Which Bacteria Show Tigecycline Resistance?
Tigecycline, a glycylcycline antibiotic, targets multidrug-resistant Gram-negative and Gram-positive bacteria but faces resistance in certain strains. Common resistant bacteria include:
- Pseudomonas aeruginosa: Inherently resistant due to low outer membrane permeability and efflux pumps like MexXY-OprM, which actively expel the drug.[1]
- Proteus species (e.g., Proteus mirabilis): Naturally resistant from poor accumulation in the periplasmic space.[1][2]
- Providencia species (e.g., Providencia stuartii): Similar mechanisms limit drug uptake.[1]
- Acinetobacter baumannii (some strains): Resistance emerges via efflux overexpression (AdeABC) or ribosomal mutations, though many remain susceptible.[2][3]
These are documented in clinical isolates and surveillance data from sources like EUCAST and CLSI breakpoints.
Why Do These Bacteria Resist Tigecycline?
Resistance stems from:
- Efflux pumps reducing intracellular concentrations.
- Reduced binding to the 30S ribosomal subunit.
- Enzymatic inactivation (rare).
Pseudomonas and Proteus/Providencia resist inherently; Acinetobacter often acquires resistance during therapy.[2][4]
How Common Is Resistance in Clinical Settings?
Resistance rates vary by region and infection type:
- P. aeruginosa: Near 100% intrinsic resistance; not recommended for use.[1]
- A. baumannii: 10-50% in ICU settings, rising in ventilator-associated pneumonia.[3][5]
- Enterobacterales like Proteus/Providencia: High intrinsic rates, but tigecycline avoids most ESBL/KPC producers.[4]
Global surveillance (e.g., TEST program) shows <20% resistance in Enterobacterales overall, but >90% in Pseudomonas.[5]
What Infections Involve Tigecycline-Resistant Strains?
Common in:
- Hospital-acquired pneumonia (Pseudomonas, Acinetobacter).
- Complicated intra-abdominal infections (Proteus in polymicrobial cases).
- Bloodstream infections with carbapenem-resistant Acinetobacter.[3][6]
Susceptibility testing is essential; tigecycline fails against confirmed resistant isolates.
Treatment Alternatives for These Bacteria?
| Bacteria | Key Alternatives | Notes |
|----------|------------------|-------|
| P. aeruginosa | Colistin, ceftolozane-tazobactam, cefiderocol | Combination therapy often needed. |
| Acinetobacter baumannii | Sulbactam, colistin, eravacycline (similar class, variable activity) | Eravacycline may work against some tigecycline-resistant strains.[7] |
| Proteus/Providencia | Carbapenems (if susceptible), aminoglycosides | Avoid tigecycline monotherapy. |
Consult local antibiograms; new agents like plazomicin target some resistant Gram-negatives.[6]
Testing and Prevention Tips
Use MIC testing per CLSI/EUCAST (tigecycline breakpoints: S ≤2 mg/L for Enterobacterales).[1] Prevent spread via infection control in ICUs. Resistance tracking shows rising Acinetobacter issues post-2020.[5]
Sources
[1]: EUCAST Tigecycline Breakpoints
[2]: CLSI M100 Guidelines
[3]: CDC Acinetobacter Report
[4]: Tigecycline Mechanism Review, Clin Infect Dis
[5]: TEST Surveillance Data, J Antimicrob Chemother
[6]: IDSA Guidance on MDR Gram-Negatives
[7]: Eravacycline vs Tigecycline, Lancet Infect Dis