CASE FILE Gas Gangrene A 77-year-old male resident of southern Colorado was brought to the emergency room somewhat disoriented and with swelling and severe pain in his leg. The trlage nurse observed that the patient's skin was discolored and blistering and had an unpleasant odor. The patlent's history revealed that he had diabetes, which was poorly controlled with metformin and had Injured his leg in a fall 2 months previously. An X ray revealed pockets of gas between tissue layers in the lower leg. Blood and tissue samples were sent for culture. The patient was moved to the ICU and treatment was immediately begun with plperacillin, moxifloxacin, and vancomycin. The patient's family was counseled that depending on the results of the culture and the progression of his disease, he might need amputation or treatment in a hyperbaric chamber. Lab Results: Exercise 21 Aerotolerance (Tube Results from left to right, 1 , 2 , 3 , 4 ) Tube 1 = Bacillus megaterium; Tube 2 = Clostridium sporogenes; Tube 3 = Pseudomonas aeruginosa Tube 4 = Escherichia coli Interpretation and Questions 1. What causes the cracking in the agari (Take a look at the Results and interpretation section) Can that same phenomenon occur in human tissue\} 2. A sample from a patient with a suspected anaerobic infection is left out too long before being taken to the laboratory for growth and identification. Why is that a problem? 3. Humans breathe oxygen and carry out aerobic respiration. How is it possible for a patient to contract tetanus, a disease caused by a coxin produced by an anaerobic organism, C . tetann 4. Why is it recommended to place the inoculated agar tubes immediately into the ice bath?.