Development of a sandwich ELISA and comparison with PCR for the detection of F11 and F165 fimbriated Escherichia coli isolates from septicaemic disease in farm animals

Common bacterial, viral, and parasitic diseases in pigeons (Columba livia): A review of diagnostic and treatment strategies

Pigeons (Columba livia) have been associated with humans for a long time now. They are raised for sport (pigeon race), exhibition (display of fancy breeds), food, and research. Most of the pigeons kept are Racing Homers, trained to compete in the pigeon race. Other breeds, such as Rollers, Nose Divers, Doneks are bred for their aerial abilities. Incorporation of a good preventive medicine program is one of the most critical factors in averting infectious diseases in pigeon flocks. This review summarizes the common bacterial, viral, and parasitic infections in pigeons. The different clinical signs, symptoms, diagnostic strategies, prevention, and treatments were described in this review. Current researches, molecular diagnostic assays, and treatment strategies such as vaccines and drug candidates were included. The information found in this review can provide insights for veterinarians and researchers studying pigeons to develop effective and efficient immunoprophylactic and diagnostic tools for pigeon diagnosis and therapeutics.

Extended-spectrum β-lactamase-producing Escherichia coli isolated from poultry: a review of current problems, illustrated with some laboratory findings

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli has been documented in humans as well as in food-producing birds, including chickens, and for unknown reasons the prevalence has increased significantly during the last decade. With E. coli as a major opportunistic pathogen in chickens and with a potential for zoonotic transfer to human beings, ESBL-producing E. coli represents a major risk both to poultry production and to human health. This review presents some of the current problems with ESBL-producing E. coli in relation to poultry production, with a focus on chickens. To illustrate issues in relation to screening and typing, two case studies are included where one collection of ESBL-producing E. coli isolates was obtained from asymptomatic carrier chickens while the other was obtained from lesions in chickens. Pulsed-field gel electrophoresis and multi-locus sequence typing revealed a highly heterogeneous population of ESBL-producing E. coli. All isolates harboured between one and three large plasmids (>100 kb). Among isolates associated with asymptomatic chickens, the ESBL types SHV and TEM dominated, while CTX-M-1 dominated in disease-associated isolates. The isolates from diseased birds were occasionally of sequence types often associated with human infections, such as ST131. With improved tools to trace and screen for ESBL-producing E. coli at farm level, strategies can be selected that aim to reduce or eliminate the presence of ESBL-producing E. coli in poultry and poultry products meant for human consumption.

Highly sensitive detection of pathogen Escherichia coli O157:H7 by electrochemical impedance spectroscopy

The presence of enterohemorrhagic Escherichia coli bacteria in food can cause serious foodborne disease outbreaks. Early detection and identification of these pathogens is extremely important for public health and safety. Here we present a highly sensitive label-free immunosensor for the detection of pathogenic E. coli O157:H7. Anti-E. coli antibodies were covalently immobilised onto gold electrodes via a self-assembled monolayer (SAM) of mercaptohexadecanoic acid and the pathogenic bacteria were detected by electrochemical impedance spectroscopy (EIS). Surface Plasmon Resonance (SPR) was used to monitor the antibody immobilisation protocol and antibody patterned surfaces were used to demonstrate the specificity of the antibody coated surfaces against the pathogenic bacteria. The immunosensor showed a very low limit of detection (2CFU/mL) and a large linear range (3 × 10-3 × 10(4)CFU/mL). Finally, the selectivity of the sensor was demonstrated and no significant adsorption of Salmonella typhimurium was observed.

Yogurt containing bioactive molecules produced by Lactobacillus acidophilus La-5 exerts a protective effect against enterohemorrhagic Escherichia coli in mice

An active fraction extracted from Lactobacillus acidophilus La5 cell-free spent medium (LAla-5AF) was incorporated in a dairy matrix and tested to assess its antivirulent effect against enterohemorrhagic Escherichia coli (EHEC). Mice in experimental groups were fed for 4 days with yogurt supplemented with LAla-5AF. On the fifth day, mice were challenged with a single dose (10(7) CFU per mouse) of E. coli O157:H7. The clinical manifestations of the infection were significantly less severe in mice fed the yogurt supplemented with LAla-5AF. EHEC attachment and colonization was attenuated by LAla-5AF. Tumor necrosis factor alpha production was down-regulated, which might indicate a protective effect in the kidney during EHEC infection. To investigate the mechanisms associated with the in vivo effects observed, LAla-5AF was tested by reverse transcription real-time PCR to confirm its effects on the expression of several virulence genes of EHEC O157. The results showed that these fractions were able to down-regulate several virulence genes of EHEC, including stxB2, qseA, luxS, tir, ler, eaeA, and hlyB.

