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PubMed2006

Class 1 integrons in Dutch Salmonella enterica serovar Dublin isolates from clinical cases of bovine salmonellosis.

Fifty-nine Salmonella enterica serovar Dublin (Salmonella Dublin) isolates from clinical cases of bovine salmonellosis between 1993 and 2004 were tested for their susceptibility to 15 antimicrobial agents and the presence of class 1 integrons. Integrons were further analyzed by conserved segment PCR-RFLP. DNA sequencing was used to identify the inserted gene cassette. Twelve (20.3%) isolates were multidrug-resistant. A combination of resistance against chloramphenicol, streptomycin and sulphonamides was the most common phenotype observed. Multidrug-resistance (MDR) was found to be strongly associated with the presence of integrons, since a class 1 integron with the aadA1 gene cassette encoding resistance to streptomycin and spectinomycin was found in all 12 multidrug-resistant isolates. The presence of the aadA1 gene in Salmonella Dublin has not been reported before. None of the integron carrying Salmonella Dublin isolates could transfer its antimicrobial resistance to E. coli K12 by conjugation. Analysis of plasmid profiles and pulsed field gel electrophoresis (PFGE) patterns showed at least some clonality among the Salmonella Dublin isolates, but 11 different types could be distinguished based on both XbaI and BlnI-PFGE patterns. Thus, the Dutch Salmonella Dublin strains were closely related but not clonal.

Animals↗
PubMed1997

Characterization of Salmonella dublin and Salmonella typhimurium (Copenhagen) isolates from cattle.

Eight Salmonella typhimurium (Copenhagen) and eight Salmonella dublin isolates from cattle were compared by their antibiotic resistance patterns, by their production of colicin, aerobactin, haemolysin and capsule, by their possession of transmissible R plasmids and the spvC gene, and by their ability to invade and replicate within cultured epithelial cells. The two groups differed in their antibiotic resistance profiles, with more of the host-adapted S. dublin isolates resistant to tetracycline than were the non-host-adapted S. typhimurium (Copenhagen) group, but more of the S. typhimurium (Copenhagen) isolates resistant to the other antibiotics tested. None of the isolates produced colicin, but all produced aerobactin. One isolate in each group was encapsulated. All of the S. typhimurium (Copenhagen) and S. dublin isolates contained plasmids, and all of them contained the spvC-homologous sequences. Four of the S. typhimurium (Copenhagen) isolates were able to transfer an R plasmid to a recipient organism by conjugation. One of the five S. dublin isolates, which showed resistance to some of the antibiotics tested, was able to transfer an R plasmid by conjugation. Both groups of isolates invaded cultured epithelial cells to a similar degree after 1 h, but the S. dublin isolates reached significantly higher levels within the cells than did S. typhimurium (Copenhagen) after 9 h. This ability may, in part, explain the association of S. dublin with more severe forms of salmonellosis and prolonged carrier states. Further study of the intracellular growth of these isolates seems warranted.

Animals↗
PubMed2004

Evaluation of an indirect serum ELISA and a bacteriological faecal culture test for diagnosis of Salmonella serotype Dublin in cattle using latent class models.

