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At least 685 records · Page 38Linked to original sources
PubMed1988

Rapid antibiotic susceptibility tests on Enterobacteriaceae by ATP bioluminescence.

The susceptibility of 76 clinical isolates of Enterobacteriaceae to ampicillin, piperacillin and gentamicin was assessed by ATP bioluminescence in a 4-h test. For most organisms tested (Escherichia, Klebsiella, Enterobacter and Serratia), there was good correlation with traditional MIC values estimated on 18-h cultures. However strains of Proteus mirabilis showed false resistance to the beta-lactam agents with the ATP method; and concordance was achieved only after manipulation of the growth conditions. Our method is simpler than those described previously, though currently it is still labour-intensive and expensive.

Adenosine Triphosphate↗
PubMed1998

Analysis of neomycin, kanamycin, tobramycin and amikacin resistance mechanisms in gentamicin-resistant isolates of Enterobacteriaceae.

Twenty-four gentamicin-resistant isolates of Enterobacteriaceae, obtained from the clinical laboratories of three health centres in Nablus, Palestine, were tested for susceptibility to neomycin, kanamycin, tobramycin and amikacin. Resistance rates were 29.2% for neomycin, 58.3% for kanamycin, 45.8% for tobramycin and 8.3% for amikacin. Fourteen (58.3%) isolates were noted to be multiresistant, i.e., resistant to gentamicin and two or more other aminoglycosides; resistance to gentamicin, kanamycin and tobramycin was the most common pattern of multiple resistance. This pattern implies the involvement of adenyltransferase ANT(")-I activity. Plasmid profiles and curing experiments suggested a plasmid localisation of gentamicin, neomycin, kanamycin and tobramycin resistance genes. However, a chromosomal location is proposed for plasmid-deficient strains. Cross-resistance in two isolates to all aminoglycosides tested suggested membrane impermeability to aminoglycosides as the mechanism of resistance.

Amikacin↗
PubMed1999

Cross-reactivity between six Enterobacteriaceae complete lipopolysaccharide core chemotypes.

To gain insight into the value of lipopolysaccharide (LPS) core determinants for cross-protective immunisation the serological relationships between six complete (LPS) core types from Enterobacteriaceae were investigated. Hyperimmune sera were raised in mice by repeated immunisation with heat-killed strains of Salmonella choleraesuis (Ra core type) or Escherichia coli (core types R1, R2, R3, R4 and K12) and characterised for reactivity with complete and incomplete core chemotypes by ELISA and immunoblotting. Three sera (anti-Ra, anti-R2 and anti-R3) reacted strongly with 3-5 different complete core types whereas the other three (anti-R1, anti-R4 and anti-K12) reacted strongly only with their homologous core types in these assays. Two approaches were used to examine further the structural bases for cross-reactivity between these cores. By the first approach the anti-complete-core sera were tested for cross-reactivity with truncated forms of the Salmonella species core (incomplete cores) derived from core-defective mutants. By the second approach, antisera raised against some core-defective mutants were tested for cross-reactivity with complete cores. The results of these investigations revealed that several pair-wise combinations of core types can be used as immunogens to elicit immune responses that recognise all six core types and that the major determinants which mediate cross-reactivity between complete cores are localised in the outer core region.

Animals↗
PubMed1996

The Bacillus subtilis genes for ribonucleotide reductase are similar to the genes for the second class I NrdE/NrdF enzymes of Enterobacteriaceae.

We have cloned and sequenced the nrd (nucleotide reductase) locus of Bacillus subtilis. The locus seems to be organized in an operon comprising four ORFs. The first three encode polypeptides highly similar to the product of the coding sequences characterizing the nrdEF operons of Enterobacteriaceae. The sequencing of the conditional lethal mutation ts-A13, localized in the nrdE cistron, and the lethality of insertional mutations targeted in the internal region of nrdE and nrdF, demonstrated the essential role of this locus. The fourth ORF, ymaB, part of the putative operon, which is not similar to any known protein, is also essential. The regulation of expression of the operon, monitored by lacZ transcriptional fusions, is similar to the regulation of the functionally relevant nrdAB operon of Escherichia coli. The operon was induced by thymidine starvation and its expression was directly or indirectly affected by RecA function. Genetic and functional analysis strongly indicates that in B. subtilis the class I ribonucleotide reductase encoded by this nrd operon is evolutionarily distant from the homologous class I enzyme of Enterobacteria.

