Detection of antibiotic-resistant canine origin and the synergistic effect of magnolol in reducing the resistance of multidrug-resistant .

BACKGROUND

The development of antimicrobial resistance in the opportunistic pathogen has become a global public health concern. Due to daily close contact, dogs kept as pets share the same with their owners. Therefore, the detection of antimicrobial resistance in canine is important, as the results could provide guidance for the future use of antibiotics. This study aimed to detect the prevalence of antibiotic-resistance of canine origin in Shaanxi province and to explore the inhibition effect of magnolol combined with cefquinome on MDR E. coli, so as to provide evidence for the use of antibiotics.

METHODS

Canine fecal samples were collected from animal hospitals. The isolates were separated and purified using various indicator media and polymerase chain reaction (PCR). Drug-resistance genes [ ] were also detected by PCR. The minimum inhibitory concentration (MIC) was determined for 10 antibiotics using the broth-microdilution method. Synergistic activity of magnolol and cefquinome against multidrug-resistant (MDR) strains was investigated using checkerboard assays, time-kill curves, and drug-resistance curves.

RESULTS

A total of 101 strains were isolated from 158 fecal samples collected from animal hospitals. MIC determinations showed that 75.25% (76/101) of the strains were MDR. A total of 22 drug-resistance genes were detected among the 101 strains. The gene exhibited the highest detection rate (89.77%). The TetA and Sul gene also exhibited high detection rate (66.34 and 53.47%, respectively). Carbapenem-resistant strains were found in Shangluo and Yan'an. Additionally, in MDR initially resistant to cefquinome, magnolol increased the susceptibility to cefquinome, with an FICI (Fractional Inhibitory Concentration Index) between 0.125 and 0.5, indicating stable synergy. Furthermore, magnolol enhanced the killing effect of cefquinome against MDR . Resistance of MDR to cefquinome decreased markedly after treatment with magnolol for 15 generations.

CONCLUSION

Our study indicates that antibiotic-resistance has been found in domestic dogs. After treatment with magnolol extracted from the Chinese herb Houpo (), the sensitivity of MDR to cefquinome was enhanced, indicating that magnolol reverses the resistance of MDR . The results of this study thus provide reference for the control of resistance.