In this study, a polysaccharide (ECP) was isolated from the mycelium of Enterobacter cloacae and was found to exhibit strong antibacterial activities against E. cloacae producing SHV-12 ESBL with the increase of the inhibition zone diameter. Its minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were 12.5 mg/L and 25 mg/L, respectively. ECP at these concentrations immediately inhibited planktonic growth of the bacteria especially at the time from 2 to 10 h. Flow cytometry analysis further revealed that almost all the bacterial cells were damaged following ECP treatment. The permeability of the cytoplasmic membrane of E. cloacae was increased when ECP concentrations increasing, as evidenced by an influx of Na and an efflux of K, P or S, the leakage of intracellular ATP and the UV-absorbing substances, as well as the depolarization of the cytoplasmic membrane, indicating that bactericidal activity of ECP was achieved by inducing cell membrane damage.

structural analysis, Enterobacter cloacae, Antibacterial mechanism, Antibacterial polysaccharide, SHV-12 extended-spectrum beta-lactamase

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
4	bDGlcp	103.42	73.86	75.98	70.02	74.85	68.54
	bDGlcp	104.12	73.54	75.19	79.82	75.91	62.27


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
4	bDGlcp	4.45	3.35	3.51	3.48	3.56	3.85-4.11
	bDGlcp	4.56	3.45	3.70	3.69	3.58	3.70-3.81


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
4	bDGlcp	103.42/4.45	73.86/3.35	75.98/3.51	70.02/3.48	74.85/3.56	68.54/3.85-4.11
	bDGlcp	104.12/4.56	73.54/3.45	75.19/3.70	79.82/3.69	75.91/3.58	62.27/3.70-3.81

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*OC[C@H]1O[C@@H](O[C@@H]2[C@@H](CO)O[C@@H](*)[C@H](O)[C@H]2O)[C@H](O)[C@@H](O)[C@@H]1O

324.282 g/mol (C₁₂H₂₀R₂O₁₀, R = next and previous repeats, not counted in mol weight)