Characterization of the quinolone resistant determining regions in clinical isolates of pneumococci collected in Canada

Table 2 In vitro activity of ciprofloxacin against S. pneumoniae with mutations in the parC gene only.

	Ciprofloxacin Minimum Inhibitory Concentration (mg/L) Number of Isolates
Substitution	0.12	0.25	0.5	1	2	4	8	16	32	64	Total
None	1	6	919	1,863	523	37	2	2	0	1	3,354
Asp-78	0	0	0	0	4	2	0	0	0	0	6
Asp-83	0	0	0	2	19	30	5	0	0	0	56
Lys-137	0	1	176	391	137	16	1	0	0	0	722
Arg-95	0	1	2	2	0	1	0	0	0	0	6
Ser-52	0	0	1	3	4	1	0	0	0	0	9
Ser-79	0	0	0	1	82	84	33	5	2	2	209
Other*	0	0	3	6	7	1	0	0	0	0	17
Tyr-129	0	0	0	3	3	1	0	0	0	0	7

*Mutations at other sites include: Ala-63 (1), Val-66 (2), Met-85 (1), Asn-91 (2) Glu-99 (1), Glu-100 (1), Gly-106 (1), Ser-107 (1), Met-108 (1), Ala-115 (2), Tyr-118 (1), Arg-122 (1), Leu-130 (1), Glu-135 (1), Thr-138 (1), Ala-158 (1). Of these, two (one with Asn-91-Asp mutation, and one with Ala-115-Pro mutation) had ciprofloxacin MICs of 4 mg/L, and one (Thr-138-Ile) had a levofloxacin MIC of 2 mg/L. All others had MIC to ciprofloxacin of < 4 mg/L, to levofloxacin of < 2 mg/L, and to moxifloxacin of < 0.5 mg/L)

ISSN: 1476-0711