What organisms are covered by Piperacillin/Tazobactam (Pip/Taz) that are not covered by Ceftriaxone and Azithromycin?

From the Guidelines

Piperacillin-tazobactam covers Pseudomonas aeruginosa and anaerobes, which are not adequately covered by the combination of ceftriaxone and azithromycin. Piperacillin-tazobactam is an antipseudomonal penicillin combined with a beta-lactamase inhibitor that provides broad-spectrum coverage against many gram-positive, gram-negative, and anaerobic organisms, as noted in the guidelines for hospital-acquired pneumonia and ventilator-associated pneumonia 1. While ceftriaxone (a third-generation cephalosporin) has good activity against many gram-positive and gram-negative bacteria, it lacks reliable coverage against Pseudomonas and many anaerobes. Azithromycin (a macrolide) primarily covers atypical pathogens like Mycoplasma, Chlamydia, and Legionella, along with some gram-positive organisms, but has limited gram-negative and no anaerobic coverage.

Some key points to consider:

• The coverage of piperacillin-tazobactam includes Pseudomonas aeruginosa, which is a common pathogen in hospital-acquired infections, particularly in patients with risk factors for multidrug-resistant (MDR) pathogens 1.
• Anaerobic coverage is also an important aspect of piperacillin-tazobactam's spectrum, making it suitable for infections where anaerobes are suspected, such as intra-abdominal infections.
• The guidelines for diabetic foot infections also mention piperacillin-tazobactam as an option for the treatment of moderate to severe infections, particularly when Pseudomonas aeruginosa is suspected 1.
• The typical adult dose of piperacillin-tazobactam is 3.375g or 4.5g IV every 6-8 hours, depending on the severity of infection and renal function, whereas standard ceftriaxone dosing is 1-2g IV daily and azithromycin is typically 500mg IV/PO daily.

In terms of specific recommendations, the choice of antibiotic should be guided by the severity of the infection, the suspected pathogens, and local antimicrobial resistance patterns. However, piperacillin-tazobactam is a valuable option for healthcare-associated infections, severe intra-abdominal infections, and complicated pneumonias where Pseudomonas or anaerobes may be involved, due to its broad-spectrum coverage and activity against MDR pathogens 1.

From the FDA Drug Label

Piperacillin and tazobactam has been shown to be active against most isolates of the following microorganisms, both in vitro and in clinical infections: Aerobic bacteria Gram-positive bacteria Staphylococcus aureus (methicillin susceptible isolates only) Gram-negative bacteria Acinetobacter baumannii Escherichia coli Haemophilus influenzae (excluding beta-lactamase negative, ampicillin-resistant isolates) Klebsiella pneumoniae Pseudomonas aeruginosa (given in combination with an aminoglycoside to which the isolate is susceptible) Anaerobic bacteria Bacteroides fragilis group (B. fragilis, B. ovatus, B. thetaiotaomicron, and B. vulgatus)

Piperacillin-tazobactam covers anaerobic bacteria and Pseudomonas aeruginosa that ceftriaxone and azithromycin don’t.

• Key differences:
  • Piperacillin-tazobactam has activity against Bacteroides fragilis group
  • Piperacillin-tazobactam has activity against Pseudomonas aeruginosa (when given in combination with an aminoglycoside) 2

From the Research

Antibiotic Coverage

Piperacillin-tazobactam covers a range of bacteria, including:

• Pseudomonas aeruginosa, which is often resistant to other antibiotics 3, 4, 5, 6
• Gram-positive and Gram-negative aerobic bacteria, including many pathogens producing beta-lactamases 6, 7
• Anaerobic bacteria, including those found in intra-abdominal and skin/soft tissue infections 6, 7

Comparison to Ceftriaxone and Azithromycin

In comparison to ceftriaxone and azithromycin, piperacillin-tazobactam has:

• Broader coverage of Pseudomonas aeruginosa and other Gram-negative bacteria 3, 4, 5, 6
• Activity against beta-lactamase-producing bacteria, which may be resistant to ceftriaxone and azithromycin 6, 7
• Efficacy in treating polymicrobial infections caused by aerobic or anaerobic beta-lactamase-producing bacteria 7

Key Points

• Piperacillin-tazobactam is effective against a wide range of bacteria, including Pseudomonas aeruginosa and beta-lactamase-producing bacteria 3, 4, 5, 6, 7
• It has a broader spectrum of activity than ceftriaxone and azithromycin, making it a useful option for treating complex infections 6, 7
• Piperacillin-tazobactam is generally well tolerated, with gastrointestinal symptoms and skin reactions being the most common adverse events 7