ResearchPad - escherichia-coli https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[A prospective study of bloodstream infections among febrile adolescents and adults attending Yangon General Hospital, Yangon, Myanmar]]> https://www.researchpad.co/article/elastic_article_13833 Bloodstream infection (BSI) is common among persons seeking healthcare for severe febrile illness in low-and middle-income countries. Data on community-onset BSI are few for some countries in Asia, including Myanmar. Such data are needed to inform empiric antimicrobial treatment of patients and to monitor and control antimicrobial resistance. We performed a one year, prospective study collecting information and blood cultures from patients presenting with fever at a tertiary referral hospital in Yangon, Myanmar. We found that almost 10% of participants had a bloodstream infection, and that Salmonella enterica serovars Typhi and Paratyphi A were the most common pathogens. Typhoidal Salmonella were universally resistant to ciprofloxacin. More than half of Escherichia coli and Klebsiella pneumoniae were resistant to extended-spectrum cephalosporins and resistance to carbapenems was also identified in some isolates. We show that typhoid and paratyphoid fever are common, and fluoroquinolone resistance is widespread. Extended-spectrum cephalosporin resistance is common in E. coli and K. pneumoniae and carbapenem resistance is present. Our findings inform empiric antimicrobial management of severe febrile illness, underscore the value of routine use of blood cultures, indicate that measures to prevent and control enteric fever are warranted, and suggest a need to monitor and mitigate antimicrobial resistance among community-acquired pathogens.

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<![CDATA[Virulence factors and antibiograms of <i>Escherichia coli</i> isolated from diarrheic calves of Egyptian cattle and water buffaloes]]> https://www.researchpad.co/article/elastic_article_8462 Diarrhea caused by Escherichia coli in calves is an important problem in terms of survivability, productivity and treatment costs. In this study, 88 of 150 diarrheic animals tested positive for E. coli. Of these, 54 samples had mixed infection with other bacterial and/or parasitic agents. There are several diarrheagenic E. coli pathotypes including enteropathogenic E. coli (EPEC), Shiga-toxin producing E. coli (STEC), enterotoxigenic E. coli (ETEC) and necrotoxigenic E. coli (NTEC). Molecular detection of virulence factors Stx2, Cdt3, Eae, CNF2, F5, Hly, Stx1, and ST revealed their presence at 39.7, 27.2, 19.3, 15.9, 13.6, 9.0, 3.4, and 3.4 percent, respectively. As many as 13.6% of the isolates lacked virulence genes and none of the isolate had LT or CNF1 toxin gene. The odds of isolating ETEC from male calves was 3.6 times (95% CI: 1.1, 12.4; P value = 0.042) that of female calves, whereas the odds of isolating NTEC from male calves was 72.9% lower (95% CI: 91.3% lower, 15.7% lower; P value = 0.024) than that in females. The odds of isolating STEC in winter was 3.3 times (95% CI: 1.1, 10.3; P value = 0.037) that of spring. Antibiograms showed 48 (54.5%) of the isolates to be multi-drug resistant. The percent resistance to tetracycline, streptomycin, ampicillin, and trimethoprim-sulfamethoxazole was 79.5, 67.0, 54.5, and 43.0, respectively. Ceftazidime (14.8%), amoxicillin-clavulanic acid (13.6%) and aztreonam (11.3%) showed the lowest resistance, and none of the isolates was resistant to imipenem. The results of this study can help improve our understanding of the epidemiological aspects of E. coli infection and to devise strategies for protection against it. The prevalence of E. coli pathotypes can help potential buyers of calves to avoid infected premises. The antibiograms in this study emphasizes the risks associated with the random use of antibiotics.

