Actividad bactericida comparativa de doxiciclina y tigeciclina frente a Acinetobacter baumannii

SHELL, C.; POSSE, G.; MOBILIA, L.; ADRIANA SARA LIMANSKY; BANTAR, C.

C¨®rdoba

Congreso; XI Congreso Argentino de Microbiolog¨ªa, AAM; 2007

In order to assess potential alternative options for treating infections caused by Acinetobacter baumannii, a time-kill study of doxycycline and tigecycline was performed against several isolates recovered from patients belonging to 10 cities in Argentina. Imipenem and sulbactam were also included for comparison purposes. Eleven isolates representing 5 distinctive clones, or different susceptibility pattern among the same clone, were finally selected. No bactericidal activity (i.e. ¡Ý3-log10a time-kill study of doxycycline and tigecycline was performed against several isolates recovered from patients belonging to 10 cities in Argentina. Imipenem and sulbactam were also included for comparison purposes. Eleven isolates representing 5 distinctive clones, or different susceptibility pattern among the same clone, were finally selected. No bactericidal activity (i.e. ¡Ý3-log10isolates representing 5 distinctive clones, or different susceptibility pattern among the same clone, were finally selected. No bactericidal activity (i.e. ¡Ý3-log10¡Ý3-log10 CFU/ml decrease) was observed at any time with sulbactam (4¦Ìg/ml) or tigecycline (1¦Ìg/ml), whereas low bactericidal rate (18% of the isolates) was shown for doxycycline (1¦Ìg/ml) and sulbactam (16¦Ìg/ml) after 24h of incubation. Doxycycline (4¦Ìg/ml) and tigecycline (8¦Ìg/ml) displayed bactericidal activity at 24h of incubation against 36% and 54% of the isolates, respectively, including the carbapenem-resistant isolate. Corresponding values for imipenem (1¦Ì/ml and 4¦Ìg/ml) against the 10 carbapenem-susceptible isolates were 60% and 90%, respectively. Points of time-kill curves of every isolate were subjected to simple linear regression analysis and the slopes of the resulting trend showing a correlation coefficient (r) >0.7 were averaged. Mean slope with negative sign was considered to represent a bactericidal trend and the absolute value was assumed to represent the velocity of bacterial killing exerted by the corresponding drug. Respective values, given as mean ¡À standard deviation, for doxycycline (4¦Ìg/ml), tigecycline (8¦Ìg/ml) and imipenem (4¦Ìg/ml) were 0.38 ¡À 0.21, 0.56 ¡À 0.20 and 0.62 ¡À 0.09 (p¡Ü0.05 for tigecycline and imipenem versus doxycycline).¡Ü0.05 for tigecycline and imipenem versus doxycycline). Results from the present study confirm the in vitro efficacy of imipenem against several clones of A. baumannii, suggest that doxycycline may be a suitable, cost-effective, alternative option and support the potential role of tigecycline in the treatment of infections associated with this organism.A. baumannii, suggest that doxycycline may be a suitable, cost-effective, alternative option and support the potential role of tigecycline in the treatment of infections associated with this organism.