The virulence regulator AbsR in avian pathogenic Escherichia coli has pleiotropic effects on bacterial physiology

Avian pathogenic Escherichia coli(APEC)belonging to extraintestinal pathogenic E.coli(ExPEC)can cause severe infections in extraintestinal tissues in birds and humans,such as the lungs and blood.MprA(microcin production regulation,locus A,herein renamed AbsR,a blood survival regulator),a member of the MarR(multiple antibiotic resistance regulator)transcriptional regulator family,governs the expression of capsule biosynthetic genes in human ExPEC and represents a promising druggable target for antimicrobials.However,a deep understanding of the AbsR regulatory mechanism as well as its regulon is lacking.In this study,we present a systems-level analysis of the APEC AbsR regulon using ChIP-Seq(chromatin immunoprecipitation sequencing)and RNA-Seq(RNA sequencing)methods.We found that AbsR directly regulates 99 genes and indirectly regulates 667 genes.Furthermore,we showed that:1)AbsR contributes to antiphagocytotic effects by macrophages and virulence in a mouse model for systemic infection by directly activating the capsular gene cluster;2)AbsR positively impacts biofilm formation via direct regulation of the T2SS(type II secretion system)but plays a marginal role in virulence;and 3)AbsR directly upregulates the acid tolerance signaling system EvgAS to withstand acid stress but is dispensable in ExPEC virulence.Finally,our data indicate that the role of AbsR in virulence gene regulation is relatively conserved in ExPEC strains.Altogether,this study provides a comprehensive analysis of the AbsR regulon and regulatory mechanism,and our data suggest that AbsR likely influences virulence primarily through the control of capsule production.Interestingly,we found that AbsR severely represses the expression of the type I-F CRISPR(clustered regularly interspaced short palindromic repeats)-Cas(CRISPR associated)systems,which could have implications in CRISPR biology and application.

Impact of an oligosaccharide-based polymer on the metabolic profiles and microbial ecology of weanling pigs experimentally infected with a pathogenic E.coli

Background Our previous study has reported that supplementation of oligosaccharide-based polymer enhances gut health and disease resistance of pigs infected with enterotoxigenic E.coli(ETEC)F18 in a manner similar to carbadox.The objective of this study was to investigate the impacts of oligosaccharide-based polymer or antibiotic on the host metabolic profiles and colon microbiota of weaned pigs experimentally infected with ETEC F18.Results Multivariate analysis highlighted the differences in the metabolic profiles of serum and colon digesta which were predominantly found between pigs supplemented with oligosaccharide-based polymer and antibiotic.The relative abundance of metabolic markers of immune responses and nutrient metabolisms,such as amino acids and carbohydrates,were significantly differentiated between the oligosaccharide-based polymer and antibiotic groups(q<0.2 and fold change>2.0).In addition,pigs in antibiotic had a reduced(P<0.05)relative abundance of Lachnospiraceae and Lactobacillaceae,whereas had greater(P<0.05)Clostridiaceae and Streptococcaceae in the colon digesta on d 11 post-inoculation(PI)compared with d 5 PI.Conclusions The impact of oligosaccharide-based polymer on the metabolic and microbial profiles of pigs is not fully understood,and further exploration is needed.However,current research suggest that various mechanisms are involved in the enhanced disease resistance and performance in ETEC-challenged pigs by supplementing this polymer.

Development of a Multivalent Inactivated Vaccine against Pathogenic Escherichia coli Infection in Forest Musk Deer

A multivalent inactivated Escherichia coli vaccine for forest musk deer by using serotypes O4,O26,and O139 with Al（OH）3 adjuvant was prepared.The vaccine did not cause any adverse reactions in forest musk deer.The immunogenic effects of the vaccine were experimentally investigated in pregnant and young forest musk deer.The serum antibody titers of pregnant and young forest musk deer were determined by performing the micro-agglutination test.The serum antibody titers of pregnant forest musk deer were more stable from 35th to 68th d after the third vaccination,and the serum antibody titers of four pregnant forest musk deer were maintained 25,25,25,and 24 on 68th d after the third vaccination.Young forest musk deer showed serum antibody titers which were obtained due to nursing.Young forest musk deer were administered the first intramuscular vaccine injection at an age of approximately 60 days due to a fall in maternal antibody titers.The serum antibody titers of young forest musk deer were higher after the third vaccination and maintained at approximately the same level until they were 137 days old.The maternal antibodies and the antibodies produced by young forest musk deer could be helpful for protecting the young musk deer from the infections of pathogenic Escherichia coli strains（serotypes O4,O26,and O139）for 137 days after birth（during the nursing period and the period when the forest musk deer were susceptible to diseases）.