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<![CDATA[A multifunctional small RNA binding protein for sensing and signaling cell envelope precursor availability in bacteria]]> https://www.researchpad.co/article/N33ff824c-2a8c-406a-b01f-54ef06db7cf6 Synthesis of glucosamine-6-phosphate (GlcN6P) by the enzyme GlmS initiates bacterial cell envelope biosynthesis. To ensure ongoing synthesis, GlcN6P homeostasis is required. Escherichia coli achieves this through a post-transcriptional control mechanism comprising the RNA-binding protein RapZ and small RNAs (sRNAs) GlmY and GlmZ. GlmZ stimulates glmS translation by base-pairing. When GlcN6P is abundant, GlmZ is cleaved and inactivated by endoribonuclease RNase E. Cleavage depends on RapZ, which binds GlmZ and recruits RNase E. Decreasing GlcN6P concentrations provoke up-regulation of the decoy sRNA GlmY which sequesters RapZ, thereby suppressing GlmZ decay. In our current study we identify RapZ as the GlcN6P sensor. GlcN6P-free RapZ interacts with and stimulates phosphorylation of the two-component system (TCS) QseE/QseF triggering glmY expression. Thereby generated GlmY sequesters RapZ into stable complexes, allowing for glmS expression. Sequestration by GlmY also disables RapZ to stimulate QseE/QseF, providing a negative feed-back loop limiting the response. When GlcN6P is replenished, GlmY is released from RapZ and rapidly degraded. Our work has revealed a complex regulatory scenario, in which an RNA binding protein senses a metabolite and communicates with two sRNAs, a TCS and ribonuclease RNase E to achieve metabolite homeostasis.

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<![CDATA[Diarrheal bacterial pathogens and multi-resistant enterobacteria in the Choqueyapu River in La Paz, Bolivia]]> https://www.researchpad.co/article/5c46656bd5eed0c484519147

Water borne diarrheal pathogens might accumulate in river water and cause contamination of drinking and irrigation water. The La Paz River basin, including the Choqueyapu River, flows through La Paz city in Bolivia where it is receiving sewage, and residues from inhabitants, hospitals, and industry. Using quantitative real-time PCR (qPCR), we determined the quantity and occurrence of diarrheagenic Escherichia coli (DEC), Salmonella enterica, Klebsiella pneumoniae, Shigella spp. and total enterobacteria in river water, downstream agricultural soil, and irrigated crops, during one year of sampling. The most abundant and frequently detected genes were gapA and eltB, indicating presence of enterobacteria and enterotoxigenic E. coli (ETEC) carrying the heat labile toxin, respectively. Pathogen levels in the samples were significantly positively associated with high water conductivity and low water temperature. In addition, a set of bacterial isolates from water, soil and crops were analyzed by PCR for presence of the genes blaCTX-M, blaKPC, blaNDM, blaVIM and blaOXA-48. Four isolates were found to be positive for blaCTX-M genes and whole genome sequencing identified them as E. coli and one Enterobacter cloacae. The E. coli isolates belonged to the emerging, globally disseminated, multi-resistant E. coli lineages ST648, ST410 and ST162. The results indicate not only a high potential risk of transmission of diarrheal diseases by the consumption of contaminated water and vegetables but also the possibility of antibiotic resistance transfer from the environment to the community.

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<![CDATA[Prophage induction, but not production of phage particles, is required for lethal disease in a microbiome-replete murine model of enterohemorrhagic E. coli infection]]> https://www.researchpad.co/article/5c40f78ad5eed0c48438634b

Enterohemorrhagic Escherichia coli (EHEC) colonize intestinal epithelium by generating characteristic attaching and effacing (AE) lesions. They are lysogenized by prophage that encode Shiga toxin 2 (Stx2), which is responsible for severe clinical manifestations. As a lysogen, prophage genes leading to lytic growth and stx2 expression are repressed, whereas induction of the bacterial SOS response in response to DNA damage leads to lytic phage growth and Stx2 production both in vitro and in germ-free or streptomycin-treated mice. Some commensal bacteria diminish prophage induction and concomitant Stx2 production in vitro, whereas it has been proposed that phage-susceptible commensals may amplify Stx2 production by facilitating successive cycles of infection in vivo. We tested the role of phage induction in both Stx production and lethal disease in microbiome-replete mice, using our mouse model encompassing the murine pathogen Citrobacter rodentium lysogenized with the Stx2-encoding phage Φstx2dact. This strain generates EHEC-like AE lesions on the murine intestine and causes lethal Stx-mediated disease. We found that lethal mouse infection did not require that Φstx2dact infect or lysogenize commensal bacteria. In addition, we detected circularized phage genomes, potentially in the early stage of replication, in feces of infected mice, confirming that prophage induction occurs during infection of microbiota-replete mice. Further, C. rodentiumstx2dact) mutants that do not respond to DNA damage or express stx produced neither high levels of Stx2 in vitro or lethal infection in vivo, confirming that SOS induction and concomitant expression of phage-encoded stx genes are required for disease. In contrast, C. rodentiumstx2dact) mutants incapable of prophage genome excision or of packaging phage genomes retained the ability to produce Stx in vitro, as well as to cause lethal disease in mice. Thus, in a microbiome-replete EHEC infection model, lytic induction of Stx-encoding prophage is essential for lethal disease, but actual phage production is not.

