Tie Zhang

Survey on tetracycline resistance and antibiotic-resistant genotype of avian Escherichia coli in North China

The experiment was performed to investigate the tetracycline resistance and antibiotic-resistant genotype of avian Escherichia coli in North China and to analyze the correlation of genotype and phenotype. The resistance of 164 E. coli isolates (from Beijing, Tianjin, inner Mongolia, Shanxi, and Hebei regions of China) to tetracycline, doxycycline, and minocycline was investigated by using a drug susceptibility test. The results show that the rate of resistance to tetracycline antibiotics was 89.63% (147/164). The higher resistance rate was 84.76% (139/164) to tetracycline and 70.12% (115/164) to doxycycline, and the lowest resistance rate was 4.88% (8/164) to minocycline. The distribution of tetracycline resistance (Tcr) genes (tetA, tetB, tetC, and tetM) in avian E. coli isolates was detected by PCR. Of the isolates, 82.32% (135/164) carried tetracycline resistance genes. The positive rates of tetA, tetB, and tetM were 57.93% (95/164), 38.41% (63/164), and 10.97% (18/164), respectively. No tetC was amplified in avian E. coli isolates. The total positive rate of resistance genes (82.32%) was almost equal to the total rate of resistance to tetracycline antibiotics (89.63%). Thus, the positive rate of genotype was basically in line with that of phenotype for tetracycline resistance. The tetracycline resistance genes are widely distributed in E. coli and their main resistance mechanism to tetracycline is the active efflux effect mediated by tetA and tetB.

Hepatoprotective Effects of a Chinese Herbal Formula, Longyin Decoction, on Carbon-Tetrachloride-Induced Liver Injury in Chickens

The objective of this study is to establish poultry liver injury model induced by (CCl4) and seek effective hepatoprotective herbals for clinical application. Different doses of CCl4 dissolved in vegetable oil (1 : 1, V/V) were injected via pectoral muscle to induce acute liver injury model in chickens. An herbal formula, Longyin decoction, was prepared for hepatoprotection test on chicken acute liver injury models. The pathologic changes of the liver were observed, and the activities of ALT and AST were, respectively, detected to evaluate the hepatoprotective effects of Longyin decoction on chickens. The chicken acute liver injury model was successfully established by injecting CCl4 via pectoral muscle. The best dose of CCl4 inducing chicken liver injury was 4.0 mL/kg·BW (body weight). The results of qualitative determination by HPTLC showed that the components of Longyin decoction contained Gentian, Capillaries, Gardenia, and Bupleurum root. In the high-dose Longyin group and the middle-dose Longyin group, the pathological changes of the damaged liver were mitigated and the activities of ALT and AST in serum were reduced significantly. Longyin decoction has obvious hepatoprotective effect on acute liver injury induced by CCl4.

Survey on sulfonamide antibiotic-resistant genotype and phenotype of avian Escherichia coli in North China

It is important for the prevention and treatment of colibacillosis to monitor drug resistance in Escherichia coli. To choose effective drugs to prevent and control avian colibacillosis in North China, we investigated the resistance of 164 E. coli isolates (from Beijing, Tianjin, Inner Mongolia, Shanxi, and Hebei regions of China) to commonly used clinical sulfonamide antibiotics using a drug susceptibility test. The results show that the rates of resistance to sulfamonomethoxine and sulfamethoxazole-trimethoprim were 90.24% (148/164) and 73.17% (120/164), respectively. To explore the reasons for wide drug resistance, sulfonamide resistance genes were detected by PCR. Of the isolates, 90.85% (149/164) carried sulfonamide resistance genes. Therefore, resistance of avian E. coli to sulfonamide antibiotics is very serious in North China, perhaps because of the existence of resistance genes, but other resistance mechanisms may also contribute to tolerogenesis.

Antibacterial Behavior of Ag-Ce-TiO2 Composite Films in the Different Irradiations

An Ag-Ce-TiO2 composite film was prepared by incorporating Ag in the Ce-TiO2 films with an impregnation method through photoreduction. The bactericidal activity of the Ag-Ce-TiO2 composite film and the effect of deposition of silver and doping cerium in the different irradiations on the antibacterial performance were assessed against Escherichia coli (E. coli). TIhrough characterization of X-ray diffraction (XRD), X-ray photoelectronic spectra (XPS) and UV/VIS diffusive reflectance spectra (DRS), it was found that the Ag-Ce-TiO2 composite film was composed of predominant anatase titania, cerium oxides (in the form of Ce2O3/CeO2) and silver nanoparticles. Moreover, the bactericidal activity of the Ag-Ce-TiO2 composite film and the effect of deposition of silver and doping cerium in the different irradiations on the antibacterial performance were assessed against Escherichia coli (E. coli). The results show that the Ag-Ce-TiO2 composite film has much higher antibacterial efficiency than that of glass and pure TiO2 film either in the room light or in the dark. Therefore, this composite film is promising in applications of antimicrobial and self-clean technologies.