Dietary supplementation of Bacillus subtilis influenced intestinal health of weaned pigs experimentally infected with a pathogenic E. coli

Background: There is growing evidence to support the beneficial effects of supplementing direct-fed microbials(DFM) on performance, health status, and immune responses of weaned pigs. Therefore, the objective of this study was to investigate dietary supplementation of Bacillus subtilis(DSM 25841) on growth performance, diarrhea, gut permeability and immunity of weaned pigs experimentally infected with a pathogenic F-18 Escherichia coli(E. coli).Results: The F18 E. coli infection reduced(P < 0.05) growth performance and intestinal villi height, whereas increased(P < 0.05) diarrhea and transcellular and paracellular permeability in the jejunum compared with non-challenged control. Supplementation of Bacillus subtilis linearly enhanced average daily gain of E. coli infected pigs from d 0 to 5 post-inoculation(PI)(P < 0.05) and d 0 to 11 PI(P = 0.058). Supplementation of high dose of Bacillus subtilis reduced(P < 0.05) both transcellular and paracellular permeability on d 5 and d11 PI compared with the E. coli infected pigs fed with control diet. E. coli infection up-regulated(P < 0.05)the m RNA expression of SLC5 A10(soluble carrier family 5 member 10) and MUC2(mucin 2) on d 5 PI, but down-regulated(P < 0.05) expression of SLC5 A10, MUC2, and CLDN1 on d 11 PI in jejunal mucosa when pigs were fed with the control diet. Supplementation of Bacillus subtilis linearly up-regulated(P < 0.05) the m RNA expression of CFTR and ZO1 on d 5 PI and SLC5 A10 and MUC2 on d 11 PI in jejunal mucosa of E. coli infected pigs. In addition, E. coli infection increased(P < 0.05) the m RNA expression of several immune genes(IL1 A, IL1 B, and IL7 on d 5 PI, and IL1 B, IL6, IL7, and TNF on d 11 PI) in the ileal mucosa of weaned pigs. Inclusion of Bacillus subtilis to control diet linearly down-regulated gene expression of IL1 A on d 5 PI(P = 0.07) and IL6 on d 11 PI(P < 0.05) in ileal mucosa of E. coli infected pigs.Conclusions: Supplementation of Bacillus subtilis(DSM 25841) enhanced growth rate and improved gut barrier function of weaned pigs experimentally infected with a pathogenic E. coli.

Distribution of Virulence-Associated Genes of Avian Pathogenic Escherichia coli Isolates in China

216 avian pathogenic Escherichia coli （APEC） isolates were obtained from poultry with colibacillosis in different areas of China. Among them, 195 were serotyped as 078, 088, and 093. Thirteen virulence-associated genes, including fimC, iucD, iss, tsh, fyuA, irp2, eaeA, hlyE, colV, papC, stx2f, vat, and astA, were submitted to PCR amplification. The fimC gene was the most prevalent with a detection rate of 93.6%, followed by iucD （70.8%）, iss （58.8%）, and tsh （51.4%） in APEC isolates. The detection rate of high pathogenicity islands （HPI）-associatedfyuA and irp2 genes were both 44.9%, with no LEE （the locus of enterocyte effacement） island-associated gene eaeA detected. In terms of distribution patterns of the 13 virulence-associated genes, 5 isolates harborbed 10 genes, 19 isolates contained onlyfimC gene, and only 4 isolates had no virulence-associated gene detected. Different correlations of the virulence-associated genes with O serotypes were also investigated and 50% 078 isolates had a gene distribution patterns of fimC^＋iucD^＋irp2^＋fyuA^＋iss^＋colV^＋tsh^＋.