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<![CDATA[A cross-sectional study on the prevalence of antibiotic use prior to laboratory tests at two Ghanaian hospitals]]> https://www.researchpad.co/article/5c478c46d5eed0c484bd141b

There has been a significant rise in global antibiotic use in recent years. Development of resistance has been linked to easy accessibility, lack of regulation of sale, increased tendency to self-medicate and the lack of public knowledge. The increase in antibiotic misuse, including self-medication, has not been well documented in developing countries. Antibiotic use prior to visiting health facilities has been found to be prevalent in developing countries. It has been identified by some studies to increase the likelihood of missed diagnoses and influence the outcome of bacteriological tests. This study is aimed at determining the prevalence of prior antibiotic use through a cross-sectional survey of patients undergoing laboratory tests at two health facilities in Ghana. Face-to-face questionnaires were used to interview 261 individuals chosen by random sampling of patients visiting the bacteriology laboratory of the hospitals within a two-month period. The questionnaire investigated participant demographic characteristics, knowledge about antibiotics and the nature of antibiotic use. Antibiotic property detection bioassay was performed on patient’s urine sample using a disk diffusion method to accurately determine antibiotic use within 72 hours. Culture results were used as an index to evaluate the effect of prior antibiotic use on bacteriological tests. Out of a 261 participants enrolled, 19.9% (95% CI, 14.9–24.9) acknowledged using antibiotics prior to their visit to the laboratory during the study period. On the contrary, 31.4% (95% CI, 25.7–37.5) of participants’ urine samples were positive for antimicrobial activity. Participants within the age ranges of 20–30, 31–40 and 41–50 years had significantly lower odds of urine antimicrobial activity. Participants who had urine antimicrobial activity were more likely to have no growth on their culture plates than participants who had no urine antimicrobial activity [OR 2.39(1.37–4.18), p = 0.002]. The most commonly used antibiotics were the penicillins, fluoroquinolones and metronidazole. Although, majority of the participant (54.8%) had knowledge of antibiotics, most of them had inadequate information on their proper use. The commonest indications for antibiotic use were aches and pains (30.3%), diarrhoea (43.3%) and urinary tract infections (28.0%). Prior antibiotic use was found to increase the likelihood of obtaining a culture negative result and can affect the outcome of bacteriological tests.

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<![CDATA[Role of a fluid-phase PRR in fighting an intracellular pathogen: PTX3 in Shigella infection]]> https://www.researchpad.co/article/5c141e72d5eed0c484d26a40

Shigella spp. are pathogenic bacteria that cause bacillary dysentery in humans by invading the colonic and rectal mucosa where they induce dramatic inflammation. Here, we have analyzed the role of the soluble PRR Pentraxin 3 (PTX3), a key component of the humoral arm of innate immunity. Mice that had been intranasally infected with S. flexneri were rescued from death by treatment with recombinant PTX3. In vitro PTX3 exerts the antibacterial activity against Shigella, impairing epithelial cell invasion and contributing to the bactericidal activity of serum.

PTX3 is produced upon LPS-TLR4 stimulation in accordance with the lipid A structure of Shigella. In the plasma of infected patients, the level of PTX3 amount only correlates strongly with symptom severity. These results signal PTX3 as a novel player in Shigella pathogenesis and its potential role in fighting shigellosis. Finally, we suggest that the plasma level of PTX3 in shigellosis patients could act as a biomarker for infection severity.