Effects of modified pulsatilla decoction on avian colibacillosis and concentrations of nitrogen oxide (NO) and tumor necrosis factor-α (TNF-α) in serum

To investigate the mechanism of the Chinese herbal formula modified pulsatilla decoction (MPD) on chicken colibacillosis, the oral herbal liquid was used to treat chickens experimentally infected with Escherichia coli . The serum nitrogen oxide (NO) and tumor necrosis factor-α (TNF-α) concentrations were determined. The results showed that the MPD oral liquid administrated at a dose of 1.5, 1.0 and 0.5 ml/kg·BW achieved effective rates of 70, 82 and 84% in the chickens infected with E. coli , respectively. The effective rates of the MPD oral liquid treated groups were significantly higher than that of the challenged group ( p <0.01). The MPD oral liquid at a dose of 1.0 ml/kg·BW reduced serum NO and TNF-α concentrations. Therefore, the MPD preparation has good curative effects on chicken colibacillosis, and the efficacy may be achieved by inhibiting the increase of serum NO and TNF-α concentrations caused by E. coli infection and resisting endotoxin-induced factors, which protects the body from inflammatory injury and controls the development of colibacillosis.

Serotype Identification and Drug Sensitive Test of the Pathogenic Escherichia coli

Thirty-eight isolates of Escherichia coli (E.coli) were isolated from chickens either ill or dead suspected with E.coli. These chickens come from chicken breeding farms in the districts of Baoding, Qinhuangdao and Beijing of China. The results of the antibiotics sensitivity test in the thirty-eight isolates to twenty-four kinds of antibiotics show that all isolates have presented antibiotic resistance disparately as well as multiresistance. All isolates are sensitive to Cephalosporins antibiotics and Aminoglycosides antibiotics such as Amikacin, Cefazolin, Cefradine, Cefoperazone and Ceftriaxone. Thirty-eight isolates are extremely resistant to Penicillins antibiotics, Lincomycins antibiotics, Tetracyclines antibiotics and Macrolides antibiotics such as Midecamycine, Lincomycin, Carbenicillin, Tetracycline, Amoxicillin. Antibiotics sensitivity test provides a guidance for antibiotic application and scientific research on poultry farms.

Detection of resistance phenotype and genotype of avian Escherichia coli in Hebei Province

We investigated the resistance of avian Escherichia coli to commonly used clinical antibiotics in Hebei Province. It is of significance to reveal the extent and mechanism of drug resistance, as well as to prevent and control colibacillosis. We investigated the resistance of 132 E. coli isolates to 5 kinds of antibiotics (including β-lactams, aminoglycosides, tetracyclines, sulfonamides, and chloramphenicol) using the Kirby-Bauer drug susceptibility test, and resistance genes were detected by PCR. The results showed that the E. coli had a higher resistance rate to ampicillin, cephalotin, gentamicin, streptomycin, tetracycline, doxycycline, sulfamethoxazole trimethoprim, sulfamonomethoxine, and florfenicol, but it had higher sensitive rate to cefepime, imipenem, spectinomycin, and minocycline. Of the resistance genes, the TEM, aac(3)-IIa, tetA, Sul1, Sul2, and forl had higher positive rates. Therefore, drug resistance of avian E. coli in Hebei Province is very serious. The resistance mechanisms may include structure changes of the target enzyme mediated by multiresistance genes, and resulting in reduced affinity and increased efflux of antibiotics.

Isolation and characterization of a Swainsonine degrading bacteria strain Stenotrophomonas maltophilia

A series of experiments were conducted to investigate the possibility of Swainsonine (SW) degradation by bacterium. In a preliminary experiment, locoweed plant material was buried in soil for 6 months, and eight swainsonine-degrading bacteria strains were isolated from the soil around the buried plant by enrichment procedure. One of the strains (YLZZ-2) was selected for further study. Based on morphology, physiologic tests, 16S rDNA sequence, and phylogenetic characteristics, this strain showed the greatest similarity to members of the Stenotrophomonap and closest to members of the Stenotrophomonas maltophilia group. The ability of YLZZ-2 to degrade SW as sole carbon source, was investigated under different culture conditions. The preferential temperature and initial pH for the strain were 25～35°C and 6.0～9.0, respectively. The optimal temperature for this strain was 30°C and the optimal pH was 7.0. There was positive correlation between degradation rate and inoculation amount. YLZZ-2 could completely degradate 400 mg/L swainsoine within 24 h. There was a linear relationship between the growth of stain YLZZ-2 and degradation of swainsonine. These results highlight the potential of this bacterium to be used in detox of SW in livestock consuming locoweed.