AIMS: To evaluate a conventional bacteriological test based on faecal culture and an indirect serum ELISA for detection of S. Dublin infected cattle. To compare the predictive values of the two tests in relation to the prevalence. METHODS AND RESULTS: A total of 4531 paired samples from cattle in 29 dairy herds were analysed for presence of S. Dublin bacteria in faeces and immunoglobulins directed against S. Dublin lipopolysaccharide in an indirect serum ELISA. Sensitivity and specificity were estimated at two ELISA cut-off values using a validation method based on latent class models, which presumably provides less biased results than traditional validation methods. Stratification of data into three age groups gave significantly better estimates of test performance of the ELISA. Receiver operating characteristic (ROC) curves were constructed for comparison of overall performance of the ELISA between the three age groups. The sensitivity of the faecal culture test was low (6-14%). ELISA appeared to have a higher validity for animals aged 100-299 days of age than older or younger animals. Overall, the negative predictive value of the ELISA was 2-10 times higher than for the faecal culture test at realistic prevalence of infection in the test population. CONCLUSIONS: The diagnostic sensitivity of the faecal culture test for detection of S. Dublin is poor, the specificity is 1. The superior sensitivity and negative predictive value of the serum ELISA makes this test preferable to faecal culture as an initial screening test and for certification of herds not infected with S. Dublin. SIGNIFICANCE AND IMPACT OF THE STUDY: A quantitative estimate of the sensitivity of a faecal culture test for S. Dublin in a general population was provided. ELISA was shown to be an appropriate alternative diagnostic test. Preferably, samples from animals aged 100-299 days of age should be used as these give the best overall performance of the ELISA. Plots of ROC curves and predictive values in relation to prevalence facilitates optimisation of the ELISA cut-off value.

Animals↗
PubMed2002

Peroxynitrite enhances the ability of Salmonella dublin to invade T84 monolayers.

In the intestine, epithelial cells continually produce and secrete low levels of nitric oxide (NO). Salmonella sp. invade epithelium by responding to environmental stimuli. The aims of this study were to determine the effect of reactive nitrogen intermediates (RNIs) on S. dublin and S. typhimurium growth and invasion of T84 epithelial monolayers. Intracellular NO formation was inhibited by 7-nitroindazole (7-NI) or N(G)-monomethyl-L-arginine, monoacetate (L-NMMA); extracellular NO and peroxynitrite were scavenged with ferro-hemoglobin or urate. The effect of authentic peroxynitrite (ONOO-); 3-morpholino-sydnonimine (SIN-1), which releases ONOO- via NO and superoxide; spermine NONOate, which releases only NO; or superoxide generated by xanthine oxidase and pterin on S. dublin and S. typhimurium growth and invasion were examined. Inhibition of NO synthesis and scavenging of extracellular NO or peroxynitrite reduced S. dublin invasion into T84 monolayers and enhanced bacterial growth. Pre-exposure of S. dublin to ONOO- and SIN-1 increased subsequent bacterial invasion into T84 monolayers. Conversely, exposure of bacteria to spermine NONOate or superoxide did not affect S. dublin invasion. In contrast, S. typhimurium invasion was not affected by pre-treatment with NO donors. In conclusion, exposure of S. dublin to ONOO- enhances the ability of the bacteria to invade epithelial cells. These results suggest that luminal ONOO- may have a novel role as an extracellular signal between invasive bacteria and epithelial cells.

Cell Division↗
PubMed1990

Murine antibody response to oral infection with live aroA recombinant Salmonella dublin vaccine strains expressing filamentous hemagglutinin antigen from Bordetella pertussis.

Two plasmids which express either nearly intact or truncated filamentous hemagglutinin (FHA) from Bordetella pertussis and which are marked with a tetracycline resistance (Tcr) gene were transformed into Salmonella dublin SL1438, an aroA deletion mutant intended for use as an attenuated oral vaccine against salmonellosis. These S. dublin recombinants, when fed to mice, induced serum immunoglobulin, immunoglobulin M (IgM), and sometimes IgA antibody responses to FHA and S. dublin. In addition, IgA antibodies against FHA were found in gut wash fluids. S. dublin carrying pDB2300, a multicopy plasmid encoding truncated FHA protein, induced a better antibody response than did S. dublin carrying pDB2000, a low-copy-number plasmid encoding full-sized FHA. Administration of tetracycline to mice enhanced the stability of recombinant plasmids, and tetracycline-treated mice developed higher anti-FHA titers. Although neither strain examined is suitable for use in a human oral vaccine, these data demonstrated that an immune response against B. pertussis FHA could be induced by oral administration of live attenuated recombinant strains of S. dublin and suggested that development of a live oral attenuated vaccine against pertussis may be possible.

