Methods: Twenty isolates in total (19 clinical isolates, including MDR and XDR strains, plus H37Rv) were tested against different concentrations of ertapenem and faropenem (with and without the addition of amoxicillin/clavulanate). Susceptibility testing was performed using two different methods (BACTEC960 and broth microdilution). A degradation assay was also performed to evaluate the stability of ertapenem.
Results: Eighteen out of twenty samples were resistant to the highest concentration of ertapenem tested (including the addition of amoxicillin/clavulanate). Half of the samples tested showed some degree of susceptibility to faropenem and the addition of amoxicillin/clavulanate further reduced the MIC level in seven isolates.
Conclusion: The results from this project have highlighted a significant level of in vitro resistance to ertapenem, whilst the clinical isolates have shown different degrees of susceptibility to faropenem. Although promising agents (in particular, faropenem), carbapenems will remain a third line choice to be used only in cases of XDR TB. There is currently no evidence to prefer the use of ertapenem despite its once daily administration.
J. Ortiz Canseco, None
E. Wey, None
F. Drobniewski, None
T. D. McHugh, None