Biomedical subjects
Publications and source records attributed to B Cryan.
The data pertaining to Irish specimens sent to the Lyme disease Laboratory at Charing Cross Hospital since 1986 is presented and discussed. In the period up to June 1990, 484 specimens were tested, 14% of these were positive by enzyme linked immunosorbent assay or indirect immunofluorescent assay. Only 13 of these were confirmed as positive by immunoblotting.
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A commercial DNA/DNA hybridisation kit for the detection of Escherichia coli heat stable enterotoxin gene sequences was compared to the suckling mouse bioassay using 183 isolates of Escherichia coli from clinical specimens. The gene probe assay had a specificity of 99% and a sensitivity of 90.4% compared to the infant mouse method. Using the colony blot method of preparing the bacterial DNA and a hybridisation temperature of 50 degrees C optimal results were obtained. The gene probe method is not affected by the incubation conditions of the test organisms. It is technically straightforward and can be applied to large numbers of specimens with fewer logistic difficulties than with the bioassay.
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In this study, a commercial DNA-DNA hybridization kit for the detection of Escherichia coli heat-stable enterotoxin is compared with a competitive enzyme-linked immunosorbent assay (ELISA) and the suckling mouse bioassay. Taking the suckling mouse assay as the "gold standard," the gene probe was the more specific and the ELISA was the more sensitive of the assays. The ELISA and the suckling mouse test are semiquantitative. The ELISA was the most rapid method, most amenable to automation, and most suitable for the examination of large numbers of specimens. The gene probe is particularly applicable in relatively primitive laboratory conditions. The suckling mouse assay was the least suitable system for the examination of large numbers of specimens.
In North America enterohaemorrhagic Escherichia coli have emerged as important enteric pathogens since their initial description in 1982. They have been associated with the idiopathic haemolytic uraemic syndrome and in outbreaks, mortality rates of up to 31% have been recorded. In this paper the recent literature pertaining to the pathogenesis, laboratory identification, epidemiology and therapy of infections by these organisms is reviewed.
In this study sorbitol MacConkey agar was used to screen E. coli isolated from 894 children with diarrhoea. Thirty-four non-sorbitol fermenters were detected. On serotyping, three organisms belonged to the O157 serogroup. Only one of these possessed the H7 antigen. This organism was a verotoxin producer. These findings suggest that E. coli O157:H7 is an uncommon enteric pathogen in Irish children.
Enterotoxigenic Escherichia coli (ETEC) are well recognised enteric pathogens. The epidemiology of heat-stable enterotoxin (STa) producing strains has not been established due mainly to difficulties encountered in performing bioassays on a large scale in baby mice. This study describes a competitive enzyme-linked immunosorbent assay (ELISA) for detecting STa and its application to clinical isolates. Compared to the bioassay, the ELISA had a specificity of 93.7% and a sensitivity of 90.9%. It detected as little as 1 microgram/l STa. Of 720 E. coli isolates from children with diarrhoea, 69 (9.6%) were positive for STa by ELISA.
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A prospective study was undertaken by the Departments of Respiratory Medicine and Medical Microbiology at the Cork University Hospital, a. to investigate the epidemiology of Farmer's Lung (F.L.) in the Republic of Ireland (pop. 3.5 million), with special reference to the South Western Region of this country (pop. 536,000) and b. to assess any relationship between the prevalence/incidence of F.L. with climatic factors in South West Ireland, between 1983 and 1996. F.L. incidence remained constant throughout the 13 yrs studied both on a national and a regional basis. A significant relationship was also found between total rainfall each summer and F.L. incidence and prevalence over the following yr (p < 0.005) in South-West Ireland. The persistence of F.L. in Ireland at a constant level suggests that farmers' working environment and farm practices need to be improved.
