Symposium review: Intramammary infections—Major pathogens and strain-associated complexity

Abstract

Intramammary infection (IMI) is one of the most costly diseases to the dairy industry. It is primarily due to bacterial infection and the major intramammary pathogens include Escherichia coli, Streptococcus uberis, and Staphylococcus aureus. The severity and outcome of IMI is dependent on several host factors including innate host resistance, energy balance, immune status, parity, and stage of lactation. Additionally, the infecting organism can influence the host immune response and progression of disease. It is increasingly recognized that not only the infecting pathogen species, but also the strain, can affect the transmission, severity, and outcome of IMI. For each of 3 major IMI-associated pathogens, S. aureus, Strep. uberis, and E. coli, specific strains have been identified that are adapted to the intramammary environment. Strain-dependent variation in the host immune response to infection has also been reported. The diversity of strains associated with IMI must be considered if vaccines effective against the full repertoire of mammary pathogenic strains are to be developed. Although important advances have been made recently in understanding the molecular mechanism underpinning strain-specific virulence, further research is required to fully elucidate the cellular and molecular pathogenesis of mammary adapted strains and the role of the strain in influencing the pathophysiology of infection. Improved understanding of molecular pathogenesis of strains associated with bovine IMI will contribute to the development of new control strategies, therapies, and vaccines. The development of enabling technologies such as pathogenomics, transcriptomics, and proteomics can facilitate system-level studies of strain-specific molecular pathogenesis and the identification of key mediators of host-pathogen interactions.

Antimicrobial Resistance in Farm Animals in Brazil: An Update Overview

“…Although different species may cause mastitis, S. aureus is one of the most frequently isolated etiological agents of these infections, which justifies the largest number of studies regarding this species [98]. Most published data are from S. aureus isolates recovered from herds localized in the Southeast and South states.…”

“…Beta-lactam resistance, especially to penicillinase-labile penicillins (PSLP; for example, amoxicillin, ampicillin, penicillin G), has been widely observed among Staphylococcus isolates recovered from bovine mastitis [91,[97][98][99][100][106][107][108]. Penicillin G resistance frequencies have ranged from 30.4% to 100% in the studies published in the last ten years [100,101,109,110].…”

The correlation and mechanism between rumen microbiota disturbance and mastitis in dairy cows

“…Mastitis, a major symptom of in ammation of the mammary gland, is one of the most serious diseases of dairy cows, and its occurrence has a massive negative effect on animal well-being and farm economics due to treatment costs and a reduction in milk production [2,3] . It is commonly believed that the major cause of mastitis is opportunistic pathogens, such as Staphylococcus aureus, Streptococcus uberis, and Escherichia coli, invade and colonize the mammary gland [4][5][6] . However, recent research has demonstrated that microbiological diagnoses of milk derived from cows that suffered from mastitis include 27.3 % culture-negative [7] .…”

Hepatic Transcriptome Analysis Identifies Divergent Pathogen-Specific Targeting-Strategies to Modulate the Innate Immune System in Response to Intramammary Infection

“…Two of the most important pathogens to cause mastitis in dairy cattle are Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). While S. aureus generally induces a chronic and subclinical mastitis (6), E. coli is an important etiological pathogen resulting in an acute and clinical mastitis (7). Furthermore, S. aureus is Gram-positive, whereas E. coli is Gram-negative (7).…”

“…The pathogenesis and infection dynamics of the respective forms of mastitis differ significantly depending on the pathogen type. Gram-negative bacteria release endotoxin or lipopolysaccharide (LPS), a component of their cell wall (6,7). Many studies consider LPS and its fractions to be a potent factor of the E. coli induced mastitis pathogenesis (7,8).…”