In vitro activity of tigecycline, a new glycylcycline, tested against 1,326 clinical bacterial strains isolated from Latin America.
The in vitro activity of tigecycline (former GAR-936), a new semisynthetic tetracycline, was evaluated in comparison with tetracycline and other antimicrobial agents.


METHODS
A total of 1,326 contemporary clinical isolates collected from the Latin American region were collected in 2000-2002 period and tested with microdilution broth according to the CLSI guidelines. The bacterial pathogens evaluated included Staphylococcus aureus (505), Streptococcus pneumoniae (269), coagulase-negative staphylococci (CoNS; 227), Haemophilus influenzae (129), Enterococcus spp. (80), Moraxella catarrhalis (54), beta-haemolytic streptococci (28), viridans group streptococci (26), and Neisseria meningitidis (8)


RESULTS
Tigecycline demonstrated excellent activity against all Gram-positive cocci, with 90% of penicillin-resistant S. pneumoniae strains being inhibited at 0.12 microg/mL, while the same isolates had an MIC90 of > 16 microg/mL for tetracycline. All Enterococcus spp. were inhibited at 0.25 microg/mL of tigecycline. Tigecycline (MIC50, 0.25 microg/mL) was eight-fold more potent than minocycline (MIC50, 2 microg/mL) against oxacillin-resistant S. aureus (ORSA); all ORSA were inhibited at < 2 microg/mL of tigecycline. Tigecycline demonstrated excellent activity (MIC50, 0.5 microg/mL) against CoNS with reduced susceptibility to teicoplanin (MIC, 16 microg/mL). Tigecycline also showed high potency against respiratory pathogens such as M. catarrhalis (MIC50, 0.12 microg/mL) and H. influenzae (MIC50, 0.5 microg/mL). No tigecycline resistant isolates were detected when the proposed susceptible breakpoints (< 4 microg/mL) was applied.


CONCLUSIONS
This results indicate that tigecycline has potent in vitro activity against clinically important pathogenic bacteria, including Gram-positive isolates resistant to both tetracycline and minocycline.
Gales
Ana C
AC
Department of Medicine, Division of Infectious Diseases, University of São Paulo, Rua Leandro Dupret 188, São Paulo, Brazil. galesac@aol.com
Jones
Ronald N
RN
Andrade
Soraya S
SS
Pereira
Andrea S
AS
Sader
Hélio S
HS
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D007843:Latin America; D008826:Microbial Sensitivity Tests; D008911:Minocycline / Q000031:analogs & derivatives* / Q000494:pharmacology; D010403:Penicillin Resistance; D013752:Tetracycline / Q000494:pharmacology*; D013753:Tetracycline Resistance; D000078304:Tigecycline; D020713:Vancomycin Resistance
D000900:Anti-Bacterial Agents; D000078304:Tigecycline; D013752:Tetracycline; D008911:Minocycline