Which structure in bacteria allows them to exchange genetic material during conjugation?

Correct Answer: A

Rationale: Pili in bacteria are responsible for conjugation, allowing the transfer of genetic material between cells. They form a bridge between donor and recipient cells, facilitating the exchange of DNA. Flagella are for movement, capsules for protection, and ribosomes for protein synthesis. Pili is the only structure directly involved in genetic material exchange.

Correct Answer: A

Rationale: The correct answer is A: Break down antibiotics like penicillin. Beta-lactamase is an enzyme produced by bacteria to inactivate beta-lactam antibiotics like penicillin by breaking the beta-lactam ring. This mechanism helps bacteria resist the antibiotic's effects. The other choices are incorrect because beta-lactamase does not enhance protein synthesis, facilitate DNA replication, or transport nutrients. It specifically targets and deactivates beta-lactam antibiotics, making choice A the most appropriate answer.

Correct Answer: D

Rationale: Rationale: - A: The mycelium is indeed made up of intertwined hyphae, which are the branching filaments of fungi. - B: Part of the mycelium does grow into the medium to acquire nutrients, forming the substrate mycelium. - C: Some parts of the mycelium remain above the medium to aid in reproduction and spore dispersal, forming the aerial mycelium. Therefore, all statements (A, B, and C) are correct, making choice D the correct answer. The mycelium exhibits both intertwined hyphae, substrate mycelium, and aerial mycelium to facilitate different functions.

Correct Answer: C

Rationale: Rationale for Correct Answer (C - Immunity): 1. Immunity refers to the body's ability to defend against foreign agents. 2. Homeostasis is the state of steady internal conditions, not specifically related to defense. 3. Infection is the invasion and multiplication of pathogens, not the overall defense mechanism. 4. Commensalism is a symbiotic relationship where one organism benefits without harming the other.

Correct Answer: B

Rationale: The correct answer is B: Anatoxin. An anatoxin is a toxin that has been rendered harmless while retaining its ability to stimulate an immune response. Gas gangrene is caused by the toxins produced by Clostridium perfringens, not the bacteria itself. Therefore, vaccination with an anatoxin can trigger the immune system to produce antibodies against the toxin, providing immunity against the disease. A: Killed whole cell vaccine - Gas gangrene is caused by toxins, not the whole bacterium. This type of vaccine may not be effective in preventing the disease. C: There is no specific prevention by vaccination - This is incorrect, as vaccination with an anatoxin can prevent gas gangrene. D: Alive attenuated vaccine - Attenuated vaccines contain live, weakened forms of the pathogen. However, for gas gangrene prevention, targeting the specific toxin with an anatoxin vaccine is more appropriate.

Correct Answer: A

Rationale: The correct answer is A because enteropathogenic E. coli (EPEC) have fimbrial adhesins that help them bind to enterocytes in the intestines, leading to colonization and infection. This is a key virulence factor of EPEC. Explanation for why other choices are incorrect: B: EPEC typically cause watery diarrhea in infants, not bloody diarrhea similar to shigellosis. C: EPEC are not part of the normal intestinal flora; they are pathogenic bacteria. D: EPEC are not invasive and do not typically produce enterotoxin; they primarily adhere to the intestinal epithelium.

Correct Answer: A

Rationale: Rationale: 1. Vaginitis is a common bacterial infection in the female reproductive system. 2. Toxic shock syndrome can be caused by certain bacterial infections. 3. Endometritis is inflammation of the endometrium often due to bacterial infections. 4. Salpingitis is inflammation of the fallopian tubes, commonly caused by bacteria. Summary: - Choice B: Nephritis is a kidney infection, not related to female reproductive system infections. - Choice C: Nephritis and cystitis are not specific to the female reproductive system. - Choice D: Cystitis is a bladder infection, not typically considered part of female reproductive system infections.

Correct Answer: A

Rationale: The correct answer is A: Psittacosis. This disease is transmitted via aerosols containing dried bird droppings or respiratory secretions from infected birds. When these aerosols are inhaled, the bacteria causing psittacosis enter the respiratory system and infect the individual. - B: Shigellosis is transmitted through contaminated food or water, not via aerosols. - C: Leptospirosis is transmitted through contact with water, soil, or food contaminated with the urine of infected animals, not via aerosols. - D: Giardiasis is transmitted through ingesting contaminated food or water, not via aerosols. Therefore, Psittacosis is the only disease in the list that is transmitted via aerosols, making it the correct answer.

Correct Answer: A

Rationale: The correct answer is A: Malaria. Two weeks after hemotransfusion, the onset of fever indicates a possible bloodborne infection. Malaria is a protozoal disease transmitted through infected blood, causing symptoms like fever. Toxoplasmosis, Leishmaniasis, and Amebiasis are not typically associated with fever following hemotransfusion. Malaria fits the timeline and mode of transmission in this scenario.