重组体pET-28a-alkB/E.coli降解页岩油泥石油烃的功能研究

为了降解页岩油泥中的石油烃,构建基因工程菌,表达石油烃降解关键酶以提高油泥的降解效果。以Pseudomonas qingdaonensis基因组为模板扩增alkB基因,连接至载体pET-28a,转化至E.coli BL21(DE3)中,SDS-PAGE和Western-blot鉴定表达的外源蛋白。pET-28a-alkB/E.coli处理原油和页岩油泥,采用气相色谱法评估降解效果。发现alkB基因在大肠杆菌中能表达外源蛋白,且14 d原油及页岩油泥的降解率分别为47.5%和47.1%,表明重组体pET-28a-alkB/E.coli具备降解页岩油泥石油烃的功能。

Exploring the modulatory role of bovine lactoferrin on the microbiome and the immune response in healthy and Shiga toxin‑producing E.coli challenged weaned piglets

Background Post-weaned piglets suffer from F18+Escherichia coli(E.coli)infections resulting in post-weaning diar-rhoea or oedema disease.Frequently used management strategies,including colistin and zinc oxide,have contrib-uted to the emergence and spread of antimicrobial resistance.Novel antimicrobials capable of directly interacting with pathogens and modulating the host immune responses are being investigated.Lactoferrin has shown promising results against porcine enterotoxigenic E.coli strains,both in vitro and in vivo.Results We investigated the influence of bovine lactoferrin(bLF)on the microbiome of healthy and infected weaned piglets.Additionally,we assessed whether bLF influenced the immune responses upon Shiga toxin-producing E.coli(STEC)infection.Therefore,2 in vivo trials were conducted:a microbiome trial and a challenge infection trial,using an F18+STEC strain.BLF did not affect theα-andβ-diversity.However,bLF groups showed a higher relative abundance(RA)for the Actinobacteria phylum and the Bifidobacterium genus in the ileal mucosa.When analysing the immune response upon infection,the STEC group exhibited a significant increase in F18-specific IgG serum levels,whereas this response was absent in the bLF group.Conclusion Taken together,the oral administration of bLF did not have a notable impact on theα-andβ-diversity of the gut microbiome in weaned piglets.Nevertheless,it did increase the RA of the Actinobacteria phylum and Bifi-dobacterium genus,which have previously been shown to play an important role in maintaining gut homeostasis.Furthermore,bLF administration during STEC infection resulted in the absence of F18-specific serum IgG responses.

The Pathogenicity of Chicken Pathogenic <i>Escherichia coli</i>Is Associated with the Numbers and Combination Patterns of Virulence-Associated Genes

Various virulence-associated genes or pathogenicity island are responsible for determining the pathogenicity of Escherichia coli strains. However, the correlation of the number and combination patterns of virulence-associated genes in Escherichia coli strains with their pathogenicity remains largely unknown. In this work, 581 chicken Escherichia coli strains were isolated from 1045 liver samples of dead chickens from 50 chicken farms at four provinces in China during 2007-2012. Based on the pathogenic test of SPF chickens, 320 chickens pathogenic Escherichia coli isolates were identified as highly (n = 193), intermediate (n = 98) and low pathogenic (n = 29) strains, respectively. Furthermore, the number of virulence genes in the 320 chicken pathogenic and 50 non-pathogenic Escherichia coli strains was examined. Our results reveal that thirteen virulence genes in Escherichia coli strains were detected, and all strains carried at least two or more than two virulence-associated genes. This study also suggests that highly pathogenic E. coli strains simultaneously carried at least 8 to13 virulence genes while intermediate pathogenic strains carried at least 5 to 8 virulence genes. The number of virulence-associated genes detected in highly pathogenic strains showed there were more significant differences than that in low pathogenic strains (P irp2, fyuA, and colV in high pathogenic strains was significantly higher than that in low and non-pathogenic strains (P irp2, fyuA, iucA, iucD, iutA, papC, iss, tsh, and colV were more often detected in highly and intermediate pathogenic E. coli strains. Taken together, our results provide evidences demonstrating that the pathogenicity of Escherichia coli strains is closely associated with the number and combination patterns of virulence-associated genes.