Amino Acid Sequence↗
PubMed2026

Prevalence and Genomic Characterization of mcr-Positive Enterobacteriaceae in Retail Meat in Thailand Following the Colistin Ban.

This study aimed to investigate the prevalence and characteristics of mcr-positive Enterobacteriaceae in retail meat in Thailand following the national ban on prophylactic colistin use in food producing animals. A total of 152 meat samples (103 chicken and 49 pork) were collected from supermarkets and open markets between July and September 2023. Samples were screened for mcr-1 to mcr-5 using multiplex PCR. None of the samples from supermarkets tested positive, whereas mcr genes were detected in 15.4% (6/39) and 13.3% (4/30) of chicken and pork samples, respectively, from open markets, with mcr-1 and/or mcr-3 identified. A total of 21 isolates were recovered from PCR-positive samples (11 from chicken and 10 from pork). Escherichia coli was the predominant species (n = 19), followed by Klebsiella pneumoniae (n = 2). All mcr-positive isolates exhibited multidrug resistance. Whole-genome sequencing was performed for 19 non-clonal isolates. One K. pneumoniae strain from a pork sample co-harbored mcr-1 and mcr-8, representing the first report of this combination in the animal sector in Thailand. In addition, virulence-associated genes, including adhesion factors, toxins, and iron acquisition systems, were identified in selected isolates. Core genome SNP-based phylogenetic analysis revealed substantial genomic diversity among the isolates, suggesting relatedness to strains reported prior to the colistin ban. These findings indicate that retail meat from open markets may serve as an important route for the transmission of mcr-positive bacteria in Thailand and highlight the urgent need to incorporate systematic retail meat surveillance into national antimicrobial resistance monitoring programs.

Animals↗
PubMed1995

Mycetome endosymbionts of tsetse flies constitute a distinct lineage related to Enterobacteriaceae.

Tsetse flies (Diptera: Glossinidae) harbour two morphologically different endosymbionts intracellularly associated with gut tissue: a primary (P) and a secondary (S) organism. The P-endosymbiont is a gram-negative rod, 8-10 microns in size, and resides intracellularly within specialized cells, mycetocytes which are organized into an organelle (mycetome), in the anterior portion of the gut. The S-endosymbiont is a smaller (1-2 microns) gram-negative rod and is harboured in the epithelial sheath cells in midgut. Phylogenetic characterization of S-endosymbionts from taxonomically distant insects including tsetse flies has shown that they are related to the free-living bacterium, Escherichia coli, and are members of the family Enterobacteriaceae within the gamma-3 subdivision of Proteobacteria. In this study, a polymerase chain reaction (PCR) based assay was designed utilizing the conserved sequences of 16S rDNA in order to phylogenetically characterize the mycetome-associated P-endosymbionts directly from tsetse mycetome tissue. Analysis from five species of flies representing the three major subgenera of genus Glossina indicates that P-endosymbionts constitute a distinct lineage within the gamma-3 subdivision of Proteobacteria. Mycetome endosymbiont phylogeny appears to parallel the classic taxonomic assignments independently developed for their insect host species. This suggests an ancient association for this symbiosis, which may have subsequently radiated with time, giving rise to the current species of tsetse flies and their modern-day endosymbionts. Based on endosymbiont phylogeny, the fusca flies constitute the most ancient subgenus, followed by the morsitans and palpalis groups.

Animals↗
PubMed1985

The scope and limitations of four methods for the rapid identification of Enterobacteriaceae in foods.

