Effects of enrofloxacin treatment on the bacterial microbiota of milk from goats with persistent mastitis

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. Antimicrobial therapies have been shown to be increasingly problematic due to the development multiple types of antimicrobial resistance (AMR) mechanisms, and for that reason, therapeutic alternatives to treat multidrug-resistant microorganisms are rapidly dwindling. Fluoroquinolones have been extensively used in human and veterinary medicine as they are considered among the most effective drugs for the treatment of bacterial infections 1,2. Enrofloxacin, is a fluoroquinolone exclusively developed for use in veterinary medicine 1,3,4. This drug is a potent inhibitor of bacterial DNA Topoisomerase II (Gyrase) and the DNA Topoisomerase IV (Topo IV), which are essential enzymes involved in key cellular processes including DNA replication 5-10. The drug has a broad spectrum of activity, being active against major pathogenic bacteria (both Gram-positive and Gram-negative), mycoplasmas 11 , and also mycobacteria 12 , but is ineffective against obligate anaerobes 13. Furthermore, 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. The active substance is characterised by a low host toxicity, being non-mutagenic with a...

Comparative Analysis of Milk Microbiomes and Their Association with Bovine Mastitis in Two Farms in Central Russia

“…as opportunistic pathogens in existing mastitis cases was discussed in previous studies [35,49]. In addition, several authors have shown that F. necrophorum may be associated with summer mastitis [50,51], which is in agreement with our period of milk sampling (from June to August). Recently, Gu and coauthors have shown that Fusobacterium causes dysbiosis [52].…”

Comparative Study on Pharmacokinetics of Four Long-Acting Injectable Formulations of Enrofloxacin in Pigs

“…On the other hand, the low antibiotic concentrations can develop antibiotic-resistant bacteria (52) and these bacteria may create side effects on humans and animals (53). The infections caused by resistant organisms are more challenging to treat than infections caused by the non-resistant organism (54).…”

Distinguishing the milk microbiota of healthy goats and goats diagnosed with subclinical mastitis, clinical mastitis, and gangrenous mastitis

“…Microbiome studies of goats ( McInnis et al, 2015 ; Zhang et al, 2017 ; Polveiro et al, 2020 ) and cows milk ( Oikonomou et al, 2014 ; Addis et al, 2016 ; Bonsaglia et al, 2017 ) in several situations have demonstrated the complexity of the interactions of pathogens and commensals present in situations of health and illness. Diseases can be the consequence of a sum of many complex variables that interact, which can go beyond the mere interaction between host, pathogen and environment, as we know it ( Hedrick, 1998 ), and milk omics analyzes have unravel new variables for understanding the different types of mastitis.…”

“…Such novel research approach has allowed the reconstruction of systems approaching this infectious disease ( Garira, 2019 ; Eckhardt et al, 2020 ). Few studies have revealed microbiota in goat milk; however, the main bacterial phyla found are Proteobacteria , Actinobacteria , Firmicutes , and Bacteroidetes , as well as a variety of genera such as Acinetobacter , Agrobacterium , Alkalibacterium , Bacteroides , Bacillus , Enterobacter , Escherichia / Shigella , Fusobacterium , Klebsiella , Massilia , Micrococcus , Pseudomonas , Phyllobacterium , Rhodococcus , Staphylococcus , Stenotrophomonas , Stenotrophomonas , Shewanella , Streptococcus , and Yersinia ( McInnis et al, 2015 ; Zhang et al, 2017 ; Polveiro et al, 2020 ).…”