Several Species Of Enterobacteriaceae Research Articles

Quantification of Colibactin-associated Genotoxicity in HeLa Cells by In Cell Western (ICW) Using γ-H2AX as a Marker.

The genotoxin colibactin is produced by several species of Enterobacteriaceae. This genotoxin induces DNA damage, cell cycle arrest, senescence and death in eukaryotic cells ( Nougayrède et al., 2006 ; Taieb et al., 2016 ). Here we describe a method to quantify the genotoxicity of bacteria producing colibactin following a short infection of cultured mammalian cells with colibactin producing E. coli.

The dualistic nature of integrative and conjugative elements.

Integrative and conjugative elements (ICEs) are mobile genetic elements that play a key role in bacterial adaptation. Such elements are found in almost every bacterial genera and species, and often code for adaptive traits conferring selective advantages to their host. ICEs maintain by integrating into and replicating along with a replicon of the host genome. ICEs can propagate by conjugative transfer toward a recipient cell following excision from the replicon as a circular covalently-closed molecule. For a long time, the excised form of ICEs was assumed to be non-replicative. This assumption predicts that excised ICEs are sensitive to loss during cell division, unless they carry stabilization systems such as addiction modules or antibiotic resistance genes. Over the past few years, growing evidence have been presented that support conditional replication of the circular intermediate as an intrinsic feature of ICEs. We recently confirmed this feature in the large family of SXT/R391 ICEs, which thrive in several species of Enterobacteriaceae and Vibrionaceae. Furthermore, we demonstrated that SXT/R391 ICEs encode a functional plasmid-like type II partition system that enhances their stability, such systems being probably encoded by other ICEs. The lifecycle of ICEs is therefore much more complex than initially thought as many ICEs may use plasmid-like features to improve their stability and dissemination.

Genetic determinants of heat resistance in Escherichia coli.

Escherichia coli AW1.7 is a heat resistant food isolate and the occurrence of pathogenic strains with comparable heat resistance may pose a risk to food safety. To identify the genetic determinants of heat resistance, 29 strains of E. coli that differed in their of heat resistance were analyzed by comparative genomics. Strains were classified as highly heat resistant strains, exhibiting a D60-value of more than 6 min; moderately heat resistant strains, exhibiting a D60-value of more than 1 min; or as heat sensitive. A ~14 kb genomic island containing 16 predicted open reading frames encoding putative heat shock proteins and proteases was identified only in highly heat resistant strains. The genomic island was termed the locus of heat resistance (LHR). This putative operon is flanked by mobile elements and possesses >99% sequence identity to genomic islands contributing to heat resistance in Cronobacter sakazakii and Klebsiella pneumoniae. An additional 41 LHR sequences with >87% sequence identity were identified in 11 different species of β- and γ-proteobacteria. Cloning of the full length LHR conferred high heat resistance to the heat sensitive E. coli AW1.7ΔpHR1 and DH5α. The presence of the LHR correlates perfectly to heat resistance in several species of Enterobacteriaceae and occurs at a frequency of 2% of all E. coli genomes, including pathogenic strains. This study suggests the LHR has been laterally exchanged among the β- and γ-proteobacteria and is a reliable indicator of high heat resistance in E. coli.

Microbial contamination and biofilms on machines of metal industry using metalworking fluids with or without biocides

Microbial contamination is commonly found in metalworking fluids (MWFs) used in metal manufacturing industry. The aim of this study was to determine whether the use of MWF containing a biocide reduces the growth and influences the biofilm-forming capacity of microorganisms from field coolants, thereby efficiently protecting MWFs from biodeterioration. Overall, 164 bacterial strains classified into 40 species were collected from 69 machines in ten plants visited. Among them, Comamonas testosteroni was the most numerous species, and Pseudomonas was the most abundant genus. The isolation of Mycobacterium immunogenum was done from MWF for the first time in Poland. The number of bacteria in MWFs and size of microbial populations in biofilms were not affected by the presence of biocides in the industrial samples. In MWFs contaminated with microorganisms with the highest biofilm-forming capacity, several species of Enterobacteriaceae were identified. The proper management of MWF delivery systems is required to control biofilm development even when MWFs containing biocides are used. Moreover, good hygiene practices are needed to prevent the metal working machines from biofilms. This case study can help in appropriate monitoring the MWF distribution systems vulnerable to microbial colonization in metal industry.

Plant growth promoting rhizobacteria (PGPR) and their effect on maize

Free-living soil bacteria beneficial to plant growth are usually referred to as plant growth promoting rhizobacteria (PGPR), capable of promoting plant growth by colonizing the plant root. Application of PGPR to increase the yield is limited by variability among the results obtained in the laboratory, in greenhouse and field. Rhizobacteria that promote plant growth (PGPR) participate in interactions with plants (rice, wheat, maize, sugarcane, sugar beet, cotton) and significantly increase their vegetative growth and yield. Apart from Azotobacter and Azospirillum, PGPR also include Acetobacter, Azoarcus and several species of Enterobacteriaceae (Klebsiella, Enterobacter, Citrobacter, and Pseudomonas). PGPR represent an alternative to plant growth enhancement chemicals.

Detection of XerC and XerD recombinases in gram-negative bacteria of the family Enterobacteriaceae

XerC and XerD are site-specific recombinases of the lambda integrase family which resolve multimeric replicons to monomers by acting at specific sites such as cer, ckr, nmr, parB, and psi, which are found in plasmids, or at the dif site found in the Escherichia coli chromosome. By using Southern hybridizations to cloned E. coli xerC and xerD genes and a cer-nmr plasmid-based resolution assay, the presence of these genes in several species of Enterobacteriaceae is shown.

