Table 3.

Beta-lactam susceptibility and prevalence of PBP amino acid sequence alterations among serotype 19A pneumococci

CC	No. (%) of isolates; MIC range (mg/l)									PBP*
	PEN			AMX			CTX			% altered amino acids; mean (s.d.)
	S (⩽0·06)	I (>0·06; ⩽2)	R (>2)	S (⩽0·5)	I (>0·5; ⩽2)	R (>2)	S (⩽0·5)	I (>0·5; ⩽2)	R (>2)	1a	2b	2x
Overall, n (%)	6 (12%)	32 (65%)	11 (23%)	21 (43%)	14 (29%)	14 (29%)	26 (53%)	19 (39%)	4 (8%)	13·9 (1·7)	7·2 (3·3)	8·7 (2·8)
CC663 (n = 14)	0	5 (36%)	9 (64%)	1 (7%)	11 (79%)	2 (14%)	3 (21%)	7 (50%)	4 (29%)	13·5 (0·8)	6·0 (1·9)	6·6 (0·7)
	1·0–16			0·5–12			0·250–32
CC230 (n = 12)	0	12 (100%)	0	12 (100%)	0	0	12 (100%)	0	0	14·1 (2·0)	4·3 (0)	6·7 (1·1)
	0·094–0·5			0·047–0·5			0·06–0·5
CC320 (n = 7)	0	7 (100%)	0	0	1 (14%)	6 (86%)	0	7 (100%)	0	13·9 (1·2)	11·3 (0·3)	12·1 (0·1)
	1·0–2·0			1·0–4·0†			1–1·5
CC156 (n = 7)	0	5 (71%)	2 (29%)	0	1 (14%)	6 (86%)	3 (43%)	4 (57%)	0	11·6 (1·9)	14·8 (2·0)	10·8 (2·9)
	1·0–4·0			1·5–8·0†			0·5–1·0
CC63, ST63 (n = 1)	0	1	0	1	0	0	1	0	0	9·5	3·6	11·3
	0·125			0·047			0·250
Singleton, ST10433 (n = 1)	0	1	0	1	0	0	1	0	0	14	6·5	6·5
	0·5			0·5			0·25
Singleton, ST10436 (n = 1)	0	1	0	0	1	0	0	1	0	14	9·4	13·1
	2			2			1·5
PEN-S group‡ (n = 6)	6 (100%)	0	0	6 (100%)	0	0	6 (100%)	0	0	0·4 (0)	0	0
	0·003–0·016			0·01–0·032			0·016–0·08

PBP, penicillin-binding protein; CC, clonal complex; MIC, minimum inhibitory concentration; PEN, penicillin; AMX, amoxicillin; CTX, ceftriaxone; S, susceptible; I, intermediate; R, resistant.

^*The proportion of altered amino acids was calculated by comparing amino acid sequences of the conserved motifs of PBP1a (positions 341–582), PBP2b (positions 375–652), and PBP2x (positions 337–661) of the study isolates with those of the R6 pneumococcal reference strain. PEN-S isolates were excluded from calculations of the overall mean.

^†In six out of seven isolates, an MIC for AMX was higher than an MIC for PEN.

^‡PEN-S group, a group of six PEN-susceptible isolates; described in Table 2.