Pathogenic Microbiology Commons^™

Characterization Of Antimicrobial Properties Of Excrement And Functional Microbiome Of Black Vultures (Coragyps Atratus), Bridgette Gray

Theses

Black vultures, Coragyps atratus, are obligate scavenging birds that consume and dispose of decaying carcasses and carrion. They fulfill a key ecological niche in the environments in which they live. It has been observed that these vultures sometimes excrete bodily waste onto their legs. This adaptive behavior could help aid them in controlling bacteria and other microbes they encounter while stepping into a carcass to eat. This study directly examined the antimicrobial properties of the excrement of black vultures across various bacterial species utilizing a zone of inhibition test and a nematode species utilizing a survival assay. The black vulture …

Elucidation Of Novel And Established Campylobacter Species With Clinical And Agricultural Significance Through Phenotypic, Genotypic, And Taxonomic Investigation, Caoimhe Lynch

Theses

Campylobacter spp. are well-established human, veterinary and economic pathogens, with a broad host range spanning from terrestrial and marine mammalian, avian and reptilian hosts. The scope of the study includes novel and notorious species within the genus, with reference to zoonotic agents Campylobacter jejuni and Campylobacter coli - the leading cause of human bacterial gastroenteritis in the EU and Ireland, Campylobacter fetus that represents the most common campylobacter causing bacteraemia and two novel species isolated from pigs not described in the literature previously. C. jejuni and C. coli isolates (n = 350) recovered from broiler caecal and neck skin samples, …

The Occurrence Of Listeria Monocytogenes In The Mushroom Production Chain And The Use Of Bacteriophage For Its Control, Vincenzo Pennone

Theses

In Agaricus bisporus production, the occurrence of L. monocytogenes is still poorly understood. A number of studies have shown the presence of L. monocytogenes in the mushroom processing environment, suggesting its source from raw materials storage areas (Viswanath et al, 2013; Murugesan et al, 2015). In this study, 10 mushroom producers and three raw material (compost and casing) producers participated in two surveys on the occurrence of L. monocytogenes in the most high-risk areas of the production environment. In the first survey, floors, drains, platforms, crates, raw materials and mushrooms were tested for L. monocytogenes presence and the results were …

Crystallographic Structure Determination Of Bacteriophage-Encoded Enzymes That Specifically Target Pathogenic Bacteria, Marta Sanz Gaitero

Theses

Antibiotic resistance is becoming a serious public health concern. Infections that some decades ago could be treated with antibiotics now sometimes do not respond to traditional treatment, causing higher mortality and economic losses. An alternative to the use of antibiotics are bacteria's natural predators, bacteriophages (or phages), and specifically their lytic enzymes. These proteins are produced by phages to degrade bacterial peptidoglycan to inject their genetic material into the bacteria (virion-associated peptidoglycan hydrolases) or to release their progeny once the infection is finished (endolysins). They can be applied exogenously to lyse Gram-positive bacteria or be genetically engineered to lyse Gram-negative …

Mycobacterium Species Identification In An Acute Hospital: Towards Rapid Identification, And Improved Epidemiology, Using Novel Mass Spectrometry Analysis, James Anthony O'Connor

Theses

Mycobacteria are a heterogeneous group of bacteria that cause a wide spectrum of disease, including Tuberculosis (TB), the single biggest killer worldwide. The genus also incorporates over 170 nontuberculosis (NTM) species, many of which are opportunistic pathogens. The aim of this project was to ascertain the burden of mycobacterial disease in the region and to determine the efficacy of Matrix-Assisted Laser Desorption/Ionisation time-of-flight (MALDI-tof) mass spectrometry (MS) for novel uses as a rapid identification method for clinical mycobacteria and as a typing tool for Mycobacterium tuberculosis complex isolates. A five-year retrospective epidemiological study of the region was conducted, the first …

Clinical Coagulase-Negative Staphylococci; Identification, Characterisation And Treatment, Emma Gabriel

Theses

The work presented in this thesis focuses on clinically significant staphylococci (with an emphasis on coagulase-negative staphylococci) in terms of their isolation, identification, characterisation, and biocontrol.

