AUTHOR=Liu Kang , Li Linqian , Weng Mengwei , Zhang Feng , Guo Rong , Huang Jinhu , Yao Wen 

TITLE=Effect of high-copper diet on transference of blaCTX−M genes among Escherichia coli strains in rats' intestine

JOURNAL=Frontiers in Veterinary Science

VOLUME=Volume 10 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2023.1127816

DOI=10.3389/fvets.2023.1127816

ISSN=2297-1769

ABSTRACT=This study aimed to evaluate the effect of dietary high copper on horizontal transfer of blaCTX-M-1 among the E. Coil. Thirty-two male SPF rats at 21 days of age were randomly assigned to four groups: control (6 mg/kg in feed copper, C-), high copper (240 mg/kg in feed copper, H-), ceftiofur (6 mg/kg in feed copper with oral ceftiofur administration, C+), and high copper plus ceftiofur (240 mg/kg in feed copper with oral ceftiofur administration, H+). All rats were orally inoculated with an E. coil strain harboring a conjugative plasmid carrying blaCTX-M-1 and the ceftiofur groups (C+ and H+) were given 10 mg/kg of body weight ceftiofur hydrochloride at 26, 27, 28 days, while the control groups (C- and H-) were given salad oil at the same dose.  Fecal samples collected at different time points were used for enumeration of E. Coil on Mac plates, or molecular analysis using PCR, PFGE, S1-PFGE and Southern-blot hybridization. Results showed that the number of the blaCTX-M-1 gene in the high copper group (H-) was higher and the loss speed of this gene was slower compared with the control group (C-). After administration of ceftiofur, the counts of cefotaxime -resistant E. Coil in ceftiofur group were significantly higher than that in corresponding control group (C+ vs C-; H+ vs H-). In vitro test, the results showed the transfer rates of the conjugation induced by high copper (12 mmol/L) were significantly higher than that of low copper (2 mmol/L) group. The indigenous sensitive isolates, which were homologous to the blaCTX-M -positive isolates of rat feces, were found by PFGE. The further analysis of S1-PFGE and Southern-blot hybridization confirmed that the blaCTX-M-1 gene in new transconjugants derived from the inoculated strain. Taken together, dietary high copper facilitates the horizontal transfer and maintenance of the resistant genes in the intestine of rats, although the effects of antibiotics on bacterial resistance appearance and maintenance is more obvious.