Akut İshalli Çocuklarda Diyarejenik Escherichia coli İzolatlarının Sıklığı

Acute inflammation in the pathogenesis of hemolytic-uremic syndrome

The Ordered Transcription of RNA Domains Is Not Essential for Ribosome Biogenesis in Escherichia coli

As part of our studies on the biological functions of polyamines, we have used a mutant of Escherichia coli that lacks all the genes for polyamine biosynthesis for a global transcriptional analysis on the effect of added polyamines. The most striking early response to the polyamine addition is the increased expression of the genes for the glutamate-dependent acid resistance system (GDAR) that is important for the survival of the bacteria when passing through the acid environment of the stomach. Not only were the two genes for glutamate decarboxylases (gadA and gadB) and the gene for glutamate-γ-aminobutyrate antiporter (gadC) induced by the polyamine addition, but the various genes involved in the regulation of this system were also induced. We confirmed the importance of polyamines for the induction of the GDAR system by direct measurement of glutamate decarboxylase activity and acid survival. The effect of deletions of the regulatory genes on the GDAR system and the effects of overproduction of two of these genes were also studied. Strikingly, overproduction of the alternative σ factor rpoS and of the regulatory gene gadE resulted in very high levels of glutamate decarboxylase and almost complete protection against acid stress even in the absence of any polyamines. Thus, these data show that a major function of polyamines in E. coli is protection against acid stress by increasing the synthesis of glutamate decarboxylase, presumably by increasing the levels of the rpoS and gadE regulators.

To determine if thyroid function affects faecal shedding of Escherichia coli O157:H7. Eight yearling cattle (n = 4 per treatment group), previously identified as shedding E. coli O157:H7, received either 0 or 10 mg 6-N-propyl-2-thiouracil (PTU) kg(-1) BW day(-1) for 14 days to reduce serum concentrations of the thyroid hormones, T(3) and T(4). Animals were monitored daily for changes in faecal shedding of E. coli O157:H7 and E. coli (EC) for the 14-day treatment period and an additional 7 days post-treatment. Body weight was measured weekly and serum concentrations of T(3) and T(4) were determined every 3 days. No differences in faecal shedding of E. coli O157:H7 were observed during the 14-day treatment period. However, compared with control animals, a greater percentage of PTU-treated cattle ejected E. coli O157:H7 on day 16 (100 vs 25%) and 18 (75 vs 0%) of the post-treatment period. Serum T(3) was lower in PTU-treated cattle during the 14-day treatment period and greater on day 18 of the post-treatment period. Cattle with chemically altered thyroid hormones had similar shedding patterns of faecal E. coli O157:H7 and EC during the 14-day treatment period. However, faecal shedding of E. coli O157:H7 tended to be greater, and serum concentrations of T(3), were greater for PTU-treated cattle immediately following the termination of PTU treatment. Short-term chemical inhibition of thyroid hormones had minimal effects on faecal shedding of E. coli O157:H7 in naturally infected cattle. However, a hyperthyroid state as observed postdosing might play a role in the seasonal shedding of E. coli O157:H7 in cattle.