CoNS are increasingly being recognised as true nosocomial pathogens yet remain under-characterised, particularly from an Irish clinical perspective. We examined a large cohort of clinically-derived CoNS, isolated from blood (n=l35), identifying them to species level. Extensive antibiotic resistance against nine clinically-relevant antibiotics was recorded. Additionally, widespread biofilm forming capabilities associated with increased virulence was detected both phenotypically and genotypically. We identified multiple species of CoNS in circulation in an Irish healthcare setting, and determined …

Identification Of The Molecular Mechanisms Governing The Osmotolerance Of The Emerging Gastrointestinal Pathogen Cronobacter Sakazakii, Audrey Feeney

Theses

Cronobacter sakazakii is an organism which has been associated with severe life- threatening diseases in infants and neonates. Mortality rates of up to 80% have been recorded in infants infected with Cronobacter sakazakii. Infants often suffer from septicaemia, necrotising enterocolitis and meningitis as a result of infection. A characteristic feature of the opportunistic foodborne pathogen Cronobacter sakazakii is its ability to survive in extremely arid environments such as powdered infant formula, making it a dangerous opportunistic pathogen of neonates. Herein, we provide a brief overview of the pathogen; clinical manifestations, environmental reservoirs and our current understanding of stress response mechanisms …

Exploiting Bacteriophages And Associated Peptidoglycan Hydrolases With Potential For Biocontrol In Food Related Applications, Lorraine Endersen

Theses

The work presented in this thesis describes the isolation and characterisation of novel bacteriophages, and the subsequent exploitation of their bactericidal properties against two opportunistic food related pathogens, Mycobacterium avium subsp. paratuberculosis (MAP) and Cronobacter sakazakii.

MAP is a proven animal pathogen known to cause Johne’s disease in cattle but has been implicated as a causative agent of Crohn’s disease in humans. Despite the fact that this association has yet to be proven, significant focus has been directed towards evaluating the consequences of consuming milk contaminated with MAP. Accordingly, six mycobacteriophages were isolated and characterised in terms of temperature and …

Gastroenteritis Viruses In Ireland: Epidemiology And Evolution, Lynda Gunn

Theses

Viral gastroenteritis is a common disease of both humans and animals. This thesis focuses on the use of classical virology, coupled with phylogenetics to study gastroenteritis viruses [Bocavirus (BoV), Coronavirus (CoV), and Rotavirus A (RVA)], isolated from selected samples from humans and animals. RVA was associated with outbreaks in elderly care facilities in Northern Ireland, isolates were genotyped and we reported the first detection of G2 lineage lie RVA in Ireland, with other common human RVA genotypes G1P[8], G2P[4] and G9P[8]. Evolutionary dynamics of human RVA VP7 genotypes was examined using codon models of evolution, results show heterogeneous selective pressure …

Detection, Identification And Characterization Of The Novel Campylobacter Species: Campylobacter Ureolyticus And Campylobacter Corcagiensis From Their Reservoirs., Monika Koziel

Theses

Campylobacter ureolyticus has been identified in a large proportion of diarrhoeal samples from patients in Ireland. However, the source of human infections has not been established and little is currently known about the potential reservoirs of C. ureolyticus in nature.

The aim of this project was to investigate a range of environmental and animal samples for the presence of this emerging pathogen using a molecular approach, to support the hypothesis of its zoonotic origin.

During the study, C. ureolyticus was detected in 30 out of 1,254 (2.4%) human diarrheic samples and isolated from 11 patients, describing, to the best of …

Characterisation Of The Enzybiotic Potential Of Selected Staphylococcus Aureus Bacteriophages, Ruth Keary

Theses

The work presented in this thesis focuses on harnessing the bactericidal potential of bacteriophage (phage) encoded peptidoglycan hydrolase enzymes to combat the significant pathogen Staphylococcus aureus. In order to identify novel peptidoglycan hydrolases lytic against S. aureus, the complete genomes of two staphylococcal temperate Siphoviridae bacteriophages, DW2 and CSl, were sequenced and annotated. Screening of these genomes identified genes for several putative peptidoglycan hydrolases including two endolysins and three virion-associated peptidoglycan hydrolases. The identification of putative genes relating to virulence and host fitness lends to the understanding of the role played by such temperate phages in the evolution of this …

