibilities. Choices A, B, and D are incorrect because the Gram stain process does not primarily focus on flagella, shape, or motility of bacteria.

Correct Answer: A

Rationale: Step-by-step rationale for why choice A is correct: 1. Helicobacter pylori, the bacteria causing helicobacteriosis, is microaerophilic, requiring low oxygen levels. 2. Cultivation conditions must mimic the natural environment of the bacteria. 3. Failure to provide a microaerophilic environment can hinder bacterial growth. 4. Thus, the ability to cultivate these bacteria requires consideration of their microaerophilic nature. Summary: - Choice A is correct because Helicobacter pylori is a microaerophilic bacteria. - Choice B (Presence of urease) is incorrect as it is a characteristic used for diagnosis, not cultivation. - Choice C (Absence of spores and capsules) is incorrect as it does not relate to cultivation requirements. - Choice D (Colonization of gastral cells) is incorrect as it pertains to bacterial behavior, not cultivation needs.

Correct Answer: B

Rationale: The correct answer is B: Linnaeus. Linnaeus developed the binomial system of nomenclature in the 18th century. He introduced the use of a two-part naming system consisting of a genus name and a species name, known as binomial nomenclature. This system helps in organizing and categorizing living organisms systematically. Pasteur (choice A) is known for his contributions to microbiology, not nomenclature. Martini (choice C) and Jenner (choice D) are not associated with the development of the binomial system of nomenclature.

Correct Answer: C

Rationale: The correct answer is C: Streptococcus. Streptococcus pneumoniae is the most common etiological factor for community-acquired pneumonia in young adults. The symptoms described align with typical pneumococcal pneumonia presentation. Presence of pleural friction rub and infiltration in the X-ray support the diagnosis. The blood work showing elevated WBC count with a left shift (increased neutrophils and low lymphocytes) and elevated ESR is consistent with a bacterial infection. Legionella and Mycoplasma typically present with atypical pneumonia symptoms such as headache, confusion, and GI symptoms, which are not described in the case. Staphylococcus pneumonia is not a common cause of community-acquired pneumonia in young adults.

Correct Answer: A

Rationale: The correct answer is A: Balantidium coli. This large ciliated protozoa with a kidney-shaped macronucleus is characteristic of Balantidium coli, an intestinal parasite known to cause foul-smelling diarrhea in humans. Balantidium coli is the only option among the choices that fits this specific description. Entamoeba histolytica causes amoebic dysentery, Giardia lamblia causes giardiasis, and Trichomonas hominis is a non-pathogenic protozoa found in the intestinal tract. Therefore, based on the morphology described in the question, Balantidium coli is the correct causative agent.