Tigecycline's Primary Targets
Tigecycline, a glycylcycline antibiotic, shows strongest activity against multidrug-resistant Gram-positive bacteria like methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE), as well as Gram-negative pathogens including Acinetobacter baumannii, Klebsiella pneumoniae (including carbapenem-resistant strains), and Escherichia coli. It bypasses common resistance mechanisms via ribosomal binding, making it effective where other tetracyclines fail.[1][2]
Gram-Negative Coverage Details
Most potent against aerobic Gram-negatives such as Enterobacter spp., Pseudomonas aeruginosa (moderate activity), and Bacteroides fragilis groups in anaerobes. MIC90 values are typically ≤2 mcg/mL for A. baumannii and ESBL-producing Enterobacterales, outperforming beta-lactams in resistant isolates.[1][3]
Gram-Positive Strengths
Excels against Streptococcus pneumoniae, Streptococcus pyogenes, and enterococcal species, with broad coverage of community- and hospital-acquired strains. Less reliable against Staphylococcus epidermidis in biofilms.[2]
Key Limitations and Resistance Patterns
Poor efficacy against Proteus spp., Providencia spp., and Pseudomonas aeruginosa due to efflux pumps; not recommended for Pseudomonas infections. Emerging resistance via tet(X) genes reduces activity in some Enterobacterales.[1][4] Avoid monotherapy for bloodstream infections from these due to bacteriostatic nature.
Clinical Use Cases by Bacteria
FDA-approved for complicated skin/skin structure infections (cSSSI) from MRSA, E. coli, and Klebsiella; intra-abdominal infections from B. fragilis, E. coli, and Bacteroides spp. Off-label for ventilator-associated pneumonia from A. baumannii.[2][5]
[1]: FDA Tigecycline Label
[2]: CDC Antibiotic Resistance Threats Report
[3]: EUCAST Tigecycline Breakpoints
[4]: Clinical Infectious Diseases Review on Tigecycline Resistance
[5]: IDSA Guidelines for cSSSI