sentences:  However, cefoxitin is a better substrate than imipenem for beta-lactamases.In the presence of cefoxitin, bacteria that make beta-lactamases will increase their production and secretion to cleave the beta lactam ring.As a cephamycin, cefoxitin is highly resistant to hydrolysis by some beta-lactamases, in part due to the presence of the 7-alpha-methoxy functional group (see skeletal formula above).