Application Value of Triton X-100 to Modified Hodge Test and Carbapenem Inactivation Method in the Detection of Acinetobacter baumannii Carbapenemase

Figures & data

Table 1 Characterization of 135 Strains and the Results of the Modified Hodge Test and Triton-Modified Hodge Test

Groups (N)	MIC Range (mg/L)	KB (mm)	Carbapenemase Genotypes (N)	MHT (N)				THT (N)
	Imipenem	Meropenem		L = 0	0 < L < 3mm	L ≥3mm	Positive (L>0) Rate (%)	L = 0	0 < L < 3mm	L ≥3mm	Positive (L>0) Rate (%)
Carbapenem resistant isolates (83)	≥16	6	OXA-51+ISAba1/OXA-23+IMP-4 (2)	-	1	1	59.03	-	-	2	100
	≥16	6	OXA-51+ISAba1/OXA-23+OXA-24 (2)	-	1	1		-	-	2
	≥16	6	OXA-51+ISAba1/OXA-23+OXA-58 (1)	-	-	1		-	-	1
	≥16	6	OXA-51+ISAba1/OXA-23+OXA-58+NDM (1)	-	1	-		-	-	1
	≥16	6–12	OXA-51+ISAba1/OXA-23 (77)	34	32	11		-	-	77
Carbapenem sensitive isolates (52)	≤1	24–32	OXA-51 (52)	52	-	-	0	52	-	-	0

Abbreviations: MHT, modified Hodge test; THT, Triton-modified Hodge test; N, number; KB, Kirby-Bauer method; L, length of E. coli ATCC25922 enhanced growth.

Table 2 Results of Carbapenem Inactivation Method, Modified Carbapenem Inactivation Method and Triton-Carbapenem Inactivation Method

Groups (N)	CIM	mCIM	TCIM
			O.05% v/v	0.1% v/v	0.25% v/v	0.5% v/v
Carbapenemase-producing isolates (83)	N (%) of isolates with positive results (bacteriostatic zone diameter = 6mm) of
	5(6.02)	7(8.43)	59(71.08)	83(100)	81(97.59)	80(96.38)
Non-carbapenemase-producing isolates (52)	N (%) of isolates with negative results (bacteriostatic zone diameter ≥ 19mm) of
	52(100)	52(100)	52(100)	52(100)	52(100)	52(100)

Abbreviations: N, number; CIM, carbapenem inactivation method; mCIM, modified carbapenem inactivation method; TCIM, Triton-carbapenem inactivation method.

Figure 1 Comparative results of modified Hodge test (MHT) and Triton-modified Hodge test (THT) in three isolates (N13, N54, N123). (A) Results of three isolates (N13, N54, N123) using the MHT; (B) Results of three isolates (N13, N54, N123) using the THT. Results obtained using a meropenem (MEM) disk (10 µg) as substrate.

Abbreviations: CRAB, carbapenem-resistant Acinetobacter baumannii; CSAB, carbapenem-sensitive Acinetobacter baumannii.

Figure 2 Comparative results of Carbapenem Inactivation Method (CIM) and Triton-Carbapenem Inactivation Method (TCIM) in three isolates (N6, N23, N101). (A) Results of three isolates (N13, N54, N123) using the CIM; (B) Results of three isolates (N13, N54, N123) using the TCIM. Results obtained using a meropenem (MEM) disk (10 µg) as substrate.

Abbreviations: CRAB, carbapenem-resistant Acinetobacter baumannii; CSAB, carbapenem-sensitive Acinetobacter baumannii.