Further studies are needed to investigate the reasons for false positives. We found that the sensitivity of MgEDTA–CAZ is higher than that of MgEDTA–IPM. This makes CAZ preferable to IPM as a substrate in DDSTs. However, one IMP-1-producing A. baumannii and two NDM-1-producing Enterobacteriaceae were positive when IPM was used, but negative when CAZ was used. Kim et al. have reported that, because these organisms have other CAZ resistant mechanisms such as ESBL and AmpC β-lactamase production, DDSTs using CAZ have difficulty detecting MBL-producing Acinetobacter [21]. Therefore, DDSTs using Mg-EDTA should use both IPM and CAZ disks as substrates

in order to further reduce false negative results. False positive results reportedly also occur with MBL phenotypic methods using EDTA and IPM. It is believed that such false positive results are attributable to increasing membrane permeability Omipalisib cell line caused by chelating agents [24, 25] and the anti-bacterial activity of EDTA [19, 24, 25]. DDSTs using Mg-EDTA yielded no false positive results among 25 non-MBL producers. The disk content SP600125 ic50 of Mg-EDTA was 10 mg, this concentration being higher than that of the EDTA was used in previous reports. Because false positive results were confirmed for P. aeruginosa and Acinetobacter spp. by the Etest MBL and combined disk test, DDST using Mg-EDTA should be evaluated for specificity using non-MBL-producing P. aeruginosa or Acinetobacter

spp. In conclusion, this is the first report to evaluate several metal-EDTA complexes as inhibitors of MBL. Use of Mg-EDTA in DDSTs is the most useful Y-27632 2HCl phenotypic method for detecting MBL producers, including NDM-1 producing strains, in clinical laboratories. Because we tested only two NDM-1 producers by the Mg-EDTA DDST method, other NDM-1 producers should be confirmed by subsequent studies in actual clinical practice.

M. Fujisaki and S. Sadamoto are employees of Eiken Chemical. “
“CD1d-restricted invariant natural killer T (iNKT) cells bear characteristics of innate and adaptive lymphocytes, which allow them to bridge the two halves of the immune response and play roles in many disease settings. Recent work has characterized precisely how their activation is initiated and regulated. Novel antigens from important pathogens have been identified, as has an abundant self-antigen, β-glucopyranosylcaramide, capable of mediating an iNKT-cell response. Studies of the iNKT T-cell receptor (TCR)–antigen–CD1d complex show how docking between CD1d–antigen and iNKT TCR is highly conserved, and how small sequence differences in the TCR establish intrinsic variation in iNKT TCR affinity. The sequence of the TCR CDR3β loop determines iNKT TCR affinity for ligand–CD1d, independent of ligand identity. CD1d ligands can promote T helper type 1 (Th1) or Th2 biased cytokine responses, depending on the composition of their lipid tails.