Identification of Streptococcus pneumoniae: Development of a Standardized Protocol for Optochin Susceptibility Testing Using Total Lab Automation

Table 4

Multivariable linear regression results for agar, imaging time point, and serotype; bold italic font: difference in mm ≥1 mm and <2 mm; bold font: difference in mm ≥2 mm; n.s.: not significant.

	mm difference	statistics	Confidence interval (95%)	value
Agar
COS_BD	−1.7	(−35.58)		<0.001
COS_bmx	−0.1	(−2.71)		<0.01
MHB_bmx	−0.3	(−5.92)		<0.001
MHF_Ox	−1.6	(−33.35)		<0.001
MHF_bmx	−1.4	(−28.19)		<0.001
TSA_Ox	0.1	(2.05)		<0.05
TSA_bmx	0.0	(⋅)		—
Imaging time point
7 h	0.6	(17.57)		<0.001
12 h	0.8	(22.50)		<0.001
18 h	0.3	(9.25)		<0.001
24 h	0.0	(⋅)		—
Serotype
1	1.0	(9.16)		<0.001
10A	0.9	(8.20)		<0.001
11A	1.5	(14.08)		<0.001
11B	1.0	(9.33)		<0.001
12A	0.7	(5.79)		<0.001
12F	1.3	(12.61)		<0.001
14	1.0	(9.27)		<0.001
15A	1.5	(14.02)		<0.001
15B	0.0	(⋅)		—
15C	1.8	(16.91)		<0.001
16F	1.2	(11.25)		<0.001
17F	0.6	(5.99)		<0.001
18C	1.9	(17.98)		<0.001
19A	1.8	(16.85)		<0.001
19F	0.7	(7.07)		<0.001
20	1.1	(10.52)		<0.001
22F	0.0	(0.17)		n.s.
23A	0.4	(4.01)		<0.001
23F	0.5	(5.20)		<0.001
24F	1.2	(11.08)		<0.001
3	2.8	(26.69)		<0.001
33A	1.0	(8.14)		<0.001
34	0.3	(2.00)		<0.05
35F	0.8	(7.29)		<0.001
38	1.3	(12.27)		<0.001
4	0.9	(8.26)		<0.001
5	1.2	(11.31)		<0.001
6A	0.9	(8.09)		<0.001
6B	1.5	(14.59)		<0.001
7F	0.9	(8.14)		<0.001
8	2.3	(22.16)		<0.001
9A	1.4	(13.68)		<0.001
9N	1.1	(10.29)		<0.001
9V	1.4	(12.83)		<0.001
TIGR4	0.5	(3.32)		<0.001
Constant	14.7