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<![CDATA[Lipids alter microbial transport through intestinal mucus]]> https://www.researchpad.co/article/5c269742d5eed0c48470f0d4

Mucus constitutes a protective layer which coats the gastrointestinal tract, controlling interactions of both commensal and pathogenic microbes with underlying tissues. Changes to the mucus barrier, for example due to altered mucin expression or external stimuli, may impact interactions with microbes and thus potentially contribute to altered gut homeostasis, onset of inflammation, or pathogen invasion. Food-associated stimuli, including lipids, have been shown to change mucus barrier properties and reduce transport of model drug carriers through mucus. Here, we explore the impact of lipids, specifically triglycerides in a model intestinal medium mimicking a fed state, on Escherichia coli (E. coli) transport through mucus by directly imaging swimming patterns and analyzing associated changes in mucus structure. Lipids in model fed state intestinal contents reduced E. coli speed and track linearity within mucus. These changes may be due in part to changes in molecular interactions within the mucus network as well as crowding of the mucus network by lipid emulsion droplets, which visibly stay intact in the mucus gel. In addition, observed physical interactions between bacteria and lipid structures may impact microbial speed and trajectories. As lipids are normal food components and thus represent safe, mild stimuli, these results support exploration of lipid-based strategies to alter the mucus barrier to control interactions with microbes and potentially prevent microbial invasion of underlying epithelium.

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<![CDATA[Meat and Fish as Sources of Extended-Spectrum β-Lactamase–Producing Escherichia coli, Cambodia]]> https://www.researchpad.co/article/5c354d25d5eed0c484dd3fc2

We compared extended-spectrum β-lactamase–producing Escherichia coli isolates from meat and fish, gut-colonized women, and infected patients in Cambodia. Nearly half of isolates from women were phylogenetically related to food-origin isolates; a subset had identical multilocus sequence types, extended-spectrum β-lactamase types, and antimicrobial resistance patterns. Eating sun-dried poultry may be an exposure route.

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<![CDATA[Acquisition of plasmid-mediated cephalosporinase producing Enterobacteriaceae after a travel to the tropics]]> https://www.researchpad.co/article/5c22a0bcd5eed0c4849ebf77

Travelers are at high risk of acquiring multi-drug resistant Enterobacteriaceae (MRE) while traveling abroad. Acquisition of extended spectrum beta-lactamase producing Enterobacteriaceae (ESBL-E) while traveling has been extensively described, but not that of plasmid-mediated cephalosporinase producing Enterobacteriaceae (pAmpC-E). Here, we characterized the pAmpC-E acquired in 574 French travelers to tropical areas enrolled in the VOYAG-R study. Among the 526 MRE isolated at return, 57 (10.8%) from 49 travelers were pAmpC-E. The acquisition rate of pAmpC-E was 8.5% (49/574) ranging from 12.8% (25/195) in Asia, 7.6% (14/184) in Latin America to 5.1% (10/195) in Africa. The highest acquisition rates were observed in Peru (21.9%), India (21.4%) and Vietnam (20%). The carriage of pAmpC-E decreased quickly after return with 92.5% of colonized travelers being negative at one month. Most enzymes were CMY types (96.5%, n = 55, only met in Escherichia coli), including 40 CMY-2 (70.2%), 12 CMY-42 (21.1%), 1 CMY-6 and two new CMY-2 variants. The remaining were two DHA observed in Klebsiella pneumoniae. CMY-2 producing strains were acquired worldwide whereas CMY-42, except for one, were all acquired in Asia. BlaCMY-2 genes were associated with different plasmid types, including IncI1 (45. 2%), IncF (10%), IncF-IncI (7.5%), IncA/C (5%) and IncR (2.5%) whereas blaCMY-42 were all associated with IncI1 plasmids. Even though the pAmpC-E acquisition rate was much lower than that of ESBL-E, it was significant, especially in Asia, showing that pAmpC-E, especially CMY-type producing E. coli have spread in the community settings of tropical regions.

