致肾盂肾炎大肠杆菌papA基因的克隆及序列分析

目的 对致肾盂肾炎大肠杆菌（ＵＰＥＣ）１３２株的ｐａｐＡ基因进行克隆和序列分析。方法 根据Ｆ１３型ｐａｐＡ基因序列设计引物,并在二引物５′端加上限制性内切酶ＥｃｏＲⅠ和ＢａｎＨⅠ的酶切位点。采用此引物扩增１３２菌株ｐ菌毛粘附基因群的ｐａｐＡ基因,扩增产物克隆人质粒,选取阳性重组质粒进行核苷酸序列分析。结果 ＵＰＥＣ１３２株经ＰＣＲ法扩增获得约７００ｂｐ的ｐａｐＡ片段,经克隆获得阳性重组质粒ｐＣＴ２     

肠毒素性大肠杆菌CS3菌毛呈现载体的构建

目的 构建大肠杆菌ＣＳ３菌毛呈现载体,实现外源表位在细菌表面的呈现。方法 通过对ＣＳ３亚基蛋白二级结构、抗原表位、亲水性及柔韧性的预测分析,确定外源表位的插入位点,重叠延伸ＰＣＲ方法进行定点突变,将口蹄疫病毒ＶＰＩ插入到ＣＳ３中以验证表现呈现能力;用重组菌腹腔注射免疫小鼠以探讨其抗原性。结果 在大肠杆菌ＣＳ３的１３６位氨基酸残在后突变插入ＢａｍＨⅠ酶切点构建成呈现载体,全细胞ＥＬＩＳＡ、电镜和免疫     

Bacteriuria among adult non-pregnant women attending Mulago hospital assessment centre in Uganda

Background

Urinary tract infections (UTIs) in women are a common problem in primary health care settings. Resistance of bacterial uropathogens to commonly used antibiotics is common in many places.

Objectives

To determine the prevalence of UTI, associated uropathogens and their antimicrobial susceptibility.

Methods

A cross section study carried out at Mulago hospital outpatients'' department. Midstream urine samples (MSU) were collected from 399 women, who gave informed consent and fulfilled other study criteria. Quantitative culture method, identification of uropathogens and antibiotic susceptibility testing using the Kirby-Bauer disc diffusion technique were applied to the isolates.

Results

Out of 399 MSU samples, 40 pure significant bacterial growths (≥10⁵ colony forming units (cfu)/ml of urine) were isolated and these included Escherichia coli, 23 (57.5%), Staphylococcus aureus, 9 (22.5%), Enterococci spp, 6 (15%) and Klebsiella pneumoniae, 2 (5.0%). Overall, sensitivities were: nitrofurantoin (98.3%), cefuroxime (89.3%), and cotrimoxazole (20%) by all uropathogens isolated.

Conclusions

Culture positive UTI among adult non-pregnant women are a common problem, occurring in 10% of the study population. Most bacterial uropathogens showed high sensitivity to nitrofurantoin but low sensitivity to SXT.

Recommendations

Nitrofurantoin should be considered as drug of choice for empirical treatment of community acquired uncomplicated UTI in adult non-pregnant women.     

Rotavirus and enteric pathogens in infantile diarrhoea in Manipal,South India

The etiology of Rotavirus in acute diarrhoeal illness in children 0–5 years of age, admitted to the pediatric wards of Kasturba Medical College Hospital, Manipal was studied over a period of 5 years. Rotavirus in the faeces detected by Latex agglutination test accounted for 19.56% of the diarrhoea with maximum incidence (65%) in the 7–12 months of age group. Bacterial aetiological agents continued to play a significant role (69.6%) in diarrhoeal diseases.Enteroaggregative E. coli was common in the age group between 25–36 months, Shigellosis in 37–60 months andSalmonella typhimurium enteritis in 7–12 months of age. The other pathogens isolated werevibrio cholerae (4.98%), species of aeromonas (15.92%), along with cryptosporidium (6.47%) and Candida albicans (3.98%). In a control group consisting of 100 children without history of diarrhoea, 2 were positive for rotavirus, 3 for cryptosporidium and 12 forEscherichia coli.     

