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Biomedical subjects

James S G Dooley

Publications and source records attributed to James S G Dooley.

13 recordsLinked to original sources
PubMed2006

Proteomics analysis and protein expression during sporozoite excystation of Cryptosporidium parvum (Coccidia, Apicomplexa).

Cryptosporidiosis, caused by coccidian parasites of the genus Cryptosporidium, is a major cause of human gastrointestinal infections and poses a significant health risk especially to immunocompromised patients. Despite intensive efforts for more than 20 years, there is currently no effective drug treatment against these protozoa. This study examined the zoonotic species Cryptosporidium parvum at two important stages of its life cycle: the non-excysted (transmissive) and excysted (infective) forms. To increase our understanding of the molecular basis of sporozoite excystation, LC-MS/MS coupling with a stable isotope N-terminal labeling strategy using iTRAQ reagents was used on soluble fractions of both non-excysted and excysted sporozoites, i.e. sporozoites both inside and outside oocysts were examined. Sporozoites are the infective stage that penetrates small intestinal enterocytes. Also to increase our knowledge of the C. parvum proteome, shotgun sequencing was performed on insoluble fractions from both non-excysted and excysted sporozoites. In total 303 C. parvum proteins were identified, 56 of which, hitherto described as being only hypothetical proteins, are expressed in both excysted and non-excysted sporozoites. Importantly we demonstrated that the expression of 26 proteins increases significantly during excystation. These excystation-induced proteins included ribosomal proteins, metabolic enzymes, and heat shock proteins. Interestingly three Apicomplexa-specific proteins and five Cryptosporidium-specific proteins augmented in excysted invasive sporozoites. These eight proteins represent promising targets for developing vaccines or chemotherapies that could block parasite entry into host cells.

Animals↗
PubMed2006

Genotypes and subtypes of Cryptosporidium spp. in neonatal calves in Northern Ireland.

Cryptosporidium spp. in diarrheic calves less than 30 days old from farms across Northern Ireland were examined over a year period by microscopic, genotyping, and subtyping techniques to characterize the transmission dynamics. Cryptosporidium oocysts were detected in 291 of 779 (37.4%) animals. The prevalence rates of rotavirus, coronavirus, and Escherichia coli K99+ were lower as seen in 242 of 806 (30.0%), 46/806 (5.7%), and 16/421 (3.8%) of animals, respectively. Of the 224 Cryptosporidium-positive specimens available for molecular analysis, Cryptosporidium parvum was identified in 213 (95.1%) specimens, Cryptosporidium bovis in eight (3.6%), and Cryptosporidium deer-like genotype in three (1.3%). Sequence analysis of the 60-kDa glycoprotein gene identified 16 IIa subtypes and a new subtype family, with 120 of the 216 (55.6%) positive specimens having the subtype IIaA18G3R1. Eight of the IIa subtypes were previously seen in humans in Northern Ireland. Several subtypes were temporally or geographically unique. The genetic diversity in calves in Northern Ireland was much greater than that reported from other areas. This work demonstrates the utility of genotyping and subtyping tools in characterizing the transmission of Cryptosporidium spp. in calves and humans.

Animals↗
PubMed2006

An examination of the diversity of a novel Campylobacter reservoir.

The diversity of eukaryotic populations, in particular protozoa, in the water supplies of intensively reared broilers has not been previously studied. This important food-rearing environment was screened for the molecular diversity of eukaryotes by the analysis of PCR-amplified 18S rRNA. DNA was extracted from filtered water samples that were collected from the poultry drinking water systems of five farms. The total genomic DNA was used to produce rRNA-PCR amplicons, which, with the application of TTGE, provided an overview of the eukaryotic population diversity. The rRNA-PCR amplicons were then used to generate 34 random clones that were subject to comparative sequence analysis. Twenty-five of the clones (73.5%) showed high similarity with yeasts and fungi (>92%) and 9 clones demonstrated similarity (>86%) with certain protozoan groups, including flagellates and alveolates. Further studies of the microbial diversity in the previously ignored niche of intensively reared poultry drinking water systems are required, along with subsequent in vitro co-culture assays of the detected protozoa and bacterial strains.

Animals↗
PubMed2006

The epidemiology of antibiotic resistance in Campylobacter.

Antibiotic resistance, particularly with the fluoroquinolones and macrolide antibiotics, has now emerged globally with thermophilic campylobacters, including Campylobacter jejuni and C. coli, giving rise to concerns about how these organisms have acquired such resistance characteristics, as well as consequences for human and animal treatment. This review examines (i) the clinical epidemiology of antibiotic resistance in human and animal thermophilic campylobacters, (ii) an update on resistance rates globally, (iii) surveillance of antimicrobial resistance in campylobacters originating from animals, particularly poultry, (iv) the role of the environment in the acquisition and transmission of antibiotic-resistant campylobacters, as well as (v) issues of biocide resistance in campylobacters.

Animals↗
PubMed2006

Detection of phosphonoacetate degradation and phnA genes in soil bacteria from distinct geographical origins suggest its possible biogenic origin.

