What is the best antibiotic for suspected Pseudomonas aeruginosa infection?

From the Guidelines

For suspected Pseudomonas aeruginosa infections, ceftolozane/tazobactam is the recommended first-line treatment option, as stated in the most recent and highest quality study 1. This recommendation is based on the study's strong recommendation and moderate certainty of evidence. The study suggests that ceftolozane/tazobactam, along with ceftazidime/avibactam, are the first-line options for targeted treatment of invasive infections caused by Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-PA) 1. Other treatment options, such as imipenem/cilastatin–relebactam, cefiderocol, and colistin-based therapy, may be considered as potential alternatives 1. It's essential to note that local resistance patterns should guide initial antibiotic selection, as pseudomonas susceptibility varies significantly between healthcare facilities and geographic regions. In addition, treatment duration typically ranges from 5-14 days, depending on the infection site and severity, and should be individualized according to infection sites, source control, underlying comorbidities, and initial response to therapy 1. Some key points to consider when treating suspected Pseudomonas aeruginosa infections include:

• Using anti-pseudomonal penicillins or cephalosporins combined with aminoglycosides when antimicrobial susceptibility testing results are interpreted as susceptible 1
• Considering combination therapy for severe infections, which may include adding an aminoglycoside or an antipseudomonal cephalosporin 1
• Adjusting empiric therapy based on culture results and antibiotic susceptibility testing when available 1

From the FDA Drug Label

Gentamicin Injection, USP is indicated in the treatment of serious infections caused by susceptible strains of the following microorganisms: Pseudomonas aeruginosa, Proteus species (indole-positive and indole-negative), Escherichia coli, Klebsiella-Enterobacter-Serratia species, Citrobacter species and Staphylococcus species (coagulase-positive and coagulase-negative) The combination of gentamicin and carbenicillin is synergistic for many strains of Pseudomonas aeruginosa

The best antibiotic for suspected Pseudomonas aeruginosa infection is not explicitly stated in the provided drug labels. However, based on the available information:

• Gentamicin is indicated for the treatment of serious infections caused by susceptible strains of Pseudomonas aeruginosa.
• The combination of gentamicin and carbenicillin has a synergistic effect against many strains of Pseudomonas aeruginosa. It is essential to note that the choice of antibiotic should be based on the results of susceptibility tests, the severity of the infection, and other important factors. In the absence of direct evidence, gentamicin may be considered as an option for the treatment of suspected Pseudomonas aeruginosa infection, possibly in combination with other antibiotics like carbenicillin 2.

From the Research

Antibiotic Options for Pseudomonas aeruginosa Infection

• The most commonly used antipseudomonal agents are extended-spectrum penicillins, aminoglycosides, cephalosporins, fluoroquinolones, polymixins, and monobactams 3.
• An aminoglycoside with a beta-lactam penicillin is usually considered the first line treatment 3.
• Pipericillin, piperacillin/tazobactam, and meropenem have good but equivalent antibacterial activity against P. aeruginosa 3.

Combination Therapy

• Combination therapy is often recommended for Pseudomonas aeruginosa infections, with a beta-lactam plus an aminoglycoside being the standard treatment 4, 5.
• The combination of piperacillin/tazobactam with amikacin, ciprofloxacin, or trovafloxacin has been shown to be synergistic against P. aeruginosa 4.
• The degree of synergy between a beta-lactam plus aminoglycoside and a beta-lactam plus fluoroquinolone seems to be comparable 5.

Specific Antibiotic Efficacy

• Ceftolozane-tazobactam has been shown to have a high in vitro susceptibility rate against P. aeruginosa, with 96.5% of isolates being susceptible 6.
• Colistin, amikacin, and ceftolozane-tazobactam are the most active antimicrobials against P. aeruginosa, with susceptibilities of 99.4%, 98.1%, and 96.5%, respectively 6.
• Piperacillin-tazobactam has been shown to be effective against P. aeruginosa, with a pharmacokinetic-pharmacodynamic index of %fT >MIC being associated with improved clinical outcomes 7.

Treatment Considerations

• Early intensive treatment for P. aeruginosa infection is advocated in order to maintain pulmonary function and postpone the onset of chronic P. aeruginosa infection 3.
• The choice of antibiotic should be based on the susceptibility of the isolate, as well as the patient's clinical condition and medical history 3, 6.