New Abx- In vitro activity of tigecycline & multiple strains Borrelia burgdorfer

[Guest guest]

In vitro activity of tigecycline against multiple strains of Borrelia

burgdorferi

Xiaohua Yang, Andrew Nguyen, Dan Qiu and Benjamin J. Luft *

 

Division of Infectious Diseases, Department of Medicine, Stony Brook

University, Stony Brook, NY 11794, USA

 

Received 30 July 2008; returned 16 October 2008; r

 

bjectives: To compare the antimicrobial activity of tigecycline and

doxycycline against multiple isolates of Borrelia burgdorferi .

 

Methods: In vitro antimicrobial assays were carried out using a

microdilution assay. The time needed to inhibit, immobilize and kill the B31

strain

of B . burgdorferi was determined. The MIC, MBC and concentration needed to

immobilize the organism were determined for each antimicrobial for various

strains of B . burgdorferi .

 

Results: Tigecycline inhibited the growth of and killed the organism more

rapidly than doxycycline. Tigecycline was able to kill B . burgdorferi

within 24 h at clinically achievable concentrations (<1 mg/L). In contrast,

doxycycline was bacteriostatic and required 48-72 h to achieve its maximal

inhibitory effect. The anti- Borrelia activity of the antibiotics was tested

against 20 different isolates from three species. Tigecycline was 16- to

1000-fold more active than doxycycline at immobilizing Borrelia for the 20

isolates tested.

 

Conclusions: We demonstrate that the in vitro activity of tigecycline

against B . burgdorferi is superior to that of doxycycline. Tigecycline acted

more rapidly and was bactericidal, whereas doxycycline was bacteriostatic

and required a more prolonged co-incubation to achieve its maximal inhibitory

effect.