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<![CDATA[Absence of genetic selection in a pathogenic Escherichia coli strain exposed to the manure-amended soil environment]]> https://www.researchpad.co/article/5c141e62d5eed0c484d265cd

Escherichia coli that express curli are more common in subsurface soil drainage when manure is surface applied. However, it is unknown whether this arises from mutations in individual strains leading to curli expression or by selection for individuals already expressing higher levels of curli. To test this, we examined curli production in pathogenic E. coli O157:H7 EDL933 as a function of manure management. Five treatments were investigated: (1) soil only, (2) soil with surface-applied E. coli O157:H7 EDL933 Δstx1-2 (EcO157), (3) soil with incorporated EcO157, (4) soil with surface-applied EcO157-inoculated manure, and (5) soil with incorporated EcO157-inoculated manure. EcO157 was reisolated from soils immediately after application and weekly thereafter for 8 weeks. EcO157 in the surface-applied treatments died faster than their incorporated treatment counterparts. Phenotypic assays revealed differences between treatments as well. Half of surface-applied manure reisolates from week 6 developed a mixed red and white colony morphology on Congo Red plates, indicating changes in curli production that were not seen in other treatments or times. In 37°C growth tests, week 6 reisolates from all treatments except soil surface-applied EcO157 left the lag phase at a significantly greater rate than week 0 isolates. We applied whole genome sequencing technology to interrogate the genetic underpinnings of these phenotypes. Surprisingly, we only found single-nucleotide polymorphisms in two of the 94 resequenced isolates from the different treatments, neither of which correlated with curli phenotype. Likewise, we found no differences in other genomic characteristics that might account for phenotypic differences including the count of gaps and the origin of discarded reads that failed to map to the parental strain. These results suggest there were no systematic genomic differences (i.e. individual-level selection) that correlated with time or treatment. We recommend future research focus on population-level selection of E. coli strains in the manure-amended soil environment.

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<![CDATA[Infected cyst in patients with autosomal dominant polycystic kidney disease: Analysis of computed tomographic and ultrasonographic imaging features]]> https://www.researchpad.co/article/5c117b35d5eed0c484698430

Purpose

To investigate the imaging features of cyst infection in autosomal dominant polycystic kidney disease (ADPKD) patients using computed tomography (CT) and ultrasonography (US).

Materials & methods

The institutional review board approved this retrospective study. Fifty-one episodes with proven cyst infection in forty-three ADPKD patients were included. Two experienced abdominal radiologists reviewed CT and US images and evaluated the following imaging features in consensus: cyst size, location, cyst shape, intracystic attenuation, intracystic echogenicity, intracystic heterogeneity, wall thickness, the presence of fluid-fluid level, septation, intracystic gas, pericystic fat infiltration, and pericystic hyperemia. Intracystic attenuation was measured for all infected cysts and two presumed normal cysts and compared using the Wilcoxon rank-sum test.

Results

On CT scans, the median size of infected cysts was 5.5 cm (range: 2.3–18.8 cm) and 46 of 51 (90.2%) infected cysts were located in the subcapsular region. Most (48 of 51, 94.1%) infected cysts showed lobulated, focal bulging or irregular shape. Discernible wall thickening (84.1%) was the most frequently found imaging feature of infected cysts followed by relatively higher intracystic attenuation compared to normal cysts (79.1%) and pericystic fat infiltration (52.9%). Fluid/fluid level was found in 3 of 51 (5.9%) infected cysts and intracystic gas was found in 3 of 51 (5.9%) infected cysts, respectively. For hepatic cysts, 11 of 14 (78.6%) infected cysts showed pericystic hyperemia. Intracystic attenuation was significantly higher in infected cysts (median; 19.0 HU) than in presumed normal cysts (median; 8.5 HU) (P<0.001), and exceeded 25 HU in 18 (35.3%) of 51 infected cysts. Among the 41 infected cysts for which US images were available, 35 (85.1%) showed heterogeneous echogenicity.

