Gonorrhea is a sexually transmitted infection (STI) caused by the diplococcus Neisseria gonorrhoeae, commonly called gonococcus (GC). This organism developed resistance to penicillin and tetracycline in the 1980s, after which fluoroquinolones were the recommended drugs for treating GC. Subsequent resistance to the fluoroquinolones has led to the current recommended treatment of injected ceftriaxone in combination with oral azithromycin. Although this approach continues to be effective, recent data from the CDC indicates that resistance to azithromycin is emerging. Fluoroquinolones act by inhibiting DNA gyrase, an enzyme involved in DNA replication. Resistance to this antibiotic is most commonly by a. due to a mutation in the gene that encodes RNA polymerase, an example of adaptive resistance. b. a change in the DNA gyrase target, an example of acquired resistance increased efflux of the drug from the target cell, an example of innate resistance. c. a change in the DNA gyrase target, an example of innate resistance. d. enzymatic modification of the ribosomal target, an example of innate resistance.

The correct answer is option b, that is, a modification in the target of DNA gyrase, is an illustration of acquired resistance.

Explanation:

The activity of DNA gyrase gets inhibit by fluoroquinolones. The enzyme that combines with the DNA and prevents its supercoiling at the time of replication is termed as DNA gyrase. It is a heterotetramer, which is formed of two subunits of GyrA and two subunits of GyrB. Due to the mutation in gene gyrA, the development of resistance takes place in N. gonorrhea against fluoroquinolones.  

Post mutation, gyrA exhibits lesser binding capacity with the fluoroquinolones, and thus, the development of resistance takes place within the bacteria against the fluoroquinolones. The phenomenon of the development of resistance taking place in any microbe against the specific antimicrobial agent for whom it was vulnerable before is termed as acquired resistance, thus, the given case is an illustration of acquired resistance.  

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation: