A total of 287 laboratories in 102 countries participated in at least one of the seven iterations of EQAS from 2000 to 2007; participation included 44 laboratories in 35 countries in 2000, 108 laboratories in 59 countries in 2001, 119 laboratories in 66 countries in 2002, 147 laboratories in 76 countries in 2003, 152 laboratories in 80 countries in 2004, 143 laboratories in 75 countries in 2006, and 143 laboratories in 73 countries in 2007. The average number of participating laboratories per EQAS iteration between 2000 and 2007 was 122, with 139 laboratories participating in at least three iterations and 102 laboratories participating in at least four iterations. The participating laboratories included veterinary, food, and public health national reference laboratories and other hospital laboratories. One or more institutions participated in at least one EQAS iteration from the following countries: Albania, Argentina, Australia, Barbados, Belarus, Bolivia, Bosnia and Herzegovina, Botswana, Brazil, Bulgaria, Cambodia, Cameroon, Canada, Central African Republic, Chile, China, Colombia, Costa Rica, Croatia, Cyprus, the Czech Republic, Democratic Republic of the Congo, Cuba, Denmark, Ecuador, Egypt, Estonia, Finland, France, Gabon, Georgia, Germany, Greece, Guatemala, Honduras, Hungary, Iceland, India, Indonesia, Ireland, Israel, Italy, Cote d'Ivoire, Jamaica, Japan, Jordan, South Korea, Kuwait, Laos, Latvia, Lebanon, Lithuania, Luxembourg, Macedonia, Madagascar, Malaysia, Malta, Mauritania, Mauritius, Mexico, Moldova, Morocco, New Caledonia, New Zealand, The Netherlands, Nigeria, Nicaragua, Norway, Oman, Panama, Papua New Guinea, Paraguay, Peru, the Philippines, Poland, Romania, Russia, Saudi Arabia, Serbia and Montenegro, Senegal, Seychelles, Singapore, Slovakia, Slovenia, Sri Lanka, South Africa, Spain, Sudan, Suriname, Syria, Taiwan, Thailand, Trinidad and Tobago, Tunisia, Turkey, Uganda, Ukraine, the United Kingdom, the United States, Uruguay, Venezuela, and Vietnam.
A total of 856 participating laboratory record sheets were received from participating laboratories during the seven EQAS iterations. Among the 856 record sheets, the proportion of susceptibility results determined by disk diffusion was 88% (range, 83% to 93% for each iteration). For the quality control strain, susceptibility results for at least one antimicrobial agent were reported on 95% of the 856 record sheets (range, 88% to 100% for each iteration). The average number of antimicrobial agents with susceptibility results for the quality control strain per participating laboratory increased from 8.6 in 2001 to 11.6 in 2007. The proportions of participating laboratories with one or more deviations for the quality control strain were 30% in 2000, 17% in 2001, 14% in 2002, 14% in 2003, 11% in 2004, 11% in 2006, and 44% in 2007. There was a higher proportion of deviations for the quality control strain for most antimicrobial agents in 2000 and 2007 than in all other years (Table ). There was an almost steady decline in deviations from 2000 to 2007 for AMP (from 27% in 2000 to 11% in 2007), CIP (from 20% in 2000 to 12% in 2007), and TET (from 42% in 2000 to 7% in 2007).
Percentage of participating laboratories with deviations for the quality control strain for each antimicrobial agent tested per the EQAS iteration from 2000 to 2007
A high proportion of participating laboratories reported deviations in susceptibility results for at least nine antimicrobial agents for one of the Salmonella isolates (an isolate of Salmonella serovar Panama) included in the 2003 EQAS. Participating laboratories reported 251 total deviations (13 minor, 18 major, and 220 very major deviations) in susceptibility results for the Salmonella Panama isolate, which accounted for 34% of the total deviations in susceptibility results in the 2003 iteration; the very major deviations with this isolate were shown for AMP (23%), CHL (22%), GEN (27%), KAN (20%), STR (13%), sulfonamides (15%), TMP (17%), SXT (23%), and TET (16%). Based on these details, the Salmonella Panama isolate was excluded from further analysis.
After excluding the Salmonella Panama isolate, there were a total of 67,229 susceptibility results for Salmonella strains reported on the 856 record sheets from participating laboratories in the seven EQAS iterations. The average number of antimicrobial agents with susceptibility results for each Salmonella strain was 9.6; by year, the average number of antimicrobial agents with susceptibility testing for each Salmonella strain was fairly consistent, from 8.1 in 2003 to 11.2 in 2006 (Table ). During the seven EQAS iterations, there were a total of 6,051 deviations (4,034 minor, 1,345 major, and 672 very major deviations). During the seven EQAS iterations, overall, 92% of the susceptibility results for Salmonella strains were correct; 5% of results had a minor deviation, 2% had a major deviation, and 1% had a very major deviation, resulting in 8% total deviations and 3% critical deviations. From 2000 to 2007, the annual percentage of total deviations (7% to 12%) in susceptibility results was almost doubled. However, the critical deviations (3% to 4%) were largely unchanged. Similarly, for the Salmonella enteritidis isolate tested in 2000, 2001, 2004, 2006, and 2007, there was little change in total deviations (20.3%, 16.9%, 6.5%, 7.5%, and 8.3%) or critical deviations (7.2%, 5.2%, 2.4%, 3.3%, and 2.9%).
Annual and overall average number of antimicrobial agents tested by participating laboratories, percent correct results, and percent minor, major, and very major deviations in the EQAS from 2000 to 2007a
Each year, the percentage of critical deviations in susceptibility results for CIP, CHL, GEN, KAN, NAL, SXT, and TMP was low compared with that for AUG, SMX, STR, and TET (Table ). The annual percentage of critical deviations in susceptibility results for each antimicrobial agent was largely unchanged from 2000 to 2007.
Annual and overall number of tests performed, percent total deviations, percent critical deviations, and percent major and total deviations for each antimicrobial agent in the EQAS from 2000 to 2007
The overall percentage of critical deviations varied by region, with a high percentage of critical deviations in central Asia and the Middle East (range, 6 to 10%), Africa (range, 2 to 10%), South America (range, 1 to 5%), and Southeast Asia (range, 2 to 7%) (Table ). In central Asia and the Middle East, Africa, South America, and Southeast Asia, 21, 29, 34, and 40 laboratories participated in 42%, 34%, 39% and 33% of the iterations during all 7 years, respectively.
Number of laboratories, by year and region, that have deviating resultsa