microbiology basic and clinical principles test bank

Correct Answer: D

Rationale: The correct answer is D because all the choices can contribute to hospital-acquired infections. New patients in the incubation period can spread infections, medical staff can inadvertently transmit infections, and contaminated medical instruments can also be a source of infections. Therefore, it is important to consider all these factors to prevent and control the spread of infections in a hospital setting.

Correct Answer: B

Rationale: The growth of bacteria is a result of water adsorption because water is essential for various metabolic processes within the bacterial cells, such as nutrient uptake, energy production, and waste removal. Water serves as a medium for chemical reactions to occur and provides structural support to the bacteria. Without sufficient water, bacteria cannot thrive and reproduce. A: Air consumption is incorrect because while bacteria may require oxygen for respiration, it is not the primary factor for their growth. C: Enzyme production is incorrect because enzymes are important for various cellular functions but do not directly influence bacterial growth. D: Radio isotopes are incorrect as they are not essential for bacterial growth and can even be harmful to bacterial cells.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pyogenes. 1. Gram-positive cocci in chains suggest streptococci. 2. Beta-hemolytic activity indicates Streptococcus pyogenes. 3. Streptococcus pyogenes is commonly associated with sore throat (pharyngitis) and fever. 4. Streptococcus pneumoniae (choice B) is alpha-hemolytic and mainly causes pneumonia. 5. Enterococcus faecalis (choice C) is not typically associated with sore throat. 6. Staphylococcus aureus (choice D) is not commonly beta-hemolytic and is not a typical cause of pharyngitis.

Correct Answer: A

Rationale: The correct answer is A: Trichomonas vaginalis. Trichomonas vaginalis is a protozoan parasite that causes trichomoniasis, a sexually transmitted infection characterized by inflammation of urogenital tracts. The description of big unicellular pyriform organisms with a sharp spike on the back end of their bodies, big nucleus, and undulating membrane matches the morphology of Trichomonas vaginalis. Trichomonas hominis and Trichomonas buccalis are different species that do not cause urogenital infections. Trypanosoma gambiense is a protozoan parasite causing African trypanosomiasis and does not match the described morphology or symptoms.

Correct Answer: A

Rationale: The correct answer is A: Delayed hypersensitivity reaction. In granuloma development in tuberculosis, macrophages present antigen to T cells, leading to a delayed hypersensitivity reaction. This triggers the recruitment of more macrophages and formation of granulomas. Antibody-dependent cytotoxicity (B) and complement-dependent cytotoxicity (C) involve antibodies and complement proteins in immediate hypersensitivity reactions, which are not the primary mechanisms in tuberculosis. Anaphylactic reaction (D) is an acute systemic allergic reaction mediated by IgE antibodies, not relevant to granuloma formation in tuberculosis.