TABLE 1.

Reversal of substitutions at amino acid positions in PBP 1A from isolate 3191 and the resulting effect of this mutagenesis on resistance levels in mutagenized R6^{3191/2X/2B/1A} strains compared to those for R6^{3191/2X/2B/1A} (penicillin MIC, 4 μg/ml; cefotaxime MIC, 2 μg/ml)

Mutagenic primer	Position of amino acids where reversal of substitutions occurred	Drug MIC (μg/ml) for mutagenized R63191/2X/2B/1A
		Penicillin	Cefotaxime
1	316, 318, 321	4	2
2	326	4	2
3	333	4	2
4	351, 358	4	2
5	382, 388	4	2
6	393, 395, 397	4	2
7	405	4	2
8	414	4	2
9	443, 447	4	2
10	458, 459	4	2
11	473, 475	4	2
12	485	4	2
13	495, 497	4	2
14	503	4	2
15	517, 518	4	2
16	533	4	2
17	539	0.5	0.5
18	540	4	2
19	546, 550	4	2
20	570, 571	4	2
21	574, 575, 576, 577	0.25	0.25
22	579	4	2
23	583, 585	4	2
24	600	4	2
25	606, 609	4	2