In vitro synergistic activity of tigecycline and colistin against XDR-Acinetobacter baumannii

Abstract

The emergence of extensive drug-resistant (XDR) Acinetobacter baumannii limits the therapeutic options and leads to high mortality in intensive care units. Combined antibiotic therapy is frequently recommended for the treatment of these infections. Colistin (CO) and tigecycline (TIG), alone or in combination with other antimicrobials, are the most commonly used antibiotics in the treatment of these resistant infections. In this study, the in vitro synergistic activity of TIG and CO were tested for 25 XDR-A. baumannii strains isolated from ventilator-associated pneumonia by the Etest method. Resistance to CO was not detected, whereas 8% of the strains were resistant to TIG. The TIG-CO combination was more synergistic than TIG-rifampin and CO-rifampin according to the fractional inhibitory concentration index. No antagonism was detected between the drugs in the study. There was no strong correlation between the activity of the combinations with reference to strains or genotypes. Our results suggest that the combined use of TIG and CO may be useful for the treatment of XDR-A. baumannii infections.

Postantibiotic Effects of Tigecycline, Colistin Sulfate, and Levofloxacin Alone or Tigecycline-Colistin Sulfate and Tigecycline-Levofloxacin Combinations against <i>Acinetobacter baumannii</i>

“…Combination therapy plays an important role in the management of severe A. baumannii infection. Similarly to other published studies [37][38][39][40] , the results of this in vitro trial provide evidence that tigecycline used in combination with either colistin sulfate or levofloxacin will produce clinically relevant synergy against A. baumannii , and that it might be useful to use tigecycline in combination with colistin sulfate or levofloxacin to produce a rapid enhancement of bactericidal activity, to prevent or delay the emergence of resistance, and to gain synergistic interaction against this organism. The purpose of this study was to examine whether the PAEs induced by drug combinations differed from the PAEs induced by the drugs alone.…”

Clonal spread of multidrug-resistant Acinetobacter baumannii in eastern Taiwan

“…11,12 Nevertheless, several studies have shown that tigecycline-or rifampicinbased regimens are more effective for treating severe infections caused by MDR A baumannii. 13,14 To date, no studies are available on the efficacy of rifampicin or combination rifampicin/colistin against A baumannii isolates in Taiwan, although rifampicin has been used for the long-term treatment of infections caused by Mycobacterium tuberculosis. Furthermore, the spread of MDR A baumannii with resistance to tigecycline, rifampicin, and colistin in hospitals has never been reported in Taiwan.…”

Confronting multidrug-resistant Acinetobacter baumannii: a review

“…Enhanced activity or bactericidal synergism occurred with TIG plus carbapenems, levofloxacin, amikacin and RIF in various in vitro studies [76][77][78]. Results of the combination of TIG with COL are controversial [79][80][81].…”

“…However, it is well documented that when used alone RIF shows rapid development of resistance, thus its combination with other antimicrobials is necessary [105,106]. Although an additive effect or synergism has been observed for combinations of RIF with various agents such as carbapenems, TIG or SAM [81,105], the most promising combination is that of RIF with COL.…”