Biomedical subjects

Paul Whyte

Publications and source records attributed to Paul Whyte.

9 recordsLinked to original sources

PubMed2006

Development and application of Multiple-Locus Variable number of tandem repeat Analysis (MLVA) to subtype a collection of Listeria monocytogenes.

In this study we report the development and application of a Multiple-Locus Variable number of tandem repeat Analysis (MLVA) strategy for subtyping Listeria monocytogenes. Genome profiles of a collection of forty-five food-borne L. monocytogenes isolates were compared using MLVA. These isolates were obtained as part of an active surveillance programme of foods in the south-east region of Ireland. MLVA successfully discriminated amongst the isolates. The method was easy to perform, relatively fast and could be deployed in any molecular laboratory with basic laboratory equipment. This approach is a valuable tool, which has the capability to provide comparable results when compared with other more established typing methods, including pulsed-field gel electrophoresis (PFGE).

Bacterial Typing Techniques↗

PubMed2006

Development and assessment of a rapid method to detect Escherichia coli O26, O111 and O157 in retail minced beef.

A molecular-based detection method was developed to detect Escherichia coli O26, O111 and O157 in minced (ground) beef samples. This method consists of an initial overnight enrichment in modified tryptone soya broth (mTSB) and novobiocin prior to DNA extraction and subsequent serogrouping using a triplex PCR. This method has a low limit of detection and results are available within 24 hours of receipt of samples. Once optimized, this rapid method was utilized to determine the prevalence of these E. coli serogroups in six hundred minced beef samples all of which were previously examined by immunomagnetic separation (IMS) and selective plating for E. coli O26 and O111. Using IMS, two E. coli O26 isolates were detected. No E. coli O111 were recovered. The multiplex PCR technique described here did not detect E. coli O111 nor O157 in any of the samples, however six minced beef samples were positive for E. coli O26 using our method, only two of these were previously detected by IMS and culture. Application of molecular methods are useful to support culture-based approaches thereby further contributing to risk reduction along the food chain.

Animals↗

PubMed2006

Comparison of Listeria monocytogenes strain types in Irish smoked salmon and other foods.

An investigation of Listeria monocytogenes in Irish retail smoked salmon products and other unrelated food products was undertaken. Serotyping and genotyping methods were applied. Twenty-six L. monocytogenes isolates cultured from ready-to-eat smoked salmon and an additional 20 L. monocytogenes isolates from various commercially available food products (other than smoked salmon) were compared. Four serotypes, 12 ribotypes, 12 amplified fragment length polymorphism (AFLP) types and 17 pulsed-field gel electrophoresis (PFGE) types were identified among the 46 isolates studied. Genotyping identified a single dominant strain that accounted for 65% of those cultured from smoked salmon and this strain was present in product obtained from three out of five of the manufacturers surveyed. When compared to the food products obtained from a variety of sources, those from smoked salmon appeared to cluster as a single group. In Irish smoked salmon this strain may have adapted, and be capable of persisting in this food product. All isolates were grouped into genetic lineages based on their EcoR1 ribotypes. The attendant risk to public health following consumption of these foods is discussed.

Animals↗

PubMed2006

Characterization of a collection of Enterobacter sakazakii isolates from environmental and food sources.

Enterobacter sakazakii has emerged as a rare cause of neonatal meningitis, septicemia and enterocolitis. Contaminated infant milk formula (IMF) has been identified as one infection route. A small number of clinical outbreaks have been epidemiologically linked to IMF contaminated post-pasteurization during manufacture and/or mishandled when reconstituted. Currently no agreed standardized typing protocol has been developed to trace E. sakazakii. The objectives of this study were to apply biochemical and genetic methods to characterize 51 environmental and food E. sakazakii isolates and 6 E. sakazakii type strains. Isolates were presumptively identified using biochemical profiles based on API 20E and ID32E methods and by culture on differential selective Druggan Forsythe Iversen (DFI) agar. Identification was subsequently confirmed by real time polymerase chain reaction (PCR). All but one of the isolates was identified as E. sakazakii by biochemical profiling. One isolate was identified as Escherichia vulneris by ID 32E and as Pantoea agglomerans by API 20E. All isolates produced green/blue colonies on DFI medium characteristic of this organism. Real time PCR could differentiate between E. sakazakii, Enterobacter spp. and other Enterobacteriacae. Analysis of RAPD banding patterns revealed 3 major clusters of E. sakazakii. There was a large degree of diversity noted amongst the remaining isolates. Our findings indicate that RAPD may be applied as a useful and reliable tool for direct comparison of E. sakazakii isolates providing traceability through the infant formula food chain.

Cluster Analysis↗

PubMed2006

Antimicrobial resistance in nontyphoidal Salmonella from food sources in Colombia: evidence for an unusual plasmid-localized class 1 integron in serotypes Typhimurium and Anatum.

