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Antimicrobial Agents and Chemotherapy, July 2007, p. 2591-2593, Vol. 51, No. 7
0066-4804/07/$08.00+0 doi:10.1128/AAC.01562-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Department of Laboratory Medicine,1 Research Institute of Bacterial Resistance,2 BK21 Project for Medical Sciences, Yonsei University College of Medicine,3 CrystalGenomics, Inc., Seoul, Korea4
Received 18 December 2006/ Returned for modification 11 January 2007/ Accepted 2 April 2007
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The bacterial enoyl-ACP reductase (FabI) is an enzyme essential for the survival of certain kinds of bacteria (5). Because FabI shows low overall sequence homology with mammalian enzymes, it is a potential target for selective antibacterial action (5, 11). A FabI inhibitor could possess antibacterial activity against those pathogens in which FabI is the sole enoyl-ACP reductase (e.g., Staphylococcus aureus, Haemophilus influenzae, Moraxella catarrhalis, and Escherichia coli), but not against S. pneumoniae, enterococci, or Pseudomonas aeruginosa, which utilize either FabK or both FabI and FabK (10).
CG400549 (M.W. 340; CrystalGenomics, Inc., Seoul, Korea) is an inhibitor of FabI (Fig. 1). Therefore, CG400549 could have antibacterial activities against organisms dependent only on FabI. An animal study showed that it has potential for the treatment of staphylococcal infections in mice and rats (4). In this study, the in vitro activities of CG400549 were compared with those of other antimicrobial agents against recent clinical staphylococcal isolates.
![]() View larger version (4K): [in a new window] |
FIG. 1. Structure of CG400549, a FabI inhibitor.
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Nonduplicate clinical isolates were collected in 2005 and 2006 from patients at a Korean tertiary-care hospital. The species were identified by conventional methods (1) or by using the Vitek system (bioMerieux SA, Marcy l'Etoile, France). Staphylococcal strains for which the MIC of CG400549 was
2 µg/ml were reidentified by using a Vitek GPI kit (bioMerieux SA) and/or 16S rRNA gene sequencing (8).
The antimicrobial susceptibilities were tested by using the CLSI agar dilution method or broth microdilution method, depending on the species (2, 9). CG400549 was provided by CrystalGenomics, Inc. The agents used in the comparison were oxacillin, penicillin G, erythromycin, and tetracycline (Sigma Chemical Co., St. Louis, MO), gentamicin (Chong Kun Dang Pharmaceutical Co., Seoul, Korea), clindamycin (Korea Upjohn, Seoul, Korea), sulfamethoxazole and trimethoprim (Dong Wha Pharmaceutical Co., Seoul, Korea), vancomycin and tobramycin (Daewoong Pharmaceutical Co., Seoul, Korea), levofloxacin (Daiichi Pharmaceutical Co., Tokyo, Japan), linezolid and amikacin (Dong-A Pharmaceutical Co., Seoul, Korea), cefoxitin and imipenem (Merck Sharp & Dohme, Rahway, NJ), ciprofloxacin (Bayer Korea Co., Seoul, Korea), clarithromycin (Hanmi Pharmaceutical Co., Seoul, Korea), and doxycycline (Pfizer Korea, Seoul, Korea). Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 were used as controls in each plate.
In our preliminary study, CG400549 had no activity against gram-positive bacteria, such as streptococci, enterococci, M. catarrhalis, Listeria monocytogenes, Nocardia spp., and nontuberculous mycobacteria, and gram-negative bacteria, such as E. coli, Klebsiella pneumoniae, Enterobacter cloacae, Citrobacter freundii, Serratia marcescens, Morganella morganii, Acinetobacter baumannii, P. aeruginosa, Aeromonas spp., Vibrio spp., H. influenzae, Campylobacter fetus, Helicobacter pylori, and Neisseria gonorrhoeae (data not shown).
In many Korean hospitals, the methicillin resistance rates of S. aureus isolates in 1998 were approximately 70% (6). In the present study, all isolates of S. aureus were inhibited by
4 µg/ml of vancomycin and linezolid and the MIC90s for these agents were 1 µg/ml and 2 to 4 µg/ml, respectively (Table 1). However, all isolates of methicillin-resistant and methicillin-susceptible S. aureus were inhibited by
1 µg/ml of CG400549.
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View this table: [in a new window] |
TABLE 1. Comparative in vitro activities of CG400549 and other antimicrobial agents against clinical staphylococcal isolates
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16 µg/ml of vancomycin and
4 µg/ml of linezolid. The MIC range and MIC90 of CG400549 for MRCNS isolates were 0.12 to 16 µg/ml and 4 µg/ml, respectively, and for MSCNS isolates, they were 0.5 to 8 µg/ml and 8 µg/ml, respectively. The MRCNS isolates with high CG400549 MICs included five S. hominis (4 to 16 µg/ml), three S. epidermidis (4 to 8 µg/ml), two S. haemolyticus (2 to 16 µg/ml), one S. saprophyticus (8 µg/ml), and one S. sciuri (4 µg/ml) isolate; the MSCNS isolates with high CG400549 MICs included three S. simulans (4 to 8 µg/ml), two S. haemolyticus (2 to 4 µg/ml), two S. hominis (4 µg/ml), and one S. epidermidis (8 µg/ml) isolate.
In conclusion, CG400549 is a FabI inhibitor with high in vitro activity against both methicillin-susceptible and -resistant S. aureus strains, including multidrug-resistant strains.
Published ahead of print on 9 April 2007. ![]()
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