Antimicrobial Susceptibility Trends Among Gram-Negative Bacilli Causing Bloodstream Infections: Results from the China Antimicrobial Resistance Surveillance Trial (CARST) Program, 2011–2020

Figures & data

Table 1 Change in MIC₅₀ and MIC₉₀ Values of Each Antimicrobial Agent Against E. coli (Units: µg/mL)

Strain and Agent	2011–2012			2013–2014			2015–2016			2017–2018			2019–2020
	MIC50	MIC90	%S/R^a	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R
E. coli	n=248			n=320			n=338			n=346			n=403
Meropenem	0.01	0.03	98.8/0.81	0.03	0.06	98.4/1.25	0.01	0.03	97.9/2.1	0.01	0.03	98.8/0.9	0.03	0.03	97.0/2.7
Imipenem	0.06	0.12	99.2/0.81	0.12	0.12	98.6/1.25	0.12	0.25	97.6/2.4	0.12	0.12	98.8/0.9	0.12	0.25	97.0/3.0
Cefoperazone-sulbactam^b	8	32	81.0/8.9	8	32	75.0/9.4	8	32	76.3/9.8	4	64	79.2/10.4	4	32	80.6/9.7
Piperacillin-tazobactam^c	2	16	90.3/5.6	2	16	90.3/5.6	2	16	92.3/4.4	2	16	91.6/5.5	2	32	88.3/7.2
Piperacillin	256	512	12.5/74.6	512	512	15.6/72.8	256	512	16.9/71.3	256	512	13.9/69.1	256	512	13.4/71.5
Cefotaxime	ND	ND	ND	64	512	37.2/62.8	4	64	44.1/52.7	32	512	42.2/57.5	32	512	42.2/57.3
Ceftazidime	4	64	52.4/38.7	1	64	61.3/34.1	2	128	60.9/32.8	1	64	62.7/30.3	1	64	65.8/25.1
Ceftriaxone	64	512	23.0/76.6	128	512	37.2/62.8	128	512	37.6/62.1	64	512	42.8/56.9	64	512	42.7/56.8
Cefoperazone	128	512	26.2/64.1	128	512	38.1/60.3	128	512	40.2/57.7	64	512	44.2/54.9	64	512	44.7/51.6
Cefepime	4	32	38.3/31.5	4	64	45.9/37.8	4	64	47.3/34.6	2	64	55.2/28.0	2	128	53.6/28.3
Aztreonam	16	128	41.5/52.0	8	256	47.8/44.4	8	128	49.1/41.4	4	128	52.0/38.4	4	128	51.9/39.0
Colistin	ND	ND	ND	0.5	0.5	-/1.9	0.5	1	-/1.8	0.5	1	-/4.6	1	1	-/1.7
Gentamicin	16	128	44.8/52.8	4	128	50.0/49.4	2	128	52.4/47.3	2	256	54.3/45.7	2	256	59.8/38.2
Amikacin	2	8	93.5/6.0	2	4	96.6/3.1	2	8	97.7/2.1	4	8	95.1/3.5	4	8	96.8/3.0
Ciprofloxacin	16	64	29.4/68.1	16	128	33.1/64.7	8	128	40.8/56.2	8	128	32.4/61.0	8	128	29.0/62.5
Tigecycline	0.25	0.5	-/-	0.25	0.5	-/-	0.25	0.5	-/-	0.25	0.5	-/-	0.5	0.5	-/-
ESBL-producing E. coli	n=180			n=187			n=188			n=182			n=204
Meropenem	0.01	0.03	100/0	0.03	0.06	99.5/0	0.01	0.03	100/0	0.01	0.03	99.5/0	0.03	0.03	100.0/0
Imipenem	0.06	0.12	100/0	0.12	0.12	100/0	0.12	0.12	100/0	0.12	0.12	99.5/0	0.12	0.25	100.0/0
Cefoperazone-sulbactam	16	64	75.6/10.6	16	64	62.6/11.8	16	64	64.4/12.8	16	64	65.4/16.5	16	64	69.6/13.7
Piperacillin-tazobactam	2	16	91.7/5.6	2	16	91.4/2.1	2	16	93.6/2.1	4	16	91.8/4.9	2	32	89.7/4.9
Piperacillin	256	512	0/94.4	512	512	0.5/97.9	512	512	0/98.4	512	512	0/98.4	512	512	0/98.0
Cefotaxime	128	512	0.6/98.9	256	512	0/100	256	512	0/100	256	512	0.0/100.0	256	512	0/100.0
Ceftazidime	8	64	40.0/47.8	16	128	40.1/51.9	8	128	41.5/49.5	8	128	37.9/50.0	8	128	42.6/40.2
Ceftriaxone	64	512	0/100.0	256	512	0/100	256	512	0/100	256	512	0/98.9	256	512	0.5/99.5
Cefoperazone	256	512	4.4/83.3	512	512	1.6/96.8	256	512	1.1/95.7	256	512	1.6/96.7	256	512	3.4/92.6
Cefepime	8	64	18.9/40.6	16	128	12.8/59.4	16	128	12.2/56.4	8	128	20.3/50.0	8	256	15.2/50.0
Aztreonam	32	128	25.0/67.2	32	256	16.0/71.1	32	256	16.5/67.0	16	256	17.6/66.5	32	256	14.2/69.6
Colistin	ND	ND	ND	0.5	0.5	-/2.1	0.5	1	98.4/1.6	0.5	1	-/4.4	1	1	-/2.0
Gentamicin	32	128	41.1/56.7	32	256	41.2/57.8	32	128	46.3/53.7	4	256	52.2/47.8	2	128	55.9/40.2
Amikacin	2	8	93.3/6.7	2	8	95.2/4.8	2	8	97.9/2.1	4	16	93.4/4.4	4	8	98.0/2.0
Ciprofloxacin	16	128	22.2/76.1	16	128	18.7/79.7	32	128	25.0/73.4	32	128	16.5/78.6	16	128	15.2/77.5
Tigecycline	0.25	0.5	-/-	0.25	0.5	-/-	0.25	0.5	-/-	0.25	0.5	-/-	0.5	1	-/-

