Rapid identification of nosocomial Acinetobacter baumannii isolated from a surgical intensive care unit in Egypt

The rapid and accurate identification of nosocomial clinical isolates is the first essential step in investigating nosocomial outbreaks. We aimed to evaluate the performance of MDR-CHROMagar Acinetobacter versus matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in rapid detection of nosocomial Acinetobacter baumannii isolated from patients admitted to the surgical intensive care unit (SICU) of Kasr Alainy- Cairo University.

Over a period of 9 months from January 2014 until September 2014, 234 samples were collected. All samples were directly cultured on MDR-CHROMagar Acinetobacter media. MALDI-TOF MS was used to identify all non-lactose fermenting colonies on conventional media. Confirmation of species identification was done by detecting the blaOXA-51 like gene by PCR.

Statistical evaluation of MDR-CHROMagar Acinetobacter against blaOXA-51 like PCR as the reference method for identification of A baumannii showed a sensitivity of 100% (95% confidence interval [CI]: 93.36% to 100%), specificity 98.8% (95% confidence interval [CI]: 96.04% to 99.68%), positive predictive value 96.4% (95%CI: 86.61% to 99.37%), negative predictive value 100% (95% CI: 97.36% to 100%). The statistical evaluation of MALDI-TOF against blaOXA-51 PCR was 100% concordance.

MALDI-TOF MS was more specific than CHROMagar in identifying Acinetobacter spp and allowed further identification of non-A Baumannii species such as A hemolyticus and A nosocomialis, which are less common Acinetobacter spp involved in hospital-acquired infections.