A repeat sequence causes competition of ColE1-type plasmids

High Prevalence of Plasmid-Mediated Quinolone Resistance among ESBL/AmpC-Producing Enterobacterales from Free-Living Birds in Poland

In this study, we investigated the occurrence of plasmid-mediated quinolone resistance (PMQR) in extended-spectrum β-lactamase- (ESBL) and/or AmpC-type β-lactamase-producing Enterobacterales isolates from free-living birds in Poland. The prevalence of the qnrB19 gene was 63%, and the distribution of isolates in terms of bacterial species was as follows: 67% (22/33) corresponded to Escherichia coli, 83% (5/6) to Rahnella aquatilis, 44% (4/9) to Enterobacter cloacae and 33% (1/3) to Klebsiella pneumoniae. The qnrB19 gene was also found in a single isolate of Citrobacter freundii. The molecular characteristics of qnrB19-positive isolates pointed to extended-spectrum beta lactamase CTX-M as the most prevalent one (89%) followed by TEM (47%), AmpC (37%) and SHV (16%). This study demonstrates the widespread occurrence of PMQR-positive and ESBL/AmpC-producing Enterobacterales isolates in fecal samples from wild birds. In this work, plasmid pAM1 isolated from Escherichia coli strain SN25556 was completely sequenced. This plasmid is 3191 nucleotides long and carries the qnrB19 gene, which mediates decreased susceptibility to quinolones. It shares extensive homology with other previously described small qnrB19-harboring plasmids. The nucleotide sequence of pAM1 showed a variable region flanked by an oriT locus and a Xer recombination site. The presence of a putative recombination site was detected, suggesting that interplasmid recombination events might have played a role in the development of pAM1. Our results highlight the broad geographical spread of ColE-type Qnr resistance plasmids in clinical and environmental isolates of Enterobacterales. As expected from the results of phenotypic susceptibility testing, no resistance genes other than qnrB19 were identified.

Nucleotide binding domain and leucine-rich repeat pyrin domain-containing protein 12: characterization of its binding to hematopoietic cell kinase

Protein-protein interactions are key to define the function of nucleotide binding domain (NBD) and leucine-rich repeat (LRR) family, pyrin domain (PYD)-containing protein 12 (NLRP12). cDNA encoding the human PYD + NBD of NLRP12 was used as bait in a yeast two-hybrid screen with a human leukocyte cDNA library as prey. Hematopoiesis cell kinase (HCK), a member of the c-SRC family of non-receptor tyrosine kinases, was among the top hits. The C-terminal 40 amino acids of HCK selectively bound to NLRP12's PYD + NBD, but not to that of NLRP3 and NLRP8. Amino acids F503, I506, Q507, L510, and D511 of HCK are critical for the binding of HCK's C-terminal 40 amino acids to NLRP12's PYD + NBD. Additionally, the C-terminal 30 amino acids of HCK are sufficient to bind to NLRP12's PYD + NBD, but not to its PYD alone nor to its NBD alone. In cell lines that express HCK endogenously, it was co- immunoprecipitated with stably expressed exogenous NLRP12. Also, NLRP12 co-immunoprecipitated and co-localized with HCK when both were overexpressed in 293T cells. In addition, in this overexpression system, steady-state NLRP12 protein expression levels significantly decreased when HCK was co-expressed. Bioinformatic analysis showed that HCK mRNA co-occurred with NLRP12 mRNA, but not with other NLRP mRNAs, in blood and marrow samples from acute myeloid leukemia (AML) patients. The mRNA of NLRP12 is also co-expressed with HCK in AML patient samples, and the levels of mRNA expression of each are correlated. Together these data suggest that NLRP12, through its binding to HCK, may have an effect on the pathogenesis of AML.

Sequence analysis and characterization of plasmid pLK39 isolated from endophytic Salmonella sp. isolated from Solanum lycocarpum

The complete nucleotide sequence of a small cryptic plasmid pLK39 isolated from endophytic Salmonella sp. was determined. This plasmid is 4,029 bp long with an overall GC content of 55.4 %. Sequence analyses of pLK39 revealed extensive homology to several plasmids: pRK10, pK, pSW200, pBERT, pST728/06-2, pSW100, pEC3, and pUCD5000. Using the ORF Finder program, 35 putative ORFs was identified, 30 showed more than 35 residues. After performing a search for homologous sequences to the pLK39 at BLASTn software on NCBI, it was ascertained that the plasmid has a ColE1-like replication origin and also a region of mobilization proteins from relaxase family (mobCABD). Besides these mobilization proteins, the pLK39 codes a putative DUF903 protein family, which is characterized as assumed external cytoplasmic membrane lipoprotein. A recombinant form of pLK39 carrying a kanamycin resistance gene is stably maintained in Escherichia coli cells grown in the absence of selection pressure. pLK39 was compatible with pUC18, pBR322, and pACYC184.