Differentiation of Avian Pathogenic <i>Escherichia coli</i>Strains from Broiler Chickens by Multiplex Polymerase Chain Reaction (PCR) and Random Amplified Polymorphic (RAPD) DNA

We examined 50 Escherichia coli (E. coli) strains isolated from broiler chickens between January 2013 to March 2014 in order to evaluate the epidemiological prevalence of avian pathogenic E. coli (APEC) in Jordan by multiplex PCR and random amplification of polymorphic DNA (RAPD) tests. The multiplex polymerase chain reaction (PCR) which was used as tentative criteria of APEC targets 8 virulence associated genes;enteroaggregative toxin (astA), Type 1 fimbria adhesion (fimH), iron-repressible protein (irp2), P fimbriae (papC), aerobactin (iucD), temperature-sensitive hemagglutinin (tsh), vacuolating autotransporter toxin (vat), and colicin V plasmid operon (cva/cvi) genes. The number of detected genes could be used as a reliable index of their virulence. E. coli strains already typed as an APEC always harbor 5 to 8 genes, but non-APEC strains harbor less than 4 genes. Assuming the criteria of an APEC is possession of 5 or more virulence associated genes;we found that all 50 E. coli strains were classified as APEC strains. The RAPD analysis showed that the E. coli strains could be grouped into 35 of RAPD types by using these two different RAPD primer sets, RAPD analysis primer 4 5'AAGAGCCCGT5', and RAPD analysis primer 6 5'CCCGTCAGCA3'. The current study confirmed the endemic nature of APEC in broiler flocks in Jordan. It is essential that the biosecurity on poultry farms should be improved to prevent the introduction and dissemination of APEC and other agents. Furthermore, farmers need to be educated about the signs, lesions, and the importance of this agent.

Field Assessment of the Level of Protection Conferred by a Newly Prepared Combined Inactivated Vaccine against E. coli and P. multocida in Rabbit in Egypt

Pasteurellosis is the most prevalent, extremely contagious bacterial disease among domestic rabbits and is considered the leading cause of deaths in rabbits, resulting in enormous economic losses to the rabbit industry. Screening for bacterial agents causing mortalities in rabbits revealed the presence of Enterobacteriacae species in approximately 42% of studied cases, with E. coli the most commonly isolated organism. The present study was designed to evaluate the immune response of rabbits vaccinated with a locally prepared, combined inactivated vaccine of Pasteurella multocida and E. coli, adjuvanated with Montanide ISA70. A total of 370 rabbits, aged 2 - 3 weeks, were divided into four groups: (G1) vaccinated with a polyvalent P. multocida vaccine, (G2) vaccinated with a polyvalent E. coli vaccine, (G3) vaccinated with a combined inactivated Montanide ISA70 vaccine of P. multocida and E. coli, and (G4) kept as a non-vaccinated control group. All rabbits received two doses of 0.5 ml of the prepared vaccines, administered one month apart, and were then challenged with virulent strains of P. multocida and E. coli three weeks after the second vaccination. The prepared vaccines were evaluated by determining humoral immunity using indirect haemagglutination (IHA) test and ELISA. The potency of the vaccines was assessed through challenge and determination of LD50. Experimental findings on the prepared polyvalent combined inactivated P. multocida and E. coli vaccine indicated that it is a potent vaccine, producing the highest antibody titers and a 90% protection rate against challenges with virulent strains of P. multocida type A, D2, and E. coli types O157, O151 and O125. Thus, this vaccine is promising in addressing both P. multocida and E. coli problems in rabbits, farms, providing significant protection, and we recommend its commercial production to help rabbit producers control these two major bacterial infections.

Isolation and Identification of a Pathogenic E.coli Strain Causing Diarrhea in Foxes

[Objectives] The study aimed to identify the pathogenic E. coli strain that caused diarrhea in foxes and to analyze its drug sensitivity.[Methods] A pathogenic E. coli strain was isolated from dead foxes with diarrhea. By conventional bacterial isolation and culture, morphological observation, pathogenicity test and K-B disc method, the isolated strain was identified as pathogenic E. coli .[Results] The isolated pathogen was highly sensitive to ceftriaxone, cefotaxime, ciprofloxacin and lincomycin, moderately sensitive to enrofloxacin, neomycin, gentamycin, spectinomycin, florfenicol, amikacin and polymyxin, and resistant to ampicillin, amoxicillin and doxycycline.[Conclusions] This study provided reference for the prevention and control of diarrheal diseases in foxes in Qinhuangdao region.