Phosphonoacetate is regarded as an antiviral xenobiotic whose mineralization can be catalysed by an enzyme, phosphonoacetate hydrolase, encoded by the phnA gene. To date the enzyme's activity has been detected in only a limited number of bacteria. Its expression has been shown to occur in a manner independent of the phosphate status of the cell, in direct contrast to the general rule of organophosphonate metabolism being under the control of the pho regulon. In this study the environmental occurrence of the phnA gene was evaluated by polymerase chain reaction amplification of DNA extracts obtained directly from various soil environments. Sensitivity of this method was improved such that a positive result was routinely obtained with soil spiked with as few as 6 colony-forming units (cfu) per gram of soil of Pseudomonas fluorescens 23F (phnA(+)). When total DNA from a variety of Northern Irish, Greek and Bolivian soils was tested, all were positive for phnA. Bacteria capable of utilizing phosphonoacetate as sole carbon, energy and phosphorus source, with the release of essentially equimolar concentrations of phosphate to the culture supernatant, were isolated from all soil samples tested. Analysis of three such isolates revealed all to be species of Pseudomonas sensu stricto, possessing phosphonoacetate hydrolase activity in cell-free extracts. Sequence determination of the phnA gene revealed a similarity of the putative protein sequences at levels of 98.3-99.3% between the Pseudomonas strains. This is the first study to use molecular methods to investigate the distribution of a gene encoding organophosphonate metabolism, and indicates that the phnA gene is ubiquitous within soils from geographically distinct regions. Such an observation supports the proposition that phosphonoacetate is a compound that may also have a biogenic origin.

Alkaline Phosphatase↗
PubMed2006

Prevalence and identity of Cryptosporidium spp. in pig slurry.

Cryptosporidium spp. were detected in 25 of 56 pig slurry samples from 33 Irish farms by PCR and DNA sequencing. The organisms detected included C. suis, Cryptosporidium pig genotype II, and C. muris. We concluded that Cryptosporidium oocysts can persist in treated slurry and potentially contaminate surface water through improper discharge or uncontrolled runoff.

Animals↗
PubMed2005

Bacterial-protozoa interactions; an update on the role these phenomena play towards human illness.

The usage of water with poor microbiological quality increases the risk of human illness. This review discusses and updates current thinking on the nature of the interaction between a range of human bacterial pathogens and waterborne protozoa. The importance of protozoa acting as protective environments for pathogenic bacteria from disinfection and of promoting extended survival in otherwise hostile environments is highlighted. The significance of biofilms in water systems, and new relationships between Salmonella and Campylobacter and water-borne protozoa are also discussed. The protection of pathogenic bacteria from disinfection within protozoa and/or biofilms has important implications for water safety.

Animals↗
PubMed2004

Infection control and the significance of sputum and other respiratory secretions from adult patients with cystic fibrosis.

BACKGROUND: There is limited data available on the environmental and public health impact of the microbiological hazards associated with sputa from patients with cystic fibrosis [CF]. Pseudomonas aeruginosa, Burkholderia cenocepacia (formerly Burkholderia cepacia genomovar III), Staphylococcus aureus and Stenotrophomonas maltophilia are bacterial pathogens which are commonly found in the sputum of CF patients. A study was performed to ascertain the amount of sputum produced relating to microbial loading, as well as the diversity of bacteria present in a population of adult patients, with particular attention to pathogenic organisms. METHODS: Sputum from adult [>18 years old] CF patients [n = 20], chosen randomly from a population of 138 CF patients, was collected over a 24 h period on admission to the in-patient CF unit and enumerated quantitatively, as well as the sputa from 138 adult CF patients was examined qualitatively for the presence of infecting microflora. In addition, all different phenotypes from the sputum of each patient were identified phenotypically employing a combination of conventional identification methods [e.g. oxidase], as well as the API Identification schemes [API 20 NE, API 20 E]. RESULTS: This study demonstrated that patients with cystic fibrosis generate large numbers of bacteria in their sputum, approximating to 10(9) organisms per patient per day. Although these organisms are introduced to the environment from the respiratory tract mainly via sputum, relatively few represent true bacterial pathogens and therefore are not clinically important to the general public who are immunocompotent. The greatest risk of such environmental microbial loading is to other patients with CF and therefore CF patients should be made aware of the hazards of acquiring such organisms from the environment, as well as socializing with other CF patients with certain transmissible types, such as Pseudomonas aeruginosa and Burkholderia cenocepacia. CONCLUSIONS: Environmental health professionals should therefore be aware that CF patients are a greater risk to their peer grouping rather than to the general public or health care workers and that good personal hygiene practices with CF patients should be encouraged to minimize environmental contamination and potential acquisition.

Journal Article↗
PubMed2002

Three drinking-water-associated cryptosporidiosis outbreaks, Northern Ireland.

Three recent drinking-water-associated cryptosporidiosis outbreaks in Northern Ireland were investigated by using genotyping and subgenotyping tools. One Cryptosporidium parvum outbreak was caused by the bovine genotype, and two were caused by the human genotype. Subgenotyping analyses indicate that two predominant subgenotypes were associated with these outbreaks and had been circulating in the community.

Animals↗
PubMedDate not supplied

Campylobacter.

Species within the genus, Campylobacter, have emerged over the last three decades as significant clinical pathogens, particularly of human public health concern, where the majority of acute bacterial enteritis in the Western world is due to these organisms. Of particular concern are the species, C. jejuni and C. coli, which are responsible for most of these gastrointestinal-related infections. Although these organisms have already emerged as causative agents of zoonoses, several aspects of their epidemiology and pathophysiology are only beginning to emerge. Trends in increasing antibiotic resistance are beginning to emerge with oral antibiotics, which may be the drug of choice for when it is necessary to intervene chemotherapeutically. This review wishes to examine (i) emerging clinical aspects of the disease, such as Guillain Barre syndrome (GBS), (ii) the association between these organisms and poultry as a natural host, (iii) environmental aspects of Campylobacter epidemiology, (iv) the emergence of atypical campylobacters (v) emerging trends in antibiotic resistance, (vi) adoption of modern methods for the detection of campylobacters.

Animals↗