1. When the few individuals still alive in a dissolved culture of Bacillus coli are transplanted on slanted agar, a culture results which possesses new characteristics. First observed by Bordet and Ciuca, this culture received the temporary name of modified coli. In the study described above, we found that this modified coli is very heterogeneous and that its three principal characteristics, resistance to lysis, lysogenic properties, and mucoid growth, are shared among different types of organisms that can be isolated when the normal original coli (coli O) is plated together with increasing quantities of the lytic agent: (a) a certain number of bacilli are just resistant enough to survive and grow in the presence of a moderate quantity of lytic agent, but they are still more or less sensitive and produce diseased, irregular, and lysogenic colonies; (b) a few of the organisms are able to resist concentrated lytic agent; they are entirely resistant and give round, healthy, and non-lysogenic colonies (coli O R 2); and (c) among these resistant bacilli only a very few are mucoid (coli 0 R 1). All these types are not motile and not fluorescent. 2. The original coli, when allowed to age, can be dissociated, as we have shown in a preceding paper (1), into two types of organisms, the non-motile coli S and the very motile coli R. Submitted to lysis, coli S gives a very small number, coli R a much greater number of resistant organisms (coli S R and coli R R), but both types never yield any mucoid growth. 3. An old culture of the modified coli obtained by Bordefand Ciuca, when streaked on agar plate, gives two types of colonies: a mucoid and fluorescent type (coli M 1) and a non-mucoid and translucent type (coli M 2). Both types are motile. Coli M 2, once isolated, keeps its individuality even after several passages in artificial media, but if again submitted to the lytic agent, a great number of mucoid bacilli are found among the organisms which are still alive. Consequently, different types of Bacillus coli differ greatly in their ability to give a mucoid growth when submitted to the lytic agent. Some, like coli S and coli R, do not possess this property at all. Others, like coli O, possess it to a certain extent, and some, like coli M 2, have it to a very high degree. 4. The mucoid and motile Bacillus coli M 1, when streaked every day on agar plates, remains indefinitely mucoid and motile, but occasionally a mucoid colony shows an indentation made up of non-mucoid growth, which, transplanted, gives a pure culture of non-mucoid and non-motile organisms, coli M 1 a. This new type possesses all the characteristics of the original strain of Bacillus coli, and therefore must be considered as a reversion. 5. The mucoid and motile Bacillus coli M 1, kept growing in synthetic medium, remains perfectly stable; on the other hand, when it is transplanted in broth, Bacillus coli M 1 turns very quickly into a non-mucoid but still very motile organism, or Bacillus coli M 1 b. This last type, which produces translucent colonies on agar and grows granular in broth, never reverts to the mucoid form, even in the presence of lytic agent. 6. A single strain of Bacillus coli has thus been made to yield eleven different forms, all distinguished by striking characteristics, but still possessing the specific properties of Bacillus coli. Nine of these forms have been submitted to antisera prepared with three different types (Bacillus coli O, Bacillus coli S, and Bacillus coli R). While seven out of these nine strains were agglutinated by any of the three antisera, only the original Bacillus coli (Bacillus coli O) and the reversion to the original type (Bacillus coli M 1 a) were not agglutinable, even by their corresponding antiserum; i.e., the serum obtained from a rabbit immunized with Bacillus coli O, which, however, agglutinated the other types.

To study the plasmid-mediated AmpC β-lactamases and the genotypes of Escherichia coli and Klebsiella spp. in children. Escherichia coli and Klebsiella spp. of strains were isolated at our division from January to December 2009. Cefoxitin disk diffusion method was used to screen Escherichia coli and Klebsiella spp. for phenotypic AmpC enzyme. Multiple PCR method was adopted to test the genotypes of AmpC enzyme-positive Escherichia coli and Klebsiella spp.strains. Of all Escherichia coli and Klebsiella spp., 65 were insensitive to cefoxitin disk and 17 strains carried DHA type AmpC gene. The prevalence of plasmid-mediated AmpC enzyme in Escherichia coli and Klebsiella spp. was 26.2% (17/65). Among plasmid-mediated AmpC enzyme isolates, 14 (38.9%) Klebsiella pneumoniae strains, 2 (7.7%) Escherichia coli strains and 1 (33.3%) Klebsiella oxytoca strains carried the DHA-1 AmpC gene. The genes of MOX, CIT, DHA, ACC, MIR and FOX were not found in other 48 strains. The identified plasmid-mediated AmpC genes are all of DHA-1 genotype in Escherichia coli and Klebsiella spp. The prevalence of plasmid-mediated AmpC enzyme in Klebsiella pneumoniae isolates is relatively high in children.

This study was conducted to investigate the presence of Escherichia (E.) coli O157 and E. coli O157:H7 and stx1 and stx2 genes on cattle carcasses and in rectal samples collected from Samsun Province of Turkey. A total of 200 samples collected from cattle carcasses and the rectal contents of 100 slaughtered cattle from two commercial abattoirs were tested using the immunomagnetic separation technique and multiplex PCR methods. E. coli O157 and E. coli O157:H7 were detected in 52 of the 200 samples (26%) tested. Of the positive samples, 49 were E. coli O157 and three were E. coli O157:H7. The E. coli O157 strain was isolated from 24 carcasses and 25 rectal samples, while E. coli O157:H7 was isolated from two carcasses and one rectal sample. Of the 49 samples positive for E. coli O157, 32 were from the rectal and carcass samples of the same animal, while two E. coli O157:H7 isolates were obtained from rectal swabs and carcasses of the same animal. The stx1 and stx2 genes were both detected in 35 E. coli O157 isolates and one E. coli O157:H7 isolate, but the stx2 gene was only detected alone in two E. coli O157 isolates. Overall, 16 carcasses tested positive for E. coli O157 and one carcass tested positive for E. coli O157:H7 based on both carcass and rectal samples. Overall, the results of this study indicate that cattle carcasses pose a potential risk to human health due to contamination by E. coli O157 and E. coli O157:H7 in the feces.

