Activity of tigecycline against ESBL-producing enterobacteria spreading in Italy

Abstract number: 1733_1187

Luzzaro F., Mugnaioli C., Gualandris S., Pallecchi L., Brigante G., Pini B., Rossolini G.M., Toniolo A.

Background: Tigecycline is a new glycylcycline active against a variety of Gram-positive and Gram-negative resistant pathogens. We evaluated tigecycline activity against a collection of clinical isolates of multidrug-resistant (MDR) enterobacteria producing different types of extended-spectrum b-lactamases (ESBL) from a recent Italian nationwide survey.

Methods: ESBL-producing enterobacteria were tested for susceptibility to tigecycline and other agents by broth microdilution (Microscan panels, Dade-Behring). The collection included isolates of Escherichia coli (n = 138), Klebsiella pneumoniae (n = 64), Klebsiella oxytoca (n = 14), Enterobacter aerogenes (n = 25), Enterobacter cloacae (n = 12), Serratia marcescens (n = 12), and Citrobacter spp. (n = 15), producing TEM, SHV and/or CTX-M type ESBLs. Detection of tetracycline resistance genes [tet(A), tet(B), tet(C) and tet(D)] was performed by PCR.

Results: Overall, 275/280 ESBL-positive isolates (98.2%) were susceptible to tigecycline (MIC ≤2 mg/L). Susceptibility rates were 100% among E. coli, including members of the CTX-M-15-producing E. coli clones causing major outbreaks in some Italian hospitals. Susceptibility rates were 97.4% among Klebsiella spp. and 95.3% among other Enterobacteriaceae. Overall, MIC50/90 of tigecycline were 0.25/1.0 mg/L. E. coli showed MIC50/90 values (0.25/0.5 mg/L) lower than those of other species (0.5/2.0 mg/L). The presence of tet(A), (B), and/or (D) determinants did not affect susceptibility to tigecycline (MIC50/90 0.25/1.0 mg/L for both tet-negative and tet-positive isolates).

Conclusion: Tigecycline showed potent in vitro activity against the vast majority of ESBL-producing enterobacteria circulating in Italy. It might thus represent a valid therapeutic option for treating selected infections caused by these MDR pathogens.

Support from Wyeth Lederle Italia SpA is gratefully acknowledged.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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