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The bone morphogenetic proteins (BMPs) are a group of transforming growth factor ,B (TGF-Pi)-related factors whose only receptor identified to date is the product of the daf-4 gene from Caenorhabditis elegans. Mouse embryonic NIH 3T3 fibroblasts display high-affinity 125I-BMP-4 binding sites. Binding assays are not possible with the isoform 125I-BMP-2 unless the positively charged N-terminal sequence is removed to create a modified BMP-2, 125I-DR-BMP-2. Cross-competition experiments reveal that BMP-2 and BMP-4 interact with the same binding sites. Affinity cross-linking assays show that both BMPs interact with cell surface proteins corresponding in size to the type I (57-to 62-kDa) and type II (75-to 82-kDa) receptor components for TGF-, and activin. Using a PCR approach, we have cloned a cDNA from NIH 3T3 cells which encodes a novel member of the transmembrane serine/threonine kinase family most closely resembling the cloned type I receptors for TGF-,B and activin. Transient expression of this receptor in COS-7 cells leads to an increase in specific 125I-BMP4 binding and the appearance of a major affinity-labeled product of -64 kDa that can be labeled by either tracer. This receptor has been named BRK-1 in recognition of its ability to bind BMP-2 and BMP-4 and its receptor kinase structure. Although BRK-1 does not require cotransfection of a type II receptor in order to bind ligand in COS cells, complex formation between BRK-1 and the BMP type II receptor DAF-4 can be demonstrated when the two receptors are coexpressed, affinity labeled, and immunoprecipitated with antibodies to either receptor subunit. We conclude that BRK-1 is a putative BMP type I receptor capable of interacting with a known type II receptor for BMPs.The transforming growth factor ,B (TGF-,B) superfamily contains a large number of growth, differentiation, and morphogenetic cytokines that are active as homo-or heterodimers.This superfamily includes the TGF-1 family, the activin family, the Mullerian inhibiting substance (MIS), and the bone morphogenetic protein (BMP)/Vg family, which composes the largest group (reviewed in reference 39). Human BMP-2 and BMP-4 and their Drosophila homolog dpp are highly related (74 to 76% sequence identity [72]), as are BMP-5, BMP-6, and BMP-7 and their Drosophila homolog 60A (69 to 73% sequence identity [21]). Given the high degree of structural similarity among these family members, it is expected that their receptors will also form a family of related molecules. activin (2, 40) have been cloned. It has recently been determined that the product of the daf-4 gene from Caenorhabditis elegans, which is involved in both inhibition of dauer larva formation and exit from the dauer stage, is a type II receptor for BMP-2 and BMP-4 (24). Each of these receptors is predicted to be a transmembrane serine/threonine kinase. Ligand binding to each of these type II receptors in a variety of cell types does not appear to require coexpression of additional receptor components, indicating that type II receptors are capable of...

Twenty-one Serratia marcescens, ten Klebsiella pneumoniae, and one Escherichia coli isolate with carbapenem resistance or reduced carbapenem susceptibility were recovered from intensive care units (ICUs) in our hospital. Enterobacterial repetitive intergenic consensus-PCR and pulsed-field gel electrophoresis demonstrated that all the S. marcescens isolates belonged to a clonal strain and the 10 K. pneumoniae isolates were indistinguishable or closely related to each other. The MICs of imipenem, meropenem, and ertapenem for all isolates were 2 to 8 g/ml, except for K. pneumoniae K10 (MICs of 128, 256, and >256 g/ml). Isoelectric focusing, PCRs, and DNA sequencing indicated that all S. marcescens isolates produced KPC-2 and a ␤-lactamase with a pI of 6.5. All K. pneumoniae isolates produced TEM-1, KPC-2, CTX-M-14, and a ␤-lactamase with a pI of 7.3. The E. coli E1 isolate produced KPC-2, CTX-M-15, and a ␤-lactamase with a pI of 7.3. Conjugation studies with E. coli (EC600) resulted in the transfer of reduced carbapenem susceptibility compared to that of the original isolates, and only the bla KPC-2 gene was detected in E. coli transconjugants. Plasmid restriction analysis showed identical restriction patterns among all E. coli transconjugants. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and ompK35/36 gene sequence analysis of outer membrane proteins revealed that K. pneumoniae K10 failed to express OmpK36, because of insertional inactivation by an insertion sequence ISEcp1. All these results indicate that KPC-2-producing S. marcescens, K. pneumoniae, and E. coli isolates emerged in ICUs in our hospital. KPC-2 combined with porin deficiency results in high-level carbapenem resistance in K. pneumoniae. The same bla KPC-2 -encoding plasmid was spread among the three different genera.

b CTX-M-producing Escherichia coli is the predominant type of extended-spectrum ␤-lactamase (ESBL)-producing E. coli worldwide. In this study, molecular typing was conducted for 139 CTX-M-producing E. coli isolates, phenotypically positive for ESBLs, isolated from environmental water, swine, healthy humans, and hospitalized patients in Hangzhou, China. The antibiotic resistance profiles of the isolates for the cephalosporins and fluoroquinolones were determined. The isolates showed 100% resistance to cefotaxime and ceftriaxone while maintaining relatively high susceptibility to cefoxitin, cefepime, and ceftazidime. A total of 61.9% (86/139) of the isolates, regardless of origin, showed high resistance to fluoroquinolones. PCRs and DNA sequencing indicated that bla CTX-M-14 was the most prevalent CTX-M-9 group gene and that bla CTX-M-15 and bla CTX-M-55 were the dominant CTX-M-1 group genes. Isolates from all sources with CTX-M types belonging to the CTX-M-1 or CTX-M-9 group were most frequently associated with epidemics. Molecular homology analysis of the isolates, conducted by phylogenetic grouping, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST), demonstrated that the dominant clones belonged to B2-ST131, D-ST648, D-ST38, or A-CC10. These four sequence types (STs) were discovered in E. coli isolates both from humans and from environmental water, suggesting frequent and continuous intercompartment transmission between humans and the aquatic environment. Seven novel sequence types were identified in the current study. In conclusion, this study is the first to report the molecular homology analysis of CTX-M-producing E. coli isolates collected from water, swine, and healthy and hospitalized humans, suggesting that pathogens in the environment might originate both from humans and from animals.

This study investigated the transmission characteristics of carbapenem-resistant Enterobacteriaceae (CRE) strains collected from a hospital setting in China, in which consistent emergence of CRE strains were observable during the period of May 2013 to February 2014. Among the 45 CRE isolates tested, 21 (47%) strains were found to harbor the blaNDM-1 element, and the rest of 24 CRE strains were all positive for blaKPC-2. The 21 blaNDM-1—borne strains were found to comprise multiple Enterobacteriaceae species including nine Enterobacter cloacae, three Escherichia coli, three Citrobacter freundii, two Klebsiella pneumoniae, two Klebsiella oxytoca, and two Morganella morganii strains, indicating that cross-species transmission of blaNDM-1 is a common event. Genetic analyses by PFGE and MLST showed that, with the exception of E. coli and E. cloacae, strains belonging to the same species were often genetically unrelated. In addition to blaNDM-1, several CRE strains were also found to harbor the blaKPC-2, blaVIM-1, and blaIMP-4 elements. Conjugations experiments confirmed that the majority of carbapenem resistance determinants were transferable. Taken together, our findings suggest that transmission of mobile resistance elements among members of Enterobacteriaceae and clonal spread of CRE strains may contribute synergistically to a rapid increase in the population of CRE in clinical settings, prompting a need to implement more rigorous infection control measures to arrest such vicious transmission cycle in CRE-prevalent areas.