A 3 month old infant has got a white deposition on the mucous membrane of his mouth, tongue and lips. The doctor suspected candidosis. What nutrient medium should be used for inoculation of the material under examination in order to confirm this diagnosis?

Correct Answer: A

Rationale: The correct answer is A: Sabouraud. Sabouraud agar is specifically designed for the cultivation of fungi and yeasts, making it ideal for identifying Candida species causing candidosis. It contains antibiotics to inhibit bacterial growth, promoting the growth of fungi. Endo, Loewenstein-Jensen, and Roux are not suitable for fungal cultures and are used for different purposes like bacterial isolation or mycobacterial cultures. Sabouraud agar is the best choice for confirming candidosis due to its fungal-selective properties.

Correct Answer: A

Rationale: The most likely diagnosis is Epidemic typhus (Choice A) based on the symptoms described. The presence of roseolous-petechial rash, high fever (41oC), hyperemia of face, reddening of scleras, tremor of the tongue, tachycardia, and splenomegaly are classic signs of epidemic typhus. The rash typically appears around the 5th day of the disease. Summary: - B: Measles typically presents with a maculopapular rash starting on the face and spreading downward. It doesn't usually present with tremor of the tongue or splenomegaly. - C: Alcohol delirium is characterized by confusion, disorientation, and hallucinations due to alcohol consumption. It doesn't match the symptoms described. - D: Leptospirosis presents with fever, muscle pain, and conjunctival suffusion. It doesn't typically present with the specific rash and trem

Correct Answer: C

Rationale: The correct answer is C: Increased active efflux from the bacterial cell. This is the most important mechanism of tetracycline resistance because it involves the bacteria actively pumping out the antibiotic, reducing its intracellular concentration. This prevents tetracycline from effectively targeting bacterial ribosomes. Choice A is incorrect as tetracycline resistance typically involves active efflux rather than reduced influx. Choice B is incorrect because tetracycline resistance mechanisms do not primarily involve altered cell membrane components affecting passive influx. Choice D is also incorrect as tetracycline resistance mechanisms do not typically involve direct enzymatic inactivation of the antibiotic.

Correct Answer: B

Rationale: The correct answer is B: Malarial plasmodiums. The description of crescent bodies with a pointed end, blue cytoplasm, and red nucleus corresponds to the characteristics of Plasmodium species seen in Romanovsky's stain. Plasmodium species are known to cause malaria and have distinct features like the ones described. Incorrect choices: A: Toxoplasmas - Toxoplasma gondii typically appear as tachyzoites or bradyzoites under staining, not crescent bodies. C: Dermotropic leishmania - Leishmania species appear as amastigotes in tissue smears, not crescent bodies. D: Viscerotropic leishmania - Similar to choice C, Leishmania species do not typically present as crescent bodies in stained specimens.

Correct Answer: B

Rationale: The correct answer is B: Shigella. On Endo agar, Shigella appears as colorless colonies due to its inability to ferment lactose. Shigella is a Gram-negative rod and is a common cause of diarrhea. Salmonella (A) and Escherichia coli (C) would typically produce pink colonies on Endo agar as they can ferment lactose. Proteus (D) is not commonly associated with diarrhea and would not be expected to grow on Endo agar.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pyogenes. 1. Gram-positive cocci in chains: characteristic of Streptococcus species. 2. Catalase-negative: Streptococcus species are catalase-negative. 3. Beta-hemolytic: S. pyogenes is beta-hemolytic on blood agar. Therefore, S. pyogenes fits all these criteria. B: Streptococcus pneumoniae is catalase-negative but alpha-hemolytic, not beta-hemolytic. C: Enterococcus faecalis is catalase-negative, but not typically beta-hemolytic or in chains. D: Staphylococcus aureus is catalase-positive and not in chains.

Correct Answer: B

Rationale: Rationale: The correct answer is B because virulence factors of bacteria are characteristics that enable them to cause disease. Colonization allows bacteria to establish and multiply in the host. Invasion refers to the ability to penetrate host tissues. Toxins are substances produced by bacteria that harm the host. Adhesion is crucial for bacteria to attach to host cells. A: Size and mutation are not typical virulence factors. Resistance is not directly related to causing disease. C: While toxins and evasion of body defenses are correct, motility and size are not universally considered virulence factors. D: Chemotaxis and fermentation are not primary virulence factors, unlike colonization and toxins.

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas aeruginosa. P. aeruginosa is a Gram-negative rod that is oxidase-positive and lactose non-fermenting. The positive oxidase test indicates the presence of cytochrome c oxidase, a characteristic of P. aerugin. E. coli is lactose fermenting. Salmonella and Shigella are also Gram-negative rods, but they are lactose fermenters, unlike the lactose non-fermenting P. aeruginosa.

Correct Answer: A

Rationale: The correct answer is A: Tetanus. The symptoms of tonic tension of the masticatory muscles following a dog bite are indicative of tetanus, caused by the bacterium Clostridium tetani. The incubation period of tetanus is usually 3-21 days, consistent with the patient's history of being bitten 12 days ago. Tetanus toxin causes muscle stiffness and spasms, leading to the inability to open the mouth. Rabies (B) presents with hydrophobia and neurological symptoms. Hysteria (C) is a psychological condition. Trigeminal neuralgia (D) is characterized by severe facial pain, not muscle stiffness.