Conclusion

Minute imaging features such as minimal wall thickening or relatively high attenuation compared to normal cysts would be helpful to detect infected cysts in ADPKD patients.

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<![CDATA[Emerging Multidrug-Resistant Hybrid Pathotype Shiga Toxin–Producing Escherichia coli O80 and Related Strains of Clonal Complex 165, Europe]]> https://www.researchpad.co/article/5c1686aed5eed0c484444579

Enterohemorrhagic Escherichia coli serogroup O80, involved in hemolytic uremic syndrome associated with extraintestinal infections, has emerged in France. We obtained circularized sequences of the O80 strain RDEx444, responsible for hemolytic uremic syndrome with bacteremia, and noncircularized sequences of 35 O80 E. coli isolated from humans and animals in Europe with or without Shiga toxin genes. RDEx444 harbored a mosaic plasmid, pR444_A, combining extraintestinal virulence determinants and a multidrug resistance–encoding island. All strains belonged to clonal complex 165, which is distantly related to other major enterohemorrhagic E. coli lineages. All stx-positive strains contained eae-ξ, ehxA, and genes characteristic of pR444_A. Among stx-negative strains, 1 produced extended-spectrum β-lactamase, 1 harbored the colistin-resistance gene mcr1, and 2 possessed genes characteristic of enteropathogenic and pyelonephritis E. coli. Because O80–clonal complex 165 strains can integrate intestinal and extraintestinal virulence factors in combination with diverse drug-resistance genes, they constitute dangerous and versatile multidrug-resistant pathogens.

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<![CDATA[Genomic Characterization of β-Glucuronidase–Positive Escherichia coli O157:H7 Producing Stx2a]]> https://www.researchpad.co/article/5c1686d0d5eed0c484444cc0

Among Shiga toxin (Stx)–producing Escherichia coli (STEC) O157:H7 strains, those producing Stx2a cause more severe diseases. Atypical STEC O157:H7 strains showing a β-glucuronidase–positive phenotype (GP STEC O157:H7) have rarely been isolated from humans, mostly from persons with asymptomatic or mild infections; Stx2a-producing strains have not been reported. We isolated, from a patient with bloody diarrhea, a GP STEC O157:H7 strain (PV15-279) that produces Stx2a in addition to Stx1a and Stx2c. Genomic comparison with other STEC O157 strains revealed that PV15-279 recently emerged from the stx1a/stx2c-positive GP STEC O157:H7 clone circulating in Japan. Major virulence genes are shared between typical (β-glucuronidase–negative) and GP STEC O157:H7 strains, and the Stx2-producing ability of PV15-279 is comparable to that of typical STEC O157:H7 strains; therefore, PV15-279 presents a virulence potential similar to that of typical STEC O157:H7. This study reveals the importance of GP O157:H7 as a source of highly pathogenic STEC clones.

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<![CDATA[Highly Pathogenic Clone of Shiga Toxin–ProducingEscherichia coliO157:H7, England and Wales]]> https://www.researchpad.co/article/5c1686c9d5eed0c484444b22

We used whole-genome sequencing to investigate the evolutionary context of an emerging highly pathogenic strain of Shiga toxin–producing Escherichia coli (STEC) O157:H7 in England and Wales. A timed phylogeny of sublineage IIb revealed that the emerging clone evolved from a STEC O157:H7 stx-negative ancestor ≈10 years ago after acquisition of a bacteriophage encoding Shiga toxin (stx) 2a, which in turn had evolved from a stx2c progenitor ≈20 years ago. Infection with the stx2a clone was a significant risk factor for bloody diarrhea (OR 4.61, 95% CI 2.24–9.48; p<0.001), compared with infection with other strains within sublineage IIb. Clinical symptoms of cases infected with sublineage IIb stx2c and stx-negative clones were comparable, despite the loss of stx2c. Our analysis highlighted the highly dynamic nature of STEC O157:H7 Stx-encoding bacteriophages and revealed the evolutionary history of a highly pathogenic clone emerging within sublineage IIb, a sublineage not previously associated with severe clinical symptoms.

