External Quality Assurance System (EQAS) of the WHO Global Salmonella Surveillance and Laboratory Support Project (Global Salm-Surv) Results from 2004
Seyfarth AM, Lo Fo Wong DMA, Hendriksen RS and Aarestrup FM
An international external quality assurance program on serotyping and antimicrobial susceptibility testing of Salmonella enterica subsp. enterica strains is performed yearly to enhance the capacity of national and regional reference laboratories in the WHO Global Salmonella Surveillance and Laboratory Support Project (WHO Global Salm-Surv). Today, the project, launched in 2000, also includes other types of foodborne pathogens than Salmonella. In 2004, the main part of the Regional Centres of WHO Global Salm-Surv established around the world, was involved in organizing the EQAS and shipping the strains to participants in their region.
In 2004, a total of 156 laboratories from 82 countries participated. When testing of the eight Salmonella strains, 80.9 % of all serotypings and 93.0 % of all susceptibility tests performed were correct. The performance was at the same level as in 2003. The results and comments from the participants indicate that the primary barrier for serotyping is lack of antisera and/or lack of high-quality antisera. Misreading of the Kauffmann-White scheme also seems to play a role.
The number of laboratories submitting Quality Control (QC) data for antimicrobial susceptibility testing (87% of the participants) and the number of correct QC testing results (89 %), have further improved compared to previous years. This indicates an increasing awareness of the importance of QC. Anyhow, inadequate standardization of the method used is still considered a barrier for high quality antimicrobial susceptibility data for at least 44% of the participating laboratories.
For identification of two strains of Campylobacter, a total of 109 laboratories participated and 83.6 % of all identifications were correct. For the blinded strain (Shigella flexneri) a total of 121 laboratories participated and 75.2 % submitted correct species identification. The results strongly indicate a need for protocols and quality assurance programs for identification procedures of other human pathogens.
It is concluded, that further improvement of global serotyping and antimicrobial susceptibility testing requires access to high-quality antisera and continuing focus on internal QC, and that there is a need for expanding the WHO Global Salm-Surv operational area to include all pathogens of human importance together with standardization of the methods needed for identification and typing.