Development Of A Recombinant Lactobacillus Salivarius For Prophylactic Applications Against Mycobacterium Avium Subspecies Paratuberculosis And Johne’S Disease, Christopher Johnston

Theses

Current whole-cell vaccines against Mycobacterium avium subsp. paratuberculosis, the etiological agent of Johne’s disease, are unable to provide complete protection against infection. Moreover, such whole-cell formulations interfere with diagnostic tests for bovine tuberculosis (Mycobacterium bovis). The development of subunit vaccines, those which are preferentially based on one, or a select few, immunodominant protective antigens is considered as the realistic next step in overcoming these issues. The (MAP) K-10 genome is a single circular chromosome of 4,829,781 base pairs and encodes 4,350 predicted ORFs. In order to identify MAP specific proteins for subsequent incorporation within a mucosal based vaccine development, a …

Identification And Characterisation Of Campylobacter Ureolyticus: A New And Emerging Gastrointestinal Pathogen, Susan Bullman

Theses

Campylobacter jejuni is universally recognized as the leading bacterial cause of human gastroenteritis. However, within recent years a growing number of non- jejuni/coli Campylobacter species have been acknowledged as emerging human and animal pathogens. Advances in molecular diagnostics and development of pioneering culture methodologies have led to the detection of a range of under-appreciated and nutritionally fastidious Campylobacter species, including C. ureolyticus. Herein, we provide the first report of C ureolyticus in the faeces of patients presenting with gastroenteritis and suggest a role for this organism as an emerging enteric pathogen.

Employing a two-tiered molecular study, we report C. ureolyticus …

The Isolation And Characterisation Of Acientobacter Baumannii Bacteriophage, Mohamed Farag M. Elbreki

Theses

Acinetobacter baumannii is a pathogen, which has an increasing prevalence of multidrug resistance. It exists widely in natural environments, and frequently in health-care settings where it has proven difficult to eradicate using antibiotic therapy. A possible alternative to conventional antibiotics is the use of bacteriophages (phages) as antibacterials. In this project, extensive screening of environmental samples such as soils, sewage and waters was undertaken to identify suitable phages. Three phages were successfully isolated from municipal waste in the Cork area. These were subsequently characterized in detail and examined by electron microscopy, which showed that they were all of the Myoviridae …

In Silico Prediction Of Protein-Protein Interactions Between Cronobacter Sakazakii And Human Host, Sean Held

Theses

The genus Cronobacter accommodates 16 biogroups of the emerging opportunistic pathogen known formerly as Enterobacter sakazakii. Cronobacter are occasional contaminants of milk powder and, consequently, powdered infant formula (PIT). Since it is a pathogen that is transmitted in infant formula it represents a significant health risk to neonates. These bacteria are opportunistic pathogens (can only cause disease when the host's resistance is low) and are linked with life-threatening infections in neonates. Some of the clinical symptoms of Cronohacter infection include necrotizing enterocolitis, bacteremia, and meningitis, with case fatality rates of 50-80% being reported (Healy et al. 2010). Infant formula manufacturers …

Examination Of The Prevalence And Persistence Of Pathogenic Staphylococci On Euro Currency, Emma Gabriel

Theses

Staphylococci are a diverse group of bacteria that cause diseases ranging from minor skin infections to life-threatening bacteremia. Methicillin-resistant S. aureus (MRSA) is the most common multidrug-resistant nosocomial pathogen in Europe estimated to cause 170,000 infections resulting in more than 5,000 deaths and additional healthcare costs of approximately €380 million annually (Kock et al., 201 1). Whilst rarely life-threatening, coagulase-negative staphylococci (CoNS), in particular S. epidermidis are responsible for the majority of indwelling medical device failures, causing intrinsically resistant biofilm infections, estimated to cost $2 billion per year in additional healthcare costs in the U.S. alone (Otto, 2009).

