Is Tazact (ceftazidime/avibactam) effective against Serratia in sputum?

Effectiveness of Ceftazidime-Avibactam (Tazact) Against Serratia in Sputum

Ceftazidime-avibactam (Tazact) is effective against Serratia marcescens in sputum and is specifically indicated for the treatment of hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia caused by Serratia marcescens. 1

Mechanism and Indications

Ceftazidime-avibactam combines:

• Ceftazidime: A third-generation cephalosporin with activity against gram-negative bacteria
• Avibactam: A novel non-beta-lactam beta-lactamase inhibitor that protects ceftazidime from degradation

The FDA-approved label specifically includes Serratia marcescens as a susceptible organism for hospital-acquired and ventilator-associated bacterial pneumonia (HABP/VABP) 1. This makes it an appropriate choice for treating Serratia infections in sputum.

Evidence Supporting Efficacy

Multiple studies confirm the effectiveness of ceftazidime-avibactam against Serratia:

• Avibactam has been shown to revert the ceftazidime MIC90 (minimum inhibitory concentration) of Serratia spp. to the epidemiological cut-off value, demonstrating its ability to overcome resistance mechanisms 2

• In vitro testing has confirmed susceptibility of Serratia marcescens to ceftazidime-avibactam, including carbapenem-resistant strains 3, 4

• A case report documents successful treatment of persistent carbapenem-resistant Serratia marcescens infection with ceftazidime-avibactam 5

Treatment Considerations

When to Use Ceftazidime-Avibactam for Serratia

1. First-line therapy: For hospital-acquired or ventilator-associated pneumonia caused by Serratia marcescens 1

2. For resistant strains: Particularly effective for carbapenem-resistant Serratia marcescens 5, 4

3. For patients with risk factors for multidrug-resistant organisms:

   • Prior antimicrobial therapy in the preceding 90 days
   • Current hospitalization exceeding 5 days
   • High frequency of resistance in the community or local hospital unit
   • Immunosuppressive disease and/or therapy 6

Dosing Recommendations

For adults with normal renal function:

• 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) administered every 8 hours by intravenous infusion over 2 hours 1

For pediatric patients:

• Dosing is based on age and weight, ranging from 25 mg/kg to 62.5 mg/kg every 8 hours 1

Duration of treatment for HABP/VABP: 7 to 14 days 1

Antimicrobial Stewardship Considerations

While ceftazidime-avibactam is effective against Serratia, several important considerations should guide its use:

1. Preserve for appropriate cases: To prevent development of resistance, use should be limited to confirmed or strongly suspected infections caused by susceptible bacteria 1

2. Susceptibility testing: Whenever possible, obtain cultures and susceptibility testing before initiating therapy 5

3. Cost and access: Be aware of potential challenges in procurement and cost, which may affect availability 5

4. Alternative options: For non-resistant Serratia, consider other antibiotics like ceftriaxone, quinolones, or antipseudomonal cephalosporins (cefepime) 6

Potential Pitfalls

1. Development of resistance: Inappropriate use may lead to development of resistance, limiting future effectiveness 5

2. Limited availability: Access to susceptibility testing and procurement processes may delay initiation of therapy 5

3. Cost considerations: Newer beta-lactam/beta-lactamase inhibitor combinations are typically more expensive than older antibiotics 5

Ceftazidime-avibactam represents an important treatment option for Serratia infections in sputum, particularly for resistant strains or in patients with risk factors for multidrug-resistant organisms. Its use should be guided by susceptibility testing whenever possible to ensure appropriate antibiotic stewardship.