儿童泌尿系感染大肠埃希菌的耐药性分析

目的 了解大肠埃希菌在儿童中的感染情况及其耐药性.方法 对中段尿标本进行分离培养及鉴定,药敏试验用K-B法,检测ESBLs用表型确证试验,药敏结果分析用WHONET 5.5软件,统计分析采用x2检验.结果 2009年1月至2011年12月从儿科门诊和病房送检的1755份中段尿标本中共检出85株大肠埃希菌,检出率为4.8％,男女比为6:11; ＜3岁的婴幼儿组57例,占67.1％;3～6岁育龄前儿童17例,占20.0％;＞6岁儿童11例,占12.9％;产ESBLs的大肠埃希菌占60.0％;85株大肠埃希菌对亚胺培南和美罗培南全部敏感,对头孢哌酮/舒巴坦、哌拉西林/他唑巴坦和阿米卡星的敏感率均为90％以上,产ESBLs的大肠埃希菌对氨苄西林、头孢唑啉、头孢他啶、头孢曲松、头孢吡肟、头孢西丁、头孢呋新酯、左旋氧氟沙星和罗红霉素的耐药率较非产ESBLs菌株的耐药率高,P值均＜0.05,差异有统计学意义.结论 儿童泌尿系感染大肠埃希菌,可以选用的抗菌素已极为有限,临床要谨慎用药,并及时根据药敏结果修正药物种类.     

Molecular comparisons of plasmids isolated from colicinogenic strains of Escherichia coli

The plasmid content of 14 colicinogenic strains of Escherichia coli has been examined. Four strains contained miniplasmids (1.2-2.0 kb). Small plasmids (4-7 kb) were detected in all the strains specifying group A colicins (colicins A, E1, E2, E3 and K; group I plasmids). Larger plasmids (55-130 kb) were detected in seven out of nine strains specifying group B colicins (colicins B, H, Ia, Ib, M, V and S1; group II plasmids). DNA-DNA hybridization with group II plasmids showed a wide variation in the degree of DNA sequence homology among its members. In contrast little (if any) DNA sequence homology was detected with the group I plasmids when the same group II plasmid DNAs were used as hybridization probes. The results of DNA-DNA hybridization studies with the two small group II plasmids (pcolG-CA46 and pcolD-CA23) suggested that these plasmids are equivalent to deleted forms of larger group II plasmids. Our hybridization data thus support the division of colicin plasmids into the two groups (I and II) that have been previously defined from genetic and physiological studies.     

Prevalence of virulence genes in Escherichia coli strains isolated from Romanian adult urinary tract infection cases

A total of 78 E. coli strains isolated from adults with different types of urinary tract infections were screened by polymerase chain reaction for prevalence of genetic regions coding for virulence factors. The targeted genetic determinants were those coding for type 1 fimbriae ( fimH ), pili associated with pyelonephritis ( pap ), S and F1C fimbriae ( sfa and foc ), afimbrial adhesins ( afa ), hemolysin ( hly ), cytotoxic necrotizing factor ( cnf ), aerobactin ( aer ). Among the studied strains, the prevalence of genes coding for fimbrial adhesive systems was 86 %, 36%, and 23% for fimH, pap , and sfa/foc , respectively. The operons coding for Afa afimbrial adhesins were identified in 14% of strains. The hly and cnf genes coding for toxins were amplified in 23% and 13% of strains, respectively. A prevalence of 54% was found for the aer gene. The various combinations of detected genes were designated as virulence patterns. The strains isolated from the hospitalized patients displayed a greater number of virulence genes and a diversity of gene associations compared to the strains isolated from the ambulatory subjects. A rapid assessment of the bacterial pathogenicity characteristics may contribute to a better medical approach of the patients with urinary tract infections.     

风湿性疾病患者尿路感染大肠埃希菌对左氧氟沙星耐药性及危险因素分析

目的研究风湿性疾病中尿路感染大肠埃希菌对左氧氟沙星耐药性及相关危险因素。方法中国医科大学附属第一医院风湿免疫科2009年1月至2013年12月125株住院患者清洁中段尿培养所分离出大肠埃希菌,依据是否耐药分为两组。分析耐药组相关危险因素。结果 5年来大肠埃希菌对左氧氟沙星耐药率呈逐渐上升趋势。耐药组对氨苄西林、环丙沙星、头孢曲松、哌拉西林、复方新诺明的耐药率高于非耐药组,两组间差异有统计学意义（P〈0.05）。慢性病程、既往喹诺酮类药物应用史、既往尿路感染、菌株产ESBLs为耐药危险因素。各风湿性疾病间耐药率比较差异未见统计学意义。结论风湿性疾病尿路感染危险因素与其他疾病尿路感染危险因素类似。临床工作中应加强对危险因素监视和控制。     

Frequent production of toxins by Escherichia coli strains isolated from human urinary tract infections: relation with haemagglutination