Chemical sensing in mammalian host–bacterial commensal associations

The mammalian gastrointestinal (GI) tract is colonized by a complex consortium of bacterial species. Bacteria engage in chemical signaling to coordinate population-wide behavior. However, it is unclear if chemical sensing plays a role in establishing mammalian host–bacterial commensal relationships. Enterohemorrhagic Escherichia coli (EHEC) is a deadly human pathogen but is a member of the GI flora in cattle, its main reservoir. EHEC harbors SdiA, a regulator that senses acyl-homoserine lactones (AHLs) produced by other bacteria. Here, we show that SdiA is necessary for EHEC colonization of cattle and that AHLs are prominent within the bovine rumen but absent in other areas of the GI tract. We also assessed the rumen metagenome of heifers, and we show that it is dominated by Clostridia and/or Bacilli but also harbors Bacteroidetes. Of note, some members of the Bacteroidetes phyla have been previously reported to produce AHLs. SdiA-AHL chemical signaling aids EHEC in gauging these GI environments, and promotes adaptation to a commensal lifestyle. We show that chemical sensing in the mammalian GI tract determines the niche specificity for colonization by a commensal bacterium of its natural animal reservoir. Chemical sensing may be a general mechanism used by commensal bacteria to sense and adapt to their mammalian hosts. Additionally, because EHEC is largely prevalent in cattle herds, interference with SdiA-mediated cattle colonization is an exciting alternative to diminish contamination of meat products and cross-contamination of produce crops because of cattle shedding of this human pathogen.     

人源性抗HBsAg单链抗体在大肠埃希菌中分泌表达条件的研究

目的 研究抗HBsAS单链抗体A-15在大肠埃希菌中的高效表达,增加该抗体在培养基中的产量.方法 改变工程菌的诱导时机、诱导剂浓度和诱导时间,以观察这些因素对单链抗体表达的影响.另外,加入不同浓度的蔗糖、甘氨酸和Triton X-100,以考察三种化学物质对单链抗体在培养基中分泌量的影响.结果 工程菌培养4 h后,加终浓度0.5 mmol/L IPTG诱导表达8 h为抗HBsAS单链抗体A-15较佳的表达条件.终浓度0.3 mol/L蔗糖,2%甘氨酸和1%Triton X-100同时加入诱导时的培养基中,可使培养基中表达的单链抗体亲和活性分别增加16.78倍.经测定抗HBsAg单链抗体A-15在培养基中最终表达量为7.4 mg/L.结论 抗HBsAg单链抗体A-15的分泌表达条件得到优化,表达量明显提高,这为更有效地制备该抗体用于其结构和功能研究提供了一个切实可行的方法.     

Transurethral instillation with fusion protein MrpH.FimH induces protective innate immune responses against uropathogenic Escherichia coli and Proteus mirabilis

Urinary tract infections (UTIs) are among the most common infections in human. Innate immunity recognizes pathogen‐associated molecular patterns (PAMPs) by Toll‐like receptors (TLRs) to activate responses against pathogens. Recently, we demonstrated that MrpH.FimH fusion protein consisting of MrpH from Proteus mirabilis and FimH from Uropathogenic Escherichia coli (UPEC) results in the higher immunogenicity and protection, as compared with FimH and MrpH alone. In this study, we evaluated the innate immunity and adjuvant properties induced by fusion MrpH.FimH through in vitro and in vivo methods. FimH and MrpH.FimH were able to induce significantly higher IL‐8 and IL‐6 responses than untreated or MrpH alone in cell lines tested. The neutrophil count was significantly higher in the fusion group than other groups. After 6 h, IL‐8 and IL‐6 production reached a peak, with a significant decline at 24 h post‐instillation in both bladder and kidney tissues. Mice instilled with the fusion and challenged with UPEC or P. mirabilis showed a significant decrease in the number of bacteria in bladder and kidney compared to control mice. The results of these studies demonstrate that the use of recombinant fusion protein encoding TLR‐4 ligand represents an effective vaccination strategy that does not require the use of a commercial adjuvant. Furthermore, MrpH.FimH was presented as a promising vaccine candidate against UTIs caused by UPEC and P. mirabilis.     