Animals↗
PubMed1989

Detection of Salmonella dublin mammary gland infection in carrier cows, using an enzyme-linked immunosorbent assay for antibody in milk or serum.

An ELISA has been developed for measurement of milk and serum IgG concentrations directed against Salmonella dublin. Four groups of cows were studied: group A--7 experimentally challenge-exposed cows (infected, recovered group); group B--6 normal uninfected randomly selected control cows; group C--7 naturally occurring S dublin carrier cows; and group D--6 normal uninfected S dublin negative cows from the same herd as group C. Group-A cows were inoculated orally, or inoculated orally and then IV, but none became a S dublin carrier. As expected, all 7 group-A cows responded with a marked increase in ELISA titer after oral exposure to virulent S dublin, starting with a mean serum titer of 17.7% and reaching a peak mean serum titer of 79.3% approximately 76 days after initial exposure. As determined by necropsy and organ culturing of the remaining cows, none of the group-A cows became carriers. The mean serum ELISA titer for group-B uninfected control cows was 14.1% (SD +/- 12.8%). The mean milk ELISA titer was -1.0% (SD +/- 5.5%). Colostrum and then milk gave false-positive results for up to 2 weeks after onset of lactation. Group-B cows were culture negative for S dublin in feces and milk during lactation, and when tissues were cultured after euthanasia. Milk and serum samples for ELISA, and milk and fecal samples for culturing were taken from all group-A and -B cows twice a week for 6 months. Statistical correlation (P less than 0.05) was found between serum and milk ELISA titers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Assessment of the excess risk of Salmonella dublin infection associated with the use of certified raw milk.

The risk of serious illness attributable to infection with Salmonella dublin associated with the consumption of certified raw milk in California was evaluated. Data were derived from case reports of S. dublin isolations from persons in the State of California during the period 1980-83 and from production figures for raw milk from the major supplier. It is estimated that more than one-third of reported S. dublin infections in California in the first 4 years of this decade were attributable to raw milk consumption. Among raw milk consumers, it is estimated that more than 95 percent of reported S. dublin infections were acquired from raw milk; this proportion corresponds to a rate of reported S. dublin infections acquired from raw milk in the range of 8 to 35 cases per 100,000 users per year. It appears that immunocompromised persons are at exceptionally high risk of becoming seriously ill or dying from S. dublin exposure, and therefore raw milk is a particular health hazard for such persons.

Aged↗
PubMed1984

Experimental concurrent infection of cattle with Ostertagia ostertagi and Salmonella dublin.

Six seven-month-old Friesian steers were given 8.1 X 10(9) Salmonella dublin orally. Four had been infected with third stage larvae of Ostertagia ostertagi on four occasions over the previous three months. All became pyrexic and excreted S dublin in the faeces for eight to 15 days. Intravenous injection of 8.7 X 10(8) S dublin six weeks later produced similarly mild effects in parasitised and control animals alike. Two parasitised animals stopped excreting S dublin after three and five weeks respectively; the other four were still excreting regularly when killed eight weeks after intravenous infection. S dublin was recovered from the carcases of all six. O ostertagi, unlike Fasciola hepatica, did not increase susceptibility to S dublin or predispose to prolonged infection.

Animals↗
PubMed1981

Responses of fluke-infected and fluke-free cattle to experimental reinfection with Salmonella dublin.

Cattle, aged nine to 18 months, were given sublethal doses of Salmonella dublin either intravenously, orally on two occasions, or by contact for 19 to 22 weeks with a persistent excretor. When challenged by intravenous injection of 10(9) S dublin at 10 to 22 weeks after their first exposure to S dublin 22 out of 36 animals survived. All similarly challenged cattle, which had not been previously exposed to S dublin, died. Infection with Fasciola hepatica did not alter the ability of cattle to survive reinfection with S dublin but the bacteria persisted in the tissues and were excreted in the faeces of fluke-infected animals for longer than in fluke-free animals. The ability to survive reinfection and to eliminate S dublin from the tissues was apparently unrelated to agglutinating antibody titres or delayed hypersensitivity.

