Other numbers: ATCC 700603, CCUG 45421, LMG 20218, strain K6. History: < CCUG < ATCC. Additional information: Quality control strain for extended-spectrum ß-lactamase (ESBL) detection (6531). Biohazard group 2. Extended-spectrum ß-lactamase reference strain (6531). Cultivation conditions: Medium 71, 37°C.