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.
Highlights
Bovine mastitis is an inflammatory disease of the mammary gland (Bradley, 2002; ThompsonCrispi et al, 2014); it represents one of the main production and economic problems confronting the global dairy industry (Zadoks and Fitzpatrick, 2009)
According to the microbiological analysis of samples, the milk from cattle with mastitis was negative in 123 samples (32%); nine samples were excluded for contamination with three or more microorganisms
Of the remaining samples (n = 254) a total of 327 microorganisms were isolated (Figure 2); three of them were identified as Candida spp. from subclinical mastitis
Summary
Bovine mastitis is an inflammatory disease of the mammary gland (Bradley, 2002; ThompsonCrispi et al, 2014); it represents one of the main production and economic problems confronting the global dairy industry (Zadoks and Fitzpatrick, 2009). Bovine mastitis disease begins with the invasion and colonization of microorganisms via the teat duct orifice, creating inflammation in the mammary gland that results in a clear productive decline and in unwanted physical and chemical changes in the milk (De Vliegher et al, 2012; ThompsonCrispi et al, 2014). Staphylococcus aureus, Escherichia coli, and Streptococcus uberis are frequently found in clinical mastitis (De Vliegher et al, 2012). Intramammary bacterial infections are the principal causes of clinical and subclinical mastitis (De Vliegher et al, 2012)
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