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<![CDATA[Respiration and the F1Fo-ATPase Enhance Survival under Acidic Conditions in Escherichia coli]]> https://www.researchpad.co/article/5989da29ab0ee8fa60b81a9a

Besides amino acid decarboxylation, the ADP biosynthetic pathway was reported to enhance survival under extremely acidic conditions in Escherichia coli (Sun et al., J. Bacteriol. 193∶ 3072–3077, 2011). E. coli has two pathways for ATP synthesis from ADP: glycolysis and oxidative phosphorylation. We found in this study that the deletion of the F1Fo-ATPase, which catalyzes the synthesis of ATP from ADP and inorganic phosphate using the electro-chemical gradient of protons generated by respiration in E. coli, decreased the survival at pH 2.5. A mutant deficient in hemA encoding the glutamyl tRNA reductase, which synthesizes glutamate 1-semialdehyde also showed the decreased survival of E. coli at pH 2.5. Glutamate 1-semialdehyde is a precursor of heme synthesis that is an essential component of the respiratory chain. The ATP content decreased rapidly at pH 2.5 in these mutants as compared with that of their parent strain. The internal pH was lowered by the deletion of these genes at pH 2.5. These results suggest that respiration and the F1Fo-ATPase are still working at pH 2.5 to enhance the survival under such extremely acidic conditions.

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<![CDATA[Small Intestine Early Innate Immunity Response during Intestinal Colonization by Escherichia coli Depends on Its Extra-Intestinal Virulence Status]]> https://www.researchpad.co/article/5989da9dab0ee8fa60ba4887

Uropathogenic Escherichia coli (UPEC) strains live as commensals in the digestive tract of the host, but they can also initiate urinary tract infections. The aim of this work was to determine how a host detects the presence of a new UPEC strain in the digestive tract. Mice were orally challenged with UPEC strains 536 and CFT073, non-pathogenic strain K12 MG1655, and ΔPAI-536, an isogenic mutant of strain 536 lacking all 7 pathogenicity islands whose virulence is drastically attenuated. Intestinal colonization was measured, and cytokine expression was determined in various organs recovered from mice after oral challenge. UPEC strain 536 efficiently colonized the mouse digestive tract, and prior Enterobacteriaceae colonization was found to impact strain 536 colonization efficiency. An innate immune response, detected as the production of TNFα, IL-6 and IL-10 cytokines, was activated in the ileum 48 hours after oral challenge with strain 536, and returned to baseline within 8 days, without a drop in fecal pathogen load. Although inflammation was detected in the ileum, histology was normal at the time of cytokine peak. Comparison of cytokine secretion 48h after oral gavage with E. coli strain 536, CFT073, MG1655 or ΔPAI-536 showed that inflammation was more pronounced with UPECs than with non-pathogenic or attenuated strains. Pathogenicity islands also seemed to be involved in host detection, as IL-6 intestinal secretion was increased after administration of E. coli strain 536, but not after administration of ΔPAI-536. In conclusion, UPEC colonization of the mouse digestive tract activates acute phase inflammatory cytokine secretion but does not trigger any pathological changes, illustrating the opportunistic nature of UPECs. This digestive tract colonization model will be useful for studying the factors controlling the switch from commensalism to pathogenicity.

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<![CDATA[Ongoing Phenotypic and Genomic Changes in Experimental Coevolution of RNA Bacteriophage Qβ and Escherichia coli]]> https://www.researchpad.co/article/5989d9d4ab0ee8fa60b65171