Abstract We have investigated the production of heat-labile enterotoxin (LT), Verotoxin (VT), cytotoxic necrotizing factor (CNF), haemolysis (Hly) and lethal activity for mice in 48 Escherichia coli strains isolated from patients with urinary tract infections. Mannose-resistant and mannose-sensitive haemagglutination in these strains were also studied. Among the total strains investigated, 50% were haemolytic, 50% synthesized CNF and 58% were lethal for mice. A total of 33 (69%) strains were toxigenic, showing positive results at least in one of the tests employed for toxin detection. No strain was positive for LT and VT production. We conclude that, in addition to haemolytic and haemagglutinating activities, the production of CNF was closely associated to virulence in E. coli strains isolated from urinary tract infections.     

Antibacterial effects of Tungsten nanoparticles on the Escherichia coli strains isolated from catheterized urinary tract infection (UTI) cases and Staphylococcus aureus

A significant proportion of all incidents of nosocomial infections in acute-care hospitals is due to contaminated catheters. Alternative strategies e.g. antibiotics as well as surface modifications have been devised in an attempt to reduce the incidence of catheter-associated urinary tract infections (CAUTI), but most have proven unsuccessful. Therefore, the race to identify such substances which can combat pathogenic bacteria is ongoing in order to improve the quality of health care. Novel technologies such as the potential use of antiseptic or antimicrobial coatings on catheters hold promise for reducing these infections in the fight against antimicrobial resistance. In this study, the bactericidal activity of newly synthesized tungsten-nanoparticles was tested on clinical multiple drug resistant Escherichia coli isolates from UTI patients with indwelling catheters and Staphylococcus aureus reference strain. The results suggest that the particles tested in this study certainly mediate the inhibition of bacterial growth. We believe that the fabrication of W-NPs on catheters could possibly prevent them from being contaminated by pathogens and hence provide continuous protection of the site. This study is the first of its type testing the antibacterial effects of W-NPs on clinical bacterial isolate from catheterized human UTI case.     

Biochemical detection of N-Acyl homoserine lactone from biofilm-forming uropathogenic Escherichia coli isolated from urinary tract infection samples

Background:

N-Acyl homoserine lactone (AHL) is found to be the main component of quorum sensing (QS) in Gram-negative bacteria and plays an important role in biofilm formation. Little information is available regarding the role of AHL in biofilm formation in Escherichia coli (E. coli). The purpose of this investigation was to biochemically detect and characterize AHL activity in biofilm-forming uropathogenic E. coli (UPEC) isolated from urine samples of the patients with urinary tract infections (UTIs) in Kerman, Iran.

Methods:

Thirty-five UPEC isolates were obtained from urine samples of the patients with UTIs referred to the Afzalipoor hospital. The isolates were identified by biochemical tests. Biofilm analyses of all the isolates were performed using the microtiter plate method at OD 490nm. N-Acyl homoserine lactone was separated from cell mass supernatants by liquid-liquid extraction (LLE) and analyzed by a colorimetric method. N-Acyl homoserine lactone functional groups were identified by Fourier Transform-Infrared Spectroscopy (FT-IR).

Results:

The biofilm formation assay identified 10 (28.57%) isolates with strong, 16 (45.71%) with moderate, and 9 (25.71%) with weak biofilm activities. The UPEC isolates with strong and weak biofilm activities were subjected to AHL analyses. It was found that isolates with the highest AHL activities also exhibited strong adherence to microplate wells (P≤0.05). Two E. coli isolates with the highest AHL activities were selected for FT-IR spectroscopy. Peaks at 1764.33, 1377.99, and 1242.90 cm^-1 correspond to the C=O bond of the lactone ring, and the N=H and C-O bonds of the acyl chain, respectively.

Conclusion:

We found that many UPEC isolates exhibited strong biofilm formation. The control of this property by AHL may contribute to the pathogenesis of the organism in UTI’s.Key Words: Biofilm, FT-IR, N-acylhomoserine lactone, Uropathogenic Escherichia coli     

Biofilm formation by Acinetobacter baumannii strains isolated from urinary tract infection and urinary catheters

Systemic infections in avian species caused by avian pathogenic Escherichia coli (APEC) are economically devastating to poultry industries worldwide. To unravel factors possibly involved in APEC pathogenicity, suppression subtractive hybridization was applied, leading to the identification of a putative APEC autotransporter adhesin gene aatA in our previous study. In this study, pathogenic mechanism of AatA was further determined. A deletion mutant of aatA was constructed in the APEC DE205B, which results in the reduced capacity to adhere to DF-1 cells, defective virulence in vivo, and decreased colonization capacity in lung during the systemic infection compared with the wild-type strain. Furthermore, these capacities were restored in the complementation strains. These results indicated that AatA makes a significant contribution to APEC virulence through bacterial adherence to host tissues in vivo and in vitro. In addition, aggregation assays for strain AAEC189 expressing aatA indicated that AatA mediates cell aggregation and settling of cells. However, this cell aggregation is blocked by Type I fimbriae. This study illustrates the first examination of the role of AatA in aggregation and systemic infection.     