Agglutinins↗
PubMed1993

Vaccination of calves with orally administered aromatic-dependent Salmonella dublin.

Genetically altered stable nonreverting aromatic-dependent (aro-) Salmonella dublin, strain SL5631, was administered orally to healthy colostrum-fed calves as vaccine. Twenty-six calves were allotted to 4 groups. There were 2 experiments, each with a vaccinated and nonvaccinated control group. Skin testing with 0.1 ml of sonicated S dublin was performed 3 days prior to challenge exposure. The IgG and IgM titers to S dublin lipopolysaccharide (LPS) antigen were determined by ELISA on sera before initial vaccination and at 1.5 to 2 weeks after each vaccination. In experiment 1, six calves received a dose of 1.7 x 10(10) colony-forming units (CFU) of aro-S dublin SL5631 orally at 2 and 4 weeks of age. After the first vaccination, 2 of 6 calves developed fever, but all 6 calves continued to have normal appetite and mental attitude. Adverse changes were not observed after the second vaccination. At the time of challenge exposure at 6 weeks of age, all 12 calves were seronegative for IgG and IgM LPS-specific antibodies, and the difference in percentage increase in skin test reaction at 48 hours was not significant. At 6 weeks of age, the 6 vaccinates and 6 controls were orally challenge-exposed with 1.5 x 10(11) CFU of virulent S dublin T2340. Protection from challenge was not evident, as 3 of 6 controls and 5 of 6 vaccinates died after challenge exposure. In experiment 2, eight calves received a dose of 5 x 10(11) CFU of aro-S dublin SL5631 orally at 2, 3.5, and 5 weeks of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed2006

Antimicrobial resistance in Salmonella enterica serovar Dublin isolates from beef and dairy sources.

Salmonella enterica serovar Dublin (S. Dublin) is a cattle-adapted Salmonella serovar, so if antimicrobial resistance in S. Dublin arises as a result of antimicrobial use this most likely occurs within the cattle reservoir without impact from antimicrobial use in humans. We tested the antimicrobial resistance of bovine-origin S. Dublin isolates from 1986 through 2004 using a standard disk diffusion method. High proportions of isolates throughout the time period were resistant to one or more antimicrobials, and a marked increase in resistance to ceftazidime occurred between 2000 and 2004. Dairy-origin isolates were more likely to be resistant to several antibiotics than were isolates from beef operations where exposure to antimicrobials is likely to be less frequent. Plasmid analysis of a subset of isolates also supported the hypothesis that antimicrobial resistance traits in the cattle-adapted serovar Dublin were acquired within the bovine host environment.

Animals↗
PubMed2002

Effect of air-pollution control on death rates in Dublin, Ireland: an intervention study.

BACKGROUND: Particulate air pollution episodes have been associated with increased daily death. However, there is little direct evidence that diminished particulate air pollution concentrations would lead to reductions in death rates. We assessed the effect of air pollution controls--ie, the ban on coal sales--on particulate air pollution and death rates in Dublin. METHODS: Concentrations of air pollution and directly-standardised non-trauma, respiratory, and cardiovascular death rates were compared for 72 months before and after the ban of coal sales in Dublin. The effect of the ban on age-standardised death rates was estimated with an interrupted time-series analysis, adjusting for weather, respiratory epidemics, and death rates in the rest of Ireland. FINDINGS: Average black smoke concentrations in Dublin declined by 35.6 mg/m(3) (70%) after the ban on coal sales. Adjusted non-trauma death rates decreased by 5.7% (95% CI 4-7, p<0.0001), respiratory deaths by 15.5% (12-19, p<0.0001), and cardiovascular deaths by 10.3% (8-13, p<0.0001). Respiratory and cardiovascular standardised death rates fell coincident with the ban on coal sales. About 116 fewer respiratory deaths and 243 fewer cardiovascular deaths were seen per year in Dublin after the ban. INTERPRETATION: Reductions in respiratory and cardiovascular death rates in Dublin suggest that control of particulate air pollution could substantially diminish daily death. The net benefit of the reduced death rate was greater than predicted from results of previous time-series studies.

