TABLE 1.

MICs of β-lactam antibiotics for strains of E. coli and K. pneumoniae

Strain	Plasmid(s)a	Porinb	MIC (μg/ml)c
			FOX	CTX	CAZ	C-Cd	P-Te	MP	IP
E. coli K-12 14R525	NDf	ND	≤0.5	≤0.5	≤0.5	≤0.125	0.5	≤0.06	≤0.125
E. coli K-12 14R525	p90	ND	≤0.5	8	16	0.25	32	≤0.06	≤0.125
K. pneumoniae 103624	p3, p90	OmpK36	>256	>256	>256	>256	>256	16	8
K. pneumoniae 103624	pSHA25K	wtOmpK36	4	2	8	0.125	2	0.125	0.75
K. pneumoniae 103624	pQE26	isOmpK36	4	2	8	ND	ND	0.125	0.75
K. pneumoniae CSUB10R	ND	None	128	512	>2,048	4	ND	4	1
K. pneumoniae CSUB10R	pSHA25K	wtOmpK36	2	16	512	0.25	ND	0.015	0.25
K. pneumoniae CSUB10R	pQE26	isOmpK36	2	16	512	0.25	ND	0.015	0.25

^aIndigenous plasmids carried by isolates 103624 (p3 and p90) and CSUB10R (not determined) are not indicated on their derivative strains for clarity. Plasmid p90 was transferred from isolate 103624 by conjugation. Porin-encoding plasmids were introduced by electroporation.

^bK. pneumoniae porins OmpK36 and OmpK35 were analyzed by SDS-PAGE. wtOmpK36 is the OmpK36 cloned from strain C3 (accession no. Z33506), and isOmpK36 is OmpK36 cloned from isolate 103624.

^cFOX, cefoxitin; CTX, cefotaxime; CAZ, ceftazidime; C-C, CAZ-clavulanate; P-T, piperacillin-tazobactam; MP, meropenem; IP, imipenem.

^dClavulanate, 4 μg/ml.

^eTazobactam, 4 μg/ml.

^fND, not determined.