According to the Red Queen hypothesis or arms race dynamics, coevolution drives continuous adaptation and counter-adaptation. Experimental models under simplified environments consisting of bacteria and bacteriophages have been used to analyze the ongoing process of coevolution, but the analysis of both parasites and their hosts in ongoing adaptation and counter-adaptation remained to be performed at the levels of population dynamics and molecular evolution to understand how the phenotypes and genotypes of coevolving parasite–host pairs change through the arms race. Copropagation experiments with Escherichia coli and the lytic RNA bacteriophage Qβ in a spatially unstructured environment revealed coexistence for 54 days (equivalent to 163–165 replication generations of Qβ) and fitness analysis indicated that they were in an arms race. E. coli first adapted by developing partial resistance to infection and later increasing specific growth rate. The phage counter-adapted by improving release efficiency with a change in host specificity and decrease in virulence. Whole-genome analysis indicated that the phage accumulated 7.5 mutations, mainly in the A2 gene, 3.4-fold faster than in Qβ propagated alone. E. coli showed fixation of two mutations (in traQ and csdA) faster than in sole E. coli experimental evolution. These observations suggest that the virus and its host can coexist in an evolutionary arms race, despite a difference in genome mutability (i.e., mutations per genome per replication) of approximately one to three orders of magnitude.

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<![CDATA[Type VI secretion system contributes to Enterohemorrhagic Escherichia coli virulence by secreting catalase against host reactive oxygen species (ROS)]]> https://www.researchpad.co/article/5989db53ab0ee8fa60bdcee5

Enterohemorrhagic Escherichia coli (EHEC) is one major type of contagious and foodborne pathogens. The type VI secretion system (T6SS) has been shown to be involved in the bacterial pathogenicity and bacteria-bacteria competition. Here, we show that EHEC could secrete a novel effector KatN, a Mn-containing catalase, in a T6SS-dependent manner. Expression of katN is promoted by RpoS and OxyR and repressed by H-NS, and katN contributes to bacterial growth under oxidative stress in vitro. KatN could be secreted into host cell cytosol after EHEC is phagocytized by macrophage, which leads to decreased level of intracellular reactive oxygen species (ROS) and facilitates the intramacrophage survival of EHEC. Finally, animal model results show that the deletion mutant of T6SS was attenuated in virulence compared with the wild type strain, while the deletion mutant of katN had comparable virulence to the wild type strain. Taken together, our findings suggest that EHEC could sense oxidative stress in phagosome and decrease the host cell ROS by secreting catalase KatN to facilitate its survival in the host cells.

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<![CDATA[Role of H- and D- MATE-Type Transporters from Multidrug Resistant Clinical Isolates of Vibrio fluvialis in Conferring Fluoroquinolone Resistance]]> https://www.researchpad.co/article/5989da09ab0ee8fa60b77088

Background

The study seeks to understand the role of efflux pumps in multidrug resistance displayed by the clinical isolates of Vibrio fluvialis, a pathogen known to cause cholera-like diarrhoea.

Methodology

Two putative MATE family efflux pumps (H- and D-type) were PCR amplified from clinical isolates of V. fluvialis obtained from Kolkata, India, in 2006 and sequenced. Bioinformatic analysis of these proteins was done to predict protein structures. Subsequently, the genes were cloned and expressed in a drug hypersusceptible Escherichia coli strain KAM32 using the vector pBR322. The recombinant clones were tested for the functionality of the efflux pump proteins by MIC determination and drug transport assays using fluorimeter.

Results

The sequences of the genes were found to be around 99% identical to their counterparts in V. cholerae. Protein structure predicting servers TMHMM and I-TASSER depicted ten-twelve membrane helical structures for both type of pumps. Real time PCR showed that these genes were expressed in the native V. fluvialis isolates. In the drug transport assays, the V. fluvialis clinical isolates as well as recombinant E. coli harbouring the efflux pump genes showed the energy-dependent and sodium ion-dependent drug transport activity. KAM32 cells harbouring the recombinant plasmids showed elevated MIC to the fluoroquinolones, norfloxacin and ciprofloxacin but H-type pumps VCH and VFH from V. cholerae and V. fluvialis respectively, showed decreased MIC to aminoglycosides like gentamicin, kanamycin and streptomycin. Decrease in MIC was also observed for acriflavin, ethidium bromide, safranin and nalidixic acid.

Significance

Increased resistance towards fluoroquinolones exhibited due to these efflux pumps from multidrug resistant clinical isolates of V. fluvialis implies that treatment procedure may become more elaborate for this simple but highly infectious disease. To the best of our knowledge, this is the first report of cloning and characterization of efflux pumps from multidrug resistant clinical isolates of V. fluvialis.

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