During examination of a 3-month old infant a pediatrician revealed that the baby's oral mucosa and tongue were covered with a thick white deposit. In the material taken from the affected site a bacteriologist revealed the presence of yeast fungi giving the reasons for suspecting a fungal infection which occurs most often in children of this age, namely:

Correct Answer: A

Rationale: The correct answer is A: Candidiasis. In infants, a thick white deposit on the oral mucosa and tongue is indicative of oral thrush, which is caused by the yeast fungus Candida. Infants are particularly susceptible to Candidiasis due to their developing immune systems and use of antibiotics. Favus (B) is a chronic fungal infection of the scalp caused by Trichophyton schoenleinii, typically not seen in infants. Epidermophytosis (C) refers to superficial fungal infections of the skin caused by dermatophytes, not commonly found in the oral cavity of infants. Actinomycosis (D) is a bacterial infection caused by Actinomyces species, not a fungal infection.

Correct Answer: B

Rationale: The correct answer is B: Bergey's Manual of Systematic Bacteriology. This manual is a comprehensive and authoritative resource specifically dedicated to bacterial taxonomy, classification, and identification. It provides detailed descriptions and classification schemes for bacteria, aiding in accurate identification and understanding of bacterial species. Gray's Anatomy (choice A) focuses on human anatomy, the WHO Manual (choice C) focuses on global health guidelines, and Darwin's Origin of Species (choice D) discusses evolution and natural selection, none of which are specialized taxonomic resources for bacteria.

Correct Answer: A

Rationale: The correct answer is A: Agglutination. Agglutination is commonly used to identify Vibrio cholerae by clumping together the bacteria with specific antibodies. This reaction occurs when antibodies bind to antigens on the bacterial surface, leading to visible clumps. In contrast, Precipitation, Western blot, and ELISA are not typically used to identify Vibrio cholerae. Precipitation involves antigen-antibody complexes becoming insoluble, Western blot is used for protein detection, and ELISA is commonly used for detecting specific antigens or antibodies in a sample. Agglutination is the most appropriate choice for identifying Vibrio cholerae due to its specific interaction with the bacteria's surface antigens.

Correct Answer: A

Rationale: Rationale for Correct Answer A (Lamblia): 1. Pyriform protozoa with twin nuclei, four pairs of flagella, and a suctorial disc match the characteristics of Giardia lamblia. 2. The presence of two supporting filaments between the nuclei is a unique feature of Giardia lamblia. 3. Giardia lamblia is known to infect the duodenum and cause symptoms such as diarrhea and abdominal pain. Summary of Incorrect Choices: B: Toxoplasma - Toxoplasma gondii is not characterized by four pairs of flagella or supporting filaments in the nuclei. C: Leishmania - Leishmania species do not typically have the described morphology or location in the duodenum. D: Intestinal trichomonad - Intestinal trichomonads do not exhibit the specific features mentioned in the question, such as twin nuclei and supporting filaments.

Correct Answer: D

Rationale: The correct answer is D: Moeller. Moeller staining method is specifically designed to detect spores due to its ability to differentiate between the spore and the vegetative cell. It involves applying multiple stains such as malachite green, safranin, and heat to visualize the endospore structure. This method is essential for proving the formation of spores as it highlights the resistant spore structures within the bacterial cell. A: Klett and Gins is not used for spore staining. B: Ziehl-Neelsen is used for acid-fast staining, not spore staining. C: Gram and Loeffler's are used for gram staining, not spore staining.