In vitro activity of tigecycline and other tetracyclines against carbapenem-resistant Acinetobacter species: report from a tertiary care centre in Karachi, Pakistan.

BACKGROUND

The Aga Khan University Hospital is a tertiary care centre in Karachi, Pakistan, where tigecycline has not been used previously. We report findings of a pre-use in vitro study to evaluate sensitivity of nosocomial Acinetobacter spp. Tigecycline minimum inhibitory concentration (MIC) was correlated with that of other tetracyclines to assess their predictive potential.

METHODS

Acinetobacter spp. were collected from hospitalized inpatients admitted to Aga Khan University Hospital from April to November 2007. Tigecycline, tetracycline, doxycycline, and minocycline MICs were determined by E-test.

RESULTS

One hundred isolates of Acinetobacter spp. were tested. Ninety-eight percent of Acinetobacter spp. were carbapenem-resistant. Tigecycline MIC(50) and MIC(90) were 1.5 and 2.0 microg/ml, respectively. Unavailability of standard breakpoints hindered categorization of these values. Minocycline was highly active, with MIC(90) of 2.0 microg/ml.

CONCLUSIONS

Tigecycline breakpoints for Acinetobacter spp. should be established to prevent injudicious use of this antibiotic based on misleading in vitro results. The therapeutic potential of minocycline needs more in-depth study.