TABLE 2.

ESBL-producing strains failing to meet CLSI criteria

Test	Enzymea
Screening test
Ceftazidime zone size >22mm	TEM-20, TEM-25, SHV-3, SHV-5, SHV-7, CTX-M-5, CTX-M-14, CTX-M-15
Cefotaxime zone size >27 mm	TEM-7, TEM-10, TEM-11, TEM-12, TEM-26, SHV-5, SHV-6, SHV-7
Aztreonam zone size >27 mm	TEM-7, TEM-20, TEM-25, SHV-3, SHV-6
Cefpodoxime zone size >17 mm	TEM-11, TEM-12, SHV-6
Ceftriaxone zone size >25 mm	TEM-7, TEM-10, TEM-11, SHV-6, SHV-18
Ceftazidime and cefotaximeb	SHV-5, SHV-7
Ceftazidime and aztreonam	TEM-20, TEM-25, SHV-3
Ceftazidime and cefpodoxime	None
Ceftazidime and ceftriaxone	None
Confirmatory test
Ceftazidime	TEM-88, SHV-2, CTX-M-14, CTX-M-15
Cefotaxime	TEM-5, TEM-7, TEM-10, TEM-11, TEM-12, TEM-26, TEM-61, SHV-5, SHV-6
Aztreonam	TEM-10, TEM-12, TEM-25, SHV-6, CTX-M-15
Cefpodoxime	Many
Ceftriaxone	Many
Ceftazidime and cefotaximec	None
Ceftazidime and aztreonam	CTX-M-15

^aThe enzyme in strains failing the CLSI screening criteria (screening test) or the enzyme in strains failing the CLSI clavulanate inhibition test (zone enhancement, <5 mm).

^bScreening test failure for both agents.

^cConfirmatory test failure for both agents.