Interspecies compatibility of selenoprotein biosynthesis in Enterobacteriaceae

Several species of Enterobacteriaceae were investigated for their ability to synthesize selenium-containing macromolecules. Seleniated tRNA species as well as seleniated polypeptides were formed by all organisms tested. Two selenopolypeptides could be identified in most of the organisms which correspond to the 80 kDa and 110 kDa subunits of the anaerobically induced formate dehydrogenase isoenzymes of E. coli. In those organisms possessing both isoenzymes, their synthesis was induced in a mutually exclusive manner dependent upon whether nitrate was present during anaerobic growth. The similarity of the 80 kDa selenopolypeptide among the different species was assessed by immunological and genetic analyses. Antibodies raised against the 80 kDa selenopolypeptide from E. coli cross-reacted with an 80 kDa polypeptide in those organisms which exhibited fermentative formate dehydrogenase activity. These organisms also contained genes which hybridised with the fdhF gene from E. coli. In an attempt to identify the signals responsible for incorporation of selenium into the selenopolypeptides in these organisms we cloned a portion of the fdhF gene homologue from Enterobacter aerogenes. The nucleotide sequence of the cloned 723 bp fragment was determined and it was shown to contain an in-frame TGA (stop) codon at the position corresponding to that present in the E. coli gene. This fragment was able to direct incorporation of selenocysteine when expressed in the heterologous host, E. coli. Moreover, the E. coli fdhF gene was expressed in Salmonella typhimurium, Serratia marcescens and Proteus mirabilis, indicating a high degree of conservation of the seleniating system throughout the enterobacteria.

Ceforanide. A review of its antibacterial activity, pharmacokinetic properties and clinical efficacy.

Ceforanide is a 'second generation' cephalosporin administered intravenously or intramuscularly. It is similar to cefamandole and cefonicid in its in vitro superiority to 'first generation' cephalosporins against several species of Enterobacteriaceae as well as its activity against Haemophilus influenzae, including beta-lactamase-producing strains. Its activity against Staphylococcus aureus is less than that of cefamandole, cefuroxime and first generation cephalosporins. The in vitro activity against Neisseria gonorrhoeae is excellent. Pseudomonas, Acinetobacter and Serratia species, and Bacteroides fragilis are resistant, as are many strains of Proteus and Providencia species. The elimination half-life is relatively long, although shorter than that of cefonicid, and in most clinical trials ceforanide has been administered twice daily. It appeared to be comparable in therapeutic efficacy to procaine penicillin and cephazolin in the treatment of patients with community-acquired pneumonia, to cephazolin in the treatment of skin and soft tissue infections due to S. aureus or beta-haemolytic streptococci and to cefapirin in S. aureus endocarditis in parenteral drug abusers. Also, it was comparable in efficacy to cephalothin in the prophylaxis of infection in patients undergoing open heart surgery or vaginal hysterectomy, and to cephazolin in patients undergoing cholecystectomy. Thus, ceforanide is an alternative to first and certain other second generation cephalosporins in several important therapeutic and prophylactic situations. It has no advantage over other cephalosporins with regard to spectrum of antibacterial activity, but has a longer half-life than other second generation cephalosporins, except cefonicid, and can be administered according to a twice daily dosage schedule.

Trimethoprim resistance in multiple genera of Enterobacteriaceae at a U.S. hospital: spread of the type II dihydrofolate reductase gene by a single plasmid.

The percentage of clinical isolates of several species of Enterobacteriaceae, particularly Escherichia coli and Klebsiella pneumoniae, resistant to trimethoprim (TMPR) has increased gradually at the Brigham and Women's Hospital (Boston) in recent years. Thirty-seven of 42 TMPR isolates from six species of gram-negative bacilli conjugally transferred TMP resistance to K12 E. coli. beta-Lactam resistance cotransferred from 21 of the 37 donors, and sulfamethoxazole (SMZ) resistance cotransferred from five of the 37 donors. Plasmids that encoded TMP resistance either alone or with SMZ resistance had a molecular size of approximately 52.5 kilobases, with identical restriction endonuclease-generated "fingerprints." Plasmids encoding beta-lactam-mediated resistance (beta R) were approximately four kilobases larger and had fragment patterns that were identical for all of the TMPR/beta R plasmids tested and had many restriction endonuclease-generated bands in common with TMPR plasmids. Radiolabeled dihydrofolate reductase (DHFR) probes identified the type II DHFR as the determinant of TMP resistance. In contrast with reports from Europe, TMP resistance in multiple species of Enterobacteriaceae was found to be spread in one hospital by a single, stable conjugative plasmid that has a wide host range and encodes the type II DHFR gene.

Differential production of acid by Enterobacteriaceae in OF media and in fermentation broth.

Several species of Enterobacteriaceae were checked for acid formation from some carbohydrates or alcohols in OF medium [OF Basal Medium, Baltimore Biological Laboratories] and in a traditional "fermentation broth". After selection of those species that formed acid only oxidatively or fermentatively in OF, it was found that acid formation in the fermentation broth could reflect fermentation or oxidation, but that it was not necessarily related to either. In oxidative species, it occurred less frequently than oxidation in OF and was usually delayed. Fermentative species (in OF) either yielded acid in fermentation broth or did not, depending on the species. Thus, OF media cannot be substituted for traditional broths, although they may be of value in differentiating certain species.