Acinetobacter are important emerging nosocomial pathogens. In this paper thirteen Acinetobacter baumanii from intensive care patients were isolated. These were initially typed using the API-20 NE biotyping system and antibiogram analysis. Results obtained using these methods failed to convincingly characterise the organisms. In this report a method to characterise these Acinetobacter baumanii isolates is described, which utilises a modified polymerase chain reaction (PCR), capable of generating genomic fingerprints, known as DNA amplification fingerprinting (DAF). Purified chromosomal DNA of cultured clinical isolates of Acinetobacter baumanii were subjected to DAF using the M13 universal sequencing primer. Polymorphic DNA bands produced, were visualised after agarose gel electrophoresis and ethidium bromide staining. Results demonstrated that six of the thirteen clinical isolates represented one group and a second group of two isolates displayed identical fingerprint patterns. The remaining four organisms were all unique. This genotype based method is rapid, simple, reproducible and may have potential as a means of specifically typing Acinetobacter spp. allowing the route(s) of nosocomial transmission to be identified and to assess the efficiency of instituted infection control measures.
The cost of providing medical care is ever-increasing but the resources available are at best static. Major savings can be made by reducing inappropriate investigations. Using serological testing for organisms causing atypical pneumonia as an example, we examined the appropriateness of requests and also physicians' understanding of the test. Of 119 patients tested, only 3 had titres indicative of acute infection. Most patients were tested within 2 days of hospital admission, before receipt of results excluding more likely diagnoses. Forty-five patients had no current or recent respiratory symptoms, in whom infection was highly unlikely. Titres were most often requested by the least experienced members of the clinical team. Of 70 patients with an acute illness in whom a definitive diagnosis, bacteriological or otherwise, was not made, in only 9 was a convalescent specimen sent for follow-up titres. Most requests for serology for organisms causing atypical pneumonia were inappropriate. Furthermore, in the majority of cases the test was incorrectly used.
This paper reports on three applications of the polymerase chain reaction (PCR) in the pathology laboratory, cystic fibrosis carrier status investigation, Staphylococcus aureus identification and HLA-DQ alpha tissue typing. Allele specific PCR was used to detect the common cystic fibrosis mutation (delta F508) in an Irish family. The genomic status of each member was shown to be either heterozygous (carrier) or homozygous (affected) for the mutation, based on the resolution of allelic amplifications in an agarose gel. Five staphylococci were subjected to PCR designed to amplify a 137 bp DNA fragment from the S. aureus protein A gene (spa). Four isolates gave a coloured "dot-blot" positive signal, the fifth was negative. In the final application the HLA-DQ alpha region was amplified using DNA obtained from four unrelated individuals. Amplified DNA was tissue typed in a reverse "dot-blot" format. All individuals had unique HLA-DQ alpha types. These examples have been chosen to demonstrate the versatility of this technique and to illustrate some of its potential applications.
Resistance to antimicrobial agents used to treat severe Campylobacter spp. gastroenteritis is increasing worldwide. We assessed the antimicrobial resistance patterns of Campylobacter spp. isolates of human and animal origin. More than half (n = 32) were resistant to sulphonamide, a feature known to be associated with the presence of integrons. Analysis of these integrons will further our understanding of Campylobacter spp. epidemiology.
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Epidemiological and bacteriological aspects of human Mycobacterium bovis disease were investigated in south-west Ireland (counties Cork & Kerry, population 536,000) over the years 1983-92 inclusive and compared to M. tuberculosis. Results showed a small, stable incidence of culture positive M. bovis human disease, mean annual incidence 0.56 per 100,000 population compared to a higher but declining incidence of culture positive M. tuberculosis (15.3 per 100,000 in 1983, 9.0 per 100,000 in 1992). Male patients were the majority, 63.4 per cent of M. bovis; 62.4% of M. tuberculosis (p = 0.03). Fifty three per cent of M. bovis cases (n = 30) were pulmonary, compared to 85% of M. tuberculosis (n = 626; p = 0.0001). M. bovis patients were older (p = 0.02), mean age 58.4 years (SD 18.9) compared to 48.5 (SD 22.2). The mycobacterial smear positive rate was similar in both groups taken as a whole. No rural-urban difference in incidence was found in either disease, suggesting in the case of M. bovis initial infection in childhood via contaminated milk in the pre-pasteurisation era.