Some readers have asked why the June 2009 issue of Treatment Guidelines (Antimicrobial Prophylaxis for Surgery) did not recommend use of ertapenem (Invanz) for prevention of infection after elective colorectal surgery. Ertapenem is a broad-spectrum carbapenem that has been approved for such use by the FDA. Medical Letter consultants do not recommend use of broad-spectrum drugs such as ertapenem, third-generation cephalosporins such as cefotaxime (Claforan), ceftriaxone (Rocephin), cefoperazone (Cefobid), ceftazidime (Fortaz, and others) or ceftizoxime (Cefizox), or fourth-generation cephalosporins such as cefepime (Maxipime) for routine surgical prophylaxis because they are expensive, some are less active than first- or second-generation cephalosporins against staphylococci, and their spectrum of activity includes organisms rarely encountered in elective surgery. These drugs should be reserved for treatment of serious infections, particularly those likely to be caused by organisms resistant to other antimicrobials.