What is the coverage of meropenem and tigecycline against various organisms?

Meropenem and Tigecycline Antimicrobial Coverage

Meropenem Coverage

Meropenem is a broad-spectrum carbapenem with excellent activity against most Gram-positive, Gram-negative aerobic, and anaerobic bacteria, but lacks activity against methicillin-resistant staphylococci and vancomycin-resistant enterococci. 1

Gram-Positive Coverage

• Staphylococcus aureus (methicillin-susceptible isolates only—no MRSA activity) 1
• Streptococcus pneumoniae (penicillin-susceptible isolates) 1
• Streptococcus pyogenes and Streptococcus agalactiae 1
• Viridans group streptococci 1
• Enterococcus faecalis (vancomycin-susceptible isolates only) 1

Gram-Negative Coverage

• Enterobacteriaceae: Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Enterobacter cloacae, Citrobacter species, Serratia marcescens, Morganella morganii 1
• Pseudomonas aeruginosa (important for nosocomial infections) 2, 1
• Haemophilus influenzae and Neisseria meningitidis 1
• Other organisms: Aeromonas hydrophila, Moraxella catarrhalis, Pasteurella multocida 1

Anaerobic Coverage

• Bacteroides fragilis group (including B. thetaiotaomicron, B. ovatus, B. uniformis, B. vulgatus) 2, 1
• Clostridium species (including C. perfringens and C. difficile) 1
• Peptostreptococcus species 1
• Fusobacterium species, Prevotella species, Propionibacterium acnes 1

Important Resistance Considerations

• Meropenem resistance rates to P. aeruginosa vary regionally (15-23% in Asia-Pacific) 2
• For carbapenem-resistant Enterobacteriaceae (CRE), meropenem retains activity when combined with other agents despite elevated MICs 2
• Extended-spectrum beta-lactamase (ESBL)-producing organisms often remain susceptible to carbapenems 2

Tigecycline Coverage

Tigecycline is a glycylcycline with broad-spectrum activity including multidrug-resistant Gram-positive and Gram-negative organisms, but has critical limitations due to low serum concentrations making it unsuitable for bloodstream infections. 3, 4

Gram-Positive Coverage

• MRSA (methicillin-resistant Staphylococcus aureus) 4
• Vancomycin-resistant Enterococcus (VRE) including E. faecium and E. faecalis 2
• Streptococcus species 4

Gram-Negative Coverage

• ESBL-producing Enterobacteriaceae 4
• Carbapenem-resistant Enterobacteriaceae (CRE) including Klebsiella pneumoniae and E. coli 2, 4
• Carbapenem-resistant Acinetobacter baumannii (CRAB) 2, 4
• Note: Tigecycline has limited activity against Pseudomonas aeruginosa and Proteus species 4

Anaerobic Coverage

• Bacteroides fragilis group with low resistance rates (5% during surveillance) 2
• Broad anaerobic coverage including other intestinal Bacteroidales 2, 4

Critical Clinical Limitations

• Tigecycline performs poorly in bacteremic patients due to low plasma concentrations and large volume of distribution 3, 4
• Should not be used as monotherapy for bloodstream infections—aminoglycosides and polymyxin-based regimens are superior for CRE bacteremia 3
• Efficacy correlates with MIC: comparable to polymyxin when MIC ≤2 mg/L, but inferior when MIC >2 mg/L 3, 4

Combination Therapy Considerations

Meropenem + Tigecycline Combinations

• Caution advised: Antagonism documented between tigecycline and meropenem in 44-56% of KPC-producing strains in animal models 5
• Clinical case reports confirm antagonistic interactions requiring cessation of combination therapy 6
• For CRE intra-abdominal infections with severe sepsis/septic shock, tigecycline-meropenem combination may be considered despite antagonism risk when options are limited 2

Preferred Combination Strategies

• For CRE infections: Tigecycline + polymyxin (colistin) shows synergy and is preferred over tigecycline + meropenem 2, 5, 7
• For CRAB infections: Colistin-tigecycline combination had lowest mortality (SUCRA 93.4%) 2
• Tigecycline + rifampin or + gentamicin demonstrates robust synergy against KPC-producing strains 5

Site-Specific Recommendations

• Intra-abdominal infections: Both agents achieve excellent tissue penetration; tigecycline particularly suitable for IAI involving VRE 2
• Urinary tract infections: Meropenem preferred; aminoglycosides superior to tigecycline for UTI with sepsis 3
• Bone infections: Tigecycline achieves high bone tissue concentrations for MDR organisms 4
• Bloodstream infections: Avoid tigecycline monotherapy; meropenem appropriate for susceptible organisms 3, 1