scholarly journals Role of L-Glutamate in the Tolerance of Osmotic Stress by Escherichia coli

1970 ◽  
Vol 25 (1) ◽  
pp. 79-81
Author(s):  
M Shariful Islam ◽  
Sunjukta Ahsan
Keyword(s):  
Escherichia Coli ◽  
Osmotic Stress ◽  
Significant Role ◽  
Cellular Response ◽  
Stress Proteins ◽  
Clinical Isolates ◽  
Chemical Stress ◽  
Nacl Concentration ◽  
Reference Strains

Studies on the cellular response to conditions of physical or chemical stress have played a very significant role in diverse areas of biology. The present investigation aims at determining concentrations of NaCl that are stressful for environmental and clinical strains of Escherichia coli and to investigate the effect of L-glutamate to counteract such stressful conditions. It was observed that growth of environmental, clinical and reference strains could be stressed by a NaCl concentration of 0.9 M. Growth decreased under conditions of stress as opposed to that without added NaCl. Clinical isolates showed much higher resistance than environmental strains to osmotic stress. Glutamate had a significant effect in overcoming osmotic stress under laboratory conditions. This was indicated by increased growth in the presence of glutamate (15 mM) compared to that occurred at 0.9 M NaCl without added glutamate. Distinct protein bands were produced under stressful conditions, which indicate that these proteins might be stress proteins that aid the isolates to counteract osmotic stress. Keywords: Osmotic stress; L-Glutamate; Escherichia coliDOI: http://dx.doi.org/10.3329/bjm.v25i1.4865 Bangladesh J Microbiol, Volume 25, Number 1, June 2008, pp 79-81

scholarly journals Polyamine Transport and Role of potE in Response to Osmotic Stress in Escherichia coli

2000 ◽  
Vol 182 (21) ◽  
pp. 6247-6249 ◽  
Author(s):  
Dirk Schiller ◽  
Daniela Kruse ◽  
Helmut Kneifel ◽  
Reinhard Krämer ◽  
Andreas Burkovski
Keyword(s):  
Escherichia Coli ◽  
Osmotic Stress ◽  
Deletion Mutant ◽  
Transport Processes ◽  
Hyperosmotic Shock ◽  
Physiological Conditions ◽  
Polyamine Transport

ABSTRACT When transport of polyamines in Escherichia coli was examined, putrescine excretion was observed under two different physiological conditions: (i) strictly correlated to growth and (ii) following a hyperosmotic shock. Spermidine was not excreted. Characterization of a deletion mutant showed that PotE is not involved in these transport processes.

scholarly journals Appraisal of the domestic kit «MICMICRO » for antimicrobial susceptibility testing by serial microdilution method

2020 ◽  
pp. 231-236
Author(s):  
Anna A. Samoilova ◽  
L.A. Kraeva ◽  
I.V. Likhachev ◽  
E.V. Rogacheva ◽  
V.N. Verbov ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Quality Control ◽  
Susceptibility Testing ◽  
New Technologies ◽  
Clinical Laboratory ◽  
Clinical Isolates ◽  
Internal Quality ◽  
Diagnostic Efficiency ◽  
Microdilution Method ◽  
Reference Strains

Objective. To assess efficiency of the “MIC-MICRO” kit developed in the Department of New Technologies of the Saint-Petersburg Pasteur Institute, on reference strains and clinical bacterial isolates. Materials and Methods. In order to assess the “MIC-MICRO” kit, several options of its execution were used, including different groups of antibiotics: aztreonam, amikacin, gentamicin, colistin, meropenem, nitrofurantoin, chloramphenicol, cefotaxime, ceftriaxone, ciprofloxacin, erythromycin. In order to determine the range of antibiotic values, the EUCAST-2020 database was used. The quality control of adsorbed antibiotics was carried out using reference strains: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213 and Escherichia coli NCTC 13846 (colistin-resistant). Acceptable and target ranges of MIC values for control strains are evaluated according to “Regular and extended internal quality control for determining MIC and disk diffusion according to EUCAST recommendations” (v10.0). A total of 28 clinical isolates of K. pneumoniae obtained from patients with nosocomial infections in St. Petersburg hospitals in 2018–2019 was used in the study. The coordination of test results was obtained in accordance with GOST R ISO 20776-1-2010. Susceptibility testing results were interpreted in accordance with EUCAST recommendations (v10.0). Results. The MIC values in relation to the reference strains obtained using the “MIC-MICRO” kit were determined in the range of recommended values of the EUCAST-2020 standard. The results obtained in relation to clinical isolates of K. pneumoniae showed that the sensitivity categories determined using the developed kit and the serial microdilution method were the same for all the studied strains. The percentage of colistin-resistant isolates (MIC > 2 mg/ml) in the serial microdilution method and determined using the “MIC-MICRO” kit was 35.7%. The percentage of susceptible strains was also similar for two types of methods (64.3%). Conclusions. Colistin susceptibility testing of K. pneumoniae strains using the “MIC-MICRO” diagnostic kit and the reference serial microdilution method in a tablet, showed comparable results. Diagnostic efficiency, ease to use and simple interpretation of results make it possible to use the developed “MIC-MICRO” kit in clinical laboratory practice.

