What are the recommended antibiotics for infections caused by Staphylococcus (Staph) saprophyticus, coagulase-negative Staphylococcus (CoNS), and Streptococcus agalactiae?

Antibiotic Treatment for Staphylococcus saprophyticus, Coagulase-negative Staphylococci, and Streptococcus agalactiae

For infections caused by Staphylococcus saprophyticus, coagulase-negative staphylococci (CoNS), and Streptococcus agalactiae, beta-lactam antibiotics are the first-line treatment for susceptible strains, with specific alternatives for resistant organisms based on infection site and severity. 1

Staphylococcus saprophyticus

Uncomplicated Infections (e.g., UTIs)

• First-line: Trimethoprim-sulfamethoxazole (TMP-SMX) 160/800 mg twice daily for 7-10 days 2
• Alternative options:
  • Nitrofurantoin 100 mg four times daily for 7 days 2
  • Fluoroquinolones (e.g., ciprofloxacin 500 mg twice daily) 2
  • Amoxicillin-clavulanate (Augmentin) 875/125 mg twice daily for 7-10 days 2

Complicated Infections

• Initial parenteral therapy followed by oral step-down therapy 2
• Consider vancomycin 15-20 mg/kg IV every 8-12 hours for severe infections 2

Coagulase-negative Staphylococci (CoNS)

Methicillin-susceptible CoNS

• First-line: Penicillinase-resistant penicillins (flucloxacillin, dicloxacillin, oxacillin) 1, 3
  • Flucloxacillin/oxacillin: 12 g/day IV in 4-6 doses for serious infections 1
• Alternatives:
  • First-generation cephalosporins (cefazolin 1 g every 8 hours IV or cephalexin 500 mg four times daily orally) 1, 3
  • Clindamycin 300-450 mg orally three times daily or 600 mg IV three times daily 1, 3

Methicillin-resistant CoNS

• First-line: Vancomycin 15-20 mg/kg IV every 8-12 hours (target trough levels 15-20 mg/L) 1
• Alternatives:
  • Daptomycin 6 mg/kg IV once daily 1
  • Linezolid 600 mg orally/IV twice daily 1
  • Teicoplanin (where available) 3, 4

For Biofilm-associated Infections (e.g., prosthetic devices)

• Combination therapy with rifampin (after 3-5 days of effective primary therapy) 1
• Consider device removal when possible 4
• Extended treatment duration (4-6 weeks for endocarditis, osteomyelitis) 4

Streptococcus agalactiae (Group B Streptococcus)

Non-severe Infections

• First-line: Penicillin G or Ampicillin 1
• Alternatives for penicillin-allergic patients:
  • Clindamycin 300-450 mg orally three times daily or 600 mg IV three times daily 1
  • Cephalosporins (if no immediate hypersensitivity to penicillin) 1

Severe Infections (including endocarditis)

• Penicillin G or Ampicillin combined with gentamicin for the first 2 weeks 1
• For penicillin-resistant strains (MIC >2 mg/L): Vancomycin 15-20 mg/kg IV every 8-12 hours 1

Special Considerations

Skin and Soft Tissue Infections

• For purulent cellulitis potentially caused by staphylococci:
  • Clindamycin 300-450 mg orally three times daily 1
  • TMP-SMX 1-2 double-strength tablets twice daily 1
  • Doxycycline 100 mg twice daily (not for children under 8 years) 1

Endocarditis

• For native valve endocarditis:
  • S. saprophyticus/CoNS: (Flu)cloxacillin or oxacillin 12 g/day IV in 4-6 doses for 4-6 weeks if methicillin-susceptible 1
  • S. agalactiae: Penicillin G or ampicillin for 4-6 weeks, with gentamicin for first 2 weeks 1

Prosthetic Valve Endocarditis

• Triple therapy with vancomycin, gentamicin, and rifampin for MRSA/resistant CoNS 1
• Extended duration therapy (≥6 weeks) 1

Common Pitfalls and Caveats

• Resistance to multiple antibiotics is common in CoNS, requiring susceptibility testing to guide therapy 5
• Teicoplanin-non-susceptible CoNS strains with inducible resistance to vancomycin are emerging, requiring vigilant monitoring 5
• Ciprofloxacin alone may lead to treatment failures in serious staphylococcal infections despite in vitro susceptibility 6
• For serious infections, parenteral therapy is generally preferred initially before transitioning to oral options 2, 4
• Cephalosporins should not be used in patients with immediate hypersensitivity reactions to penicillins 3