A polymorphism in a variable region of the agr locus comprises nucleotide sequences encoding AgrD, the C-terminal two-thirds of AgrB, and a portion of the N-terminal half of AgrC, which has led to the assignation of S. aureus isolates into four classes [2, 5]. In addition to the agr polymorphism, mutations of wild-type S. aureus click here strains resulting in agr deletions alter exoprotein biosynthesis [6]. However, the relationship between the agr polymorphism and TSST-1 production is unknown. We previously Foretinib concentration analyzed images from two-dimensional electrophoresis (2-DE) and found that two clinical methicillin-resistant S. aureus (MRSA)

isolates produce relatively large amounts of superantigenic exotoxins [7]. Since the amount of toxins produced is probably directly related to the virulence of S. aureus, evaluating the concentration of toxins produced by each strain might be useful for controlling infection. The aim of this study was to determine whether TSST-1 production varies among clinical

MRSA strains and whether it is related to variations in agr class and structure. Results Detection of the tst gene and agr classes We detected the tst gene in 115 (75.7%) of 152 strains after PCR CYC202 molecular weight amplification. Among them, 53 of 66 strains from the nation-wide collection (80.3%) and 62 isolated from 86 blood samples (72.0%) harbored the gene. We identified 147 of 152 isolates (96.7%) as agr class 2, and 3 isolates as agr class 1 (1.9%). We did not identify any isolates of agr classes 3 or 4. The classes of 2 strains were unidentifiable. Among 112 tst-positive strains, 111 belonged to agr class 2. These results indicated the clonal dissemination of a specific group of tst-positive and agr class 2 MRSA in Branched chain aminotransferase Japanese hospitals. Evaluation of TSST-1 production We measured the amount of TSST-1 produced in 34 randomly selected strains. The densities of the bands detected by Western blotting correlated in a semi-log manner with the amount of rTSST-1 produced. The amounts of TSST-1 secreted

into culture supernatants evaluated by comparison with the standard curve ranged from 0.8 to 14.0 μg/ml. Thus, the amount of TSST-1 produced varied 170-fold among clinical MRSA isolates that were cultured under the same conditions. Sequencing of the agr operon To determine how the structure of the agr locus influences the amount of TSST-1 secretion, we sequenced this region in strains 1, 2, 3, 7, 8, 9, 10, 11 and 16, which generated a TSST-1 concentration range of 0.8 to 14.0 μg/ml (Table 1). Table 1 Production of TSST-1 evaluated by Western blotting. No. Strain μg/ml No. Strain μg/ml 1 N315 3.5 ± 0.22 18 2680 1.4 ± 0.19 2 A36 14 ± 1.01 19 2681 1.3 ± 0.05 3 3429 5 ± 0.12 20 2682 1.0 ± 0.25 4 3472 1.3 ± 0.31 21 2683 1.0 ± 0.01 5 3337 1.1 ± 0.20 22 2684 0.8 ± 0.02 6 1785 1.2 ± 0.02 23 2685 1.6 ± 0.23 7 2271 2.0 ± 0.