It is …

Enhanced Surveillance And Characterisation Of Three Significant Gram-Positive Pathogens, Annmarie Mollaghan

Theses

Clinical microbiology has been revolutionised in recent years by the introduction of molecular biology. Traditionally, the gold standard for diagnosis in the clinical microbiology laboratory has been culture, which in some cases, is gradually being replaced by molecular detection methods, particularly where the pathogen is difficult to grow or to identify, or when the significance of an organism is dependent on the detection of specific markers of pathogenicity, such as toxins. Many fastidious bacteria which are difficult to culture and present public health implications, i.e. Mycobacterium tuberculosis. Chlamydia trachomatis and Neisseria gonorrhoea, can now be detected using commercial molecular assays …

Purification, Characterisation And Applications Of A Cloned Staphylococcal Bacteriophage Lysin For The Control Of Multi-Drug Resistant Staphylococcus Aureus Including Mrsa, Mark Fenton

Theses

The work presented in this thesis focuses on the purification, characterisation and practical applications of an anti-staphylococcal lysin (LysK) and its single-domain truncated derivative (CHAP_k) against pathogenic staphylococci including meticillin resistant Staphylococcus aureus (MRSA). Both proteins were purified to greater than 90% homogeneity. Affinity chromatography was applied as the optimum method for LysK purification and ion-exchange chromatography was successfully applied to CHAP_k. The lytic spectrum of LysK was investigated by zymogram analysis where the enzyme exhibited strong activity against a range of staphylococci regardless of their origin, sequence type (ST) or antibiotic resistant profile. This analysis …

Phage Lysins - Structure, Genetics And Applications, Jennifer Garry

Theses

Antibiotics are of the utmost importance in the fight against pathogenic bacteria, however, in recent years there has been a continual increase in the development of antibiotic resistance among bacteria. As a result it has become essential to develop new technologies to combat these pathogens. One such technology is the application of phage lysins as antimicrobial agents against pathogenic infections. A promising phage lysin is LysK, a 495 amino-acid protein derived from Staphylococcal Phage K. LysK can lyse a wide range of staphylococcal species including MRSA. It is also capable of killing both live and dead cells increasing its potential …

The Rapid Identification Of Novel Anti-Mycobacterial Drugs And The Transporters Involved In Their Resistance, James Carroll

Theses

Despite the success of anti-mycobacterial drugs over the past 70 years, mycobacterial disease, particularly tuberculosis is still responsible for millions of deaths worldwide. Additionally, the emergence of Multidrug Resistant (MDR-TB) and Extensively Drug Resistant (XDR-TB) Tuberculosis throughout the world has motivated calls by the World Health Organization for novel mycobacterial drugs, vaccines and diagnostic tests. Consequently, this study sought to identify and evaluate the efficacy of a range of anti-mycobacterial compounds against a representative cohort of pathogenic mycobacterial species. The development and employment of the rapid, robust and inexpensive microtitre alamarBlue assay (MABA) facilitated the assessment of a vast array …

Isolation And Molecular Characterization Of Mycobacterium Avium Subsp. Paratuberculosis In Ireland, Pierre Emmanuel Douarre

Theses

MAP is a proven animal pathogen causing Johne's disease, one of the most widespread and economically important diseases of ruminants. Since 1992 and the opening of the European market, the prevalence of MAP in Ireland has increased considerably. Improvements in diagnostic strategies for Ireland and elsewhere are urgently required. MAP infects a wide host range and has emerged as a potential threat to human health and has been associated with Crohn's disease. The control of paratuberculosis infection requires a better understanding of the genetic diversity of the pathogen. The objective of this study was to isolate and characterize this enteric …

Identification And Molecular Characterisation Of Mycobacteriophages And Their Lysis Proteins, Marine Henry

Theses

Given their potential as specific and natural biocontrol agents, bacteriophages and their associated proteins have become the focus of renewed interest over the last decade. This study reviews the current state of mycobacterial diseases control worldwide and presents how phage therapy and the production of recombinant bacteriophage lysis proteins can be applied as novel biocontrol strategies for mycobacteria.

Chapter 11 presents an overview of the predicted LysA and LysB proteins in all the mycobacteriophages sequenced to date and proposes an in silico 3D predictive model of the lysin B of a recently isolated and characterised mycobacteriophage. Our data also confirms …

Development Of Pcr Assays To Detect And Characterise Salmonella Isolates From Cheese And Meat Products By Utilizing An Integrated Genomics Approach, Noelle Geraldine Mccarthy

Theses

Salmonella is an extremely important foodborne pathogen which is responsible for millions of cases of gastroenteritis annually. Salmonella outbreaks have been associated with numerous common food stuffs such as meat, dairy and seafood. Traditional culture based methods for the detection Salmonella are labourious and costly. Rapid detection and serovar identification would dramatically decrease the time required to identify Salmonella outbreaks and potential health risks.

