Antibacterial impact of biosynthesized zinc oxide nanoparticles on uropathogenic Escherichia coli and in vivo assessment of physiological and histological alterations

Abstract

Zinc oxide nanoparticles (ZnO NPs) possess various medical potentials that qualify them to be promising antibacterial agents, particularly for uropathogens. The present study investigated in vitro and in vivo antibacterial impact of biosynthesized ZnO NPs against uropathogenic E. coli strain. Values of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of ZnO NPs were detected to be 3.2 mg/mL and 3.9 mg/mL, respectively. The in vivo study included twenty-four female albino rats that were divided into four equal groups: group 1 (control), group 2 (infected), group 3 (infected + ZnO NPs), and group 4 (ZnO NPs). The bactericidal efficacy of ZnO NPs (50 mg/Kg) was confirmed by a recovery percentage of 83.3% after the fourth dose and a survival rate of 100% after eight doses. Erythrocytosis and thrombocytopenia were observed in the infected group, while ZnO NPs-administrated groups exhibited normal red blood cells and platelets counts, and a significant increase in white blood cells count. A significant decrease in urea level and a slight increase in liver enzymes were observed in the infected group, unlike ZnO NPs-administrated groups. Moreover, ZnO NPs-administrated groups exhibited a significant decrease in uric acid and glucose levels. The histological sections of vital body organs showed the aggressive bacterial-induced inflammatory response in stomach, liver, spleen, kidney, and heart of the infected group, whereas ZnO NPs-treated group exhibited effective suppression of the bacterial infection.

Fig. 1

Identification of the bacterial strain. (a) Escherichia coli strain appeared on CLED agar as lactose fermenter, opaque, bright yellow colonies “reproduced from ref 2”. (b) Phylogenetic tree based on 16S rRNA sequence of Escherichia coli (arrowed) aligned with closely related strains accessed from the GenBank. Bacillus subtilis is included in the tree as outgroup strain. Escherichia coli OR064346 showed 99.72–99.93% identity and 99–100% coverage with several strains of the same species including the type strain E. coli NBRC102203 (NR_114042).

Fig. 2

Characterization of biosynthesized ZnO NPs. (a) XRD patterns confirmed the highly crystalline hexagonal wurtzite structure of ZnO NPs. (b) TEM image exhibited the hexagonal shape of ZnO NPs. “reproduced from ref”.

Fig. 3

Antibacterial effect of ZnO NPs on E. coli compared to amoxicillin/clavulanate (20/10 μg) disc as a positive control “PC” and glycerol and water (4:1 v/v) disc as a negative control “NC”.

Fig. 4

Urine cultures performed on CLED agar with Andrade indicator confirmed the antibacterial effect of ZnO NPs. (a) Luxurious growth after 24 h of infection induction. (b) Reduction in the bacterial growth after 24 h of applying the 1st dose of ZnO NPs. (c) No growth after 24 h of applying the 4th dose of ZnO NPs.

Fig. 5

Photomicrograph of stomach sections. Group 1 exhibited (a) normal structure of stomach layers (× 10) and (b) patchy infiltration in submucosa with few congested capillaries (× 40). Group 2 exhibited (c) moderate infiltration in submucosa (× 10) and (d) inflammatory cells with multiple congested capillaries (× 40). Group 3 exhibited (e) normal mucosa and mucosal glands (× 10) and (f) mild infiltration by inflammatory cells in submucosa (× 40). Group 4 exhibited (g) normal mucosa and mucosal glands (× 10) and (h) mild infiltration by inflammatory cells in submucosa with few congested capillaries (× 40).

Fig. 6

Photomicrograph of liver sections. Group 1 exhibited (a) normal lobular architecture of liver (× 10) and (b) preserved central vein, hepatocytes in a normal cording growth pattern, and normal hepatic sinusoids (× 40). Group 2 exhibited (c) patchy lobular inflammatory reaction and dilated central venules (× 10), (d) frequent inflammation of portal areas included mainly lymphocytes and plasma cells (× 40), (e) focal mild proliferation of bile ductules and focal congestion of hepatic sinusoids (× 40) and (f) focal mild hepatocyte swelling and vacuolation (× 40). Group 3 exhibited (g) normal lobular architecture with patchy mild lobular inflammatory reaction (× 10) and (h) inflammation of portal areas and mild proliferation of bile ductules (× 40). Group 4 exhibited (i) normal lobular architecture with no inflammatory reaction (× 10) and (j) minimal inflammation of portal areas (× 40).

Fig. 7

Photomicrograph of kidney sections. Group 1 exhibited (a) normal renal architecture (× 10) and (b) uniform renal tubules and normal renal glomeruli with preserved Bowman’s space (× 40). Group 2 exhibited (c) focal relative raised congestion of capillary glomerular tufts with multiple aggregates of inflammatory cells (× 40) and (d) focal congestion of capillaries (× 40). Group 3 exhibited (e) patchy inflammatory reaction (× 40) and (f) few congested stromal capillaries (× 40). Group 4 exhibited (g) minimal inflammatory reaction (× 40) and (h) few congested stromal capillaries (× 40).

Fig. 8

Photomicrograph of spleen sections. Group 1 exhibited (a) normal architecture with uniform lymphoid follicles and preserved central arterioles (× 10), and (b) mild inflammatory reaction in the red pulp with few congested capillaries (× 40). Group 2 exhibited (c) variable-sized lymphoid follicles (× 10) and (d) moderate inflammatory reaction in the red pulp with raised vascularity and congested capillaries (× 40). Group 3 exhibited (e) slightly variable-sized lymphoid follicles (× 10) and (f) moderate inflammatory reaction in the red pulp (× 40). Group 4 exhibited (g) slightly variable-sized lymphoid follicles (× 10) and (h) mild inflammatory reaction in the red pulp (× 40).

Fig. 9

Photomicrograph of heart sections. Group 1 exhibited (a) normal cardiac muscle (× 10) and (b) uniform arrangement of muscle bundles, uniform nuclei and identified cardiac striations (× 40). Group 2 exhibited (c) cardiac muscle with uniform arrangement of muscle bundles (× 10) and (d) mild focal pericardial inflammatory reaction with few dilated capillaries (× 40). Group 3 exhibited (e) cardiac muscle with uniform arrangement of muscle bundles (× 10) and (f) few dilated capillaries with no inflammation reaction (× 40). Group 4 exhibited (g) cardiac muscle with uniform arrangement of muscle bundles (× 10) and (h) no inflammation reaction (× 40).