In vitro activity of colistin mono- and combination therapy against colistin-resistant Acinetobacter baumannii, mechanism of resistance, and clinical outcomes of patients infected with colistin-resistant A. baumannii at a Thai university hospital

Figures & data

Table 1 Antibiotic minimum inhibitory concentration (μg/mL) in colistin-resistant Acinetobacter baumannii

CoR-AB isolate	COL	SUL	TIG	IMP	MEP	SMT	AMK	FOS
1	16	8	1.5	8	32	16	>4,096	256
2	32	12	2	16	32	8	>4,096	384
3	128	6	1.5	8	32	>32	>4,096	256
4	64	3	0.38	8	16	16	4,096	512
5	32	8	1.5	8	32	12	4,096	128
6	32	8	1.5	8	32	6	4,096	256
7	128	1.5	0.38	8	128	12	4,096	256
8	512	1.5	0.25	8	16	16	4,096	256
9	32	8	2	8	32	6	>4,096	384
10	32	128	1	8	32	0.38	4,096	256
11	128	32	2	32	64	>32	4,096	256
12	128	128	2	32	128	>32	>4,096	512
13	64	8	0.5	16	16	6	16	512
14	128	128	2	16	64	>32	4,096	512
15	>512	16	0.5	8	32	4	16	512
16	>512	>1,024	1	8	32	4	16	256
17	512	>1,024	2	16	128	>32	>4,096	128

Abbreviations: AMK, amikacin; COL, colistin; CoR-AB, colistin-resistant Acinetobacter baumannii; FOS, fosfomycin; IMP, imipenem; MEP, meropenem; SMT, trimethoprim–sulfamethoxazole; SUL, sulbactam; TIG, tigecycline.

Table 2 Clonal relationship, presence of carbapenemase genes and mcr-1, and efflux pump detection in colistin-resistant Acinetobacter baumannii

REP-PCR group	CoR-AB isolate	COL (MIC; μg/mL)	COL+CCCP (MIC; μg/mL)	Resistant genes
				blaIMP	blaNDM	blaKPC	blaOXA-23	blaOXA-40	blaOXA-58	mcr-1
A	1	16	0.5	✓	×	✓	✓	×	×	×
B	2	32	0.25	✓	✓	✓	✓	×	×	×
B	3	128	0.5	✓	✓	✓	✓	×	×	×
B	4	64	0.5	✓	✓	✓	✓	×	×	×
B	6	32	0.25	✓	✓	✓	✓	×	×	×
B	7	128	0.5	✓	✓	✓	✓	×	×	×
B	8	512	0.5	✓	✓	✓	✓	×	×	×
B	9	32	0.25	✓	✓	✓	✓	×	×	×
B	13	64	0.25	✓	✓	✓	✓	×	×	×
C	5	32	0.25	×	×	×	✓	×	×	×
C	10	32	0.25	×	×	×	✓	×	×	×
C	11	128	0.5	×	×	×	✓	×	×	×
C	12	128	0.5	×	×	×	✓	×	×	×
C	14	128	0.5	×	×	×	✓	×	×	×
C	15	>512	0.25	×	×	×	✓	×	×	×
C	17	512	0.5	×	×	×	✓	×	×	×
D	16	>512	0.25	×	×	×	✓	×	×	×

Notes:

✓ Target gene present.

× Target gene absent.

Abbreviations: CCCP, cyanide 3-chlorophenylhydrazone; COL, colistin; CoR-AB, colistin-resistant Acinetobacter baumannii; MIC, minimum inhibitory concentration; REP-PCR, repetitive element palindromic polymerase chain reaction.

Table 3 Characteristics and outcomes of patients infected with colistin-resistant Acinetobacter baumannii

Patient number	Age (years)	Sex	Comorbidity	Diagnosis	ICU	Septic shock	Prior colistin use	Regimen	Treatment duration (days)	Clinical outcome
1	58	M	DM	VAP	Yes	Yes	No	COL IMP	14	Improvement
2	81	M	DM, ESRD with HD	VAP	Yes	Yes	Yes	SUL LVX	5	Death
3	67	M	SCLC, RF	VAP	Yes	Yes	Yes	COL FOS	14	Death
4	91	F	PAD, HT, DLP, RF	Septicemia	Yes	Yes	No	COL SUL	11	Death
5	61	M	BPH, HT, RF	UTI	No	No	No	COL SUL	10	Improvement
6	90	F	HT, RF	Bacterial peritonitis	Yes	Yes	Yes	COL IMP	3	Death
7	77	M	DM, CA	Cholangitis	No	Yes	No	COL IMP	14	Death
8	81	M	HT, COPD	HAP	No	Yes	No	COL IMP	17	Improvement
9	63	F	DM, HD	Cellulitis	Yes	Yes	Yes	COL IMP	13	Death
10	82	M	HT, RF	VAP	Yes	Yes	Yes	COL MEP	12	Death
11	21	M	AKI with CVVHDF	Septicemia	Yes	Yes	No	COL MEP	4	Death
12	55	M	ALL, AKI	Septicemia	Yes	Yes	No	COL IMP	11	Death
13	80	F	HT, DM	Septicemia	No	Yes	No	COL IMP	21	Cure
14	83	M	HT, DM	Cholangitis, septicemia	No	Yes	No	COL IMP	18	Cure
15	63	F	DM	Cholangitis, septicemia	No	Yes	No	COL FOS	10	Death
16	76	M	HT, ESRD with HD	Septicemia	Yes	Yes	No	COL IMP	11	Death
17	85	F	AKI with HD	VAP with pleural effusion	Yes	Yes	No	TIG SUL	25	Death

Abbreviations: AKI, acute kidney injury; ALL, acute lymphoblastic leukemia; BPH, benign prostatic hyperplasia; CA, cancer; COL, colistin; COPD, chronic obstructive pulmonary disease; CVVHDF, continuous veno-venous hemodiafiltration; DLP, dyslipidemia; DM, diabetes mellitus; ESRD, end-stage renal disease; FOS, fosfomycin; HAP, hospital-acquired pneumonia; HD, hemodialysis; HT, hypertension; ICU, intensive care unit; IMP, imipenem; LVX, levofloxacin; MEP, meropenem; PAD, peripheral artery disease; RF, renal failure; SCLC, small cell lung cancer; SUL, sulbactam; TIG, tigecycline; UTI, urinary tract infection; VAP, ventilator-associated pneumonia.