In the US 99% of all Salmonella infections are caused by members of Salmonella enterica subspecies 1. Serovars within subspecies 1 can vary due to host specificity and pathogenicity. DNA sequencing projects have provided valuable genomic …

Mupirocin Resistance In Staphylococci: An Investigation Of Current Status And Potential Alternative Therapies, Susan O'Shea

Theses

Mupirocin is a topical antibiotic used in hospital infection control practices to control transmission of staphylococci, in particular MRSA, which has become a major problem in Irish hospitals and has a significant impact on patient morbidity and mortality. Overreliance on mupirocin to eradicate MRSA carriage and to prevent infection has led to mupirocin resistance among staphylococcal species. Two distinct types of resistance have developed within strains: low'-level mupirocin resistance (LMR) and high-level mupirocin resistance (HMR).

The aim of this study was to assess the prevalence and types of mupirocin resistance in a large population of clinical staphylococcal isolates including Methicillin …

Epidemiology And Drug Resistant Profiles Of Candida Species, In Cork Hospitals., Emma Mccurtin

Theses

Candida causes superficial infections in healthy individuals; however in the immunocompromised host Candida can cause invasive, systemic infections and is a significant cause of morbidity and mortality. This is not due to a more virulent phenotype but to a weakened immune system unable to fight this opportunistic pathogen. The immunocompromised population is ever increasing, due to medical advancements and more aggressive treatments, and hence is the need for epidemiological data of these potentially life threatening infections. The aim of this study was to provide an epidemiological snapshot, of Candida infections from the immunocompromised population in Cork hospitals. Surveillance programmes from …

Molecular Epidemiology Of Antibiotic Resistant Salmonella Enterica Strains From Different Animal And Human Sources In Ireland, David George Lee

Theses

In this study, 176 isolates of Salmonella were collected from different laboratories in Ireland. All isolates were confirmed to be of the genus Salmonella by performing bacteriological and biochemical tests. Briefly, all isolates were cultured onto XLD agar after which pure cultures were verified and stocked at this institute. Definitive identification was carried out using the API 20-E system and a separate urease test was also performed on all isolates. After confirmation of the genus, all isolates were prepared for antibiotic susceptibility testing and r-types were determined using sixteen antibiotics. Depending on the antibiotic resistance profiles, isolates were selected for …

Validation Of An Immunomagnetic-Electrochemiluminescence Detection System For The Detection Of Escherichia Coli 0157 In Food And Comparison With An Iso Standard Method, Eimear Carney

Theses

Rapid and sensitive methods for detecting Escherichia coli 0157 in contaminated food, water and other biological samples are important in limiting and preventing the spread of this pathogen. Traditional culture based methods for bacterial identification and detection can be time consuming and labour intensive. Modem alternative methods should be faster whilst maintaining sensitivity. Immunomagnetic separation (IMS) methodology has been investigated and appears promising for rapid bacterial detection in unrelated food and environmental samples. In this study, a commercial sensor which combined IMS with electrochemiluminescence (ECL) was evaluated for the detection of E. coli 0157 in unrelated food matrices. Emitted signals …

The Molecular Characterisation Of Selected Epidemic Associated Gram Negative Pathogens In Southern Ireland, Mairéad Daly

Theses

This study was undertaken to evaluate various molecular techniques for the analysis of Gram negative bacterial associated epidemics. The first investigation dealt with bovine mastitis outbreaks, where the causative agent was identified as Pseudomonas aeruginosa. Epidemiological findings, suggested that all herds were infected from teat wipes that were contaminated with this organism. Initial investigations using the polymerase chain reaction (PCR), indicated a possible clonal relationship between all outbreak linked strains, with one exception. This finding was confirmed following pulsed-field gel electrophoresis (PFGE) and ribotype analysis. PCR was again employed to study a rather unusual epidemic, involving Salmonella tel-el-kebir over a …