Notes: ^aCLSI 2021 breakpoints were applied. ^bCefoperazone-sulbactam was tested at a ratio of 2:1, and the breakpoint of cefoperazone was used here for cefoperazone-sulbactam. ^cTazobactam was tested in combination with piperacillin at a fixed concentration of 4 µg/mL. Adapted from Liu XJ, Lyu Y, Li Y, et al. Trends in antimicrobial resistance against Enterobacteriaceae strains isolated from blood: a 10-year epidemiological study in mainland China (2004–2014). Chin Med J. 2017;130(17):2050–2055¹³ and J Glob Antimicrob Resist, 17, Zhang F, Li Y, Lv Y, et al. Bacterial susceptibility in bloodstream infections: results from China Antimicrobial Resistance Surveillance Trial (CARST) program, 2015–2016. 276–282, Copyright 2019, with permission from Elsevier.¹⁴

Abbreviations: ESBL, extended-spectrum β-lactamase; MIC, minimum inhibitory concentration; MIC₅₀ and MIC₉₀, MIC for 50% and 90% of the organisms, respectively; S, percent susceptible; R, percent resistant; ND, not determined; -, no breakpoint.

Figure 1 Changes over time in the prevalence of ESBL-producing EC in CSEC (A), ESBL-producing KP in CSKP (B), Imipenem-NS PA (C) and Imipenem-NS AB (D) overall and in different regions of China (2011–2020).

Notes: ^#Means that data in South China in the 2011–12 period were not available.

Abbreviations: ESBL, extended-spectrum β-lactamase; EC, Escherichia coli; CSEC, carbapenem-susceptible Escherichia coli; KP, Klebsiella pneumoniae; CSKP, carbapenem-susceptible Klebsiella pneumoniae; Imipenem-NS, imipenem-non-susceptible; PA, Pseudomonas aeruginosa; AB, Acinetobacter baumannii.