Background and Objective: Currently, many valuable drugs have lost their impact on Escherichia coli, and Escherichia coli drug resistance is the major reason for the treatment failure of nosocomial infections caused by this bacterium. This study aims to investigate the effect of silver nanoparticles using yogurt Lactobacillus flora on Escherichia coli with multiple drug resistance. Materials and Methods: This cross-sectional-experimental study was conducted in 2019 on Escherichia coli strain from some clinical centers in Ardabil, Iran. The isolates were performed based on approved biochemical tests to identify Escherichia coli bacteria. Antibiotic susceptibility testing was carried out by diffusion method. Then, its physical and chemical properties were determined by spectrophotometry (UV), SEM microscopy, and FESEM. Then, the synergistic effect of silver nitrate growth inhibitor was investigated using yogurt Lactobacillus flora by disk diffusion method according to standard (CLSI). Findings: In the present study, out of 100 samples, 37 strains of Escherichia coli were positive. The highest resistance of Escherichia coli isolates was to ciprofloxacin with 87% and the highest susceptibility was to nitrofurantoin with 76%. The size of silver nanoparticles according to the image of TEM and FESEM was both shown to be 16 nm in diameter. Silver nitrate using yogurt lactobacilli flora was able to reduce the combination of Escherichia coli strains with antibiotics, especially ciprofloxacin. Conclusion: The results of the present study showed that silver nanoparticles synthesized using yogurt lactobacilli flora with a diameter of 16 nm have antimicrobial activity against Escherichia coli. Considering the effectiveness of silver nanoparticles using yogurt Lactobacillus flora on ciprofloxacin-positive Escherichia coli, it can be used as a candidate drug against Escherichia coli in the future.

The Escherichia coli fumarate-nitrate reduction regulator (FNR) protein is the paradigm for bacterial O2-sensing transcription factors. However, unlike E. coli, some bacterial species possess multiple FNR proteins that presumably have evolved to fulfill distinct roles. Here, three FNR proteins (ANR, PP_3233, and PP_3287) from a single bacterial species, Pseudomonas putida KT2440, have been analyzed. Under anaerobic conditions, all three proteins had spectral properties resembling those of [4Fe-4S] proteins. The reactivity of the ANR [4Fe-4S] cluster with O2 was similar to that of E. coli FNR, and during conversion to the apo-protein, via a [2Fe-2S] intermediate, cluster sulfur was retained. Like ANR, reconstituted PP_3233 and PP_3287 were converted to [2Fe-2S] forms when exposed to O2, but their [4Fe-4S] clusters reacted more slowly. Transcription from an FNR-dependent promoter with a consensus FNR-binding site in P. putida and E. coli strains expressing only one FNR protein was consistent with the in vitro responses to O2. Taken together, the experimental results suggest that the local environments of the iron-sulfur clusters in the different P. putida FNR proteins influence their reactivity with O2, such that ANR resembles E. coli FNR and is highly responsive to low concentrations of O2, whereas PP_3233 and PP_3287 have evolved to be less sensitive to O2.

