What is the specific bacterial coverage of cefoxitin?

Bacterial Coverage of Cefoxitin

Spectrum of Activity

Cefoxitin provides broad-spectrum coverage against gram-positive cocci (excluding enterococci), gram-negative facultative bacteria (excluding Pseudomonas), and critically, anaerobic bacteria including Bacteroides fragilis, making it particularly valuable for polymicrobial infections. 1

Gram-Positive Coverage

• Staphylococcus aureus (methicillin-susceptible, including penicillinase-producing strains) 1
• Staphylococcus epidermidis (methicillin-susceptible isolates only) 1
• Streptococcus pneumoniae 1
• Streptococcus pyogenes and other streptococci 1
• Streptococcus agalactiae (Group B Streptococcus) 1
• Peptococcus niger and Peptostreptococcus species 1

Gram-Negative Coverage

• Escherichia coli 1
• Klebsiella species 1
• Proteus mirabilis 1
• Proteus vulgaris 1
• Morganella morganii 1
• Providencia species (including P. rettgeri) 1
• Haemophilus influenzae 1
• Neisseria gonorrhoeae (including penicillinase-producing strains) 1
• Eikenella corrodens (non-β-lactamase producers) 1

Anaerobic Coverage

Cefoxitin's distinguishing feature is its excellent activity against anaerobes, particularly Bacteroides fragilis, which sets it apart from many other cephalosporins. 2, 1

• Bacteroides fragilis 1, 3
• Bacteroides species (including B. distasonis, B. ovatus, B. thetaiotaomicron) 1
• Clostridium species (including C. perfringens) 1
• Prevotella bivia 1

Critical Coverage Gaps

Cefoxitin has NO activity against the following clinically important organisms: 1

• Enterococcus species (including E. faecalis) - this is a critical gap requiring alternative coverage when enterococcal infection is suspected 1
• Pseudomonas aeruginosa - documented treatment failures have occurred with Pseudomonas infections 4
• Chlamydia trachomatis - when treating pelvic inflammatory disease, appropriate anti-chlamydial coverage (doxycycline) must be added 2, 1
• Methicillin-resistant Staphylococcus aureus (MRSA) - only methicillin-susceptible strains are covered 1

Mechanism of Resistance Stability

Cefoxitin demonstrates high stability against beta-lactamase degradation due to its 7-alpha-methoxyl group, allowing it to remain active against many organisms resistant to other cephalosporins. 1, 5, 3

• Active against penicillinase-producing staphylococci 1
• Resistant to most beta-lactamases produced by gram-negative and gram-positive bacteria 1, 3
• Maintains activity against many cephalothin-resistant gram-negative bacteria 3

Clinical Implications

The combination of aerobic and anaerobic coverage makes cefoxitin particularly effective for polymicrobial infections, especially in intra-abdominal and pelvic infections where mixed flora is common. 6, 7

• In clinical studies of pelvic infections, an average of 2.5 bacteria per patient were isolated, with 37% having mixed aerobic-anaerobic infections 6
• The drug achieved 92% clinical response rates in mixed aerobic-anaerobic pelvic infections when used as monotherapy 6
• However, cefoxitin's anaerobic coverage advantage over ceftriaxone has been questioned, as the clinical necessity of Bacteroides fragilis coverage for all pelvic infections remains unproven 2, 7

Common Pitfalls to Avoid

• Never use cefoxitin alone for suspected enterococcal infections - add ampicillin or vancomycin if enterococci are likely 1
• Always add doxycycline when treating pelvic inflammatory disease - cefoxitin has no activity against Chlamydia trachomatis 2, 1
• Do not use for Pseudomonas infections - documented treatment failures with Serratia and Pseudomonas have occurred 4
• Resistance can develop during therapy - particularly with initially moderately susceptible organisms like Serratia marcescens 4