scholarly journals Mass Spectrometry–Based Escherichia coli H Antigen/Flagella Typing: Validation and Comparison with Traditional Serotyping

2016 ◽  
Vol 62 (6) ◽  
pp. 839-847 ◽  
Author(s):  
Keding Cheng ◽  
Yi-Min She ◽  
Huixia Chui ◽  
Larissa Domish ◽  
Angela Sloan ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Escherichia Coli ◽  
Whole Genome Sequencing ◽  
Genome Sequencing ◽  
Close Correlation ◽  
Clinical Isolates ◽  
Whole Genome ◽  
Sequence Coverage ◽  
E Coli ◽  
Reference Strains

Abstract BACKGROUND Escherichia coli H antigen typing with antisera, a useful method for flagella clinical identification and classification, is a time-consuming process because of the need to induce flagella growth and the occurrence of undetermined strains. We developed an alternative rapid and analytically sensitive mass spectrometry (MS) method, termed MS-based H antigen typing (MS-H), and applied it at the protein sequence level for H antigen typing. We also performed a comparison with traditional serotyping on reference strains and clinical isolates. METHODS On the basis of international guidelines, the analytical selectivity and sensitivity, imprecision, correlation, repeatability, and reproducibility of the MS-H platform was evaluated using reference strains. Comparison of MS-H typing and serotyping was performed using 302 clinical isolates from 5 Canadian provinces, and discrepant results between the 2 platforms were resolved through whole genome sequencing. RESULTS Repeated tests on reference strain EDL933 demonstrated a lower limit of the measuring interval at the subsingle colony (16.97 μg or 1.465 × 107 cells) level and close correlation (r2 > 0.99) between cell culture biomass and sequence coverage. The CV was <10.0% among multiple repeats with 4 reference strains. Intra- and interlaboratory tests demonstrated that the MS-H method was robust and reproducible under various sample preparation and instrumentation conditions. Using discrepancy analysis via whole genome sequencing, performed on isolates with discrepant results, MS-H accurately identified 12.3% more isolates than conventional serotyping. CONCLUSIONS MS-H typing of E. coli is useful for fast and accurate flagella typing and could be very useful during E. coli outbreaks.

Increase and diversity of carbapenemase-producing Escherichia coli isolates, Italy

2019 ◽  
Vol 14 (12) ◽  
pp. 1035-1042 ◽  
Author(s):  
Serena Simoni ◽  
Sara Caucci ◽  
Andrea Brenciani ◽  
Gianluca Morroni ◽  
Eleonora Giovanetti ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Rectal Swab ◽  
Sequence Type ◽  
Clinical Isolates ◽  
Surveillance Period ◽  
Clinical Specimens ◽  
Transfer Data ◽  
Conjugative Plasmids ◽  
Antibiotic Susceptibilities

Aim: This study reports on a surveillance in an Italian hospital focused on carbapenemase-producing Escherichia coli (CP-Ec). Materials & methods: Eighteen isolates (nine from clinical specimens and nine from rectal swab) were characterized for antibiotic susceptibilities, typing features, main carbapenemase, extended-spectrum ß-lactamases (ESBLs) and other bla genes, and their transferability by conjugation and transformation. Results: An increase in CP-Ec isolates was observed during 3-year surveillance period. Compared with the clinical isolates, all belonging to one sequence type (ST), ST131, those from rectal swab were very heterogeneous and belonged to eight STs. Transfer data confirmed the role of conjugative plasmids in the spreading of carbapenemase genes. Conclusion: The prevalence of CP-Ec in Italy has risen, with a substantial increase over the last year.

