Table 1.

Evolution of MIC₅₀ and geometric mean MIC (expressed in μg/ml) in Pen^s and Pen^ns isolates of N. meningitidis

Year	MIC50a values and no. of isolates at indicated concn according to resistance category												Geometric mean MIC
	Pens						Penns
							Peni				Penr
	≤0.012	0.016	0.023	0.032	0.047	0.064	0.094	0.125	0.19	0.25	0.38	0.5	Total	Pens	Penns
2000	33	22	49	72	41	23	3	4	1	4			0.029	0.027	0.152
2001	46	65	96	78	24	20	7	15	4	3			0.027	0.023	0.133
2002	12	59	77	46	17	6	8	10	7	3			0.029	0.023	0.138
2003	11	23	61	58	21	6	4	12	5	2	1		0.032	0.026	0.144
2004	3	8	31	37	26	14	7	7	5	3	1	1	0.042	0.032	0.152
2005	8	13	48	43	13	6	10	10	7	3		1	0.037	0.027	0.140
2006	1	4	26	32	24	9	3	17	6	2	4	1	0.050	0.033	0.164
2007	5	8	22	57	22	18	2	6	7	3	2		0.041	0.033	0.174
2008	1	3	7	17	21	16	8	8	10	8	3		0.067	0.040	0.167
2009	1	3	10	21	22	19	2	7	3	8	2		0.055	0.039	0.184
2010	0	0	6	9	22	15	10	7	3	9	7		0.078	0.044	0.177

^aMIC₅₀, MIC at which 50% of the tested isolates are inhibited. MIC₅₀ values are shaded.