Phenotypic and genotypic characterization of enteroaggregative Escherichia coli isolates from pediatric population in Pakistan

Enteroaggregative Escherichia coli (EAEC) are a leading cause of diarrhea among children. The objective of this study was to define the frequency of EAEC among diarrheal children from flood‐affected areas as well as sporadic cases, determine multidrug resistance, and evaluation of virulence using an in vivo model of pathogenesis. Stool samples were collected from 225 diarrheal children from 2010 to 2011 from flood‐affected areas as well as from sporadic cases in Pakistan. Identified EAEC isolates were characterized by phylogrouping, antibiotic resistance patterns including the extended‐spectrum beta lactamase spectrum, single nucleotide polymorphism detection in gyrA and parC, and virulence potential using wax worm, G. mellonella. A total of 35 (12.5%) confirmed EAEC isolates were identified among 225 E. coli isolates. EAEC isolates displayed high resistance to tetracycline, ampicillin, and cefaclor. A total of 34.28% were ESBL positive. Single nucleotide polymorphism detection revealed 37.14% and 68.57% isolates were positive for SNPs in gyrA (A₆₆₀‐T₆₆₀) and parC (C₃₃₀‐T₃₃₀), respectively. Phylogrouping revealed that B2 phylogroup was more prevalent among all EAEC isolates tested followed by D, A, B1, and non‐typeable (NT). Infection of G. mellonella with EAEC showed that killing infective dose was 100% higher than E. coli DH5 alpha control. EAEC are prevalent among Pakistani children with diarrhea, they are highly resistant to antibiotics, and predominantly fall into B2 phylogroup. Epidemiologic surveillance of EAEC and other E. coli pathotypes is critical to assess not only the role of these pathogens in diarrheal disease but also to determine the extent of multidrug resistance among the population.     

Distribution of virulence determinants among antimicrobial-resistant and antimicrobial-susceptible Escherichia coli implicated in urinary tract infections

Introduction: Uropathogenic Escherichia coli (UPEC) rely on the correlation of virulence expression with antimicrobial resistance to persist and cause severe urinary tract infections (UTIs). Objectives: We assessed the virulence pattern and prevalence among UPEC strains susceptible and resistant to multiple antimicrobial classes. Methods: A total of 174 non-duplicate UPEC strains from patients with clinically significant UTIs were analysed for susceptibility to aminoglycoside, antifolate, cephalosporin, nitrofuran and quinolone antibiotics for the production of extended-spectrum β-lactamases and for the presence of six virulence determinants encoding adhesins (afimbrial, Type 1 fimbriae, P and S-fimbriae) and toxins (cytotoxic necrotising factor and haemolysin). Results: Relatively high resistance rates to nalidixic acid, ciprofloxacin, cephalothin and trimethoprim-sulfamethoxazole (82%, 78%, 62% and 59%, respectively) were observed. Fourteen distinct patterns were identified for the virulence determinants such as afaBC, cnfI, fimH, hylA, papEF and sfaDE. The toxin gene, cnfI (75.3%), was the second most prevalent marker to the adhesin, fimH (97.1%). The significant association of sfaDE/hylA (P < 0.01) among antimicrobial resistant and susceptible strains was also observed notwithstanding an overall greater occurrence of virulence factors among the latter. Conclusions: This study provides a snapshot of UPEC complexity in Jamaica and highlights the significant clonal heterogeneity among strains. Such outcomes emphasise the need for evidence-based strategies in the effective management and control of UTIs.     

Farm level risk factors for fluoroquinolone resistance in E. coli and thermophilic Campylobacter spp. on poultry farms

Data on husbandry practices, performance, disease and drug use were collected during a cross-sectional survey of 89 poultry meat farms in England and Wales to provide information on possible risk factors for the occurrence of fluoroquinolone (FQ)-resistant bacteria. Faeces samples were used to classify farms as “affected” or “not affected” by FQ-resistant (FQr) Escherichia coli or Campylobacter spp. Risk factor analysis identified the use of FQ on the farms as having by far the strongest association, among the factors considered, with the occurrence of FQr bacteria. Resistant E. coli and/or Campylobacter spp. were found on 86% of the farms with a history of FQ use. However, a substantial proportion of farms with no history of FQ use also yielded FQr organisms, suggesting that resistant bacteria may transfer between farms. Further analysis suggested that for Campylobacter spp., on-farm hygiene, cleaning and disinfection between batches of birds and wildlife control were of most significance. By contrast, for E. coli biosecurity from external contamination was of particular importance, although the modelling indicated that other factors were likely to be involved. Detailed studies on a small number of sites showed that FQr E. coli can survive routine cleaning and disinfection. It appears difficult to avoid the occurrence of resistant bacteria when FQ are used on a farm, but the present findings provide evidence to support recommendations to reduce the substantial risk of the incidental acquisition of such resistance by farms where FQ are not used.