Objective To investigate the common pathogens of neonatal bacterial meningitis in the past 5 years, and to evaluate the brain injury in the acute phase through amplitude-integrated electroencephalogram (aEEG), brainstem auditory evoked potential (BAEP) and brain MRI. Methods Sixty children were selected from the past 5 years who were treated in Department of Neonatology, Guangzhou Women and Children's Medical Center in March 2011 to March 2015 as the objects of study.According to the results of etiological culture, the children were divided into streptococcus lactis group (14 cases), escherichia coli group (10 cases), other positive bacteria group (11 cases) and culture-negative group (25 cases). The results of aEEG, BAEP and brain MRI of brain injury in the acute phase of these 4 groups were compared. Results Twenty-nine cases of the 60 patients (48.3%) showed positive blood culture, and 14 cases (23.3%) showed positive cerebrospinal fluid(CSF) culture.Streptococcus lactics and escherichia coli were found to be the most common pathogens that caused neonatal bacterial meningitis.By evaluating the cerebral function in the acute phase of 57 cases, it was found that aEEG total abnormal rate was 61.4%, escherichia coli group abnormal rate was 80.0%, while moderate to severe damage seemed to be the most remarkable feature.The abnormal rate was of statistical significance between escherichia coli group and culture-negative group(χ2=3.941, P=0.047). Forty-eight cases manifested potential anomaly evoked by brainstem auditory, with the total abnormal rate as 84.2%.A significant increase in the ratio of severe hearing loss was found in children with bacterial meningitis which was caused by escherichia coli and streptococcus agalactiae.The abnormal rate was of statistical significance between escherichia coli group and culture-negative group (χ2=4.399, P=0.036), and hearing damage caused by escherichia coli was more serious than that in other bacteria group.Of these 57 cases, MRI total abnormal rate was 77.2%, with hydrocephalus as the most common complication.Of the 44 abnormal cases, 16 cases showed hydrocep-halus, 6 cases of which were from the escherichia coli group.The second most common complication was subdural effusion.And another 5 cases showed cerebral softening, 3 cases of which were from the escherichia coli group.The data suggested that escherichia coli meningitis easily combined hydrocephalus and brain softening. Conclusions The main pathogens of neonatal bacterial meningitis is streptococcus agalactiae and escherichia coli.The brain injury in neonatal bacterial meningitis caused by escherichia coli is more serious than those caused by other pathogens. Key words: Bacterial meningitis; Pathogens; Amplitude-integrated electroencephalogram; Brainstem auditory evoked potential; Electroencephalogram; Infant, newborn

Objective To define the microbial epidemiology and outcome of Extended-spectrum β-lactamases (ESBLs) -producing Klebsiella spp. and Escherichia coli in bloodstream infections (BSI) after liver transplantation. Methods From January 1998 to December 2009, a retrospective analysis of ESBLs-producing Klebsiella spp. and Escherichia coli were conducted. Results BSI occurred in 19 (2.5%) patients of the 768 patients, in which a total 23 gram-negative bacilli (GNB) were isolated. The most frequent pathogens were Escherichia coli and Klebsiella spp. enterobacter cloacae, pseudomonas aeruginosa, Enterobacter aerogenes were few. Carbapenems were the most consistently active against the Escherichia coli and Klebsiella spp which were resistant to ceftriaxone. No significance in 15-day, 30-day, 1-year mortality between ESBL-producing and non-ESBL-producing Klebsiella spp. and Esche-richia coli. Conclusion ESBL-producing Klebsiella spp. and Escherichia coli after liver transplantion are resistant to agents but active to Carbapenems commonly, which can not increase 15-day, 30-day, 1-year mortality simultneously. Key words: Escherichia coli; Klebsiella pneumoniae; Epidemiology; Bacteriology; Extended-spectrum β-lactamases; Susceptibility; Mortality

