Clindamycin is NOT effective against which bacteria?

Clindamycin is a lincosamide antibiotic effective against gram-positive organisms and many anaerobes. It is NOT effective against Clostridioides difficile (formerly Clostridium difficile). In fact, clindamycin disrupts normal gut flora, which can allow C. difficile to proliferate and cause pseudomembranous colitis — a serious complication. Clindamycin is active against Bacteroides fragilis, Peptostreptococcus, and Staphylococcus aureus (non-MRSA strains).