In vitro activity of tigecycline against multidrug-resistant Gram-negative clinical isolates

Abstract number: P1183

Zarkotou O., Kopsari K., Korou E., Tsimettas J., Mantzouratou P., Gianneli D., Poulopoulou C.

Objectives: To evaluate the antimicrobial performance of tigecycline against multi-drug resistant (MDR) Gram-negative (GNs) clinical isolates.

Methods: A total of 78 MDR GN bacterial stains were studied. They were isolated from various clinical specimens, during a 10-month period (2/07–11/07), from both ICU and non-ICU patients. Only one isolate per patient was included in the study. P. aeruginosa and Proteae strains were excluded, as tigecycline exhibits reduced antimicrobial potency to these species. Species identification and MIC values determination for 37 antibiotics were performed by the VITEK 2 Compact Automated System (bioMerieux, France). The MICs for tigecycline and ampicillin/sulbactam were determined by the E-test method (AB Biodisk, Sweden). The susceptibility breakpoints for tigecycline were those approved by the FDA.

Results: The majority of the MDR strains derived from ICU-patients (51/78, 65.4%) as expected, followed by surgical patients (19/78, 24.4%). They were isolated from blood (35/78), pus (19/78), catheters (11/78), bronchial secretions (7/78) and other sources (6/78). The bacterial species were: K. pneumoniae (31/78), A. baumannii (27/78), Enterobacter spp. (10/78), E. coli (5/78) and others (5/78). Out of the 78 MDR strains five were pan-drug resistant and ten of them were susceptible only to colistin. Susceptibility to tigecycline was detected to 4/5 of pan drug resistant isolates (one was intermediately susceptible) and to 6/10 of colistin-only susceptible isolates (two of them were tigecycline resistant). MIC90 and MIC50 for tigecycline was 2 and 0.75 mg/l respectively (MIC range: 0.064–8 mg/l). Acinetobacter baumannii exhibited higher MIC90 and MIC50 values (3 and 2 mg/l, range: 0.125–8 mg/l) compared with Klebsiella pneumoniae (1, 5 and 0, 38 mg/l, range: 0.094–8). Resistance to tigecycline was detected to 2 MDR isolates (2, 6%) with MICs of 8 mg/l, while in 5 strains (6.4%) MICs were 3–4 mg/l. Among ICU-patients 8 were treated with tigecycline. No significant differences were observed to the MIC values of tigecycline for the strains derived from these patients before and after treatment.

Conclusion: The emergence of multidrug-resistance poses a serious threat. Tigecycline may represent an option for the treatment of infections caused by MDR GNs where our choices are limited. Any potential for selection of resistance should be monitored.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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