Reference no: EM132486674

A group of researchers at the university veterinary diagnostics laboratory isolated a new bacterium from the blood and stool of several horses that became ill and died at a local farm. Prior to death, symptoms included disorientation, loss of motor function, and flaccid paralysis, so the researchers suspected central nervous system involvement and possible production of neurotoxin. Based on 16S rRNA comparison, they found that the new bacterium was related to the gram-positive bacterium Clostridium botulinum, and they subsequently named it Clostridium equiniae. They also determined that the bacterium was sensitive to metronidazole but resistant to beta-lactam antibiotics, such as penicillin, and to macrolide antibiotics, such as erythromycin and azithromycin. However, although C. equiniae was resistant to azithromycin, the researchers found that when they treated infected mice with metronidazole in combination with azithromycin, the 50% lethal dose (LD50) value went from 10 for a control without antibiotic treatment to 104 for treatment with metronidazole alone to 107 for combined treatment of metronidazole plus azithromycin, and the mice recovered from paralysis much sooner with the combined treatment than with metronidazole treatment alone. Interestingly, when they were plating out the bacteria to determine the LD50 values, the re- searchers observed that the colonies isolated from the control mice and mice treated with metronidazole alone were mucoid, but those from mice treated with both antibiotics were not.

A. What possible mechanism(s) could account for all of these observations (i.e., change in the LD50 value, faster recovery from paralysis, and change in the mucoid phenotype)? Be sure to provide your rationale.

B. Provide an experiment that could be performed to confirm your hypothesis.