Bacterial Coverage Comparison: Bactrim vs Cephalexin

Spectrum of Activity

Cephalexin has limited activity against gram-negative organisms, with poor coverage of Haemophilus influenzae, and no activity against atypical pathogens, according to the American Academy of Otolaryngology-Head and Neck Surgery 1
Cephalexin has no activity against methicillin-resistant Staphylococcus aureus (MRSA), as stated by the Infectious Diseases Society of America 2
Bactrim has good activity against many gram-positive and gram-negative organisms, including MRSA in community-acquired infections, as recommended by the Infectious Diseases Society of America 2
Bactrim is active against many Enterobacteriaceae, but has limited activity against streptococci, including β-hemolytic streptococci, according to the European Society of Clinical Microbiology and Infectious Diseases 4

Cephalexin is preferred for uncomplicated cellulitis without purulent drainage, where streptococci are the predominant pathogens, as recommended by the Infectious Diseases Society of America 2
Bactrim is often preferred for purulent skin infections where MRSA is suspected, according to the Infectious Diseases Society of America 2
Bactrim has historically been considered first-line for uncomplicated UTIs due to its efficacy against common uropathogens, as stated by the European Society of Clinical Microbiology and Infectious Diseases 4

Increasing resistance to Bactrim has been observed in many regions, and local antibiogram data should guide empiric therapy decisions, as recommended by the Infectious Diseases Society of America 7
Bactrim use may select for resistant organisms more readily than cephalexin, according to the Infectious Diseases Society of America 7

Cephalexin is typically dosed 500 mg 4 times daily or 3 times daily, and Bactrim is typically dosed as 1 double-strength tablet (160/800 mg) twice daily, as stated by the American Urological Association 8

Bactrim should not be used as monotherapy for cellulitis without purulent drainage due to poor streptococcal coverage, as recommended by the Infectious Diseases Society of America 2
Cephalexin should not be used when MRSA is suspected, according to the Infectious Diseases Society of America 2
Bactrim carries risk of adverse effects including rash, Stevens-Johnson syndrome, and bone marrow suppression, as stated by the Infectious Diseases Society of America 7