Biofilms in device-related infectionsDownloads

A 37-year-old woman with a history of anorectal abscesses complains of pain in the perianal region. Physical examination reveals mild swelling, tenderness, and erythema of the perianal skin. She is prescribed oral ampicillin and asked to return for follow-up. Two days later, the patient presents with a high-grade fever, syncope, and increased swelling. Which of the following would be the most common mechanism of resistance leading to the failure of antibiotic therapy in this patient?

A 63-year-old man comes to the physician for evaluation of fever and a nonproductive cough for the past 2 weeks. During this period, he has also had fatigue, myalgia, and difficulty breathing. Five weeks ago, he underwent an aortic prosthetic valve replacement due to high-grade aortic stenosis. The patient has a history of hypertension, asthma, and type 2 diabetes mellitus. A colonoscopy 2 years ago was normal. The patient has smoked one pack of cigarettes daily for the past 40 years. He has never used illicit drugs. Current medications include aspirin, warfarin, lisinopril, metformin, inhaled albuterol, and a multivitamin. The patient appears lethargic. Temperature is 38.6°C (101.5°F), pulse is 105/min, and blood pressure is 140/60 mm Hg. Rales are heard on auscultation of the lungs. A grade 2/6, diastolic blowing murmur is heard over the left sternal border and radiates to the right sternal border. A photograph of his right index finger is shown. Laboratory studies show a leukocyte count of 13,800/mm3 and an erythrocyte sedimentation rate of 48 mm/h. Which of the following is the most likely causal organism?