Table 2 Change in MIC₅₀ and MIC₉₀ Values of Each Antimicrobial Agent Against K. pneumoniae (Units: µg/mL)

Strain and Agent	2011–2012			2013–2014			2015–2016			2017–2018			2019–2020
	MIC50	MIC90	%S/R^a	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R
K. pneumoniae	n=122			n=179			n=241			n=259			n=273
Meropenem	0.01	0.03	96.7/3.3	0.03	1	89.9/10.1	0.03	128	83.4/16.2	0.03	128	79.5/20.5	0.03	128	84.6/15.0
Imipenem	0.12	0.25	98.4/1.6	0.12	2	89.4/8.9	0.12	64	82.6/17.4	0.12	64	79.5/19.7	0.12	32	84.6/15.4
Cefoperazone-sulbactam^b	2	32	80.3/9.0	4	256	70.4/21.2	0.5	512	71.8/23.2	1	512	67.2/29.0	1	512	67.8/27.1
Piperacillin-tazobactam^c	2	64	83.6/9.8	4	512	83.8/13.4	4	512	76.8/21.6	4	512	70.7/25.1	4	512	78.4/17.6
Piperacillin	64	512	46.0/48.4	256	512	44.1/53.1	16	512	53.1/41.5	16	512	50.2/46.3	16	512	52.4/44.0
Cefotaxime	ND	ND	ND	16	512	47.5/52.0	0.06	512	60.2/39.4	0.12	512	55.2/44.8	0.12	512	58.2/41.4
Ceftazidime	0.5	64	73.0/22.1	1	128	63.1/35.2	0.25	256	65.1/32.0	0.5	512	61.8/35.1	0.5	256	64.5/30.0
Ceftriaxone	0.25	256	52.5/46.7	16	512	48.0/52.0	0.12	512	60.6/39.4	0.12	512	55.2/44.8	0.12	512	59.3/40.7
Cefoperazone	4	512	54.1/39.3	32	512	49.7/49.2	0.5	512	60.6/38.2	2	512	55.6/43.6	1	512	60.4/38.8
Cefepime	0.25	32	66.4/17.2	1	64	56.4/31.3	0.06	128	66.0/25.3	0.06	256	59.5/34.7	0.06	256	64.1/31.9
Aztreonam	0.25	128	66.4/31.1	1	256	56.4/39.1	0.12	512	65.1/34.9	0.12	512	61.0/37.8	0.12	512	62.3/35.9
Colistin	ND	ND	ND	0.5	1	-/1.1	1	2	-/2.5	1	4	-/13.5	1	2	-/5.1
Gentamicin	0.5	128	67.2/31.1	1	128	66.5/33.0	1	512	71.0/28.2	0.5	512	71.8/27.0	1	512	73.6/25.3
Amikacin	1	2	93.4/6.6	2	4	92.2/7.8	1	512	86.3/12.4	2	512	86.9/12.7	2	512	88.6/11.4
Ciprofloxacin	0.12	32	59.8/29.5	0.12	32	60.3/34.1	0.06	64	58.1/35.3	0.5	256	48.6/46.3	0.12	128	54.9/40.3
Tigecycline	0.5	2	-/-	1	2	-/-	0.5	2	-/-	1	4	-/-	1	4	-/-
ESBL-producing K. pneumoniae	n=49			n=77			n=54			n=63			n=71
Meropenem	0.01	0.06	100.0/0.0	0.03	0.06	93.5/6.5	0.03	0.06	94.4/3.7	0.03	0.12	96.8/3.2	0.03	32	85.9/12.7
Imipenem	0.12	0.25	100.0/0.0	0.12	1	96.1/3.9	0.12	0.5	92.6/7.4	0.12	0.25	96.8/3.2	0.25	16	87.3/12.7
Cefoperazone-sulbactam	16	64	65.3/14.3	16	128	51.9/28.6	32	128	46.3/35.2	32	128	46.0/38.1	64	256	28.2/53.5
Piperacillin-tazobactam	4	32	79.6/6.1	4	256	83.1/11.7	8	512	74.1/22.2	8	512	63.5/22.2	8	512	69.0/19.7
Piperacillin	512	512	0.0/98.0	512	512	0.0/97.4	512	512	1.9/96.3	512	512	0.0/100.0	512	512	2.8/97.2
Cefotaxime	64	256	2.0/95.9	128	512	0.0/98.7	128	512	0.0/98.1	256	512	0.0/100.0	256	512	0.0/98.6
Ceftazidime	8	128	49.0/38.8	16	128	37.7/59.7	16	128	24.1/66.7	32	256	28.6/60.3	16	128	22.5/60.6
Ceftriaxone	64	512	2.0/95.9	256	512	3.9/98.7	256	512	0.0/100.0	256	512	0.0/100.0	512	512	1.4/98.6
Cefoperazone	128	512	4.1/79.6	512	512	6.5/90.9	512	512	1.9/94.4	512	512	0.0/96.8	512	512	2.8/94.4
Cefepime	8	32	30.6/34.7	16	64	18.2/54.5	8	128	18.5/46.3	16	512	17.5/60.3	32	256	12.7/73.2
Aztreonam	16	256	32.7/61.2	64	256	20.8/68.8	64	256	16.7/83.3	64	512	22.2/74.6	64	512	11.3/85.9
Colistin	ND	ND	ND	0.5	1	-/2.6	1	2	-/5.6	1	4	-/17.5	1	2	-/2.8
Gentamicin	32	512	34.7/65.3	64	256	33.8/64.9	32	256	42.6/55.6	8	256	47.6/49.2	32	512	39.4/56.3
Amikacin	1	512	85.7/14.3	2	64	90.9/9.1	2	32	90.7/9.3	2	8	90.5/9.5	2	512	88.7/11.3
Ciprofloxacin	1	128	28.6/53.1	2	64	27.3/61.0		256	13.0/68.5	16	512	12.7/74.6	8	256	15.5/77.5
Tigecycline	1	2	-/-	1	4	-/-	1	2	-/-	1	4	-/-	1	4	-/-

