TABLE 4.

β-Lactam challenge-induced β-lactamase expression in B. ubonensis^a

Gene	Treatment
	Untreated		MEM		IMP		CAZ
	Normalized fold mRNA expression ± SD	P value	Normalized fold mRNA expression ± SD	P value	Normalized fold mRNA expression ± SD	P value	Normalized fold mRNA expression ± SD	P value
penA*	1.00 ± 0.05	NA	0.79 ± 0.10	0.98	0.47 ± 0.03	0.94	0.75 ± 0.05	0.35
penB	1.00 ± 0.13	NA	336.94 ± 35.58	<0.001	371.00 ± 45.40	<0.001	17.65 ± 1.41	<0.001
ampC	1.00 ± 0.12	NA	64.43 ± 9.03	<0.001	99.31 ± 6.81	<0.001	9.09 ± 0.77	<0.001
oxa	1.00 ± 0.07	NA	0.80 ± 0.17	0.98	0.86 ± 0.05	0.99	0.70 ± 0.07	0.28

^aCells of Bu278 (wild type) were grown to log phase in LB medium. Equal portions of the cell cultures remained untreated or were treated with subinhibitory concentrations of meropenem (MEM; 8 μg/ml), imipenem (IMP; 8 μg/ml), or ceftazidime (CAZ; 3 μg/ml). Total RNA was isolated after an additional 1 h of incubation at 37°C. The penA*, penB, ampC, and oxa mRNA levels were determined by RT-qPCR. The penA*, penB, ampC, and oxa mRNA levels were determined by RT-qPCR. Standard deviations (SD) between three biological replicates are indicated. Two-way ANOVA and Sidak’s multiple-comparison test were used to determine the significance of the change in fold mRNA expression levels between treated (with MEM, IPM, or CAZ) and untreated strains. P values of <0.05 were considered significant. NA, not applicable.