Urinary tract infections are commonly caused by staphylococcus saprophyticus and escherichia coli, less commonly caused by proteus mirabilis. you have a mixed culture of these pathogens, which you inoculate onto both macconkey agar and nutrient agar, and then you incubate the plates at optimal growth conditions. on the macconkey agar, e. coli appears pink, p. mirabilis appears colorless, and s. saprophyticus does not grow. all three microorganisms appear cream on the nutrient agar plate. what is the best explanation for this data?

Mr. j, age 42, is a construction worker in las vegas. he recently noticed that a mole on his face seemed to be getting larger and darker. at first he did not worry because he was in the sun a lot and assumed the change may have been caused by sunburn. after a month, not only was the mole larger and darker, but it appeared to be “bumpy.” his doctor diagnosed a malignant melanoma skin cancer following biopsy of the nevus. mr. j reports pain in his right shin that does not go away when he puts his feet up or sleeps. discussion questions 1. relate mr. j’s skin changes to the warning signs for malignant melanoma. (see malignant melanoma.) 2. discuss the normal progression of this malignancy. what is the significance of the bone pain that mr. j is experiencing? (see malignant melanoma.) 3. discuss the treatment available for this patient and the prognosis for recovery. (see malignant melanoma.)