What antibiotics are effective against Pseudomonas aeruginosa (Pseudomonas) and skin infections, specifically bacterial skin infections such as cellulitis or abscesses?

From the Guidelines

For pseudomonas skin infections, ceftolozane/tazobactam and ceftazidime/avibactam are currently the first-line options for targeted treatment, as recommended by the Italian Society of Infection and Tropical Diseases 1.

Treatment Options

• Ceftolozane/tazobactam: a novel β-lactam agent with strong activity against Pseudomonas aeruginosa, including strains with difficult-to-treat resistance (DTR-PA) 1.
• Ceftazidime/avibactam: another novel β-lactam agent with broad-spectrum activity, including against Pseudomonas aeruginosa, and is recommended as a first-line option for targeted treatment 1.

Alternative Treatments

• Piperacillin-tazobactam (4.5g IV every 6-8 hours) or meropenem (1g IV every 8 hours) may be considered for more severe infections, as they have been shown to be effective against Pseudomonas aeruginosa in various studies 1.
• Ciprofloxacin (500-750mg orally twice daily) or levofloxacin (750mg orally once daily) for 7-14 days may be effective for less severe infections, as they have been shown to have good activity against Pseudomonas aeruginosa 1.

Wound Care

Good wound care is essential alongside antibiotic therapy, including regular cleaning, debridement of necrotic tissue if present, and appropriate dressing changes. If the infection doesn't improve within 48-72 hours of treatment, reassessment and possibly changing antibiotics based on culture results is recommended.

Important Considerations

• Pseudomonas aeruginosa is a gram-negative bacterium that often causes infections in burns, wounds, and in immunocompromised patients, and is naturally resistant to many antibiotics due to its outer membrane permeability, efflux pumps, and ability to form biofilms.
• Treatment should be guided by culture and sensitivity testing whenever possible, as resistance patterns vary.
• The choice of antibiotic should be based on the severity of the infection, the susceptibility of the organism, and the potential for resistance.
• It is essential to monitor the patient's response to treatment and adjust the antibiotic regimen as needed to ensure optimal outcomes.

From the FDA Drug Label

1. 5 Skin and Skin Structure Infections Tobramycin for Injection is indicated for the treatment of skin and skin structure infections caused by susceptible isolates of P. aeruginosa, Proteus spp., E. coli, Klebsiella spp., Enterobacter spp., and S. aureus in adult and pediatric patients.

Table 1: Susceptibility Interpretive Criteria for Gentamicin Susceptibility Interpretive Criteria Pathogen Minimal Inhibitory Concentration (mcg/mL) Zone Diameter (mm) (S) (I) (R) (S) (I) (R) Pseudomonas aeruginosa ≤4 8 ≥16 ≥15 13 to 14 ≤12

Gram-Negative Bacteria Pseudomonas aeruginosa Serratia marcescens Activity in vitro and in vivo Levofloxacin has in vitro activity against Gram-negative and Gram-positive bacteria

Effective antibiotics against Pseudomonas aeruginosa and skin infections:

• Tobramycin (2)
• Gentamicin (3)
• Levofloxacin (4)

Key points:

• Tobramycin and gentamicin are effective against Pseudomonas aeruginosa and skin infections, including cellulitis or abscesses.
• Levofloxacin also has in vitro activity against Pseudomonas aeruginosa and skin infections.
• The choice of antibiotic should be based on susceptibility testing and clinical judgment.