scholarly journals Role of CD14 in Responses to Clinical Isolates of Escherichia coli: Effects of K1 Capsule Expression

2007 ◽  
Vol 75 (11) ◽  
pp. 5415-5424 ◽  
Author(s):  
Shalaka Metkar ◽  
Shanjana Awasthi ◽  
Erick Denamur ◽  
Kwang Sik Kim ◽  
Sophie C. Gangloff ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Bacterial Infections ◽  
Clinical Isolates ◽  
Necrosis Factor Alpha ◽  
Lethal Effects ◽  
E Coli ◽  
Tnf Α ◽  
Positive Isolate ◽  
K1 Capsule

ABSTRACT Severe bacterial infections leading to sepsis or septic shock can be induced by bacteria that utilize different factors to drive pathogenicity and/or virulence, leading to disease in the host. One major factor expressed by all clinical isolates of gram-negative bacteria is lipopolysaccharide (LPS); a second factor expressed by some Escherichia coli strains is a K1 polysaccharide capsule. To determine the role of the CD14 LPS receptor in the pathogenic effects of naturally occurring E. coli, the responses of CD14−/− and CD14+/+ mice to three different isolates of E. coli obtained from sepsis patients were compared; two isolates express both smooth LPS and the K1 antigen, while the third isolate expresses only LPS and is negative for K1. An additional K1-positive isolate obtained from a newborn with meningitis and a K1-negative isogenic mutant of this strain were also used for these studies. CD14−/− mice were resistant to the lethal effects of the K1-negative isolates. This resistance was accompanied by significantly lower levels of systemic tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) in these mice than in CD14+/+ mice, enhanced clearance of the bacteria, and significantly fewer additional gross symptoms. In contrast, CD14−/− mice were as sensitive as CD14+/+ mice to the lethal effects of the K1-positive isolates, even though they had significantly lower levels of TNF-α and IL-6 than CD14+/+ mice. These studies show that different bacterial isolates can use distinctly different mechanisms to cause disease and suggest that new, nonantibiotic therapeutics need to be directed against multiple targets.

scholarly journals Stability of the Osmoregulated Promoter-DerivedproPmRNA Is Posttranscriptionally Regulated by RNase III in Escherichia coli

2015 ◽  
Vol 197 (7) ◽  
pp. 1297-1305 ◽  
Author(s):  
Boram Lim ◽  
Kangseok Lee
Keyword(s):  
Escherichia Coli ◽  
Osmotic Stress ◽  
Cellular Response ◽  
Rna Binding ◽  
Binding Capacity ◽  
Rnase Iii ◽  
Content Type ◽  
Steady State Levels ◽  
The Stability

ABSTRACTThe enzymatic activity ofEscherichia coliendo-RNase III determines the stability of a subgroup of mRNA species, includingbdm,betT, andproU, whose protein products are associated with the cellular response to osmotic stress. Here, we report that the stability ofproPmRNA, which encodes a transporter of osmoprotectants, is controlled by RNase III in response to osmotic stress. We observed that steady-state levels ofproPmRNA and ProP protein are inversely correlated with cellular RNase III activity and, in turn, affect the proline uptake capacity of the cell.In vitroandin vivoanalyses ofproPmRNA revealed RNase III cleavage sites in a stem-loop within the 5′ untranslated region present only inproPmRNA species synthesized from the osmoregulated P1 promoter. Introduction of nucleotide substitutions in the cleavage site identified inhibited the ribonucleolytic activity of RNase III onproPmRNA, increasing the steady-state levels and half-life of the mRNA. In addition, decreased RNase III activity coincided with a significant increase in both the half-life and abundance ofproPmRNA under hyperosmotic stress conditions. Analysis of the RNA bound to RNase III viain vivocross-linking and immunoprecipitation indicated that this phenomenon is related to the decreased RNA binding capacity of RNase III. Our findings suggest the existence of an RNase III-mediated osmoregulatory network that rapidly balances the expression levels of factors associated with the cellular response to osmotic stress inE. coli.IMPORTANCEOur results demonstrate that RNase III activity onproPmRNA degradation is downregulated inEscherichia colicells under osmotic stress. In addition, we show that the downregulation of RNase III activity is associated with decreased RNA binding capacity of RNase III under hyperosmotic conditions. In particular, our findings demonstrate a link between osmotic stress and RNase III activity, underscoring the growing importance of posttranscriptional regulation in modulating rapid physiological adjustment to environmental changes.

