DNA transfer from one bacterium to another through phages is termed as:

Correct Answer: B

Rationale: The correct answer is B: Transduction. In bacterial genetics, transduction refers to the process of DNA transfer from one bacterium to another via bacteriophages. During transduction, the bacteriophage infects a bacterium, incorporating bacterial DNA into its own genome, which is then transferred to another bacterium upon infecting it. Rationale: A: Transfection is the process of introducing foreign DNA into eukaryotic cells, not bacteria. C: Induction is the process of activating gene expression in a cell. D: Infection is a general term for the invasion of pathogens into a host organism, not specific to DNA transfer via phages in bacteria.

Correct Answer: C

Rationale: Step 1: Chlorhexidine belongs to the group of biguanides, which are commonly used for disinfecting hands, skin, and mucous membranes. Step 2: It is known to have broad-spectrum antimicrobial activity against various pathogens. Step 3: The usage of chlorhexidine in healthcare settings for preoperative skin preparation and surgical hand scrub is well-established. Step 4: The effectiveness and safety profile of chlorhexidine make it a preferred choice for disinfection purposes. Summary: - Option A is incorrect as chlorhexidine is not characterized by strong human toxicity. - Option B is incorrect as chlorhexidine is not classified as an alcohol and is primarily used for disinfecting hands, skin, and mucous membranes. - Option D is incorrect as chlorhexidine has a wide range of applications in disinfection, especially in healthcare settings.

Correct Answer: D

Rationale: Interferon is a cell-specific protein that is produced and released from infected cells in response to viral infections. It acts extracellularly to interfere with viral replication, not to inactivate the virus itself. Interferon is not coded for by cellular DNA, but by viral RNA during infection. Therefore, the correct answer, D, is that interferon is not virus-specific but is cell-specific. This is because interferon can be produced by various cell types in response to different types of viral infections, making it a broad-spectrum antiviral defense mechanism.

Correct Answer: A

Rationale: The correct answer is A: Escherichia coli. E. coli typically produces red colonies on Endo agar due to its ability to ferment lactose. This results in the production of acid, causing the colonies to appear red. Salmonella and Shigella are non-lactose fermenters, so they would appear colorless or transparent on Endo agar. Proteus vulgaris is not commonly associated with red colonies on Endo agar. Therefore, based on the characteristic lactose fermentation pattern, E. coli is the most likely microorganism in this scenario.

Correct Answer: A

Rationale: The correct answer is A: Treponema pallidum. This bacterium is responsible for causing syphilis due to its unique spiral shape and ability to penetrate mucous membranes. It is transmitted through sexual contact or from mother to child during childbirth. Neisseria gonorrhoeae causes gonorrhea, Chlamydia trachomatis causes chlamydia, and Escherichia coli is a common bacterium found in the gut. Therefore, they are not responsible for syphilis.

Correct Answer: B

Rationale: The correct answer is B: Phage typing of the obtained culture. This method is used for typing Mycobacterium tuberculosis strains based on susceptibility to specific bacteriophages. If the culture shows susceptibility, it confirms the presence of M. tuberculosis. In this case, the absence of cord factor indicates that the bacteria are unlikely to be M. tuberculosis. Option A (Inoculation of laboratory animals) is unethical and not necessary when other methods are available. Option C (Allergy skin test) is not relevant for confirming a diagnosis of renal tuberculosis. Option D (Toxigenicity testing) is not specific for confirming or refuting a diagnosis of M. tuberculosis.

Correct Answer: C

Rationale: The correct answer is C: ELISA, Western blot. These tests are commonly used for diagnosing Lyme borreliosis due to their high sensitivity and specificity in detecting antibodies against Borrelia burgdorferi, the causative agent. ELISA is the initial screening test, while Western blot is used for confirmation. Widal agglutination test (A) is used for diagnosing typhoid fever, not Lyme disease. Cultivation on blood and chocolate agar (B) is not commonly used for diagnosing Lyme borreliosis as Borrelia species are difficult to culture. Ascoli thermoprecipitation test (D) is used for diagnosing pneumonia caused by Streptococcus pneumoniae, not Lyme disease.

Correct Answer: C

Rationale: The correct answer is C: Erysipelas. Erysipelas is a type of acute infection caused by group A Streptococcus bacteria. This bacteria infects the upper dermis and superficial lymphatics, leading to a distinct raised, well-demarcated, erythematous skin lesion. The other choices are incorrect because: A Carbuncle is a deep skin infection involving hair follicles, B Impetigo is a superficial skin infection caused by Staphylococcus or Streptococcus bacteria, and D Acne is a chronic inflammatory skin condition not typically caused by group A Streptococcus.

Correct Answer: C

Rationale: The correct answer is C: Up to 3 months. Hepatitis B has an average incubation period of 60-90 days, which aligns with the timeframe of up to 3 months. This period refers to the time between exposure to the virus and the onset of symptoms. One week to 10 days (choice A) is too short for hepatitis B, as it typically takes longer to manifest. One month to 45 days (choice B) is also shorter than the average incubation period for hepatitis B. Up to 6 months (choice D) is too long for hepatitis B, as the virus typically shows symptoms within 3 months.