Table 3. Antibiotic disk diffusion test and quantification of the resistant mutant subpopulations of the 38 P. aeruginosa CF isolates.

Isolate	MRS genesa	Ceftazidime		Ciprofloxacin		Imipenem		Meropenem		Tobramycin
		DD	RMS	DD	RMS	DD	RMS	DD	RMS	DD	RMS
1a	-	S	+++	S	++	S	+++	S	+++	S	++
1b	-	S	+++	I	++	S	+++	S	+++	R	*
1c	+	S	++	S	-	S	-	S	++	S	-
2a	-	R	*	R	*	S	+++	S	+++	S	+++
2b	+	S	+	S	-	S	-	S	+	S	-
3a	-	I	++	I	-	S	+++	S	+++	I	+++
3b	-	R	*	I	++	I	+++	S	+++	I	+++
3c	-	S	+++	S	+++	S	+++	S	+++	S	++
4a	+	S	-	S	-	S	-	S	-	S	-
4b	+	S	-	S	-	S	-	S	-	S	-
5a	-	S	-	R	*	S	++	S	+++	S	+
6a	+	S	-	S	-	S	-	S	-	S	-
7a	+	S	-	I	-	S	-	S	-	S	-
8a	+	S	-	R	*	S	+++	S	+++	S	-
9a	-	S	++	S	+++	S	+++	S	+++	S	+++
10a	-	S	++	S	++	S	+++	S	-	S	+++
11a	+	S	-	S	-	S	-	S	-	R	*
12a	+	S	-	S	-	S	-	S	-	S	-
13a	+	S	-	R	*	S	-	S	-	R	*
14a	+	S	-	S	-	S	-	S	-	S	-
15a	+	S	-	S	-	S	-	S	-	S	-
16a	+	S	-	S	-	S	-	S	-	S	-
17a	+	S	-	I	-	R	*	I	-	S	-
17b	-	S	-	S	-	I	+++	S	++	S	+
18a	+	S	-	S	-	S	-	S	-	S	-
18b	+	S	-	R	*	S	-	S	-	S	-
18c	+	S	-	S	-	S	-	S	-	S	-
18d	-	S	+++	R	*	R	*	S	+++	R	++
19a	-	R	*	R	*	R	*	R	*	R	*
20a	+	S	-	S	-	S	-	S	-	S	-
20b	-	S	+++	R	*	R	*	S	+++	S	+++
21a	-	S	+++	R	*	S	++	S	+++	S	+++
21b	-	S	+++	R	*	S	+++	S	+++	S	+++
22a	-	S	-	S	-	S	++	S	+++	S	+++
23a	+	S	-	S	-	S	-	S	++	S	-
24a	+	S	-	S	-	S	-	S	-	S	-
25a	+	S	-	S	-	S	-	S	-	S	-
26a	+	S	-	S	-	S	-	S	-	S	-

^aMRS genes was considered positive (+) when the sequences of mutS and mutL genes were wild type and negative (−) when were mutated.

DD, diffusion diameter zone; RMS, resistant mutant subpopulation: +<10 mutants; ++ 10 to 100 mutants; +++ >100 mutants.

Zone diameter interpretative criteria was according to CLSI: S, susceptible; I, intermediate resistance; R, resistant.

*lack of diffusion zone that prevents the resistant mutant subpopulation to be quantified.