Microscan walkaway 40 plus system

Ascitic fluid samples were stained using Gram stain and cultured on HK semi-fluid plates (Kyokuto Pharmaceutical Co., Tokyo, Japan), Brucella HK (RS) agar plates (Kyokuto Pharmaceutical Co.), chocolate agar plates No. 2 (Kyokuto Pharmaceutical Co.), and Trisoy blood agar plates (sheep) No. 2 (Kyokuto Pharmaceutical Co.). Depending on the results of Gram staining, a DHL (Deoxycholate Hydrogen sulfide Lactose) agar plate (Kyokuto Pharmaceutical Co., Tokyo, Japan) and sheep blood plate (Nissui Pharmaceutical Co., Ltd., Tokyo) were added to the culture. Enterococci cultured on blood agar plates were identified by the MicroScan WalkAway 40 plus System (Beckman Coulter Japan, Tokyo, Japan) until November 6, 2016, and, thereafter, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry on a MALDI Biotyper (Bruker Daltonics Co. Ltd., Billerica, MA, USA). Susceptibility testing was performed using the MicroScan WalkAway 40 plus System until October 14, 2018; thereafter, the DxM 1096 Microscan WalkAway (Beckman Coulter Inc., Carlsbad, CA, USA). The interpretive criteria used to determine antibiotic susceptibility were in accordance with the CLSI’s susceptibility testing standards for enterococci, document M100-S22 (2012) [15 ]. M100-S22(2012) has not changed breakpoints with ampicillin and vancomycin by the current M100-Ed33(2023) [16 ].

Protocols for obtaining bacterial isolates collected for infection diagnosis were approved by the MEE Institutional Review Board (IRB). Since this study only included discarded bacterial isolates that were frozen in our pathogen repository, written informed consent was waived by the MEE IRB. In total, 68 consecutive MRSA isolates recovered from January 2014 to June 2016 were analyzed for this study. For patients from whom multiple isolates from the same eye were obtained for infection diagnosis within a period of 6 months, only the first isolate was included. Specimens were obtained by the attending ophthalmologist or resident physician following institutional guidelines and submitted to the clinical laboratory for processing. Suspected S. aureus colonies were routinely identified using a combination of phenotypic methods including detection of coagulase and protein A by latex agglutination, followed by confirmation of species and antimicrobial susceptibility testing using the MicroScan Walkaway 40 Plus System (Beckman Coulter, Brea, CA). Isolates were stored at −80°C in Microbank™ cryopreservative tubes (ProLab Diagnostics). Frozen isolates were cultured twice on blood agar before further testing.

This study was approved by the Massachusetts Eye and Ear Institutional Review Board. In total, 262 S. aureus isolates were included in this study (Table 1). Sinus samples reflect swabs of sinus secretions identified on endoscopic examination, or sinus puncture in some cases. Purulent discharges from otitis cases were collected with a sterile swab and in some cases middle ear fluids were collected via tympanocentesis. Ocular samples were obtained via corneal scraping, conjunctival swabbing, or aqueous/vitreous aspirate. Suppurative collections from infected soft tissues of the orbit (orbital cellulitis) were collected with a sterile swab. Patient specimens were cultured on Blood Agar (sheep’s blood, 5%, Remel), Chocolate Agar (Remel), and MacConkey Agar (Remel) at 37°C. Suspected S. aureus colonies were routinely identified using a combination of phenotypic methods including detection of coagulase and protein A by latex agglutination, followed by confirmation of species and antimicrobial susceptibility testing using the MicroScan Walkaway 40 Plus System (Beckman Coulter, Brea, CA). Isolates were stored at -80°C in Microbank cryopreservative tubes (ProLab Diagnostics). Frozen isolates were cultured twice on blood agar before further molecular analysis.