Carbapenemase OXA-423: A Novel OXA-23 Variant in Acinetobacter baumannii

Figures & data

Table 1 Primers Used in This Study

Primer	Sequence (5′-3′)	Target	Amplicon Size (bp)	Purpose
OXA-23-like F	ACCCCGAGTCAGATTGTTCAAGG	blaOXA-23-like	606	Screening
OXA-23-like R	CCAGCCCACTTGTGGTTTTATAT
OXA-24-like F	GTCCCTGCATCAACATTTAAGATGC	blaOXA-24-like	477	Screening
OXA-24-like R	CACCCAACCAGTCAACCAACCTACCT
OXA-51-like F	GCTATGGTAATGATCTTGCTCGTGC	blaOXA-51-like	509	Screening
OXA-51-like R	TCCAGTTAACCAGCCTACTTGTGGG
OXA-58-like F	ATATGGCACGCATTTAGACCGAG	blaOXA-58-like	515	Screening
OXA-58-like R	CAACAAAACCCACATACCAACCC
OXA-23-EXT-F	CTATTTTTGTCGTGTACAGAGC	blaOXA-23-like	1008	Sequencing
OXA-23-EXT-R	GGATCACAACAACTAAAAGCACTG
NdeI-OXA-23F^a	GGAATTCCATATGTTTAAAATGAATAAATATTTTAC	blaOXA-23-like	828	Expressing
XhoI-OXA-23R^a	CCGCTCGAGTTAAATAATATTCAGCTGT

Note: ^aThe restriction sites for NdeI and XhoI are underlined.

Figure 1 Sequence alignment of OXA-423 with several OXA-23-like carbapenemases. Conserved motifs are boxed. The Val128Ala substitution in OXA-423 was indicated by a black arrow.

Table 2 Antibiotic Susceptibilities of A. baumannii WY-0713 and E. coli Transformants

Antibiotic(s)	MIC (μg/mL)
	A. baumannii WY-0713	E. coli Rosetta(DE3)
		pET-OXA-23	pET-OXA-423	pET^a
Ampicillin	>512	128	8	2
Ampicillin+SUL^b	256	32	4	2
Amoxicillin	>512	128	16	2
Amoxicillin+CLA^b	128	32	8	2
Piperacillin	256	64	8	1
Piperacillin+TAZ^b	128	16	2	0.5
Cefotaxime	256	≤0.06	≤0.06	≤0.06
Ceftazidime	256	≤0.06	≤0.06	≤0.06
Aztreonam	512	≤0.06	≤0.06	≤0.06
Imipenem	8	4	1	0.12
Meropenem	16	2	0.25	0.06
Ertapenem	16	8	2	≤0.06
Doripenem	8	1	0.12	≤0.06

Notes: ^aE. coli Rosetta (DE3) harboring solely pET-28b(+) as negative control. ^bSUL, sulbactam.

Abbreviations: CLA, clavulanic acid; TAZ, tazobactam were used with a fixed concentration of 4, 2, 4 μg/mL, respectively.

Figure 2 Active-site tertiary structure comparison of OXA-23-meropenem complex (A) with the model of OXA-423-meropenem complex (B). Distances (Å) are displayed as yellow dashed lines.