Antibiotics Combinations and Chitosan Nanoparticles for Combating Multidrug Resistance Acinetobacter baumannii

Figures & data

Figure 1 Dendrogram of ERIC-PCR analysis of the 51 isolates of A. baumannii; the different clusters at 97% similarity are arbitrarily designated as Clusters 1–9.

Table 1 FICI Values of Two Tested Antibiotic Combinations (CT+MEM, TGC+MEM and TGC+CT) Against Nine Selected MDR A. baumannii

Isolate Code	∑FIC
	CT+MEM	Int.	TGC+MEM	Int.	CT+TGC	Int.
A3	0.257	S	0.515	D	8.0	A
A8	0.253	S	0.503	D	12.0	A
A11	0.257	S	0.265	S	6.0	A
A20	0.257	S	0.503	D	10.0	A
A25	0.253	S	0.503	D	12.0	A
A26	0.503	D	0.315	S	5.3	A
A31	0.507	D	0.503	D	12.0	A
A35	0.257	S	0.257	S	8.0	A
A42	0.128	S	0.257	S	8.0	A

Notes: ∑FIC, Sum of the fractional inhibitory concentration; Int., (interpretation); S, Synergism ≤0.5; D, Additive >0.5 ≥1; I, Indifference >1 and ≤4.0; and antagonistic when ƩFIC is > 4.

Abbreviations: CT, colistin; MEM, meropenem; TGC, tigecycline.

Figure 2 Characterization of chitosan nanoparticles. (A) Zeta potential characterization, (Surface net charge) of CNPs (+37.7 mV), (B) Zeta Sizer characterization of CNPs (441.7 nm), (C) HR-TEM micrograph of CNPs.

Table 2 Average of Inhibition Diameter (Mm) ±SD of CNPs Against MDR A. baumannii Isolates (n=9)

MDR A. baumannii Isolate Code	Average of Inhibition Diameter (mm) ±SD
A3	25± 0.35
A8	30± 0.24
A11	24± 0.26
A20	25± 0.25
A25	25± 0.25
A26	30± 0.25
A31	25± 0.3
A35	30± 0.3
A42	31± 0.25

Table 3 MIC Values CNPs (1, 2.5, 5 mg/ml) Against the MDR A. baumannii Isolates (n=51) by Broth Dilution

Concentrations of CNPs (mg/mL)	MIC (mg/mL)	MDR A. baumannii Isolate Code
1	0.5	A1, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A26, A27, A29, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39, A40, A41, A43, A44, A45, A46, A47, A48, A49, A50, A51
	0.25	A2, A3, A4, A25, A28, A42
2.5	0.31	A1, A2, A3, A5, A6, A7, A9, A10, A12, A13, A14, A15, A16, A17, A19, A20, A21, A22, A24, A25, A26, A27, A28, A30, A31, A32, A33, A34, A35, A36, A37, A38, A39, A41, A42, A44, A45, A47, A48, A49, A50
	0.16	A4, A8, A11, A18, A23, A29, A40, A46, A51
5	0.16	A2, A3, A4, A6, A7, A8, A9, A10, A11, A12, A14, A15, A17, A18, A19, A20, A21, A22, A23, A24, A25, A26, A27, A28, A29, A30, A31, A32, A33, A34, A35, A36, A37, A38, A40, A41, A42, A44, A45, A46, A47, A48, A49, A51
	0.31	A1, A5, A13, A16, A39, A43, A50

Table 4 Effects of CNPs (5 mg/ml) on the MIC of MEM, TGC and CT (Each Alone or in Combinations)

Isolate Code	CT		TGC		MEM		CT+MEM		TGC+MEM		CT+TGC
	MIC (µg/mL)	MDF	MICs (µg/mL)	MDF	MICs (µg/mL)	MDF	MICs (µg/mL)	MDF	MICs (µg/mL)	MDF	MICs (µg/mL)	MDF
A3	0.5	4	0.5	4	16	4	0.064	4	0.25	2	4	2
A8	0.125	8	0.125	4	16	4	0.064	4	0.25	2	4	3
A11	0.25	4	0.5	4	4	8	0.032	8	0.066	4	3	2
A20	0.25	8	0.125	4	16	4	0.064	4	0.25	2	4	2.5
A25	0.125	8	0.25	2	16	4	0.015	16	0.25	2	4	3
A26	0.125	8	1.0	3	4	16	0.25	2	0.04	8	5.0	1
A31	0.5	2	0.25	2	16	4	0.25	2	0.25	2	4	3
A35	0.25	4	0.125	16	8	8	0.032	8	0.064	4	8	1
A42	0.25	4	0.25	8	4	16	0.032	4	0.032	8	8	1

Abbreviations: MIC, minimum inhibitory concentration; MDF, MIC decrease factor; CT, colistin; MEM, meropenem; TGC, tigecycline.