Short communication: Outbreak of methicillin-resistant Staphylococcus aureus (MRSA)-associated mastitis in a closed dairy herd

Abstract

Cows are probably the main source of contamination of raw milk with Staphylococcus aureus. Mammary glands with subclinical mastitis can shed large numbers of Staph. aureus in milk. Because of the risk of this pathogen to human health as well as animal health, the aim of this paper was to describe an outbreak of mastitis caused by methicillin-resistant Staph. aureus (MRSA), oxacillin-susceptible mecA-positive Staph. aureus (OS-MRSA), and methicillin-susceptible Staph. aureus (MSSA) on a dairy farm. Milk samples were obtained from all quarters, showing an elevated somatic cell count by the California Mastitis Test. The isolates were identified by phenotypic and genotypic methods. Staphylococcus spp. were isolated from 53% (61/115) of the milk samples, with 60 isolates identified as Staph. aureus (98.4%) and 1 isolate identified as Staphylococcus epidermidis (1.6%). The presence of the mecA gene was verified in 48.3% of Staph. aureus isolates. Of the Staph. aureus isolates, 23.3% were MRSA and 25.0% were OS-MRSA. The total of mastitis cases infected with MRSA was 12.2%. The detection of this large percentage of mastitis cases caused by MRSA and OS-MRSA is of great concern for the animals' health, because β-lactams are still the most important antimicrobials used to treat mastitis. In addition, Staph. aureus isolates causing bovine mastitis represent a public health risk.

Characterization of Coa Gene and Antimicrobial Profiles of Staphylococcus Aureus Isolated from Bovine Clinical and Subclinical mastitis

“…A relatively higher prevalence (54%) of S.aureus was recorded by Berchtold et al (2014). Moreover, a higher prevalence (49.3%) was also recorded in Zimbabwe by Katsande et al (2013),in South Ethiopia (51.2%) by Abebe et al (2016), and in Brazil (53%) by Guimarães et al (2016). However, lower prevalence than the present findings was reported by many authors all over the world Wang et al 2014;Wang et al 2016).…”

Antimicrobial Resistance in Farm Animals in Brazil: An Update Overview

“…From a total of 103 cows investigated, 12.2% of the mastitis cases were caused by S. aureus. In this collection of isolates, mecA was also detected in isolates that did not express the resistance phenotype (OS-MRSA-oxacillin-susceptible mecA-positive S. aureus) [119]. Haubert et al (2017) reported MRSA isolation, identified by phenotypic methods, in herds from the Rio Grande do Sul State (S).…”

“…They detected neither the mecA nor the mecC genes among the isolates [101]. Guimarães et al (2017) reported an outbreak of MRSA intramammary infections in Dutch cows from a dairy herd in São Paulo (SE). From a total of 103 cows investigated, 12.2% of the mastitis cases were caused by S. aureus.…”

The main spoilage-related psychrotrophic bacteria in refrigerated raw milk

“…In addition to lactic acid bacteria, other microorganisms were evaluated in the present study; these may have originated from cases of mastitis, a common disease in high production animals (such as those in dairy farms) and include Staphylococcus (Felipe et al, 2017;Guimarães et al, 2017), Streptococcus (Taponen et al, 2017), and Aerococcus (Saishu et al, 2015).…”