Comparative genomics of Escherichia coli strains causing urinary tract infections

The virulence determinants of uropathogenic Escherichia coli have been studied extensively over the years, but relatively little is known about what differentiates isolates causing various types of urinary tract infections. In this study, we compared the genomic profiles of 45 strains from a range of different clinical backgrounds, i.e., urosepsis, pyelonephritis, cystitis, and asymptomatic bacteriuria (ABU), using comparative genomic hybridization analysis. A microarray based on 31 complete E. coli sequences was used. It emerged that there is little correlation between the genotypes of the strains and their disease categories but strong correlation between the genotype and the phylogenetic group association. Also, very few genetic differences may exist between isolates causing symptomatic and asymptomatic infections. Only relatively few genes that could potentially differentiate between the individual disease categories were identified. Among these were two genomic islands, namely, pathogenicity island (PAI)-CFT073-serU and PAI-CFT073-pheU, which were significantly more associated with the pyelonephritis and urosepsis isolates than with the ABU and cystitis isolates. These two islands harbor genes encoding virulence factors, such as P fimbriae (pyelonephritis-associated fimbriae) and an important immunomodulatory protein, TcpC. It seems that both urovirulence and growth fitness can be attributed to an assortment of genes rather than to a specific gene set. Taken together, urovirulence and fitness are the results of the interplay of a mixture of factors taken from a rich menu of genes.     

The prevalence of plasmid-mediated quinolone resistance genes among Escherichia coli strains isolated from urinary tract infections in southwest Iran

Molecular Biology Reports - The extensive and inappropriate use of quinolones, which are frequently used as an effective treatment for urinary tract infection (UTI) patients, has led to resistance...     

The prevalence and molecular typing of enterotoxigenic Escherichia coli strains isolated from diarrheic stools in Malatya, Turkey

This study was performed from June 2002 to November 2003 year in Malatya, eastern Turkey. Stools of 172 diarrheic patients and 90 healthy controls were analysed for enterotoxigenic Escherichia coli (ETEC). Heat-labile (LT) and heat-stable (ST) toxins were investigated by passive latex agglutination and enzyme immunoassay, respectively. Nine ETEC strains were isolated from 172 diarrheic stools (5.2%). Seven of the ETEC strains (10.1%) were isolated from 69 children in the 0-5 year age group. Two of these pediatric isolates were ST positive (2.9%) and five were LT positive (7.2%). ETEC was not isolated in the 6-18 year age group. Two ST producing E. coli strains were detected in diarrheic adult patients (> 18 years). In the 90 controls, two ETEC strains were detected (2.2%). One of them was a LT producer (1.1%) and the other was a ST producer (1.1%). E. coli strains producing both toxins simultaneously were not observed. ETEC positivity was higher in the diarrheic group than in the control group but statistically not significant (p > 0.05). The rate of resistance among ETEC strains to cefuroxime axetil, ampicillin, piperacillin, and trimethoprim-sulfamethoxazole was 72.7%, 54.5%, 45.5%, and 36.4%, respectively whereas the resistance rate to the same antibiotics in non-ETEC strains was 14%, 62%, 54%, and 66%, respectively. All ETEC isolates were intermediately resistant to cephalothin and fully susceptible to other antibiotics tested. Typing of the ETEC strains was done by arbitrary primed polymerase chain reaction (AP-PCR). Only two LT strains of the 11 typed strains had a unique profile. The remaining nine were mixed LT and ST strains and divided into two groups. The first group had three strains having a similarity coefficient ranging from 70-90%. The other one had six strains, five of them were similar and one was subtype isolate. It can be concluded that ETEC strains might be considerably important enteropathogens especially in pediatric patients in the 0-5 year age group. High clonal relation indicated that ETEC strains were epidemiologically related.     

Antibiotic susceptibility and genotype patterns of Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa isolated from urinary tract infected patients

Thirty nine isolates of Escherichia coli, twenty two isolates of Klebsiella pneumoniae and sixteen isolates of Pseudomonas aeruginosa isolated from urinary tract infected patients were analyzed by antimicrobial susceptibility typing and random amplified polymorphic DNA (RAPD)-PCR. Antibiotic susceptibility testing was carried out by microdilution and E Test methods. From the antibiotic susceptibility, ten patterns were recorded (four for E. coli, three for K. pneumoniae and three for P. aeruginosa respectively). Furthermore, genotyping showed seventeen RAPD patterns (seven for E. coli, five for K. pneumoniae and five for P. aeruginosa respectively). In this study, differentiation of strains of E. coli, K. pneumoniae and P. aeruginosa from nosocomial infection was possible with the use of RAPD.