Characteristics of β-Lactamase Synthesis in E. coli and K. pneumanie Strains in Nosocomial Infections

Background: Recently micro-organisms that synthesize extended-spectrum β-lactamase (ESBLs) were increased. The peculiarities of ESBL synthesis of Escherichia coli and Klebsiella pneumoniae strains that cause nosocomial urinary tract infections, surgical site infections and pneumonia in surgical clinic were studied. ESBL synthesis were observed 38.9% of E. coli strains obtained from urine, 92.3% of strains obtained from surgical site infections, and 50% of strains obtained from sputum. ESBL synthesis were observed 37.5% of K. pneumoniae strains obtained from urine, 85.7% of strains obtained from surgical site infections, and 60% of strains obtained from sputum. Different levels of ESBL synthesize of E. coli and K. pneumoniae strains isolated from different pattern is discussed. Conclusion. ESBL synthesis is common in E. coli and K. pneumoniae strains, which cause nosocomial infections. The frequency of occurrence of ESBL s synthesis among of these strains depends on clinical forms of nosocomial infections.

E.coli HPI通过NLRP3/caspase-1信号通路诱导细胞焦亡而促进肠道炎症

目的:探究大肠埃希菌(Escherichia coli,E.coli)强毒力岛(high-pathogenicity island,HPI)对细胞焦亡及肠道炎症的影响。方法:用含HPI的E.coli株(HPI+)、HPI缺失的E.coli株(△HPI)和脂多糖(lipopolysaccharide,LPS)分别处理昆明小鼠和IPEC-J2细胞(猪小肠上皮细胞)。测定小鼠肠道乳酸脱氢酶(lactate dehydrogenase,LDH)活性、超氧化物歧化酶(superoxide dismutase,SOD)活性、IgA表达和分泌性IgA(secretory IgA,SIgA)含量;HE和TUNEL染色观察肠道损伤;RT-qPCR、免疫组织化学染色和Western blot检测小鼠肠组织和IPEC-J2细胞中核苷酸结合寡聚化结构域样受体蛋白3(nucleotide-binding oligomerization domain-like receptor protein 3,NLRP3)/caspase-1信号通路关键调控点的表达;ELISA检测小鼠血清和IPEC-J2细胞培养上清液中白细胞介素1β(interleukin-1β,IL-1β)和IL-18含量;共聚焦显微镜观察NLRP3与caspase-1的共定位。siRNA沉默IPEC-J2细胞的NLRP3,验证NLRP3在E.coli HPI感染中的关键调控功能。结果:相对于△HPI感染,E.coli HPI显著降低小鼠肠道SOD活性,增加IgA+B细胞,并促进LDH的释放和SIgA的分泌;ELISA、HE染色和TUNEL染色结果显示,E.coli HPI促进了小鼠肠道上皮细胞DNA断裂、组织损伤和炎症;Western blot结果显示,相对于△HPI,E.coli HPI感染使得小鼠肠道消皮素D的N端片段(gasdermin D N-terminal fragment,GSDMD-N)蛋白水平显著升高;RT-qPCR和免疫组织化学染色结果显示,E.coli HPI显著促进了小鼠肠道和IPEC-J2细胞中NLRP3、含caspase募集结构域的凋亡相关斑点样蛋白(apoptosis-associated speck-like protein containing a caspase recruitment domain,ASC)、caspase-1、GSDMD、IL-1β和IL-18的mRNA和蛋白表达,IL-1β和IL-18分泌增加;共聚焦显微镜观察发现,相对于△HPI感染,E.coli HPI显著促进了NLRP3炎症小体的组装,使得NLRP3与caspase-1发生共定位;此外,在NLRP3沉默的IPEC-J2细胞中观察到E.coli HPI诱导的细胞炎症、细胞损伤及NLRP3/caspase-1信号通路的激活被缓解。结论:HPI的存在增强了E.coli的毒力水平,促进肠道炎症;NLRP3/caspase-1信号通路调控的细胞焦亡参与了E.coli HPI诱导的肠道损伤。

The Transport and Persistence of Escherichia coli in Leachate from Poultry Litter Amended Soils

