The territory of an old burial ground for animal refuse that hasn't been used for over 50 years is meant for house building. But soil investigation showed the presence of viable spores of a causative agent causing a very dangerous disease. What microorganism might have been preserved in soil for such a long period of time?

Correct Answer: A

Rationale: The correct answer is A: Bacillus anthracis. This bacterium is known to form highly resistant spores that can survive for long periods in soil. Bacillus anthracis causes anthrax, a dangerous disease that can be transmitted to humans and animals. The other choices, Francisella tularensis, Brucella abortus, and Yersinia pestis, do not form spores as resistant as Bacillus anthracis. Therefore, only Bacillus anthracis is likely to have survived in the soil of the old burial ground for animal refuse for over 50 years.

Correct Answer: A

Rationale: The correct answer is A: Gram staining method. The rationale is as follows: 1. Gentian violet is a primary stain used in the Gram staining procedure to stain the bacterial cells. 2. Lugol's solution is a mordant that helps to fix the crystal violet stain in Gram-positive bacteria. 3. 95% alcohol is used as a decolorizing agent in the Gram staining process to remove the stain from Gram-negative bacteria. 4. Watermagenta is not a standard reagent in the Gram staining method. Therefore, based on the reagents mentioned, the staining method applied in this case is the Gram staining method. Other choices are incorrect: B: Ziehl-Nielsen's - This staining method is used for acid-fast staining, not for lobar pneumonia. C: Romanovsky - This staining method is used for blood smears, not for bacterial staining in pneumonia. D: Neisser - This staining method is not commonly used in routine bacterial staining procedures.

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.

Correct Answer: A

Rationale: The correct answer is A: The polysaccharide capsule. The capsule of Neisseria meningitidis plays a crucial role in its virulence by preventing phagocytosis, allowing the bacteria to evade the host's immune system. This leads to increased survival and colonization in the host. Choice B: The beta lactamase is incorrect because it is an enzyme that breaks down beta-lactam antibiotics and does not directly contribute to the virulence of Neisseria meningitidis. Choice C: The erythrogenic toxin is incorrect as this toxin is produced by Streptococcus pyogenes, not Neisseria meningitidis. Choice D: None of the above is incorrect as the polysaccharide capsule is indeed a key virulence factor of Neisseria meningitidis.

Correct Answer: A

Rationale: The correct answer is A because lipophilization is the process of removing water from cells under deep vacuum in a frozen state. Dehydration of the cell at a low temperature helps to preserve the cellular structure and components. Choice B is incorrect as hydration does the opposite of what lipophilization aims to achieve. Choice C is incorrect as lipophilization does not involve enriching cells with proteins. Choice D is incorrect as lipophilization does not involve removing protein content from cells.

Correct Answer: A

Rationale: Rationale: A: Incorrect - The complement system is not directly involved in the viral neutralization reaction. B: Correct - Specific antibodies neutralize viruses by blocking their ability to infect cells. C: Incorrect - Antibodies are titrated, but only one serum sample is required for neutralization testing. D: Incorrect - Viral neutralization is primarily used to measure antibody response, not to identify newly isolated viruses.

Correct Answer: D

Rationale: The correct answer is D: PCR. PCR (Polymerase Chain Reaction) is the most suitable method for detecting genitourinary chlamydiosis due to its high sensitivity and specificity in detecting the genetic material of Chlamydia trachomatis. PCR can detect even low levels of the pathogen, providing accurate results. A: Cultural diagnostic is not as sensitive as PCR and may take longer to produce results. B: ELISA detects antibodies, which may not be present in early stages of infection, leading to false-negative results. C: CFT (Complement Fixation Test) is an older method with lower sensitivity compared to PCR for detecting chlamydiosis.

Correct Answer: A

Rationale: Rationale: 1. Thin, pale pink microorganisms with spiral coils suggest Treponema pallidum, the causative agent of syphilis. 2. Staining with Romanovsky-Giemsa method highlights the characteristic morphology of T. pallidum. 3. Syphilis presents with various stages and symptoms, correlating with the lymph node involvement. 4. Leptospirosis is caused by Leptospira interrogans, presenting with different clinical features. 5. Relapsing fever is caused by Borrelia species, which do not match the description. 6. Trypanosomiasis is caused by Trypanosoma species, which have distinct morphology and staining properties.

Correct Answer: B

Rationale: The correct answer is B: Transduction. In bacterial genetics, transduction refers to the process of DNA transfer from one bacterium to another via bacteriophages. During transduction, the bacteriophage infects a bacterium, incorporating bacterial DNA into its own genome, which is then transferred to another bacterium upon infecting it. Rationale: A: Transfection is the process of introducing foreign DNA into eukaryotic cells, not bacteria. C: Induction is the process of activating gene expression in a cell. D: Infection is a general term for the invasion of pathogens into a host organism, not specific to DNA transfer via phages in bacteria.