During sanitary and bacteriological testing of water with the membrane filter technique there were revealed two red colonies on a membrane filter (Endo agar) through which 500 ml of water was filtred. Calculate the coli index and coli titer of the analyzed water:

Correct Answer: C

Rationale: The correct answer is C (coli index of 250 and coli titer of 4). The coli index is calculated by multiplying the number of colonies by the reciprocal of the volume filtered, which gives 2 colonies x (1/0.5 L) = 4. The coli titer is obtained by dividing the volume filtered by the number of colonies, which gives 0.5 L / 2 colonies = 0.25 L or 250 ml. This indicates the concentration of coliform bacteria in the water sample. Choice A (4 and 250) is incorrect because it has the correct coli index but the values are reversed for coli index and coli titer. Choice B (2 and 500) is incorrect as it provides the correct coli titer value but the values are reversed for coli index and coli titer. Choice D (500 and 2) is incorrect because it reverses the values for both coli index and coli titer.

Correct Answer: D

Rationale: The correct answer is D, "All of the above." Staphylococcus aureus, Escherichia coli, and Neisseria meningitidis all produce endotoxins that can lead to septic shock. Endotoxins are part of the outer membrane of Gram-negative bacteria, such as E. coli and N. meningitidis, which can trigger a severe immune response leading to septic shock. S. aureus, a Gram-positive bacterium, produces toxins that can also contribute to septic shock. Therefore, all of these bacteria can produce endotoxins responsible for septic shock. Choices A, B, and C are incorrect because they only identify individual bacteria that produce endotoxins, whereas the correct answer encompasses all bacteria listed.

Correct Answer: B

Rationale: The correct answer is B because Q-fever is not transmitted only after ticks bite; it can also be transmitted through inhalation of contaminated aerosols. Rickettsia mooseri and Rickettsia provazekii can cause spotted fevers, making choice A correct. Mediterranean fever is associated with a recurrent pattern of fever, not maculopapular rash, making choice C incorrect. "None of the above" is not correct in this case as choice B is incorrect.

Correct Answer: A

Rationale: The correct answer is A: Tuberculin. In this clinical scenario, the patient presents with symptoms suggestive of tuberculosis, including chronic cough, night sweats, weight loss, and hemoptysis. The Mantoux test, also known as the tuberculin skin test, is used to screen for tuberculosis. Tuberculin, a purified protein derivative (PPD) derived from Mycobacterium tuberculosis, is injected intradermally. The test elicits a delayed-type hypersensitivity reaction in individuals who have been exposed to the organism in the past. A positive Mantoux test indicates exposure to tuberculosis and does not differentiate between active infection and prior exposure. Explanation for other choices: B: Measles - Measles is a viral infection that presents with a characteristic rash and fever, not consistent with the symptoms described in the case. C: Tetanus and diphtheria toxoids vaccine (Td) - Td vaccine is not used for tuberculosis screening and does not elicit

Correct Answer: A

Rationale: Osmosis is the correct answer because it is the process by which water molecules move across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration. This movement occurs passively, driven by the concentration gradient. Facilitated diffusion (B) involves the transport of specific molecules with the help of carrier proteins, not water. Phagocytosis (C) is a process where cells engulf solid particles, not water molecules. Exocytosis (D) is the process of releasing substances from a cell by fusion of vesicles with the cell membrane, not the transport of water across the membrane.

Correct Answer: B

Rationale: The correct answer is B: Jenner. Edward Jenner is credited with performing the first successful vaccination against smallpox in 1796. He used cowpox virus to inoculate individuals, leading to immunity against smallpox. Jenner's experiment laid the foundation for modern vaccination. Pasteur (A) is known for developing the germ theory of disease. Semmelweis (C) advocated for handwashing to prevent infections. Koch (D) identified the causative agents of several diseases but did not develop the smallpox vaccine.

Correct Answer: B

Rationale: The correct answer is B: Order. The suffix -virales is used in virology to denote the order level in the taxonomy of viruses. Orders are higher taxonomic ranks compared to species, family, and genus. The suffix -virales is specifically assigned to virus orders, making choice B the correct one. The other choices (A, C, D) are incorrect because the suffix -virales does not apply to species, family, or genus in the taxonomic classification of viruses.

Correct Answer: D

Rationale: The correct answer is D, Vancomycin, because it is not a beta-lactam antibiotic. Beta-lactam antibiotics contain a beta-lactam ring in their molecular structure, which Vancomycin lacks. Benzylpenicillin, Cephalosporin, and Monobactam all contain the beta-lactam ring, making them beta-lactam antibiotics. Vancomycin belongs to a different class of antibiotics called glycopeptides.

Correct Answer: C

Rationale: Step-by-step rationale for Choice C (Streptococcus pyogenes) being the correct answer: 1. Erysipelas is a skin infection characterized by well-defined red, inflamed skin areas. 2. Streptococcus pyogenes is a common causative agent of erysipelas. 3. This bacterium produces enzymes that break down skin proteins, leading to the characteristic symptoms of erysipelas. 4. Streptococcus pyogenes is known for causing skin infections, including erysipelas. Summary of why the other choices are incorrect: A. Pseudomonas aeruginosa: Typically causes opportunistic infections, but not commonly associated with erysipelas. B. Staphylococcus aureus: Can cause skin infections, but not typically associated with erysipelas. D. Candida albicans: Fungal infection, not a bacterium, and not known to cause erysipelas.