Tigecycline

Tigecycline, a glycylcycline, is a new broad-spectrum antimicrobial agent for parenteral use, which has been designed specifically to overcome the problem of resistance to tetracyclines. In Germany, tigecycline was introduced for clinical use in May 2006. Here, we report the results of a nationwide surveillance trial (German Tigecycline Evaluation Surveillance Trial; G-TEST) that was conducted to evaluate the susceptibility of hospital isolates of common aerobic Gram-positive and Gram-negative bacterial species to tigecycline prior to its clinical use in comparison to established antimicrobial agents.

Tigecycline is the most recently developed analog of a newly introduced, semi-synthetic broad-spectrum antibiotic class, the glycylcyclines. It is a 9-t-butylglycylamido derivative of minocycline. Due to this structural modification, tigecycline is known to overcome the two major determinants of tetracycline resistance: the active efflux of the drug from inside the bacterial cell, and the protection of ribosomes. It exhibits potent activity against a broad spectrum of Gram-positive and Gram-negative bacteria. Tigecycline was found to be highly active in vitro againstEnterobacteriaceae, regardless of the presence or absence of ESBLs. However, tigecycline has limited in vitro activity against Pseudomonas aeruginosa, and reduced activity against indole-positive Proteae and Proteus mirabilis.

Tigecycline is a new tetracycline antibiotic. It is widely used because of high activity against a large number of both gram-positive and gram-negative microorganisms. The main impurities in tigecycline are 4-epimer, a known impurity, and oxidation degradation products. Tige-cycline is sensitive to moisture and oxidation. Some degra-dation products are produced readily during the production of tigecycline and during storage. The clinical effect will be impacted because of the reduction of these impurities’ anti-bacterial activities and the increase of these impurities’ tox-icities. Therefore, it is necessary to characterize and control these oxidation degradation impurities in tigecycline. Tige-cycline is listed in Chinese state food and drug administra-tion standard now. We are drafting the monograph tige-cycline of the Chinese Pharmacopoeia. This work intended to serve for the preparation of such monograph.

Consequently, biofilm-associated bacteria are 100 to 10,000 times more resistant to antibiotics than planktonic bacteria. Previous stud-ies showed that rifampin has the ability to penetrate through the biofilm, but the use of this antibiotic alone was associated with the emergence of rifampin-resistant strains, and for this reason, this antibiotic compound should be combined with other antibiotic agents. Tigecycline, a novel glycylcycline antibiotic, has demonstrated excellent in vitro and in vivo activity against a large number of Gram-positive bacteria, including methicillin-resistant S. aureus(MRSA) strains (Aybar et al. 2012). The tigecycline/rifampin combination has been investigated in vitro and in animal models. In in vitro studies, the addition of rifampin to tigecycline resulted in an antagonism for two of four tested S. aureusstrains (Mercier et al. 2002). In other studies, antagonism was not observed for the tigecycline/rifampin combination against MRSA strains (Petersen et al. 2006). Data from the rabbit model experiment, although limited to one strain, demonstrated that the combination of tigecycline with rifampin exhibited complete infection clearance from the tibia. However, the authors underline that the eradication of the staphylococcal biofilm was also very high, when the tigecycline alone was tested (Yin et al. 2005).