MS-2370

A 47-year-old man presents to his GP with complaints of coughing up green phlegm and experiencing chest pain on his left side. Upon examination, crackles are heard in the base of his left lung and bronchial breathing is present. Additionally, he has reduced chest expansion on his left side and a history of penicillin allergy. An x-ray confirms a diagnosis of pneumonia and he is prescribed doxycycline. What is the mechanism of action of doxycycline?