Four methods for the identification of Enterobacteriaceae in cooked frozen meat have been appraised. Although these methods could be modified to improve efficiency they could be clearly classified into two categories: (i) those that allow identification to genus level and which often cannot discriminate between two genera without the help of additional reactions; (ii) those that allow identification to species level and which only occasionally require additional reactions to differentiate one species from another. A different evaluation criterion was followed for each of these categories. In the first, as methods lead to final identification by means of data furnished by the manufacturer or via a number code which does not indicate probability, reactions were compared with those obtained by classical methods. In the second group, every number code admits three possibilities and indicates a probable biotype for each, thus reducing the risk of faulty interpretation on the part of the operator while also compensating for deficiencies of certain reactions. Evaluation was therefore based on the percentage of correctly identified cases per species. Efficiencies of the main biochemical reactions are also discussed.

Bacteriological Techniques↗
PubMed1986

O-demethylation, dehydroxylation, ring-reduction and cleavage of aromatic substrates by Enterobacteriaceae under anaerobic conditions.

Four fermentative facultative anaerobes, members of the genera Enterobacter and Escherichia, were tested for their ability to transform an aromatic lignin derivative, 3-methoxy-4-hydroxy-cinnamic acid (ferulic acid), under anaerobic (fermentative) conditions. The pure cultures studied were shown to O-demethylate, dehydroxylate, reduce the double bond in the side-chain, decarboxylate the aromatic ring to the stage of benzoate and to reduce the ring to an alicyclic acid. Aromatic hydrocarbons (toluene, ethylbenzene and propylbenzene), as well as phenols (phenol, o-cresol, p-cresol, 2-ethylphenol and 3-hydroxy-4-ethylphenol) were also produced. In addition, during 3 months incubation, the cleavage of the aromatic ring occurred, whereby a small fraction of the substrate was converted to straight-chain and branched (methylated, ethylated) five- to eight-carbon aliphatic acids. The results indicate that pure cultures of fermentative facultative anaerobes might be capable of degrading substituted aromatic acids to aliphatic products under strictly anaerobic (fermentative) conditions. These abilities, which have so far been found only in denitrifying pseudomonads among facultative anaerobes, might be common in Enterobacteriaceae. It is conceivable that these bacteria are important as degraders of aromatic compounds in anaerobic ecosystems.

Anaerobiosis↗
PubMed1986

Differences in adhesiveness among type 1 fimbriate strains of Enterobacteriaceae revealed by an in vitro HEp2 cell adhesion model.

Ten type 1 fimbriate strains of Enterobacteriaceae were examined in an in vitro adhesion assay with HEp2 epithelial cells. The range of HEp2 cell adhesiveness, which was characteristic for each strain, was affected by motility, type 1 fimbriation and production of mannose sensitive haemagglutinin. Nevertheless, not all type 1 fimbriate strains adhered well in this model. The findings are discussed with regard to the possibility that different type 1 fimbriate enterobacteria, though all are mannose sensitive, recognize different mannose-containing receptors present or available on the surfaces of the HEp2 cells.

Bacterial Adhesion↗
PubMed1988

Identification of Enterobacteriaceae with the Minitek system.

A total of 417 strains (361 Enterobacteriaceae, 56 Vibrionaceae) was examined in all the available Minitek system tests. The results were processed through four successive identification schemes devised by the manufacturer and the proportion of strains correctly identified, not identified or incorrectly identified determined for each scheme. From the results, a probability matrix was constructed incorporating all 35 Minitek tests. Test results for each strain were then processed through this matrix to determine its success in identification. From the matrix the order of separating value of the tests was determined. Forty-three of the strains were each tested three times to assess the level of test reproducibility; the corrected error rate was 0.85%.

Bacteriological Techniques↗
PubMed1994

Assessment of the marker value of various components of the coli-aerogenes group of Enterobacteriaceae and of a selection of Enterococcus spp. for the official monitoring of drinking water supplies.

The traditional indicators Escherichia coli (in practice currently, though ecologically inaccurately, represented by 'thermotolerant coliforms' at 44 degrees C) and Enterococcus spp. proved to be suitable for the diagnosis of heavy and frequent faecal pollution observed in potentially dangerous waters, especially those originating from karstic aquifers. On the other hand, natural and treated waters, slightly and inconsistently contaminated, occasionally showed a variable Gram-negative flora, difficult to classify by routine tests. In that case, complete identification of isolates may be necessary to ensure a valid decision on the potability of the supply. At any rate some of the Enterobacteriaceae contained in the 'faecal coliform' group and many other 'coliforms', distinct from E. coli, lack sanitary significance although their presence at certain levels may indicate inadequate disinfection, hiatuses in the integrity of the distribution system or both.

