Clindamycin is not a broad-spectrum antibiotic; it is ineffective against gram-negative bacteria. It inhibits gram-positive bacteria such as Streptococcus pneumoniae, other streptococci, and most anaerobes. Because clindamycin is found in relatively high concentrations in human bones and joints, it is often used to treat septic osteomyelitis and septic arthritis caused by sensitive bacteria. It is also used to treat some soft tissue infections, anaerobic infections resulting from deep trauma to the limbs, and pelvic inflammatory disease with anaerobic infections in the pelvic cavity and other areas.