Adolescent↗
PubMed1998

An outbreak of an unusual strain of Serratia marcescens in two Dublin hospitals.

We describe a serious outbreak of infection caused by a strain of Serratia marcescens in two Dublin hospitals which occurred over an 11 week period and affected a total of 15 patients. A contaminated bed-pan macerator in the Intensive Care Unit of one hospital was identified as the possible source of infection and spread of the organism probably occurred via hand transmission by hospital personnel and via patient transfer to a second hospital. All isolates of S. marcescens involved in the outbreak had the same antimicrobial susceptibility pattern, with reduced susceptibility to gentamicin, cefotaxime and ciprofloxacin. Epidemiological typing revealed that the strains of S. marcescens isolated in the outbreak were of an uncommon serotype, O21:K14, and using pulsed-field gel electrophoresis, XbaI DNA macrorestriction profiles clustered at 90% similarity. The DNA patterns of the outbreak strain were also highly similar to S. marcescens isolates of the same serotype recovered from a separate Dublin hospital during the same time period as the outbreak described here. In addition, the isolates clustered at 82% similarity with strains of the same serotype from a retrospective collection of S. marcescens isolates from various hospitals in the Dublin area, indicating that these may be genetic variants of the same strain. Although the outbreak was brought under control following implementation of infection control measures, a significant number of similar O:21 isolates of S. marcescens have since been identified in four Dublin hospitals. These results suggest the unique spread of a single strain of S. marcescens in Dublin hospitals.

Cross Infection↗
PubMed2005

Genomic comparisons of Salmonella enterica serovar Dublin, Agona, and Typhimurium strains recently isolated from milk filters and bovine samples from Ireland, using a Salmonella microarray.

Salmonella-induced enterocolitis is the leading food-borne illness with a lethal outcome and causes millions of cases of gastroenteritis each year. We examined genomic variation among 12 environmental, veterinary, and clinical Salmonella enterica serovar Dublin, Agona, and Typhimurium strains isolated in Ireland between 2000 and 2003, as well as two clinical isolates from Canada and four archival isolates, which belonged to serovars Dublin and Agona. Using DNA-DNA hybridization to a microarray consisting of most of the predicted protein-encoding sequences of the S. enterica serovar Typhimurium LT2 genome, we identified a number of genomic regions that were absent in one or more serovars. The 34 genomic regions encoded proteins involved in sugar metabolism, transport, fimbrial and phage biogenesis, and transcriptional regulation, as well as inner and outer membrane-associated proteins. Two of the four prophages identified in strain LT2, prophages Gifsy-1 and Gifsy-2, were present in all six serovar Typhimurium strains examined. Prophage Fels-1 was absent from all 18 isolates examined, and Fels-2 was completely absent from the serovar Typhimurium isolates and the Salmonella Reference Collection B serovar Dublin strain Du2. All five Salmonella pathogenicity islands were present in all isolates. Plasmid pSLT was absent from all serovar Agona isolates, and only homologues of the spv genes were present in eight of the nine serovar Dublin strains. Only limited intraserovar diversity was found among the nine serovar Dublin, three serovar Agona, and six serovar Typhimurium isolates examined even though these isolates had extensive geographic, temporal, and source differences.

Animals↗
PubMed1996

Endogenous and exogenous interleukin-12 augment the protective immune response in mice orally challenged with Salmonella dublin.

Following oral challenge with Salmonella dublin, we observed significant increases in interleukin-12 (IL-12) protein expression in the mesenteric lymph nodes. The importance of this endogenous cytokine production in the immune response against S. dublin was demonstrated by in vivo depletion of IL-12 with an anti-IL-12 monoclonal antibody prior to oral S. dublin challenge. Mice pretreated with anti-IL-12 antibody had increased salmonellosis and reduced survival times compared with mice receiving control antibody. Furthermore, administration of exogenous murine recombinant IL-12 dramatically increased survival times of mice challenged orally with S. dublin. Together, these results demonstrate that endogenous and exogenous IL-12 significantly augment the mucosal immune response against the intracellular pathogen S. dublin.

