openstax microbiology test bank

Correct Answer: D

Rationale: The correct answer is D: All of the above. Streptococcus pneumoniae, Mycobacterium tuberculosis, and Escherichia coli can all cause pneumonia, but through different mechanisms. S. pneumoniae is a common cause of community-acquired pneumonia, M. tuberculosis can lead to tuberculosis-related pneumonia, and E. coli can cause pneumonia in immunocompromised individuals. Therefore, all three bacteria can be responsible for causing pneumonia, making option D the correct choice. Option A, Streptococcus pneumoniae, is correct but does not cover all possible causes of pneumonia. Option B, Mycobacterium tuberculosis, is too specific and does not include other common causes. Option C, Escherichia coli, is also a possible cause of pneumonia but does not account for all potential pathogens.

Correct Answer: A

Rationale: The correct answer is A: Trichomonas vaginalis. Trichomonas vaginalis is a flagellated protozoa that causes the sexually transmitted infection trichomoniasis. The presence of an undulating membrane in vaginal discharge samples is characteristic of Trichomonas vaginalis. Giardia lamblia causes gastrointestinal illness, not vaginal infections. Trypanosoma brucei causes African sleeping sickness transmitted by tsetse flies. Leishmania donovani causes visceral leishmaniasis transmitted by sandflies.

Correct Answer: A

Rationale: The correct answer is A: Acid-fast stain. This stain is used for diagnosing tuberculosis due to the unique cell wall composition of Mycobacterium tuberculosis, which resists decolorization by acid-alcohol. This allows the bacteria to retain the primary stain (carbol fuchsin) and appear red under a microscope. Gram stain (B) is not suitable for Mycobacterium tuberculosis as it is gram-positive but does not retain the crystal violet-iodine complex. Negative stain (C) is not used for bacterial identification. Simple stain (D) does not differentiate acid-fast bacteria like Mycobacterium tuberculosis.

Correct Answer: B

Rationale: The correct answer is B: Plasmids. Plasmids are extrachromosomal DNA molecules found in bacteria that can replicate independently of the bacterial chromosome. They carry additional genetic information, such as antibiotic resistance genes or virulence factors. Mesosomes (choice A) are not involved in carrying genetic information; they are infoldings of the cell membrane. Ribosomes (choice C) are cellular organelles responsible for protein synthesis, not carriers of genetic information. Choice D is incorrect as plasmids are indeed extrachromosomal carriers of genetic information in bacteria.

Correct Answer: B

Rationale: The correct answer is B: Yersinia enterocolitica. Y. enterocolitica is known to cause gastroenteritis and diarrhea in humans. It is often associated with contaminated food or water. Bordetella pertussis causes whooping cough, not diarrhea. Corynebacterium diphtheria causes respiratory diphtheria. Neisseria meningitidis is associated with meningitis and septicemia, not diarrhea. Therefore, based on the patient's symptoms and history, Y. enterocolitica is the most likely cause of the diarrhea in this case.