Which bacteria is commonly associated with hospital-acquired infections?

Correct Answer: C

Rationale: The correct answer is C: Staphylococcus aureus. This bacterium is commonly associated with hospital-acquired infections due to its ability to cause a wide range of infections and its resistance to multiple antibiotics. Staphylococcus aureus can cause skin infections, pneumonia, bloodstream infections, and surgical site infections, making it a significant threat in healthcare settings. Escherichia coli (choice A) is more commonly associated with foodborne illnesses. Clostridium difficile (choice B) is known for causing antibiotic-associated diarrhea. Bacillus anthracis (choice D) is primarily associated with anthrax infections, which are not typically acquired in hospital settings.

Correct Answer: A

Rationale: The correct answer is A: Urogenital trichomoniasis. The presence of pyriform protozoa with a spine, flagella at their front, and an undulating membrane in a vaginal smear indicates Trichomonas vaginalis, the causative agent of urogenital trichomoniasis. Trichomonas vaginalis is sexually transmitted and causes vaginal discharge, itching, and inflammation. Lambliasis (choice B) is caused by Giardia lamblia, which is not characterized by the described features. Intestinal trichomoniasis (choice C) is caused by a different species, Tritrichomonas foetus, and presents with diarrhea in cattle. Toxoplasmosis (choice D) is caused by Toxoplasma gondii and typically affects the brain and other organs, not the genital tract.

Correct Answer: C

Rationale: The correct answer is C: Campylobacter jejuni. This bacterium is Gram-negative and comma-shaped, commonly causing respiratory infections. Vibrio cholerae (A) causes cholera, not respiratory infections. Shigella dysenteriae (B) causes dysentery, not respiratory infections. Helicobacter pylori (D) is associated with gastric ulcers, not respiratory infections. Therefore, Campylobacter jejuni is the most likely causative agent based on the given information.

Correct Answer: A

Rationale: Step-by-step rationale for the correct answer (A: Epstein-Barr virus): 1. Epstein-Barr virus is a member of the Herpesviridae family, known for causing infectious mononucleosis. 2. Members of Herpesviridae have double-stranded DNA genomes and enveloped virions. 3. They establish latent infections in host cells and can reactivate periodically. 4. Poxvirus (B) belongs to the Poxviridae family, not Herpesviridae. 5. SARS (C) is caused by a coronavirus, not a herpesvirus. 6. HIV (D) belongs to the Retroviridae family, not Herpesviridae. Summary: The correct answer is A because Epstein-Barr virus is a member of the Herpesviridae family, exhibiting specific characteristics distinct from the other choices.

Correct Answer: A

Rationale: The correct answer is A: viruses. Viruses are always in a parasitic form of interaction with the individual because they cannot survive or reproduce outside of a host cell. They rely on host cells to replicate and cause harm. Non-pathogenic bacteria (choice B) do not always cause harm and can coexist with the individual. Facultative pathogenic bacteria (choice C) can switch between being beneficial and harmful. Therefore, the correct answer is A as viruses always rely on a host for survival and reproduction.

Correct Answer: C

Rationale: The correct answer is C: Janssen. In the 16th century, Zacharias Janssen and his father Hans Janssen are credited with inventing the compound microscope. They constructed a simple tube with lenses at each end, allowing for magnification of small objects. This innovation laid the foundation for the development of modern microscopes. Van Leeuwenhoek is known for his contributions to microbiology but did not invent the compound microscope. Semmelweis is known for his work in handwashing and preventing infections. Hooke made significant contributions to microscopy but did not invent the compound microscope.

Correct Answer: A

Rationale: The correct answer is A: Vibrio cholerae. This is because Vibrio cholerae is a Gram-negative, comma-shaped bacterium known to cause cholera. The characteristic shape and the association with cholera make it the most likely causative agent in this case. Explanation for incorrect choices: B: Shigella dysenteriae - Shigella dysenteriae is a Gram-negative bacterium that causes bacillary dysentery, not cholera. C: Salmonella typhi - Salmonella typhi is a Gram-negative bacterium that causes typhoid fever, not cholera. D: Campylobacter jejuni - Campylobacter jejuni is a Gram-negative bacterium that commonly causes foodborne gastroenteritis, not cholera.

Correct Answer: C

Rationale: The correct answer is C: halophiles. Halophiles are bacteria that thrive in high salt concentrations due to their ability to regulate osmotic pressure. They have adapted mechanisms to survive in such extreme environments. Option A, acidophiles, thrive in acidic conditions, not high salt concentrations. Option B, thermophiles, thrive in high temperature environments. Option D, mesophiles, thrive in moderate temperature conditions, not necessarily high salt concentrations. Therefore, the correct choice is C as it specifically refers to bacteria that thrive in high salt concentrations.

Correct Answer: D

Rationale: The correct answer is D: All of the above. Tuberculosis, Q-fever, and Legionnaires disease all can infect the respiratory tract. Tuberculosis is a bacterial infection affecting the lungs, Q-fever is caused by a bacterium that primarily affects the lungs, and Legionnaires disease is a severe form of pneumonia. All three diseases specifically target the respiratory system, making them the correct choices. Choices A, B, and C are incorrect because each of them individually infects the respiratory tract, not just one or two of them.