Administration, Oral↗
PubMed1997

The spv genes on the Salmonella dublin virulence plasmid are required for severe enteritis and systemic infection in the natural host.

The pathogenic role of the spv (Salmonella plasmid virulence) genes of Salmonella dublin was determined in the natural, bovine host. Since the lack of overt signs of enteritis or enterocolitis due to Salmonella infections in mice has limited the development of a convenient experimental system to study enteric disease, we used calves to study the contribution of the spv genes to S. dublin-induced salmonellosis. Since the SpvR transcriptional regulator is required for expression of the spvABCD operon, we constructed an spvR knockout mutation in a calf-virulent strain of S. dublin. Calves were infected with the wild-type strain, an spvR mutant, and an spvR mutant containing a complementing plasmid. Calves that were infected with the wild type or the complemented spvR mutant rapidly developed severe diarrhea and became moribund. Calves that were infected with the spvR mutant showed little or no clinical signs of systemic salmonellosis and developed only mild diarrhea. The survival and growth of the wild-type strain and the spvR mutant were determined by using blood-derived bovine monocytes. Wild-type S. dublin survived and grew inside cells, while the spvR mutant did not proliferate. These results suggest that the spv genes of S. dublin promote enhanced intracellular proliferation in intestinal tissues and at extraintestinal sites in the natural host.

Animals↗
PubMed1980

Veterinary surgeons as vectors of Salmonella dublin.

Salmonella dublin is an important bovine pathogen, causing dysentery, abortion, and death from septicaemia. S dublin dermatitis, a little-recognised occupational hazard for veterinary surgeons, does not cause serious disability or inconvenience. During a survey of brucellosis in south-west Wales four cases of S dublin dermatitis were seen in veterinary surgeons. One surgeon was reinfected three years later. On all five occasions the veterinary surgeons had not worn or had discarded polyethylene gloves. An apparently healthy cow may serve as a latent carrier of S dublin. Thus when disease starts in a closed, protected herd reactivation of infection within the herd is usually blamed and its introduction by extraneous agents considered to be unlikely. Veterinary surgeons should be regarded as potential vectors of S dublin.

Animals↗
PubMed1992

Non-fatal deliberate self-poisoning in Dublin's north inner city--an overview.

It is almost three decades since a survey of attempted suicide in Dublin City Hospitals was published. In 1962, 159 cases in the City of Dublin and Borough of Dun Laoghaire were studied and reported. Over a six month period (November 1989-April 1990) 147 cases of deliberate self-poisoning were admitted to the Mater Hospital, Dublin, of which 100 case notes were appropriate for examination. In 1973, a six month survey of attempted suicide was carried out at the Mater Hospital, Dublin where 38 patients were admitted following non-fatal deliberate self-poisoning. In our study, the female to male ratio was 2:1, 50% of cases took more than one drug type,, benzodiazepines being the most commonly ingested compound. Alarmingly over a quarter (28%) of females under 25 had overdosed on paracetamol either alone or in conjunction with other compounds. Alcohol was consumed in 46% of all cases. 40% of cases involved a past history of deliberate self-poisoning and 60% had a past history of psychiatric intervention. Our survey outlines current trends in deliberate self-poisoning in Dublin's North Inner City. We have compared our 1990 survey to the similar survey conducted by our unit seventeen years ago. Several characteristics remain unaltered. The number of overdoses has almost trebled. We have noted a sharp rise in unemployment, alcohol abuse and psychiatric history among female overdoses. We have noted the disturbing introduction of paracetamol overdose particularly among young females (25%). Finally we have documented the introduction of overdosing amongst the homeless population which did not exist in the 1973 survey, but which accounts for 12% of our survey.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaminophen↗