Cefixime is Not Recommended for Treating Serratia marcescens Infections
Cefixime should not be used as first-line therapy for Serratia marcescens infections due to limited activity against this organism and potential for resistance development. 1
Evidence on Cefixime and Serratia marcescens
- According to the FDA drug label, while cefixime has in vitro activity against Serratia marcescens, its clinical efficacy for treating infections caused by this organism has not been established in adequate and well-controlled clinical trials 1
- Serratia marcescens is known to produce various beta-lactamases, and cefixime may have limited activity against Enterobacteriaceae producing extended-spectrum beta-lactamases (ESBLs) 1
- Surveillance studies have shown variable resistance patterns in Serratia marcescens isolates, with increasing resistance to certain cephalosporins 2, 3
Recommended Treatment Options for Serratia marcescens
First-line Options:
- For severe Serratia marcescens infections, an extended-spectrum cephalosporin (e.g., ceftazidime, ceftriaxone, or cefotaxime) together with an aminoglycoside is recommended for a minimum of 6 weeks of therapy 4
- Carbapenems (imipenem or meropenem) are recommended for bloodstream infections and severe infections due to resistant Enterobacterales 4
- Gentamicin has shown very low resistance rates (0.6%) against Serratia marcescens in surveillance studies and may be an effective option 2
For Specific Infection Types:
- For central nervous system infections like ventriculitis, continuous-infusion meropenem has demonstrated effectiveness with adequate CSF penetration 5
- For non-severe urinary tract infections, aminoglycosides or IV fosfomycin may be considered when active in vitro 4
- Cefotaxime has shown very low resistance rates (0.6%) and may be suitable for susceptible isolates 2
Resistance Considerations
- Resistance rates to different cephalosporins vary significantly - one study found resistance rates of 22.7% to ceftriaxone and 19.6% to ceftazidime 2
- Serratia marcescens can develop resistance during treatment, particularly in cases of osteomyelitis or in immunocompromised patients 6
- Surveillance data from Taiwan showed consistently high susceptibility to ceftazidime (93.8%) and imipenem (99.3%) over an 8-year period 3
- Extended-spectrum β-lactamase (ESBL) production can limit the effectiveness of many cephalosporins 2
Special Populations and Situations
- For immunocompromised patients or those with prosthetic material infections, combination therapy may be necessary 4
- In patients with carbapenem-resistant Serratia marcescens, newer agents like ceftazidime-avibactam, meropenem-vaborbactam, or cefiderocol may be considered based on susceptibility testing 4
- For multidrug-resistant isolates, susceptibility testing is crucial to guide therapy, as resistance patterns can vary significantly 7
Clinical Pearls and Pitfalls
- Do not rely on cefixime for serious Serratia marcescens infections despite its listing in the FDA label as having in vitro activity 1
- Monitor for development of resistance during therapy, especially in prolonged courses or in immunocompromised patients 6
- Consider combination therapy for severe infections to prevent emergence of resistance 4
- Fluoroquinolone resistance in Serratia marcescens has been increasing, warranting caution with this class 3
- Antibiotic susceptibility testing is essential before initiating definitive therapy due to variable resistance patterns 2, 7