Notes: ^aCLSI 2021 breakpoints were applied. ^bCefoperazone-sulbactam was tested at a ratio of 2:1, and the breakpoint of cefoperazone was used here for cefoperazone-sulbactam. ^cTazobactam was tested in combination with piperacillin at a fixed concentration of 4 µg/mL. Adapted from Liu XJ, Lyu Y, Li Y, et al. Trends in antimicrobial resistance against Enterobacteriaceae strains isolated from blood: a 10-year epidemiological study in mainland China (2004–2014). Chin Med J. 2017;130(17):2050–2055¹³ and J Glob Antimicrob Resist, 17, Zhang F, Li Y, Lv Y, et al. Bacterial susceptibility in bloodstream infections: results from China Antimicrobial Resistance Surveillance Trial (CARST) program, 2015–2016. 276–282, Copyright 2019, with permission from Elsevier.¹⁴

Abbreviations: ESBL, extended-spectrum β-lactamase; MIC, minimum inhibitory concentration; MIC₅₀ and MIC₉₀, MIC for 50% and 90% of the organisms, respectively; S, percent susceptible; R, percent resistant; ND, not determined; -, no breakpoint.

Table 3 Change in MIC₅₀ and MIC₉₀ Values of Each Antimicrobial Agent Against E. cloacae (Units: µg/mL)

