Antibiotic resistance profile of gram-negative bacteria isolated from dog nasal swab samples, and antibacterial and antioxidant activities of aqueous extracts of Alpinia purpurta (Vieill.) K. Schum (Zingiberaceae)

Abstract

The indiscriminate use of antibiotics in veterinary medicine and their negligent use among dog owners have contributed to the rise of antibiotic resistance in microorganisms found in pets. In addition, the search for medicinal plants with antibacterial properties has made the evaluation of aqueous extracts of Alpinia purpurata (Vieill.) K. Schum an important issue. Thus, the aim of this work was to determine the antibiotic resistance profile of gram-negative bacteria isolated from nasal swab samples of dogs and assess the antibacterial activity of the aqueous extracts of leaves and rhizomes of A. purpurata. The bacteria identified were tested using the agar disc diffusion assay for the evaluation of antibiotic resistance. A total of 16 isolates were obtained from the 19 samples collected, with a high prevalence of Escherichia coli (n=5). There was a high rate of resistance to ?-lactams, where the highest percentage was seen for amoxicillin (72.5%). Aqueous leaf extracts had high levels of total phenolic compounds (637.47 µg GAE mg-1), differing significantly (p < 0.05) from aqueous rhizome extracts (228.64 µg GAE mg-1). There was no significant difference in EC50 of DPPH values between the aqueous extracts; however, the antioxidant capacity of rhizome extracts had higher values than leaf extracts. The minimum inhibitory concentration (MIC) of leaves and rhizomes for the evaluated bacteria ranged from 9000 to 32,000 µg mL-1. For the minimum bactericidal concentration (MBC), most bacteria showed an MBC over 38,400 µg mL-1 for the rhizome. In conclusion, the bacteria isolated from dog nasal swabs showed a high resistance profile for the antibiotics of the penicillin class. Additionally, the results from the analysis of the aqueous extracts of rhizomes and leaves of A. purpurata showed an antimicrobial effect possibly associated with a high content of total phenolic compounds; these results can create a scope for using these extracts together with conventional antibiotics to control the emergence of antibiotic resistance among microbial species.