What microorganisms is tigecycline (generic name) effective against?

Tigecycline Antimicrobial Coverage

Tigecycline is a broad-spectrum glycylcycline antibiotic with activity against most Gram-positive organisms (including MRSA and VRE), many Gram-negative bacteria (including ESBL-producing Enterobacteriaceae), anaerobes, and atypical pathogens, but it should not be used for bacteremia or urinary tract infections due to inadequate serum and urinary concentrations. 1, 2, 3

Gram-Positive Coverage

Tigecycline demonstrates excellent activity against resistant Gram-positive organisms:

• Staphylococcus aureus (both methicillin-susceptible and methicillin-resistant strains) 1, 2
• Enterococcus species including vancomycin-resistant Enterococcus (VRE): E. faecalis (vancomycin-susceptible and -resistant), E. faecium (vancomycin-susceptible and -resistant), E. avium, E. casseliflavus, and E. gallinarum 1, 3
• Streptococcus species: S. pneumoniae (penicillin-susceptible), S. pyogenes, S. agalactiae, and Streptococcus anginosus group 1
• Staphylococcus epidermidis (methicillin-susceptible and -resistant) and S. haemolyticus 1
• Listeria monocytogenes 1

Critical Limitation for MRSA

While tigecycline has in vitro activity against MRSA, it is not recommended as a first-line agent for most MRSA infections and should never be used for MRSA bacteremia due to low plasma concentrations 2. Preferred agents include vancomycin, linezolid, daptomycin, telavancin, and clindamycin 2.

Gram-Negative Coverage

Tigecycline maintains activity against many Gram-negative pathogens, including multidrug-resistant strains:

• Enterobacteriaceae: Escherichia coli, Klebsiella pneumoniae, K. oxytoca, Enterobacter cloacae, E. aerogenes, Citrobacter freundii, C. koseri, Serratia marcescens 1, 4
• Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae with MICs ranging from 0.19 to 4 μg/mL 4, 5
• Carbapenem-resistant Enterobacteriaceae (CRE) - tigecycline is recommended for intra-abdominal infections caused by CRE, often in combination with polymyxin or meropenem for severe sepsis 6
• Acinetobacter baumannii (though resistance can develop during treatment via MDR efflux pumps, requiring more frequent monitoring) 1
• Haemophilus influenzae (including ampicillin-resistant strains) and H. parainfluenzae 1
• Legionella pneumophila 1
• Stenotrophomonas maltophilia 1
• Aeromonas hydrophila and Pasteurella multocida 1

Anaerobic Coverage

Tigecycline provides comprehensive anaerobic coverage:

• Bacteroides species: B. fragilis, B. thetaiotaomicron, B. uniformis, B. vulgatus, B. distasonis, B. ovatus 1
• Clostridium perfringens 1
• Peptostreptococcus micros and other Peptostreptococcus species 1
• Porphyromonas species and Prevotella species 1

Atypical Pathogens

• Mycobacterium abscessus and M. fortuitum 1

Mechanism of Resistance Evasion

Tigecycline overcomes common tetracycline resistance mechanisms (ribosomal protection and efflux) and is not affected by β-lactamases (including ESBLs), macrolide efflux pumps, or enzyme target changes 1, 7. However, some ESBL-producing isolates may still be resistant via alternative mechanisms, and Acinetobacter species can develop resistance through MDR efflux pumps during treatment 1.

Critical Clinical Limitations by Site of Infection

Contraindicated Uses:

• Bacteremia/Bloodstream infections: Large volume of distribution (7-9 L/kg) results in inadequate serum levels; never use for VRE bacteremia or any bacteremic infection 3, 8, 7
• Urinary tract infections: Poor urinary concentrations make tigecycline unsuitable for UTIs, including those caused by susceptible organisms; only consider as absolute last resort for pan-resistant organisms in lower UTIs (cystitis), never for pyelonephritis 8

Optimal Uses:

• Intra-abdominal infections: Drug of choice for VRE-associated IAI with 97.6% success rate; achieves high peritoneal penetration 6, 3
• Complicated skin and soft tissue infections: Effective for polymicrobial infections involving MRSA, anaerobes, and Gram-negatives (excluding diabetic foot infections) 2, 7
• Community-acquired pneumonia: Approved indication with demonstrated efficacy 5

Dosing:

Standard dosing is 100 mg IV loading dose, followed by 50 mg IV every 12 hours for 5-14 days depending on infection site and clinical response 3, 1. Reduce maintenance dose by 50% in severe hepatic impairment (Child-Pugh class C); no adjustment needed for renal impairment 7.