Search

Proteus mirabilis isolates commonly have decreased susceptibility to imipenem. Previously, we found P. mirabilis hfq mutant was more resistant to imipenem and an outer membrane protein (OMP) could be involved. Therefore, we investigated the role of this OMP in carbapenem susceptibility. By SDS-PAGE we found this OMP (named ImpR) was increased in hfq mutant and LC-MS/MS revealed it to be the homologue of Salmonella YbfM, which is a porin for chitobiose and subject to MicM (a small RNA) regulation. We demonstrated that ImpR overexpression resulted in increased carbapenem MICs in the laboratory strain and clinical isolates. Chitobiose induced expression of chb (a chitobiose utilization operon). Real-time RT-PCR and SDS-PAGE were performed to elucidate the relationship of hfq, impR, chb and MicM in P. mirabilis. We found MicM RNA was decreased in hfq mutant and chbBC-intergenic region (chbBC-IGR) overexpression strain (chbIGRov), while impR mRNA was increased in hfq mutant, micM mutant and chbIGRov strain. In addition, mutation of hfq or micM and overexpression of chbBC-IGR increased ImpR protein level. Accordingly, chitobiose made wild-type have higher levels of ImpR protein and are more resistant to carbapenems. Hfq- and MicM-complemented strains restored wild-type MICs. Mutation of both impR and hfq eliminated the increase in carbapenem MICs observed in hfq mutant and ImpR-complementation of hfq/impR double mutant resulted in MICs as hfq mutant, indicating that the ImpR-dependent decreased carbapenem susceptibility of hfq mutant. These indicate MicM was antisense to impR mRNA and was negatively-regulated by chbBC-IGR. Together, overexpression of ImpR contributed to the decreased carbapenem susceptibility in P. mirabilis. [ABSTRACT FROM AUTHOR]

Abstract: Cell adhesion to synthetic biomaterials is a prerequisite for anchorage cell culture and tissue engineering. The current study investigated utilization of an avidin–biotin binding system in enhancing chondrocyte adhesion to tissue culture polystyrene (TCPS). Biotinylated chondrocytes adhered to avidin-coated TCPS more quickly than untreated chondrocytes to bare TCPS. Also the avidin–biotin binding system enhanced cell initial spreading. However, the effects were only transient. The growth of biotinylated chondrocytes was first decreased during the first 3 days but increased afterwards. The progeny of biotinylated chondrocytes still maintained the ability in expressing cartilage extracellular matrix proteins such as type II collagen, type IX collagen and aggrecan. These results show potential for the application of the avidin–biotin binding system to cell culture and tissue engineering. [Copyright &y& Elsevier]