An investigation on first-week mortality in layers

The quality of day-old chick placement and management upon arrival have a major impact on first-week mortality (FWM) and subsequent welfare in layers. The present study investigated FWM and causes of FWM in 50 flocks of layers. Post mortem results from 983 chickens showed that 50% died from infections, whereas noninfectious causes, in particular dehydration and nephropathy with visceral gout, made up the remaining causes of mortality. Escherichia coli and Enterococcus faecalis were identified as the most significant bacterial pathogens associated with FWM. Statistical analysis demonstrated a significant correlation between FWM and total mortality during rearing, and a model predicting total mortality in the rearing period based on FWM was established. A statistically significant correlation between FWM and uniformity of the flock was not demonstrated at 1-2 wk of age or at approximately 15 wk of age. Genetic characterization of E. coli and E. faecalis provided evidence for a polyclonal nature of these infections in affected flocks, indicating different sources of infection. Results obtained underline the importance of minimizing FWM to a level less than 1%.

Clonality and virulence traits of Escherichia coli associated with haemorrhagic septicaemia in turkeys

Fifty-five clinical isolates of avian pathogenic Escherichia coli (APEC) from seven outbreaks of acute haemorrhagic septicaemia in turkeys were characterized by serotyping, plasmid profiling including restriction analysis with HindIII, ribotyping with EcoRI and HindIII, multilocus sequence typing (MLST) and virulence profiling. A clonal relationship was demonstrated for each outbreak according to serotype, plasmid profiling, ribotyping, and MLST. In addition, isolates demonstrated highly similar virulence profiles, as all isolates were positive for F11 pili and possessed genes encoding aerobactin (iucD), increased serum survival (iss), temperature-sensitive haemagglutinin (tsh) and colicin V plasmid operon genes (cva/cvi). However, only 20% of the isolates produced colicin V and 42% exhibited serum resistance. All strains with O group O111 and a single O18ac strain (demonstrating non-clonal DNA profiles) were positive for enteroaggregative heat-stabile toxin (EAST1), while isolates of a single outbreak all possessed the enteroaggregative toxin gene (astA). All isolates were negative for genes encoding verocytotoxins (vtx/stx), iron-repressible protein (irp2), P-fimbria (papC), invasion plasmid antigen (ipaH), attaching and effacing gene (eae), enterohaemolysin (ehxA), and enterotoxins LT, STIa (ST(p)) and STIb (ST(h)). In conclusion, highly similar virulence profiles were demonstrated for isolates of E. coli associated with a single well-defined lesion type of colibacillosis in turkeys; acute haemorrhagic septicaemia. The isolates obtained, however, demonstrated a different phylogenetic background, underlining the importance of using well-defined strain collections for characterization of APEC pathotypes.

Label-free capacitive immunosensor based on quartz crystal Au electrode for rapid and sensitive detection of Escherichia coli O157:H7

A label-free capacitive immunosensor based on quartz crystal Au electrode was developed for rapid and sensitive detection of Escherichia coli O157:H7. The immunosensor was fabricated by immobilizing affinity-purified anti-E. coli O157:H7 antibodies onto self-assembled monolayers (SAMs) of 3-mercaptopropionic acid (MPA) on the surface of a quartz crystal Au electrode. Bacteria suspended in solution became attached to the immobilized antibodies when the immunosensor was tested in liquid samples. The change in capacitance caused by the bacteria was directly measured by an electrochemical detector. An equivalent circuit was introduced to simulate the capacitive immunosensor. The immunosensor was evaluated for E. coli O157:H7 detection in pure culture and inoculated food samples. The experimental results indicated that the capacitance change was linearly correlated with the cell concentration of E. coli O157:H7. The immunosensor was able to discriminate between cellular concentrations of 10(2)-10(5) cfu mL(-1) and has applications in detecting pathogens in food samples. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were also employed to characterize the stepwise assembly of the immunosensor.