Objective To compare the clinical characteristics and antibiotics resistance of neonatal sepsis caused by Klebsiella pneumoniae and Escherichia coli in order to provide guidance for early diagnosis and appropriate treatment. Methods Forty-two newborns with Klebsiella pneumoniae sepsis and 50 newborns with Escherichia coli sepsis in the neonatal intensive care unit of Yuying Children's Hospital of Wenzhou Medical College from January 2000 to October 2009 were enrolled into this study. The clinical data, laboratory examinations and prognosis of these newborns were retrospectively analyzed and compared. The antibiotic resistance data of different onset age of the two diseases were compared. Early-onset sepsis was defined as the age at the onset ≤3 days, and late-onset sepsis was defined as the age at the onset ＞3 days. Results (1) Comparison of clinical characteristics: Klebsiella pneumoniae sepsis caused higher incidence of apnea or gasp compared with Escherichia coli sepsis (61.9% vs 6.0% ,x2= 17. 34, P＜0. 05); the time of developing to multiple organ dysfunction syndrome or disseminated intravascular coagulation of the newborns with Klebsiella pneumoniae sepsis [(40±28) h] was shorter than that of the newborns with Escherichia coli sepsis [(89±26) h] (t= -3.17, P＜0.05); while the incidence of purulent meningitis of Klebsiella pneumoniae sepsis was lower ( 4. 8% vs 30. 0 %, x2 = 9.65, P ＜ 0. 05 ). ( 2 ) Comparison of non-specific laboratory examinations: compared with Escherichia coli sepsis, Klebsiella pneumoniae sepsis caused higher incidence of the leucocyte count ＞ 25 × 109/L (42. 9% vs 22.0%, x2 = 4. 60,P＜0. 05), platelet count ＜ 100 × 109/L (52.4% vs 18.0%, x2 = 12.07, P＜0. 05) and C-reaction protein ＞8 mg/L (95.2% vs 76.0% ,x2 =6. 55, P＜0. 05). (3) Comparison of results of antibiotic resistance: the resistance rate of Klebsiella pneumoniae (81.8%00-100. 0%) to Cephalosporins was higher than that of Escherichia coli (17. 2%-63. 2%) (x2 =6.97-11.92, P＜0. 05); the resistance rates of late-onset sepsis of Klebsiella pneumoniae to Amoxicillin/clavulanic-acid and Cefoperazone/sulbactam were higher than those of Escherichia coli (75.0% vs 0.0%, x2 =26.67, P＜0. 05;83. 3%vs 0. 0%, x2 = 12.53, P＜0. 05 respectively); no resistance to Imipenem were found. The percentages of extended spectrum β-lactamases (ESBLs) positive Escherichia coli and Klebsiella pneumoniae were obviously higher in neonates with late-onset sepsis than those early-onset ones (65.0% vs 17. 8%,x2 = 11.06, P＜0. 05; 100. 0 % vs 30. 0 %, x2 = 20. 22, P＜0. 05 respectively); and positive ESBLs rate of the late-onset Klebsiella pneumoniae sepsis was higher than that of Escherichia coli sepsis (100. 0% vs 65.0%, x2 =9.16, P＜0. 05). (4) Comparison of mortality rate: the mortality rate of Klebsiella pneumoniae sepsis was higher than that of Escherichia coli sepsis (21.4% vs 4. 0%,x2=6.59, P ＜ 0. 05 ) . Conclusions Compared with Escherichia coli septicemia, Klebsiella pneumoniae septicemia has more severe symptoms, developed to multiple organ dysfunction syndrome or disseminated intravascular coagulation quicker, and has higher mortality rate. The percentage of ESBLs positive Escherichia coli and Klebsiella pneumoniae increased rapidly. The clinical use of antibiotics should be rationale. Key words: Sepsis; Klebsiella pneumoniae; Escherichia coii; Drug resistance,bacterial; Infant,newborn

Distinct Renal Pathology and a Chemotactic Phenotype after Enterohemorrhagic Escherichia coli Shiga Toxins in Non-Human Primate Models of Hemolytic Uremic Syndrome

The widely conserved ω subunit encoded by rpoZ is the smallest subunit of Escherichia coli RNA polymerase (RNAP) but is dispensable for bacterial growth. Function of ω is known to be substituted by GroEL in ω-null strain, which thus does not exhibit a discernable phenotype. In this work, we report isolation of ω variants whose expression in vivo leads to a dominant lethal phenotype. Studies show that in contrast to ω, which is largely unstructured, ω mutants display substantial acquisition of secondary structure. By detailed study with one of the mutants, ω6 bearing N60D substitution, the mechanism of lethality has been deciphered. Biochemical analysis reveals that ω6 binds to β' subunit in vitro with greater affinity than that of ω. The reconstituted RNAP holoenzyme in the presence of ω6 in vitro is defective in transcription initiation. Formation of a faulty RNAP in the presence of mutant ω results in death of the cell. Furthermore, lethality of ω6 is relieved in cells expressing the rpoC2112 allele encoding β'2112, a variant β' bearing Y457S substitution, immediately adjacent to the β' catalytic center. Our results suggest that the enhanced ω6-β' interaction may perturb the plasticity of the RNAP active center, implicating a role for ω and its flexible state.

Acute Bloody Diarrhea: A Medical Emergency for Patients of All Ages