Abstract
Antibiotic resistance has become a major concern for human and animal health. As fluoroquinolones have been extensively used in human and veterinary medicine, there has also been the rapid emergence and spread of antimicrobial resistance around the world. Here, we analysed the microbiome of goat milk using samples from healthy goats and those diagnosed with persistent mastitis and treated using the antibiotic enrofloxacin with 16S rRNA amplicon sequencing. We selected a group of 11 goats and 22 samples of milk that did not respond clinically to enrofloxacin treatment. Milk samples were evaluated before and after treatment to verify changes of the microbiota; the three first lactating goats were selected from the healthy control group. The milk samples from the healthy control animals presented a larger abundance of different species of bacteria of the Staphylococcus genus, but a smaller number of different genera, which indicated a more specific niche of resident bacteria. The Firmicutes phylum was predominantly different between the studied groups. Samples from before-treatment animals had a higher number of new species than those from the control group, and after being treated again. These microbiota received new bacteria, increasing the differences in bacteria even more in relation to the control group. Genotypes such as Trueperella and Mannheimia, between other genera, had a high abundance in the samples from animals with persistent mastitis. The dysbiosis in this study, with marked evidence of a complex microbiota in activity in cases of the failure of antimicrobial treatment for persistent chronic mastitis, demonstrates a need to improve the accuracy of pathogen identification and increases concern regarding antibiotic treatments in milk production herds.
Highlights
Antibiotic resistance has become a major concern for human and animal health
We selected 25 samples of goat milk, three samples from healthy controls (H), 11 samples from before treatment (B) and 11 samples from after treatment (A) from the same animals, which showed clinical and bacteriological persistence when properly treated for clinical mastitis in another study[50] with the antibiotic enrofloxacin 1,4,19,51
The development of antimicrobial resistance (AMR) raises concerns related to food safety, as it may lead to a decrease in the availability of antibiotics for use in production animals, and limit the ability of professionals to control disease in animals raised for the production of food[49]
Summary
Antibiotic resistance has become a major concern for human and animal health. As fluoroquinolones have been extensively used in human and veterinary medicine, there has been the rapid emergence and spread of antimicrobial resistance around the world. Samples from before-treatment animals had a higher number of new species than those from the control group, and after being treated again These microbiota received new bacteria, increasing the differences in bacteria even more in relation to the control group. Genotypes such as Trueperella and Mannheimia, between other genera, had a high abundance in the samples from animals with persistent mastitis. The drug has a broad spectrum of activity, being active against major pathogenic bacteria (both Gram-positive and Gram-negative), mycoplasmas[11], and mycobacteria[12], but is ineffective against obligate anaerobes[13] In both mammalian and non-mammalian species, enrofloxacin is partially metabolised in the liver to ciprofloxacin, a primary metabolite of which is cyclopropyl, a potent antimicrobial agent itself[14]. Metagenomics represents a powerful tool to achieve these goals using sequence-based and functional-based approaches[6,21]
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