Agent	2011–2012 (n=29)			2013–2014 (n=62)			2015–2016 (n=71)			2017–2018 (n=59)			2019–2020 (n=57)
	MIC50	MIC90	%S/R^a	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R
Meropenem	0.03	1	93.1/6.9	0.03	1	91.9/4.8	0.03	0.5	94.4/5.6	0.03	4	86.4/10.2	0.06	2	89.5/7.0
Imipenem	0.25	1	93.1/6.9	0.5	2	88.7/4.8	0.25	1	93.0/7.0	0.25	2	89.8/8.5	0.25	2	87.7/8.8
Cefoperazone-sulbactam^b	8	64	65.5/24.1	1	128	75.8/17.7	1	64	76.1/14.1	1	128	79.7/15.3	1	64	64.9/21.1
Piperacillin-tazobactam^c	4	256	72.4/13.8	4	128	75.8/12.9	4	128	77.5/15.5	4	256	79.7/15.3	4	128	66.7/19.3
Piperacillin	128	512	24.1/55.2	4	512	58.1/30.6	8	512	60.6/26.8	4	512	62.7/30.5	8	512	57.9/38.6
Cefotaxime	ND	ND	ND	0.5	512	56.5/43.5	1	512	52.1/42.3	1	512	54.2/45.8	2	256	49.1/45.6
Ceftazidime	32	256	34.5/62.1	0.5	256	62.9/33.9	1	256	66.2/32.4	0.5	512	62.7/33.9	1	256	52.6/43.9
Ceftriaxone	64	256	27.6/72.4	0.5	512	54.8/45.2	1	512	53.5/40.8	0.5	512	57.6/40.7	1	512	50.9/49.1
Cefoperazone	64	512	41.4/55.2	2	512	66.1/27.4	2	512	67.6/29.6	1	512	69.5/28.8	1	512	57.9/36.8
Cefepime	4	32	48.3/34.5	0.06	16	83.9/12.9	0.25	32	76.1/12.7	0.06	32	76.3/15.3	0.12	16	77.2/14.0
Aztreonam	32	256	41.2/58.6	0.12	128	67.7/29.0	0.25	256	62.0/36.6	0.25	256	62.7/33.9	0.25	64	56.1/38.6
Gentamicin	0.5	128	65.5/34.5	0.5	64	87.1/12.9	0.5	16	87.3/11.3	1	128	88.1/11.9	0.5	4	91.2/8.8
Amikacin	1	8	93.1/6.9	2	4	98.4/1.5	1	4	97.2/1.4	2	8	96.6/1.7	2	8	94.7/5.3
Ciprofloxacin	0.25	16	51.7/41.4	0.06	1	72.6/17.7	0.03	4	69.0/15.5	0.03	1	66.1/15.3	0.03	8	73.7/24.6
Levofloxacin	0.5	32	58.6/27.6	0.12	2	74.2/14.5	0.12	2	77.5/14.1	0.12	2	71.2/11.9	0.06	16	77.2/19.3
Tigecycline	ND	ND	ND	1	2	-/-	1	4	-/-	1	4	-/-	0.5	1	-/-

Notes: ^aCLSI 2021 breakpoints were applied. ^bCefoperazone-sulbactam was tested at a ratio of 2:1, and the breakpoint of cefoperazone was used here for cefoperazone-sulbactam. ^cTazobactam was tested in combination with piperacillin at a fixed concentration of 4 µg/mL. Adapted from Liu XJ, Lyu Y, Li Y, et al. Trends in antimicrobial resistance against Enterobacteriaceae strains isolated from blood: a 10-year epidemiological study in mainland China (2004–2014). Chin Med J. 2017;130(17):2050–2055¹³ and J Glob Antimicrob Resist, 17, Zhang F, Li Y, Lv Y, et al. Bacterial susceptibility in bloodstream infections: results from China Antimicrobial Resistance Surveillance Trial (CARST) program, 2015–2016. 276–282, Copyright 2019, with permission from Elsevier.¹⁴

Abbreviations: MIC, minimum inhibitory concentration; MIC₅₀ and MIC₉₀, MIC for 50% and 90% of the organisms, respectively; S, percent susceptible; R, percent resistant; ND, not determined; -, no breakpoint.

