Comparative in vitro activity of tigecycline against staphylococci and enterococci from patients on ICU- and non-ICU wards: results of the German T.E.S.T. Surveillance Program 2005

Abstract number: 1733_1327

Kresken M., Brauers J., Geiss H., Halle E., Leitner E., Peters G., Surveillance Program H. Seifert on behalf of the German T.E.S.T.

Objectives: Tigecycline (TGC), the first glycylcycline antibacterial agent, has been shown to be highly effective against a wide range of bacteria including methicillin (oxacillin)-resistant staphylococci and vancomycin-resistant enterococci. G.-T.E.S.T. is a surveillance programme comprising 15 German laboratories which monitors the susceptibility of bacterial pathogens to TGC. The objective of this study was to evaluate the in vitro activity of TGC against both ICU- and non-ICU isolates of four clinically important Gram-positive pathogens, namely Enterococcus faecalis (Es), Enterococcus faecium (Em), Staphylococcus aureus (Sa) and Staphylococcus epidermidis (Se).

Methods: A total of 271 ICU isolates (52 Ef, 67 Em, 77 Sa, 75 Se) and 452 non-ICU isolates (88 Ef, 69 Em, 208 Sa, 87 Se) were tested against TGC, doxycycline (DOX), oxacillin (OXA), moxifloxacin (MXF), gentamicin (GEN), linezolid (LZD), vancomycin (VAN) and other drugs. MICs were determined by broth microdilution according to German DIN guidelines in a central laboratory. The MICs of TGC and LZD were interpreted by EUCAST criteria. DIN breakpoints were applied to the other drugs.

Results: The rates of OXA resistance in ICU/non-ICU isolates of Sa and Se were 61/57% and 81/74%, respectively. The susceptibility rates of ICU/non-ICU isolates to MXF and GEN were 47/45% and 81/87% for Sa compared to 57/60% and 32/39% for Se. In contrast, all staphylococci were susceptible to VAN and LZD. TGC exhibited excellent in vitro activity against all staphylococci including OXA-resistant isolates. It was equally active against ICU- and non-ICU isolates. Only one OXA-resistant Sa strain isolated from an ICU patient was resistant to TGC (MIC 1 mg/L). Compared to DOX, MIC₉₀s of TGC were 16- and 2-fold lower for ICU- and non-ICU isolates of Sa, respectively, and 8fold lower for both ICU- and non-ICU isolates of Se. TCG also exhibited excellent activity against enterococci. All strains were inhibited by TGC at 0.25 mg/L. In contrast, 7% and 14% of the ICU/non-ICU Em isolates were resistant to VAN. High-level resistance to GEN in ICU/non-ICU isolates of Ef and Em ranged from 30 to 54%.

Conclusion: TGC demonstrated excellent in vitro activity against staphylococci and enterococci isolated from both ICU- and non-ICU patients. TGC seems to be a useful drug for the treatment of infections caused by multiple resistant enterococci and staphylococci, even in patients on intensive care units.