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The identification of species and biovars of Brucella field strains isolated in outbreaks is essential to fully understand the epidemiology of the disease and to trace sources of infection, thereby improving the outcome of brucellosis eradication programmes. It is important to identify the presence of Brucella strains in livestock populations and to determine the presence of new strains that might previously have been considered exotic. In this study, 732 Brucella strains isolated from livestock were submitted for typing by the Italian Istituti Zooprofilattici Sperimentali to the National Reference Laboratory for brucellosis between 2001 and 2006. Animal species affected, biovars typed and spatial distribution of isolates are discussed. Brucella field strains were identified using both conventional bacteriological methods and molecular techniques. Species identification was performed using the AMOS (AbortusMelitensis OvisSuis)-polymerase chain reaction. For biovar identification, amplification of omp2a, omp2b and omp31 genes was performed, followed by restriction fragment length polymorphism. Final biovar identification was performed by growth in the presence of basic fuchsin and thionin, using the slide agglutination test with Brucella A- and M- specific antisera.

Seven monoclonal antibodies (MAbs) specific for Escherichia coli O157:H7, one of the major causes of haemorrhagic colitis in humans, were produced by immunising Balb/c mice with the strain E. coli O157:H7. These monoclonal antibodies do not cross-react with other bacteria such as Salmonella enterica serovar Typhimurium, E. coli O14, E. coli JM109, S. enterica serovar Enteritidis, S. panama, S. saintpaul, S. derby, S. muenchen, S. bredeney, S. hadar, Yersinia enterocolitica, Proteus vulgaris, Shigella flexneri, Listeria ivanovii, L. monocytogenes 13M, L. innocua, Enterobacter cloacae, E. agglomerans, E. amnigenus, Citrobacter freundii, Escherichia fergussoni or Klebsiella pneumoniae. Of the seven MAbs obtained, MAb 8B8C3 was selected to prepare a high-sensitivity sandwich ELISA method specific for O157:H7.

Salmonella enterica serovars Enteritidis and Typhimurium are the serotypes most frequently isolated from human cases. Traditional surveillance systems, based on serological characterisation and epidemiology, are not able to identify these common strains that cause outbreaks in humans. Innovative techniques are therefore necessary to accurately characterise these serotypes and hence accelerate the identification of the primary sources. Within a larger study, the goal of which was to develop an active surveillance system for outbreaks of food-borne diseases, characterisation of 42 Salmonella strains was performed using molecular techniques (pulsed field gel electrophoresis [PFGE] and random amplified polymorphic DNA [RAPD]), together with the Kirby-Bauer antibiotic assay. Results showed that both techniques were unable to satisfactorily characterise the Enteritidis serotype, while only PFGE identified the Typhimurium serotype.

The determination of the origin of foodborne diseases is one of the top priorities for the world health community. Gastroenteritis caused by zoonotic Salmonella serovars is one of the major threats to human health. It is essential that surveillance systems are able to monitor the incidence of human cases and to provide useful data to plan and implement effective prevention strategies. Surveillance systems generate information that is of value both for the early detection of infection and for the identification of epidemiological trends and risk factors. The authors describe a surveillance system for the identification of the sources of infection foodborne disease outbreaks caused by Salmonella in the Abruzzo region of Italy between April 2000 and October 2002.

In the European Union, RB51 vaccine can be used only under strictly controlled conditions for the immunisation of cattle at risk of infection with Brucella abortus. A test is therefore necessary to distinguish vaccinated from unvaccinated animals. The complement fixation test with RB51 antigen (RB51-CFT), dot-blot and gamma-interferon used to identify vaccinated animals have been described, but sensitivity of the tests has been poor and positivity transient after calfhood vaccination. To avail of a rapid and accurate diagnostic tool, the authors produced, controlled and evaluated an experimental brucellin prepared from strain RB51 (RB51 brucellin). The potency of this brucellin was evaluated in guinea-pigs sensitised with RB51 and compared with a commercially available brucellin. Both allergens produced similar biological activity in guinea-pigs. The RB51 brucellin skin test was performed in 10 cattle 414 days after calfhood vaccination with RB51 when they were negative to the RB51-CFT. The skin test revealed 60% sensitivity (with a confidence interval of 95%, CI 30.8%-83.3%) and 100% specificity (CI 60.7%-100%). These findings limit the use of the skin test only for screening to detect RB51 vaccinated herds, not individual animals. Nevertheless, following intradermal inoculation of RB51 brucellin, a transient antibody increase to the RB51-CFT was observed, from day 9 to day 20 post inoculation with RB51 brucellin. This transient antibody increase, when evaluated in parallel with the RB51 brucellin skin test results, enables detection of individual vaccinated animals (sensitivity 100%; CI 76.2%-100%).

Brucella field strains were identified using molecular techniques. A polymerase chain reaction (PCR) method, based on amplification of the insertion sequence IS711, was used to identify the isolates at species level. Subsequently, restriction fragment length polymorphism analysis of the omp2a and omp2b genes was used to assign the Brucella species to the different biovars. A total of 248 field strains were processed and complete agreement was obtained with the species/biovar identifications made by conventional bacteriological methods. PCR based tests were more rapid and proved valuable in overcoming some of the drawbacks of conventional methods.