Table 4 Change in MIC₅₀ and MIC₉₀ Values of Each Antimicrobial Agent Against P. aeruginosa (Units: µg/mL)

Strain and Agent	2011–2012			2013–2014			2015–2016			2017–2018			2019–2020
	MIC50	MIC90	%S/R^a	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R
P. aeruginosa	n=78			n=122			n=130			n=137			n=155
Meropenem	0.5	16	70.5/25.6	0.5	16	73.8/18.9	0.5	16	80.8/13.1	0.5	64	66.4/26.3	1	32	69.7/24.5
Imipenem	2	16	71.8/23.1	2	32	72.1/22.1	2	16	72.3/17.7	2	32	64.2/32.1	2	32	62.6/31.0
Cefoperazone-sulbactam^b	8	64	71.8/16.7	8	64	75.4/15.6	8	64	80.8/12.3	4	128	75.2/19.0	8	128	68.4/20.0
Piperacillin-tazobactam^c	4	128	74.4/12.8	4	128	74.6/13.1	4	64	80.0/10.0	8	256	74.5/20.4	8	256	73.5/19.4
Piperacillin	8	256	65.4/19.2	8	128	73.0/13.1	8	128	75.4/11.5	4	256	73.0/19.0	16	256	62.6/20.6
Ceftazidime	2	64	73.1/24.4	2	32	82.0/12.3	2	32	84.6/11.5	2	64	80.3/17.5	2	64	73.5/21.9
Cefepime	2	32	73.1/14.1	2	32	83.6/10.7	2	16	86.9/7.7	2	128	78.1/16.8	2	32	74.8/12.3
Aztreonam	8	512	65.4/24.4	8	64	69.7/20.5	8	32	69.2/19.2	8	64	65.7/19.7	8	64	58.7/27.7
Gentamicin	2	512	71.8/25.6	2	512	82.0/14.8	2	8	86.2/8.5	2	128	87.6/11.7	4	8	78.7/9.7
Amikacin	4	512	82.1/17.9	4	16	90.2/8.2	2	8	94.6/5.4	4	8	97.1/2.2	4	16	94.8/3.2
Ciprofloxacin	0.25	32	60.2/33.3	0.12	8	73.8/16.4	0.25	2	83.1/13.1	0.25	32	72.3/21.9	0.5	8	69.7/18.1
Colistin	2	2	-/3.8	2	2	-/7.4	2	2	-/9.2	1	2	-/2.9	2	2	-/7.7
Imipenem-NS P. aeruginosa	n=22			n=34			n=36			n=49			n=58
Meropenem	16	64	13.6/86.4	8	64	20.6/64.7	4	64	38.9/41.7	16	512	12.2/73.5	16	512	31.0/62.1
Imipenem	16	256	0.0/81.8	16	64	0.0/79.4	8	32	0.0/63.9	16	512	0.0/89.8	16	512	0.0/82.8
Cefoperazone-sulbactam	32	256	40.9/45.5	32	256	41.2/38.2	16	128	55.6/30.6	32	512	46.9/46.9	32	512	41.4/37.9
Piperacillin-tazobactam	64	256	45.5/31.8	32	512	44.1/29.4	16	512	61.1/25.0	32	512	46.9/44.9	16	512	50.0/37.9
Piperacillin	64	512	31.8/36.4	32	512	38.2/29.4	16	512	61.1/25.0	32	512	49.0/42.9	32	512	39.7/39.7
Ceftazidime	32	512	31.8/63.6	32	512	61.8/26.5	4	128	69.4/25.0	4	128	57.1/40.8	8	128	53.4/39.7
Cefepime	16	64	22.7/45.5	8	512	58.8/26.5	4	128	63.9/22.2	8	512	51.0/38.8	8	512	53.4/27.6
Aztreonam	64	512	13.6/63.6	8	512	38.2/55.9	8	256	50.0/38.9	16	512	28.6/44.9	32	512	34.5/55.2
Gentamicin	32	512	31.8/59.1	32	512	64.7/26.5	2	512	63.9/22.2	2	512	77.6/12.2	4	32	63.8/19.0
Amikacin	8	512	54.5/45.5	4	512	76.5/20.6	4	256	86.1/13.9	4	16	91.8/6.1	4	16	91.4/6.9
Ciprofloxacin	4	32	22.7/68.2	1	64	41.2/38.2	0.5	64	55.6/36.1	1	64	40.8/46.9	1	32	48.3/39.7
Colistin	2	2	-/4.5	2	2	-/2.9	2	4	-/11.1	1	2	-/2.0	2	2	-/8.6

