ESBL screening and confirmation by phenotypic methods: The isolates showing reduced susceptibility to ceftazidime or cefotaxime or both were tested for ESBL production by double disk-diffusion test
(DDDT) using four disks (p.
28) This test can be used in place of the oxacillin disk-diffusion test
for S aureus and CNS.
A triple disk-diffusion test
with erythromycin, clindamycin, and josamycin was performed to test resistance inducibility.
Antibiotic disk-diffusion test
results are checked by the Resistance Monitoring Center for all resistance mechanisms, report appropriate comments, and flag unlikely results.
Although susceptibility standards are not available for this organism, it was considered susceptible to penicillin and ampicillin by combining the disk-diffusion test
with the MICs, as determined by the Etest (0.
The susceptibility to [beta]-lactam antibiotics was determined by the disk-diffusion test
, following recommendations of the National Committee for Clinical Laboratory Standards (4,5).
A double disk-diffusion test
, carried out with standard disks placed 20 mm apart (center-to-center), showed synergy between clavulanate and aztreonam.
Failure to detect ESBL production by routine disk-diffusion tests
has been well documented (6,7).