Antibacterial Effect of Copper on Microorganisms Isolated from Bovine Mastitis

Abstract

The antimicrobial properties of copper have been recognized for several years; applying these properties to the prevention of diseases such as bovine mastitis is a new area of research. The aim of the present study was to evaluate in vitro the antimicrobial activity of copper on bacteria isolated from subclinical and clinical mastitis milk samples from two regions in Chile. A total of 327 microorganisms were recovered between March and September 2013, with different prevalence by sample origin (25 and 75% from the central and southern regions of Chile, respectively). In the central region, Escherichia coli and coagulase negative Staphylococci (CNS) were the most frequently detected in clinical mastitis cases (33%), while in the southern region S. uberis, S. aureus, and CNS were detected with frequencies of 22, 21, and 18%, respectively. Antibiotic susceptibility studies revealed that 34% of isolates were resistant to one or more antibiotics and the resistance profile was different between bacterial species and origins of isolation of the bacteria. The minimum inhibitory concentration of copper (MIC-Cu) was evaluated in all the isolates; results revealed that a concentration as low as 250 ppm copper was able to inhibit the great majority of microorganisms analyzed (65% of isolates). The remaining isolates showed a MIC-Cu between 375 and 700 ppm copper, and no growth was observed at 1000 ppm. A linear relationship was found between the logarithm of viable bacteria number and time of contact with copper. With the application of the same concentration of copper (250 ppm), CNS showed the highest tolerance to copper, followed by S. uberis and S. aureus; the least resistant was E. coli. Based on these in vitro results, copper preparations could represent a good alternative to dipping solutions, aimed at preventing the presence and multiplication of potentially pathogenic microorganisms involved in bovine mastitis disease.

Resistome diversity in bovine clinical mastitis microbiome, a signature concurrence

“…The use of heavy metals in soluble forms as an alternative to prevent bovine CM 271 appears as a novel promising idea supported by several earlier studies 1,22 Enterobacter species (≤25.5 μ g/mL) ( Supplementary Table 2). 294…”

“…The CmeABC operon is highly potent against multiple antibiotics, 395 promotes the emergence of ARGs, and confers exceedingly high-level resistance to 396 fluoroquinolones 33 . Therefore, multidrug resistance to efflux pumps and multiple heavy 397 metals resistance represented ubiquitous resistance mechanisms among CM microbiomes, 398 which might be associated with unethical overuse of antibiotics in dairy animals 8,9,15,[19][20][21] and 399 extensive application of toxic chemicals and metals in agricultural use 1,22,34 or might have a 400 function in the gut microbiome that is still unknown 13,29,35,36 . The RATC genes detected in 401 this study are of particular interest because there is concern that the use of this class of 402 antibiotics or metals in veterinary medicine, particularly for food animals, may contribute to 403 the development of resistance to this class of antimicrobial options in human 29,35 .…”

“…Bacteria residing in the bovine 97 gastrointestinal tract and udder may become resistant to these antibiotics and, once released 98 into the milk, they may transfer ARGs to other CM bacteria of contagious and environmental 99 origin 8,20 . Efficacy of antimicrobial therapy against bovine CM pathogens is low 8 , and the use 100 of antibiotics, confined to selected severe CM cases necessitates the accurate identification 101 and characterization of pathogens and antibiotic selection for its better prevention and 102 control 1,8 . Furthermore, antimicrobial resistance (AMR) is a global health concern in both 103 human and veterinary medicine 10 , and thus, monitoring the emergence of AMR bacterial 104 strains is an essential component of bovine CM prevention and control strategies 8,21 .…”

Evaluation of a new vaccine against Staphylococcus aureus mastitis in dairy herds of southern Chile. I. Challenge trial

“…Common mastitis control measures, such as hygiene during milking time, post-milking teat dipping, dry-cow therapy, lactation treatment of clinical cases, and disinfection of the milking machine at the end of the milking, have been applied in Chile for more than 40 years, however, mastitis still remains as one of the most frequent and costly diseases of dairy herds, with S. aureus being the most frequent mastitis pathogen, particularly in southern Chile (San Martín et al 2002, Reyes-Jara et al 2016. Most infections with this pathogen are subclinical and of long duration and the major economic effect of this type of mastitis is reduced milk yield.…”

“…S. aureus is considered the most contagious mastitis pathogen of dairy cattle in most countries and it is normally related to subclinical or chronic mastitis. In Chile, S. aureus has been the most frequently mastitis pathogen isolated from clinical and subclinical mastitis during the last decades in dairy herds, accounting for 30-50% of all mastitis cases (San Martín et al 2002, Reyes-Jara et al 2016. The major reservoir for infection is the udder and transmission occurs during milking time (Middleton et al 2006), therefore control has been focused on milking hygiene and dry cow therapy (Dodd et al 1969).…”