Vaginal infections that are resulting from an overgrowth of normal flora are called:

Correct Answer: A

Rationale: The correct answer is A: endogenous infections. This term refers to infections caused by microorganisms that are normally present in or on the body. In the context of vaginal infections, an overgrowth of the normal flora can lead to an imbalance and result in infection. Choice B, chronic infections, does not specifically address the source of the infection. Choice C, iatrogenic infections, refers to infections caused by medical intervention, not normal flora overgrowth. Choice D, fatal infections, is incorrect as it does not describe the nature or source of the infection. In summary, the term "endogenous infections" accurately describes the scenario of vaginal infections caused by an overgrowth of normal flora.

Correct Answer: A

Rationale: The correct answer is A: yeast and molds. Yeast and molds can resist acidic pH due to their ability to maintain a stable internal pH through various mechanisms such as ion transport and cell wall composition. Bacteria, including E. coli, are generally more sensitive to acidic conditions. Choice D is incorrect as yeast and molds are known to thrive in acidic environments.

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas aeruginosa. P. aeruginosa is a Gram-negative rod that is a lactose non-fermenter commonly associated with deep tissue infections. It is an opportunistic pathogen known for its ability to cause infections in immunocompromised individuals. P. aeruginosa is often resistant to multiple antibiotics and can form biofilms, making it difficult to treat. Summary of why other choices are incorrect: B: Escherichia coli is a Gram-negative rod that ferments lactose and is commonly found in the gastrointestinal tract. It is not typically associated with deep tissue infections. C: Salmonella typhi is a Gram-negative rod that causes typhoid fever, primarily affecting the gastrointestinal system, not deep tissue infections. D: Shigella dysenteriae is a Gram-negative rod that causes bacillary dysentery, which primarily affects the gastrointestinal tract and does not typically cause deep tissue infections.

Correct Answer: D

Rationale: The correct answer is D: S phase. During the S phase of the cell cycle, DNA replication takes place to ensure each daughter cell receives a complete set of genetic material. This phase is characterized by the synthesis of new DNA strands. In contrast, choices A, B, and C (G phase, Prophase, Metaphase) are not associated with DNA replication. The G phase is a period of cell growth, Prophase is the initial stage of mitosis, and Metaphase is when chromosomes align. Therefore, the S phase is the specific stage where DNA replication occurs, making it the correct answer.

Correct Answer: A

Rationale: Step-by-step rationale for choice A being correct: 1. Parvovirus B19 is a single-stranded DNA (ssDNA) virus. 2. The prefix "parvo-" indicates small size, characteristic of ssDNA viruses. 3. ssDNA viruses replicate in the host cell by converting their ssDNA genome into double-stranded DNA (dsDNA). 4. Therefore, the correct answer is A: Its genome consists of dsDNA. Summary of why other choices are incorrect: B: Parvovirus B19 is a non-enveloped virus, making choice B incorrect. C: Parvovirus B19 has a linear ssDNA genome, not segmented, making choice C incorrect. D: Parvovirus B19 has two structural proteins - VP1 and VP2, making choice D incorrect.

Correct Answer: A

Rationale: The correct answer is A: Helicobacter pylori. This bacterium is the most likely causative agent of gastric ulcers. Here's the rationale: 1. Helicobacter pylori is commonly associated with gastric ulcers. 2. It is a gram-negative bacterium that grows on chocolate agar and is oxide reductase-positive. 3. The slow growth on the fifth day is characteristic of H. pylori. 4. Campylobacter jejuni and Campylobacter fetus are not typically associated with gastric ulcers. 5. Mycoplasma hominis is a bacterium that lacks a cell wall and is not commonly found in gastric ulcers.

Correct Answer: A

Rationale: Step 1: Rubella virus belongs to the Togaviridae family, which typically exhibits icosahedral symmetry. Step 2: Icosahedral symmetry refers to a structure with 20 equilateral triangular faces, which is characteristic of many viruses, including rubella. Step 3: Therefore, choice A is correct as rubella virus indeed has icosahedral type of symmetry. Summary: - Choice B is incorrect as rubella virus is an ssRNA virus, not ssDNA. - Choice C is incorrect as rubella virus does have an envelope derived from the host cell membrane. - Choice D is incorrect as rubella virus does have glycoprotein spikes on its surface.

Correct Answer: A

Rationale: Step 1: Viruses can have either DNA or RNA, not both, hence they have only one type of nucleic acid. Step 2: The extracellular form of viruses is called virion, not viroid. Step 3: Viruses are obligate intracellular parasites, meaning they rely on host cells for replication. Step 4: Viruses are measured in nanometers, not micrometers. Therefore, the correct answer is A.

Correct Answer: B

Rationale: The correct answer is B: Contains single-stranded RNA with negative polarity. Measles virus is an enveloped virus with a single-stranded RNA genome that is negative-sense. This means it must first be transcribed into positive-sense RNA before it can be translated. Choice A is incorrect as the measles virus does have an outer envelope. Choice C is incorrect as measles virus belongs to the family Paramyxoviridae, not Togaviridae. Choice D is incorrect as measles virus can be grown on cell cultures, specifically on Vero cells.