Fecal coliform bacteria such as Escherichia coli (E. coli) are one of the main sources of groundwater pollution. An assessment of the transport and Persistence of E. coli in poultry litter amended Decatur silty Clay soil and Hartsells Sandy soil was conducted using soil columns and simulated groundwater leaching. Enumeration of initial E. coli was determined to range from 2.851 × 103 to 3.044 × 103 CFU per gram of soil. These results have been used in a batch study to determine the persistence rate of E. coli in Decatur silty Clay soil and Hartsells Sandy soil. Results prove that E. coli survival growth rate increases for clay soil later than and at a higher rate than sandy soil. The column study has determined that E. coli was transported at a rate of 3.7 × 106 CFU for Decatur silty loam and 6.3 × 106 CFU for Hartsells sandy per gram of soil. Further, linear regression analysis predictions show higher porosity and soil moisture content affect transport, and Hartsells sandy soil has higher transport of E. coli due to its higher porosity and lower volumetric water content.

Growth Inhibition of Escherichia coli and Staphylococcus epidermidis from Various Types of Honey

Honey has long been considered a wound treatment used to keep cuts and other epidermal injuries clean. This study tested that claim by comparing manuka honey used in medicine today, local unprocessed honey taken straight from a hive, and pasteurized honey found at a store, on strains of E. coli and S. epidermidis. The study evaluated the effects these honeys had on bacterial growth to determine which had the greatest inhibition of bacterial growth. To determine this, plates streaked with strains of E. coli or S. epidermidis bacteria and agar wells filled with one of the honeys were incubated and subsequently the diameter of the zone of inhibition was measured. After 20 trials using each honey and bacteria type, manuka and unprocessed were shown to have a statistically significant advantage over the pasteurized honey at inhibiting the growth of E. coli and S. epidermidis, though it was variable whether manuka had an advantage over the unprocessed honey.

Evaluating the Potential of Nitrofurantoin and Fosfomycin for E.coli UTIs: A Susceptibility Study

This study was designed to find the susceptibility of Nitrofurantoin and Fosfomycin among urinary isolates of Escherichia.coli.Four hundred(400)urine samples were collected for susceptibility of nitrofurantoin and fosfomycin among urinary isolates of E.coli.All indoor and outdoor patients'urinary samples yielded growth of E.coli.Mid-stream urine specimens were inoculated on blood agar and CLED agar and incubated at 35±2°C.Growth was observed,and Escherichia coli was identified by Gram staining,Catalase,Motility test and API 20E(Bio murex)as per standard procedure.Antimicrobial susceptibility testing of isolates for nitrofurantoin and fosfomycin was carried out by the modified Kirby-Bauer disc diffusion method according to CLSI guidelines ATCC 25922.E.coli was used as a quality control strain.A total of 400 samples were tested susceptibility of nitrofurantoin and fosfomycin among urinary isolates of E.coli during this period.A total of 400 samples yielded the growth of E.coli,out of which 178(44.5%)were male and 222(55.5%)were female samples.Among males,18(10%)were tolerant to nitrofurantoin,and 2(1.1%)were tolerant to fosfomycin.Among females,9(4.09%)were susceptible to nitrofurantoin while 6(2.72%)were susceptible to fosfomycin.Among age groups below 45 years old,6(4.76%)were tolerant to nitrofurantoin,and 2(1.58%)were sensitive to fosfomycin.Between 46-66 years old,4(2.81%)were sensitive to nitrofurantoin,and 3(2.11%)were sensitive to fosfomycin.Between 67-90 years old,17(12.87%)were sensitive to nitrofurantoin,and 4(3.03%)were tolerant to fosfomycin.Fosfomycin and nitrofurantoin showed good susceptibility in urinary isolates of E.coli and can be used empirically in our setup.

Detection of High Pathogenicity Island(HPI) in Pathogenic Escherichia coli of Mink by PCR

[Objective] The paper was to analyze the carrying status of high pathogenicity island （HPI） in pathogenic Escherichia coli of mink. [Method] Eight strains of E. coli were isolated from dead mink, and conducted pathogenicity test of artificial infection. The carrying status of HPI （irp2, fyuA） was detected by PCR. [Result] Eight strains of E. coli were pathogenic E. coli, and the carrying rate of HPI （irp2, fyuA） was 100%, positively correlated with the pathogenicity. [Conclusion] The results lay a foundation for further exploring the pathogenic mechanism of E. coli..