Seventy-two isolates representing 18 serotypes recovered from various food samples collected in Colombia were tested for antimicrobial susceptibilities. The collection was further characterized for extended-spectrum cephalosporin, aminoglycoside, and tetracycline resistance markers. Multidrug resistant (MDR) isolates were further investigated for class 1 integrons and were evaluated for the presence of conjugative plasmids along with a determination of the incompatibility group by polymerase chain reaction (PCR). Antibiogram analysis showed that the incidence rate of ceftiofur resistance was moderately high (15%). A similar level of resistance to neomycin and oxytetracycline (11% and 10%, respectively) was also observed. There was a high prevalence of gene cassettes as part of one or more class 1 integrons (61%), many of which contained determinants that contributed to the resistance profile. Class 1 integrons identified in MDR Salmonella enterica serotypes Typhimurium and Anatum isolates were characterized. Sequencing identified several incomplete open reading frames (ORFs) as part of a gene cassette (bla-( imp-13 ), dfr7, blr1088, and aac8) along with a complete gene cassette (bla-(oxa2)) in each case. A mosaic of gene cassettes was identical in the two Salmonella serotypes. These integrons were located to a conjugative replicon. Plasmid profiling and incompatibility typing identified three plasmids belonging to Inc groups A/C, P, and W. Our study highlights the role of integrons, contributing to a MDR phenotype that is capable of dissemination to other bacteria.

Anti-Bacterial Agents↗

PubMed2006

Multi-drug resistance in Salmonella enterica: efflux mechanisms and their relationships with the development of chromosomal resistance gene clusters.

Bacterial drug resistance represents one of the most crucial problems in present day antibacterial chemotherapy. Of particular concern to public health is the continuing worldwide epidemic spread of Salmonella enterica serovar Typhimurium phage type DT104 harbouring a genomic island called Salmonella genomic island I (SGI-1). This island contains an antibiotic gene cluster conferring resistance to ampicillin, chloramphenicol, florfenicol, streptomycin, sulfonamides and tetracyclines. These resistance genes are assembled in a mosaic pattern, indicative of several independent recombinational events. The mobility of SGI-1 coupled with the ability of various antibiotic resistance genes to be integrated and lost from the chromosomal resistance locus allows for the transfer of stable antibiotic resistance to most of the commonly used antibiotics and adaptation to new antibiotic challenges. This, coupled with the incidence of increasing fluoroquinolone resistance in these strains increases the risk of therapeutic failure in cases of life-threatening salmonellosis. Fluoroquinolone resistance has largely been attributed to mutations occurring in the genes coding for intracellular targets of these drugs. However, efflux by the AcrAB-TolC multi-drug efflux pump has recently been shown to directly contribute to fluoroquinolone resistance. Furthermore, the resistance to chloramphenicol-florfenicol and tetracyclines in DT104 isolates, is due to interaction between specific transporters for these antibiotics encoded by genes mapping to the SGI-1 and the AcrAB-TolC tripartite efflux pump. The potential for the use of efflux pump inhibitors to restore therapeutic efficacy to fluoroquinolones and other antibiotics offers an exciting developmental area for drug discovery.

ATP Binding Cassette Transporter, Subfamily B↗

PubMed2005

Antimicrobial resistance in isolates of Salmonella spp. from pigs and the characterization of an S. Infantis gene cassette.

One hundred and seven Salmonella isolates of various serotypes were investigated for resistance to a panel of nine antimicrobial agents by standardized methods. Thirty four isolates were susceptible to the selected antimicrobial agents. Thirty-six (of 107) were resistant to three or more antimicrobial agents and defined as multidrug resistant (MDR). Salmonella Typhimurium was the most resistant serotype. All resistant isolates were examined for the presence of class 1 integrons. Thirty-two integron-associated gene cassettes (of varying sizes) were identified. A 1,000-bp amplicon similar to that flanking the distal region of the Salmonella Genomic Island (SGI)-1 in Salmonella Typhimurium was detected in a majority of the S. Typhimurium isolates in this study. In contrast, a 1,800-bp amplicon was identified in all Salmonella Infantis isolates. This amplicon was completely characterized in one isolate. The presence of class 1 integrons in Salmonella spp. in pigs may be important if these zoonotic pathogens were to enter the food chain.

Abattoirs↗

PubMed2005

Prevalence and characterization of Escherichia coli O26 and O111 in retail minced beef in Ireland.

Verocytotoxigenic Escherichia coli (VTEC) O157 are recognized as bacterial pathogens with significant public health impact. However, other serogroups, including O26, O111, O103, and O145, have the potential to cause the same spectrum of illness. In this study, 800 minced (ground) beef samples covering a large geographical region in Ireland were collected and tested for Escherichia coli (E. coli) O26 and E. coli O111 by conventional microbiological protocols. Two minced beef samples (0.25%) tested positive for E. coli O26, indicating fecal contamination. None of these isolates possessed verocytotoxin-encoding genes, (vt1/vt2 also known as stx1/stx2), the hemolysinencoding gene (hlyA), or the E. coli attachment-effacement (eae) gene, as determined by polymerase chain reaction (PCR). None of the beef samples analyzed contained E. coli O111. Although the E. coli O26 isolates were nonvirulent, the presence of these isolates in raw minced beef is an indication of fecal contamination and therefore potentially of public health significance.

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↗