Otitis externa

A 66-year-old woman goes to the emergency department for evaluation of a painful left ear. She was evaluated one week ago for her symptoms by her primary care physician, who prescribed otic ofloxacin drops. The patient has been taking her medication as prescribed without relief of symptoms and now has worsening discharge from the ear and pain with chewing. Medical history is notable for hypertension, hyperlipidemia, and insulin-dependent diabetes. The patient's temperature is 38.7°C (101.7°F), pulse is 110/min, respirations are 18/min, and blood pressure is 168/75 mmHg. Physical examination reveals the following finding:


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Which of the following pathogens is most likely responsible for this patient’s condition?