Combined Coverage of Septra and Cefadroxil
Septra (trimethoprim-sulfamethoxazole) plus cefadroxil provides broad-spectrum coverage against both gram-positive cocci (including Staphylococcus aureus and Streptococcus species) and gram-negative bacteria, making this combination particularly effective for mixed skin and soft tissue infections where both MRSA and streptococcal pathogens may be present. 1, 2
Bacterial Coverage Profile
Gram-Positive Coverage
- Staphylococcus aureus (including MRSA): Septra provides excellent coverage for both methicillin-sensitive and methicillin-resistant strains 2
- Streptococcus pneumoniae: Covered by both agents 3
- Group A Streptococcus (Streptococcus pyogenes): Primarily covered by cefadroxil, as Septra alone should not be used for cellulitis due to potential streptococcal resistance 2
Gram-Negative Coverage
- Escherichia coli: Covered by Septra 3
- Klebsiella species: Covered by Septra 3
- Enterobacter species: Covered by Septra 3
- Proteus mirabilis and Proteus vulgaris: Covered by Septra 3
- Morganella morganii: Covered by Septra 3
- Haemophilus influenzae: Covered by Septra 3
Additional Pathogens
- Shigella flexneri and Shigella sonnei: Covered by Septra for enteritis 3
- Nocardia species: Septra is the treatment of choice for cutaneous Nocardia infections 1
- Pneumocystis jirovecii: Covered by Septra 3
Clinical Applications
Skin and Soft Tissue Infections
- Purulent infections (abscesses, furuncles, carbuncles): Septra effectively treats MRSA-associated purulent infections 2
- Mixed cellulitis: The combination covers both staphylococcal and streptococcal pathogens, addressing the limitation of Septra monotherapy which has poor streptococcal coverage 2
- Infected cysts with surrounding cellulitis: When cellulitis is present, adding a beta-lactam like cefadroxil to Septra ensures streptococcal coverage 2
Urinary Tract Infections
- Septra covers the most common uropathogens including E. coli, Klebsiella, Enterobacter, and Proteus species 3, 1
- Cefadroxil is listed as an alternative for uncomplicated cystitis when local E. coli resistance is <20% 1
Respiratory Infections
- Acute exacerbations of chronic bronchitis: Septra covers S. pneumoniae and H. influenzae 3
- Acute otitis media: Septra covers S. pneumoniae and H. influenzae in pediatric patients 3
Important Coverage Gaps
What This Combination Does NOT Cover Well
- Anaerobic bacteria: Septra has poor activity against anaerobes, so this combination is not ideal for polymicrobial infections involving anaerobic organisms 2
- Pseudomonas aeruginosa: Neither agent provides reliable coverage
- Enterococcus species: Limited coverage with this combination
Clinical Pitfalls and Considerations
When to Avoid Septra Monotherapy
- Never use Septra alone for non-purulent cellulitis due to intrinsic resistance of Group A Streptococcus 2
- For mixed infections or when streptococcal involvement is suspected, the addition of cefadroxil (or another beta-lactam) is warranted 2
Resistance Patterns
- Cefadroxil should only be used when local E. coli resistance is <20% for urinary tract infections 1
- In vitro studies show bacterial resistance develops more slowly with Septra's dual mechanism (trimethoprim plus sulfamethoxazole) than with either component alone 3