How do people get infected with diphtheria

Correct Answer: C

Rationale: The correct answer is C because diphtheria is primarily spread through respiratory droplets and physical contact with an infected person. The bacteria responsible for diphtheria is transmitted through coughing, sneezing, or sharing personal items. Swimming in contaminated water (A) does not spread diphtheria. Transmission (B) is a broad term and does not specifically address the mode of transmission for diphtheria. Contaminated food (D) is not a typical route of diphtheria transmission. Therefore, option C is the most accurate choice based on the known mode of transmission for diphtheria.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is known for producing a capsule that helps it evade the immune system. The capsule acts as a protective barrier, making it difficult for the immune system to recognize and attack the bacteria. Streptococcus pneumoniae is a common cause of pneumonia and meningitis. Explanation for why other choices are incorrect: B: Escherichia coli does not typically produce a capsule for immune evasion. It is more commonly associated with gastrointestinal infections. C: Salmonella enterica also does not produce a capsule for immune evasion. It is known for causing foodborne illness. D: Bacillus subtilis is a soil bacterium that is not known for producing a capsule to avoid the immune system.

Correct Answer: C

Rationale: The correct answer is C because cultural characteristics of bacteria refer to their growth patterns on different culture media, including liquid and solid agars. Bacteria exhibit unique growth patterns that can be observed and studied on these media. Choice A is incorrect as it refers to isolation techniques, not cultural characteristics. Choice B is incorrect as it describes metabolic activities, not cultural characteristics. Choice D is incorrect as it dismisses the essential aspect of bacterial growth on culture media.

Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This protozoan parasite causes amoebic dysentery and is characterized by cysts with four nuclei in fecal smears. It is commonly associated with chronic diarrhea. Balantidium coli (B) presents with large ciliated trophozoites, not cysts. Giardia lamblia (C) has trophozoites with flagella and causes giardiasis, not cysts with four nuclei. Trichomonas hominis (D) typically has a pear-shaped trophozoite and is not associated with cysts with four nuclei.

Correct Answer: C

Rationale: The correct answer is C: Vibrio. Cholera is caused by Vibrio cholerae bacteria. These bacteria produce a toxin that causes severe diarrhea and dehydration. Escherichia (choice A) and Salmonella (choice B) are known for causing other types of gastrointestinal infections but not cholera. Acinetobacter (choice D) typically causes respiratory infections, not gastrointestinal illnesses like cholera. Therefore, the correct choice is Vibrio as it is specifically associated with cholera.

Correct Answer: D

Rationale: The correct answer is D: Blastospores. Blastospores are a type of fungal spore that requires a moist environment to survive. They are commonly found in water bodies like ponds, streams, lakes, and oceans. Mycorrhizae (A) are symbiotic associations between fungi and plant roots, not solely dependent on a moist environment. Armillaria gallica (B) is a type of fungus that can survive in various environmental conditions, not specifically reliant on a moist environment. Choice C is a duplicate of Blastospores, making it incorrect.

Correct Answer: A

Rationale: The correct answer is A: Reinfection. This is because the patient fully recovered from the initial syphilis infection after antibiotic therapy, indicating the elimination of the pathogen. Subsequently getting infected again with Treponema pallidum suggests a new exposure to the same pathogen, resulting in a new infection. Recurrence (B) would imply the reactivation of the same infection, which is not the case here. Superinfection (C) refers to a new infection that occurs on top of an existing infection, which is not the scenario described. Secondary infection (D) typically refers to an infection that occurs after an initial infection weakens the immune system, which is not the case in this scenario.

Correct Answer: C

Rationale: The correct answer is C: Enhancing virulence by preventing phagocytosis. Bacterial capsules help bacteria evade the immune system by preventing phagocytosis, a process where immune cells engulf and destroy pathogens. This enhances the bacteria's virulence and ability to cause infections. Choices A, B, and D are incorrect because bacterial capsules do not directly contribute to protein synthesis, protect against desiccation, or facilitate motility.

Correct Answer: A

Rationale: The correct answer is A: Staphylococcus epidermidis. The presence of Gram-positive cocci in clusters, along with being catalase-positive and coagulase-negative, is indicative of Staphylococcus species. Staphylococcus epidermidis is commonly found on the skin, making it likely to cause wound infections. Summary: B: Staphylococcus aureus is catalase-positive and coagulase-positive. C: Streptococcus pyogenes is catalase-negative. D: Enterococcus faecalis is catalase-negative.