Chlorhexidine reduced susceptibility associated to tetracycline resistance in clinical isolates of Escherichia coli

2021 ◽  
Author(s):  
Guilhem ROYER ◽  
Jose-Manuel Ortiz de la Rosa ◽  
Xavier Vuillemin ◽  
Beatrice Lacombe ◽  
Francoise Chau ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Transport System ◽  
Resistance Mechanisms ◽  
Clinical Isolates ◽  
Cross Resistance ◽  
E Coli ◽  
K 12 ◽  
Phospholipid Transport

Chlorhexidine is a widely used antiseptic in hospital and community healthcare. Decreased susceptibility to this compound has been recently described in Klebsiella pneumoniae and Pseudomonas aeruginosa, together with cross-resistance to colistin. Surprisingly, few data are available for Escherichia coli, the main species responsible for community and healthcare-associated infections. In order to decipher chlorhexidine resistance mechanisms in E. coli, we studied both in vitro derived and clinical isolates through whole-genome sequence analysis. Comparison of strains grown in vitro under chlorhexidine pressure identified mutations in the gene mlaA coding for a phospholipid transport system. Phenotypic analyses of single-gene mutant from the Keio collection confirmed the role of this mutation in the decreased susceptibility to chlorhexidine. However, mutations in mlaA were not found in isolates from large clinical collections. In contrast, genome wide association studies (GWAS) showed that, in clinical strains, chlorhexidine reduced susceptibility was associated with the presence of tetA genes of class B coding for efflux pumps and located in a Tn10 transposon. Construction of recombinant strains in E. coli K-12 confirmed the role of tetA determinant in acquired resistance to both chlorhexidine and tetracycline. Our results reveal two different evolutionary paths leading to chlorhexidine decreased susceptibility: one restricted to in vitro evolution conditions and involving a retrograde phospholipid transport system; the other observed in clinical isolates associated with efflux pump TetA. None of these mechanisms provides cross-resistance to colistin or to the cationic surfactant octenidine. This work demonstrates the GWAS power to identify new resistance mechanisms in bacterial species.

scholarly journals Autotransporter-Encoding Sequences Are Phylogenetically Distributed among Escherichia coli Clinical Isolates and Reference Strains

2007 ◽  
Vol 73 (5) ◽  
pp. 1553-1562 ◽  
Author(s):  
Concetta Restieri ◽  
Geneviève Garriss ◽  
Marie-Claude Locas ◽  
Charles M. Dozois
Keyword(s):  
Escherichia Coli ◽  
Urinary Tract ◽  
Clinical Isolates ◽  
Phylogenetic Groups ◽  
Allelic Variants ◽  
E Coli ◽  
Multiplex Pcr Assay ◽  
Strain Collection ◽  
Tract Infections ◽  
Reference Strains

ABSTRACT Autotransporters are secreted bacterial proteins exhibiting diverse virulence functions. Various autotransporters have been identified among Escherichia coli associated with intestinal or extraintestinal infections; however, the specific distribution of autotransporter sequences among a diversity of E. coli strains has not been investigated. We have validated the use of a multiplex PCR assay to screen for the presence of autotransporter sequences. Herein, we determined the presence of 13 autotransporter sequences and five allelic variants of antigen 43 (Ag43) among 491 E. coli isolates from human urinary tract infections, diarrheagenic E. coli, and avian pathogenic E. coli (APEC) and E. coli reference strains belonging to the ECOR collection. Clinical isolates were also classified into established phylogenetic groups. The results indicated that Ag43 alleles were significantly associated with clinical isolates (93%) compared to commensal isolates (56%) and that agn43K12 was the most common and widely distributed allele. agn43 allelic variants were also phylogenetically distributed. Sequences encoding espC, espP, and sepA and agn43 alleles EDL933 and RS218 were significantly associated with diarrheagenic E. coli strains compared to other groups. tsh was highly associated with APEC strains, whereas sat was absent from APEC. vat, sat, and pic were associated with urinary tract isolates and were identified predominantly in isolates belonging to either group B2 or D of the phylogenetic groups based on the ECOR strain collection. Overall, the results indicate that specific autotransporter sequences are associated with the source and/or phylogenetic background of strains and suggest that, in some cases, autotransporter gene profiles may be useful for comparative analysis of E. coli strains from clinical, food, and environmental sources.

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