Impact of Escherichia coli vaccine on parent stock mortality, first week mortality of broilers and population diversity of E. coli in vaccinated flocks

In the present investigation 20,000 broiler parents were vaccinated during rearing with Nobilis Escherichia coli vaccine and were placed in two out of four identical houses, with the remaining two houses on the same farm accommodating 20,000 unvaccinated control birds. During the production period a total of 335 dead birds (including 171 vaccinated and 164 control birds) randomly selected from the four houses were subjected to post-mortem examination. Although the overall mortality between the vaccinated and control flocks did not differ, mortality due to E. coli infections made up only 8.2% in vaccinated birds compared with 24.6% in unvaccinated birds. All E. coli isolates recovered from internal organs were assigned to the same phylogenetic group (B2), but a major genetic diversity was outlined by multilocus sequence typing. Only a single isolate was demonstrated to harbour a gene encoding the P-fimbriae variant F11, a key component of the Nobilis vaccine. Significant differences in average first week mortality, calculated average weight at 38 days and food conversion rate among broiler flocks originating from vaccinated and control birds, respectively, were not found. Further investigations are needed to explain the protection observed and the impact on the genetic diversity of E. coli.

Development of a polyclonal antibody-based AC-ELISA and its comparison with PCR for diagnosis of canine parvovirus infection

A polyclonal antibody-based antigen-capture ELISA (AC-ELISA) has been developed for detection of Canine parvovirus (CPV) antigens in faecal samples of dogs. The assay uses rabbit anti-CPV polyclonal antibody as the capture antibody, guinea pig anti-CPV polyclonal antibody as tracing antibody and anti-guinea pig HRPO conjugate as the detection system. The optimum dilution of the capture antibody and the tracing antibody capable of detecting the CPV-2 antigens was found to be 1:1 600 and 1:400, respectively, in the check-board titration. In this study, a total of 152 samples (129 faecal samples and 23 cell culture supernatant) were tested both by AC-ELISA and by polymerase chain reaction (PCR). Of the samples tested, 69 and 78 samples were found positive by AC-ELISA and PCR, respectively. The AC-ELISA had relative sensitivity, relative specificity and accuracy of 88.4%, 100.0% and 91.4% respectively. The analytical sensitivity of AC-ELISA was estimated to be 10^2.8 TCID₅₀/mL whereas PCR sensitivity was 10^0.8 TCID₅₀/mL. The AC-ELISA is a simple, quick and reliable method for screening large numbers of faecal samples of dogs suspected of CPV infection.

Avian colibacillosis and salmonellosis: a closer look at epidemiology, pathogenesis, diagnosis, control and public health concerns

Avian colibacillosis and salmonellosis are considered to be the major bacterial diseases in the poultry industry world-wide. Colibacillosis and salmonellosis are the most common avian diseases that are communicable to humans. This article provides the vital information on the epidemiology, pathogenesis, diagnosis, control and public health concerns of avian colibacillosis and salmonellosis. A better understanding of the information addressed in this review article will assist the poultry researchers and the poultry industry in continuing to make progress in reducing and eliminating avian colibacillosis and salmonellosis from the poultry flocks, thereby reducing potential hazards to the public health posed by these bacterial diseases.

The studies on the aetiology of diarrhoea in neonatal calves and determination of virulence gene markers of Escherichia coli strains by multiplex PCR

The purpose of this study was to determine aetiological agents of diarrhoea in neonatal calves and to investigate virulence gene markers of Escherichia coli strains isolated from calves by multiplex polymerase chain reaction (PCR). Eighty‐two diarrhoeic calves and 18 healthy calves were used as subjects. Faeces were taken from the rectums of all the calves and were subjected to bacterial culture. Antigen enzyme‐linked immunosorbent assay (ELISA) was performed to detect rotavirus, coronavirus and E. coli K99 in faeces of all the calves. A multiplex PCR was used to characterize E. coli strains in all the calves. Escherichia coli was isolated from 37 faeces samples, Enterococcus ssp. was isolated from 22 faeces samples and Salmonella was isolated from one faeces sample in diarrhoeic calves. Furthermore, only E. coli was isolated from all 18 faeces samples of healthy calves. Of the 37 E. coli isolated from diarrhoeic calves, K99 (18.9%), F41 (18.9%), heat‐stable enterotoxin a (STa) (18.9%), Shiga toxin 1 (Stx1; 13.5%) and Shiga toxin 2 (Stx2; 5.4%) and intimin (8.1%) genes were identified by multiplex PCR. Of the 18 E. coli isolated from healthy calves, K99 (16.6%) and intimin (55.5%) genes were identified by PCR. A total of 15 rotavirus, 11 coronavirus and 11 E. coli K99 were detected in diarrhoeic calves by the antigen ELISA. As a result, this study shows that rotavirus, coronavirus, E. coli and Enterococcus ssp. were determined to play a role in the aetiology of diarrhoea in the neonatal calves. K99, F41, STa, Stx1 and Stx2 were found as the most common virulence gene markers of E. coli strains isolated from calves with diarrhoea. Multiplex PCR may be useful for characterization of E. coli isolated from calves.