Biomarkers↗
PubMed1996

Biofilm formation by the enterobacteriaceae: a comparison between salmonella enteritidis, Escherichia coli and a nitrogen-fixing strain of Klebsiella pneumoniae.

A simple laboratory reactor, which simulates biofilm formation in pipes, was used to compare biofilm formation by three members of the Enterobacteriaceae, namely, an environmental, nitrogen-fixing strain of Klebsiella pneumoniae, a pathogen, Salmonella enteritidis, and a faecal indicator, Escherichia coli. All three attached to CVCP pipe surfaces in the reactor and formed substantial biofilm populations of over a million bacteria cm-2 within 24 h. These populations increased by approximately 10-fold over the next 48 h. Estimates of the numbers of metabolically active cells and the ratios of viable to direct counts showed that Kl. pneumoniae formed the densest and most metabolically active biofilms, followed by Salm. enteritidis and E. coli, respectively. Nitrogen fixation and polysaccharide production (EPS) by Kl. pneumoniae occurred only in mature biofilms and were of no selective advantage in the initiation of biofilms. Despite producing more EPS the rate of attachment of Salm. enteritidis was lower than for Kl. pneumoniae.

Biofilms↗
PubMed1995

UreR activates transcription at multiple promoters within the plasmid-encoded urease locus of the Enterobacteriaceae.

Urease activity is produced by members of the family Enterobacteriaceae that contain the plasmid-encoded urease locus only when urea is present in the growth medium. The plasmid-encoded urease locus contains seven tandem urease structural and accessory genes (ureDABCEFG). Previously we showed that transcription of the first gene in this cluster, ureD, is initiated at a urea-dependent promoter (ureDp). Expression from ureDp requires the product of ureR, which is transcribed divergently from the plasmid-encoded ureDABCEFG. From DNA sequence analysis, UreR is predicted to be a 34 kDa protein with identity to the AraC family of transcriptional activators. In this report we demonstrate that there are two additional urea and UreR-dependent promoters within the plasmid-encoded urease locus: ureRp and ureGp. A low-level constitutive promoter was also identified upstream of ureE (ureEp). Three major mRNA transcripts were induced when urea was present in the growth medium: a transcript containing ureDABCEF, a transcript corresponding to ureG, and a transcript corresponding to ureR. These results indicate that expression of each of the plasmid-encoded urease genes is transcriptionally regulated in response to urea and suggest that there is autogenous regulation of ureR. Therefore UreR is one of three AraC family members described thus far that are positively auto-regulated.

Blotting, Northern↗
PubMed1990

Prevalence and antimicrobial susceptibility of Enterobacteriaceae, Pseudomonadaceae and Acinetobacter in human periodontitis.

This study examined the occurrence of non-oral gram-negative facultatively anaerobic rods in advanced adult periodontitis. Speciation and in vitro antimicrobial susceptibility testing was performed using the MicroScan micromethod system. A total of 42 taxa of Enterobacteriaceae, Pseudomonadaceae and Acinetobacter were isolated from 427 of 3,050 (14.0%) patients. In 159 (5.2%) patients, these organisms comprised more than 5% of the cultivable subgingival microflora. Enterobacter cloacae, Klebsiella pneumoniae, Pseudomonas aeruginosa, Klebsiella oxytoca and Enterobacter agglomerans accounted for more than 50% of all strains isolated. Virtually all study strains demonstrated high in vitro susceptibility to ciprofloxacin, but exhibited variable susceptibility patterns to 18 other antimicrobial agents tested. In 3 "refractory" periodontitis patients heavily infected with enteric rods, systemic ciprofloxacin therapy (500 mg BiD for 10 days) led to resolution of the subgingival infections and improved clinical periodontal status. The present findings indicate that 5% of severe periodontitis lesions may harbor high levels of non-oral, gram-negative, facultatively anaerobic rods. Systemic ciprofloxacin appears to be capable of eradicating these potential pathogens from deep periodontal pockets.

