Clindamycin is an antibiotic used to treat a variety of bacterial infections, particularly those caused by susceptible anaerobic bacteria and certain aerobic gram-positive bacteria. It is FDA-approved and commonly used for:

• Septicemia (blood infections)
• Intra-abdominal infections (such as peritonitis and abscesses)
• Lower respiratory tract infections (including pneumonia, empyema, and lung abscess)
• Gynecological infections (such as endometritis, pelvic inflammatory disease, tubo-ovarian abscess, and postsurgical vaginal infections)
• Bone and joint infections (including acute osteomyelitis caused by Staphylococcus aureus)
• Skin and skin structure infections, including those caused by methicillin-resistant Staphylococcus aureus (MRSA)
• Streptococcal pharyngitis (strep throat)
• Acne vulgaris (topical use)
• Bacterial vaginosis caused by Gardnerella vaginalis

It is also used off-label for infections such as pneumocystis pneumonia, toxoplasmosis in HIV patients, babesiosis, anthrax, and malaria (in combination with quinine)

. Clindamycin is effective against:

• Aerobic gram-positive cocci, including Staphylococcus aureus (methicillin-susceptible and some MRSA), Streptococcus pneumoniae, and Streptococcus pyogenes
• Anaerobic bacteria such as Clostridium perfringens, Fusobacterium species, Peptostreptococcus anaerobius, Prevotella melaninogenica, and Bacteroides fragilis (though resistance is increasing in Bacteroides fragilis)
• Some protozoa and other specific pathogens like Chlamydia trachomatis and Capnocytophaga canimorsus

It is not effective against aerobic gram-negative bacilli like Pseudomonas, Legionella, Haemophilus influenzae, or enterococci

. Clindamycin is often chosen for patients allergic to penicillin and for outpatient treatment of skin infections due to its effectiveness and availability

. In summary, clindamycin treats serious infections of the blood, abdomen, lungs, bones, joints, skin, and female reproductive organs caused by susceptible bacteria, especially anaerobes and gram-positive cocci, including MRSA. It is also used topically for acne and bacterial vaginal infections