Notes: ^aCLSI 2021 breakpoints were applied. ^bCefoperazone-sulbactam was tested at a ratio of 2:1, and the breakpoint of cefoperazone for Enterobacteriaceae was used here for cefoperazone/sulbactam. ^cTazobactam was tested in combination with piperacillin at a fixed concentration of 4 µg/mL. Adapted from J Glob Antimicrob Resist, 17, Zhang F, Li Y, Lv Y, et al. Bacterial susceptibility in bloodstream infections: results from China Antimicrobial Resistance Surveillance Trial (CARST) program, 2015–2016. 276–282, Copyright 2019, with permission from Elsevier.¹⁴

Abbreviations: MIC, minimum inhibitory concentration; MIC₅₀ and MIC₉₀, MIC for 50% and 90% of the organisms, respectively; S, percent susceptible; R, percent resistant; -, no breakpoint; imipenem-NS P. aeruginosa, imipenem-non-susceptible P. aeruginosa.

Table 5 Change in MIC₅₀ and MIC₉₀ Values of Each Antimicrobial Agent Against A. baumannii (Units: µg/mL)

Strain and Agent	2011–2012			2013–2014			2015–2016			2017–2018			2019–2020
	MIC50	MIC90	%S/R^a	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R	MIC50	MIC90	%S/R
A. baumannii	n=70			n=138			n=160			n=169			n=186
Meropenem	32	64	30.0/68.6	64	128	24.6/74.6	32	64	26.3/73.8	32	64	20.1/79.3	32	128	29.6/70.4
Imipenem	16	64	30.0/68.6	32	128	25.4/73.9	32	64	25.6/73.1	32	64	20.1/79.9	32	64	29.6/70.4
Ampicillin-sulbactam^b	ND	ND	ND	64	128	23.2/73.2	64	128	23.8/71.9	64	128	20.7/75.7	64	128	29.6/68.3
Cefoperazone-sulbactam^c	32	128	30.0/47.1	64	128	26.1/65.2	64	128	26.3/58.1	64	128	23.1/67.5	64	128	33.3/61.3
Piperacillin-tazobactam^d	256	512	28.6/70.0	512	512	23.2/75.4	512	512	23.1/76.3	512	512	18.9/81.7	512	512	29.0/69.9
Piperacillin	256	512	18.6/72.9	512	512	10.1/77.5	512	512	11.3/76.9	512	512	14.8/96.4	512	512	18.8/71.0
Ceftazidime	64	512	28.6/70.0	128	512	24.6/74.6	128	512	24.4/75.0	128	512	21.3/76.9	128	512	31.2/68.8
Ceftriaxone	512	512	7.1/70.0	512	512	5.8/76.8	512	512	5.6/76.9	512	512	7.7/75.7	512	512	6.5/68.8
Cefotaxime	256	512	8.6/71.4	512	512	10.9/76.1	512	512	12.5/76.3	512	512	12.4/75.1	512	512	13.4/68.8
Cefepime	32	256	28.6/60.0	128	256	20.3/74.6	64	256	22.5/75.0	64	256	19.5/76.3	64	256	29.0/68.8
Gentamicin	512	512	30.0/70.0	512	512	26.1/73.2	512	512	25.6/71.9	512	512	24.3/71.6	512	512	36.0/59.1
Amikacin	512	512	35.7/62.9	512	512	34.1/65.9	512	512	33.8/66.3	512	512	38.5/61.5	512	512	47.3/52.7
Ciprofloxacin	32	64	30.0/70.0	64	128	23.2/76.8	64	128	23.8/76.3	64	256	24.3/75.7	64	256	31.2/68.8
Colistin	1	2	-/4.3	0.5	1	-/4.3	1	2	-/1.9	1	2	-/5.3	1	2	-/5.4
Tigecycline	ND	ND	ND	4	4	-/-	2	2	-/-	2	4	-/-	4	8	-/-
Imipenem-NS A. baumannii	n=48			n=103			n=119			n=135			n=131
Meropenem	32	128	0.0/100.0	64	128	0.0/100.0	32	64	0.8/99.2	32	64	1.5/98.5	64	128	0.0/100.0
Imipenem	32	128	0.0/100.0	64	128	0.0/99.0	32	64	0.0/98.3	32	64	0.0/100.0	64	128	0.0/100.0
Ampicillin-sulbactam	ND	ND	ND	64	128	1.9/93.2	64	128	0.8/94.1	64	128	2.2/93.3	64	256	0.0/96.9
Cefoperazone-sulbactam	64	128	4.2/64.6	64	128	3.9/85.4	64	128	4.2/76.5	64	128	4.4/84.4	64	128	5.3/87.0
Piperacillin-tazobactam	256	512	2.1/97.9	512	512	0.0/99.0	512	512	0.8/99.2	512	512	0.7/99.3	512	512	0.0/98.5
Piperacillin	512	512	2.1/97.9	512	512	0.0/100.0	512	512	0.0/99.2	512	512	0.7/99.3	512	512	0.0/99.2
Ceftazidime	128	512	4.2/95.8	256	512	1.9/98.1	256	512	2.5/96.6	256	512	3.7/95.6	256	512	3.1/96.9
Ceftriaxone	512	512	0.0/95.8	512	512	0.0/98.1	512	512	0.0/99.2	512	512	0.0/94.1	512	512	0.0/96.9
Cefotaxime	512	512	0.0/97.9	512	512	1.0/98.1	512	512	0.0/98.3	512	512	0.7/93.3	512	512	0.0/96.9
Cefepime	32	256	2.1/83.3	128	256	0.0/97.1	128	256	0.0/98.3	128	256	0.7/94.8	128	256	0.0/96.9
Gentamicin	512	512	4.2/95.8	512	512	6.8/92.2	512	512	5.0/92.4	512	512	5.9/88.9	512	512	11.5/81.7
Amikacin	512	512	12.5/85.4	512	512	13.6/86.4	512	512	15.1/84.9	512	512	23.0/77.0	512	512	25.2/74.8
Ciprofloxacin	32	64	4.2/95.8	64	128	1.9/98.1	64	256	1.7/98.3	128	256	5.9/94.1	128	256	3.1/93.1
Colistin	1	2	-/6.3	0.5	1	-/3.9	1	2	-/1.7	1	2	-/3.0	1	2	-/4.6
Tigecycline	2	4	-/-	4	4	-/-	2	4	-/-	4	8	-/-	4	8	-/-