Acinetobacter↗
PubMed1979

A lipopolysaccharide-binding cell-surface protein from Salmonella minnesota. Isolation, partial characterization and occurrence in different Enterobacteriaceae.

1. Protein extracts obtained from Salmonella minnesota Re mutant cells by treatment with EDTA/NaC1 solution contain a protein which exhibits high affinity to bacterial lipopolysaccharides. The isolation and partial characterization of this lipopolysaccharide-binding protein is described. 2. The protein was purified from EDTA extracts by a two-step procedure consisting of ion-exchange chromatography on CM-Sephadex and preparative polyacrylamide gel electrophoresis at pH 9.5. The yield of the total purification procedure was around 16%. 3. The resulting protein preparation was homogeneous on the basis of disc gel electrophoresis, dodecylsulfate gel electrophoresis, isoelectric focusing in polyacrylamide gel and immunoelectrophoresis. 4. The isoelectric point of the protein was found to be 10.3 at 4 degrees C. Its molecular weight determined by dodecylsulfate gel electrophoresis is 15000. Its amino acid composition is characterized by the absence of histidine and proline, a low content in tyrosine and high amounts of alanine, lysine, aspartic and glutamic acid residues, or their respective amides. 5. The lipopolysaccharide-protein association was shown to be mainly due to ionic interactions of the basic protein with negatively charged groups (probably phosphate and pyrophosphate groups) of the lipid A moiety. 6. Purified lipopolysaccharide-binding protein is immunogenic in rabbits, thus enabling the preparation of specific antiserum. 7. The protein is located at the surface of Salmonella minnesota Re mutant cells as revealed by antiserum absorption with total bacteria. Ferritin-labelling studies further demonstrated that it is evenly spread over the entire cell surface. 8. Comparative antiserum absorption studies using smooth and rough strains of Salmonella minnesota, Salmonella typhimurium, Escherichia coli, Klebsiella and Shigella revealed the presence of lipopolysaccharide-binding protein (or a serologically cross-reacting antigen) in most of the strains tested. From these results the protein can be considered as a common antigen of Enterobacteriaceae.

Amino Acids↗
PubMed1981

Structural studies on the hexose region of the core in lipopolysaccharides from Enterobacteriaceae.

The structures for the hexose regions of cores from Enterobacteriaceae lipopolysaccharides have been investigated, using specific degradations and 1H NMR studies as the principal methods. Complete structures for these regions in the Salmonella, the Escherichia coli R1, R2, R3, R4, the E. coli K12 and E. coli B cores are proposed. Some complementary information on the structure of the heptose region has also been obtained.

Carbohydrate Conformation↗
PubMed1995

Evaluation of the BBL Crystal Enteric/Nonfermenter kit for the identification of water-derived environmental Enterobacteriaceae.

The Crystal Enteric/Nonfermenter (E/NF) identification kit (Becton Dickinson Microbiology Systems, USA) was evaluated using water-derived bacterial isolates and results compared to those obtained by the API 20E system (BioMérieux, UK). Both the E/NF and 20E systems correctly identified 93% of the Enterobacteriaceae reference cultures. Both systems agreed in the identification of 64.9% of environmental isolates. The E/NF system gave a positive identification to 88.0% of isolates and the 20E to 79.5% of isolates. The principal tests which gave differing reactions between the two systems were arginine dihydrolase, lysine decarboxylase, urease and citrate utilization.

Bacterial Typing Techniques↗
PubMed1995

Salmonella enterotoxin (stn) gene is prevalent among strains of Salmonella enterica, but not among Salmonella bongori and other Enterobacteriaceae.

All strains and serovars of Salmonella enterica such as serovar Typhimurium, Enteritidis, Dublin, Typhi, etc. were found to carry the Salmonella enterotoxin determinant stn as far as examined in PCR and hybridization studies. However, using MDCK cells for testing the toxicity of the strains under investigation, only a limited number of stn positive strains revealed phenotypically the Salmonella enterotoxin Stn. In contrast to S. enterica, other Enterobacteriaceae including Salmonella bongori were found neither genotypically nor phenotypically Stn toxin positive.

Base Sequence↗