Table 3. Molecular characterization of porin OprD in SCV and mucoid P. aeruginosa isolates.

	Isolate	MIC (mg/L) of imipenem	OprD size (aa)	Amino acid changes in OprD sequence	Insertion/deletion	OprD loops affected	OprD expression†	2-ΔΔCt (OprD)‡
SCV isolates	Ps270, Ps339, Ps602, Ps608, Ps686	>32	189	D43N, S57E, S59R	Deletion of 11 bp at codon 130 (nt 390)	L1	No	0.45±0.16
Mucoid isolates	Ps338, Ps599, Ps600, Ps601, Ps604, Ps605, Ps607, Ps684, Ps685	0.25–1.5	441	D43N, S57E, S59R, E202Q, I210A, E230K, S240T, N262T, A267S, A281G, K296Q, Q301E, R310G, V359L	Loop 7-short	L1, L4, L5, L6, L7	Yes	1.85±0.71
	Ps606, Ps683	4–6	441	L11Q, D43N, S57E, S59R, E202Q, I210A, E230K, S240T, N262T, A267S, A281G, K296Q, Q301E, R310G, V359L	Loop 7-short	L1, L4, L5, L6, L7	Yes	1.99±0.29
	Ps603	6	326	D43N, S57E, S59R, E202Q, I210A, E230K, S240T, N262T, A267S, A281G, K296Q, Q301E, R310G, Q327STOP		L1, L4, L5, L6	No	1.17

†Determined by SDS-PAGE of outer membrane proteins

‡oprD mRNA expression determined by RT-qPCR. Relative gene expression was calculated by 2^-ΔΔCT method. The rpsL gene was used as reference and P. aeruginosa PAO1 strain as calibrator (value of P. aeruginosa PAO1 = 1).