Fosfomycin Resistance in Avian Pathogenic Escherichia coli Isolates

Fosfomycin, a broad-spectrum antibiotic against both Gram-positive and Gram-negative bacteria, is very important in the clinic but many fosfomycin-resistant bacteria have been isolated from patients. In this study, the resistance mechanism of three fosfomycin-resistant avian pathogenic Escherichia coli （APEC） strains （JE1, IF7 and CD11） isolated from septicemic chickens were analyzed. The results showed that their fosfomycin-resistance mechanisms were different. An alteration in the glpT transport system was the main reason of the fosfomycin-resistance mechanisms of strain IF7. Compared with the control stain BL21, the capacity of fosfomycin-uptake was low in all these three stains （JE 1 〉IFT〉CD 11）. Sequence results of murA showed that there were more than 10 sites of nucleotide mutation, but only one amino acid mutation T116A showed in CD11. Real-time detection test showed that the expression level of the murA gene of the three stains was significantly increased （four times increase in strain CD11 and two times increase in strains JE1 and IFT）. The transformation and recombinant test showed that the recombinant bacteria with the murA of JE1 and CD11 showed high minimal inhibitory concentration （MIC） against fosfomycin. From the results of this research, it showed that most of the fosfomycin- resistance mechanisms once showed in patient bacteria have appeared in the APEC strains and the fosfomycin-resistance mechanism of the three APEC isolates was different.

Prevalence of multi-drug resistant uropathogenic Escherichia coli in Potohar region of Pakistan

Objective:To scrutinize patterns of multi-drug-resistant uropathogenic Escherichia coli(UPEC) strains and particularly of fluoroquinolone-resistance this is an alternative choice for the treatment of urinary tract infections.Methods:Bacterial samples(n = 250) were collected from out-patients from August 2012 to August 2014 Islamabad.Antibiotic susceptibility profiling and determination of minimum inhibitory concentrations(MICs) and minimum bactericidal concentrations were performed according to the guidelines of Clinical and Laboratory Standards Institute(CLSI,2012).Genes,qnrA,qnrB and qnrS were identified by DNA amplification and sequencing.Results:The highest percentage of UPEC isolates were resistant to co-trimoxazole(82%) followed by cephalothin(80%),2nd Gen,3rd Gen and 4th Gen cephalosporins,respectively.Resistance against gentamicin,amikacin remained 29% and 4%.For other drugs including nitrofurantoin,tetracycline,carbapenem and beta-lactam inhibitors remained below 10%.Altogether,59% of the isolates were resistant to at least three antibiotics including one fluoroquinolone.Overall,MICs for ciprofloxacin remained(MIC≥256 μg/mL) and for levofloxacin(MIC≥16 μg/mL and 32 μg/mL).No significant differences were observed regarding MIC values of extended spectrumβ-lactamase(ESBL) and non-ESBL producers.For qnrS and qnrB positive isolates MICs remained above 32 μg/mL.Prevalence of UPEC was significantly higher among females and 40% of the isolates were ESBL producers.Conclusions:Higher percentages of ESBL producing UPEC were associated with urinary tract infections.Moreover,the majority of these isolates were multi-drug resistant and fluoroquinolone-resistant.

Pathogenicity of Escherichia coli O_(123) from Rex Rabbit on White Mice

[Objective]The paper was to analyze the pathogenesis of Escherichia coli O123 from rex rabbit. [Method]E. coli O123 isolated from rabbit liver with diarrhea symptom in scale rex rabbit farm was intraperitoneally injected into 18- 22 g Kunming mice,and its pathogenicity was determined by clinical symptoms and pathological examination. [Result]When the inoculation concentration was about 8. 5 × 107 CFU /mL,Kunming mice appeared the clinical symptoms of drooping spirit,diarrhea and gathering,and the mortality reached 50%. Anatomical examination found that intestinal wall was thinning and intestinal mucosa was bleeding. [Conclusion]E. coli from rex rabbit has strong pathogenicity,and establishing animal model with Kunming mice to study its pathogenesis is of great reference significance for diagnosis and prevention of E. coli disease of rex rabbit.