Notes: ^aCLSI 2021 breakpoints were applied. ^bAmpicillin-sulbactam were tested in a ratio of 2:1. ^cCefoperazone-sulbactam was tested at a ratio of 2:1, and the breakpoint of cefoperazone for Enterobacteriaceae was used here for cefoperazone/sulbactam. ^dTazobactam was tested in combination with piperacillin at a fixed concentration of 4 µg/mL. Adapted from J Glob Antimicrob Resist, 17, Zhang F, Li Y, Lv Y, et al. Bacterial susceptibility in bloodstream infections: results from China Antimicrobial Resistance Surveillance Trial (CARST) program, 2015–2016. 276–282, Copyright 2019, with permission from Elsevier.¹⁴

Abbreviations: MIC, minimum inhibitory concentration; MIC₅₀ and MIC₉₀, MIC for 50% and 90% of the organisms, respectively; S, percent susceptible; R, percent resistant; -, no breakpoint; imipenem-NS A. baumannii, imipenem-non-susceptible A. baumannii.

Liu XJ, Lyu Y, Li Y, et al. Trends in antimicrobial resistance against Enterobacteriaceae strains isolated from blood: a 10-year epidemiological study in mainland China (2004–2014). Chin Med J. 2017;130(17):2050–2055. doi:10.4103/0366-6999.213407.

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Zhang F, Li Y, Lv Y, et al. Bacterial susceptibility in bloodstream infections: results from China Antimicrobial Resistance Surveillance Trial (CARST) program, 2015–2016. J Glob Antimicrob Resist. 2019;17:276–282. doi:10.1016/j.jgar.2018.12.016

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