Comparison of Sensititre microdilution method to other standard methods for susceptibility testing of coagulase-negative staphylococci from paediatric blood cultures

Abstract

Susceptibility testing on 60 isolates of Staphylococcus epidermidis and 20 isolates of Staphylococcus hominis was performed using the Sensititre (Trek Diagnostics, Cleveland, OH, USA) method and compared with Vitek-2 automated susceptibility testing (bioMèrieux, Marcy l'Etoile, France), MICE strips for minimum inhibitory concentration determination (Oxoid, Basingstoke, UK), and disc diffusion (MAST, Bootle, UK). The categorical agreement between Vitek and Sensititre was greater than 90% for agents tested against S. epidermidis except for tetracycline (52%) and oxacillin (67%), and for S. hominis, the agreement was greater than 90% except for tetracycline (80%), gentamicin (65%), and oxacillin (75%). The categorical agreement between disc diffusion and Sensititre was greater than 90% for antimicrobials tested against S. epidermidis except for tetracycline (45%), moxifloxacin (70%), clindamycin (88%), and cefoxitin (80%), while against S. hominis, the categorical agreement was greater than 90% for antimicrobials tested except for gentamicin (65%), tetracycline (75%), moxifloxacin (80%), and ciprofloxacin (75%). Categorical agreement between MICE strips and Sensititre for S. epidermidis and S. hominis was greater than 95% for vancomycin and daptomycin. Sensititre method shows good categorical agreement with other standard methods for susceptibility testing of S. hominis and S. epidermidis.

Keywords: CoNS; Coagulase negative staphylococci; Sensititre; Susceptibility testing.