Vitek 2 compact system

Data on pathogens isolated from patients admitted to the hospital were retrospectively obtained from FAHZU. The isolates were identified by the VITEK 2 compact system (bioMérieux), and antibiotic susceptibility was determined by either the disc diffusion method18 or the VITEK 2 compact system. The results were then interpreted uniformly in accordance with the Clinical and Laboratory Standards Institute criteria.18 To guarantee the reproducibility of testing methodologies, we used E. faecalis ATCC 29212, S. aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, and Escherichia coli ATCC 25922 as reference strains.
The pathogens included in this study were Klebsiella pneumoniae, E. coli, A. baumannii, P. aeruginosa, S. aureus, coagulase-negative Staphylococcus (CNS), E. faecalis, and E. faecium, which were the most frequent isolates in our hospital for the past 10 years. The isolation density for each species was the number of isolates per 10,000 patient-days (10,000-pd). The susceptibility rate of each antibiotic was calculated as the number of susceptible isolates divided by the total isolation number.

Forty-two CRKP isolates were tested for antimicrobial susceptibility by the VitekII Compact system (bioMérieux, Marcy l’Etoile, Lyon, France) and the K-B disk diffusion method, with the results based on the standards of the Clinical and Laboratory Standards Institute (CLSI) 2021-M100.5 Quality control strains were Escherichia coli ATCC25922 and K. pneumoniae ATCC700603 (purchased from China National Health Inspection Center).

STEC strains were isolated and identified according to the guidelines in the Standards for Processing and Ingredients of Specifications Livestock Products in Korea with slight modifications [27 (link)]. Briefly, 434 meat samples were collected from packaged raw beef, pork, and chicken meats from retail markets in Korea during 2006 to 2012. Twenty-five grams of each fresh meat sample was taken aseptically and homogenized with 225 mL of buffered peptone water (Oxoid, UK). For E. coli isolation, 10 mL of the homogenized mixture were blended in 90 mL of Brilliant Green Bile Broth (Oxoid) and incubated at 37℃ for 24 to 48 h. One loop of the enrichment culture was streaked onto Eosin Methylene Blue agar (Oxoid). Plates were examined for typical E. coli colonies after incubation at 37℃ for 18 to 24 h. From each positive sample, typical colonies were transferred onto Tryptone Soy Agar (TSA; BD Diagnostics) and incubated at 37℃ for 18 to 24 h. The resultant colonies were kept at −80℃ as 40% (v/v) glycerol stocks. Each isolate was identified by using the Vitek II Compact system (bioMé rieux, France). In addition, all isolates were confirmed by performing polymerase chain reaction (PCR) with primers specific to E. coli 16S rDNA and stx gene [27 (link)].

Imipenem resistance was analyzed by minimum inhibitory concentration (MIC) method and VITEK‐2 compact system (BioMerieux), ≦1 μg/mL is defined as sensitive and ≧4 μg/mL is defined as resistance based on Clinical and Laboratory Standards Institute (CLSI). Three replicates for every isolate were performed.