Examining the effect of intramammary infections with minor mastitis pathogens on the acquisition of new intramammary infections with major mastitis pathogens—A systematic review and meta-analysis

Abstract

Major mastitis pathogens such as Staphylococcus aureus, Streptococcus agalactiae, Streptococcus uberis, Streptococcus dysgalactiae, and the coliforms are usually considered more virulent and damaging to the udder than minor mastitis pathogens such as Corynebacterium bovis and coagulase-negative staphylococci (CNS). The current literature contains several studies detailing analyses with conflicting results as to whether intramammary infection (IMI) with the minor pathogens decreases, increases, or has no effect on the risk of a quarter acquiring a new intramammary infection (NIMI) with a major pathogen. To investigate the available scientific evidence regarding the effect of IMI with minor pathogens on the acquisition of NIMI with major pathogens, a systematic review and meta-analysis were conducted. The total extant English-and Frenchlanguage literature in electronic databases was searched and all publications cited by relevant papers were investigated. Results from 68 studies were extracted from 38 relevant papers. Random-effects models were used to investigate the effects of CNS and C. bovis on acquisition of new IMI with any of the major pathogens, as well as individually for the minor pathogens and Staph. aureus. Significant heterogeneity among studies exists, some of which could be accounted for by using meta-regression. Overall, observational studies showed no effect, whereas challenge studies showed strong and significant protective effects, specifically when major pathogens were introduced into the mammary gland via methods bypassing the teat end. Underlying risk can account for several unmeasured factors, and studies with higher underlying risk found more protective effects of minor pathogens. Larger doses of challenge organisms reduced the protective effect of minor pathogens, and studies with more stringent diagnostic criteria for pathogen IMI identified less protection. Smaller studies (those utilizing fewer than 40 cows) also showed a greater protective effect than larger studies.

An update on environmental mastitis: Challenging perceptions

“…It has been suggested that presence of minor pathogens (non‐aureus staphylococci, corynebacteria) at the teat end may protect against infection with major pathogens (Reyher et al., ). The authors of a recent review (Reyher et al., ) concluded that observational studies showed no such effect, “whereas challenge studies showed strong and significant protective effects, specifically when major pathogens were introduced into the mammary gland via methods bypassing the teat end.” Physical or physicochemical characteristics of the teat end may contribute to that discrepancy, such as the amount of keratin present, peak flow rate and teat canal length (Capuco et al., ; Lacy‐Hulbert & Hillerton, ). In some modern large herds, for example, in the High Plains area of the western United States, milk production is measured per hour rather than per cow, acre or person.…”

“…For most mastitis pathogens, the teat end is considered the porte d'entree into the mammary gland. It has been suggested that presence of minor pathogens (non-aureus staphylococci, corynebacteria) at the teat end may protect against infection with major pathogens (Reyher et al, 2012). The authors of a recent review (Reyher et al, 2012) concluded that observational studies showed no such effect, "whereas challenge studies showed strong and significant protective effects, specifically when major pathogens were introduced into the mammary gland via methods bypassing the teat end."…”

Major components of orange oil inhibit Staphylococcus aureus growth and biofilm formation, and alter its virulence factors

“…The most common causative agent of mastitis is Staphylococcus aureus (Contreras & Rodríquez, 2011;Makovec & Ruegg, 2003;Reyher et al, 2012;Wilson et al, 1997). It is an infectious bacterial pathogen, which is usually spread between cows during the milking process.…”

Mastitis in buffalo herds and their susceptibility to antimicrobial

“…As bactérias S. aureus, S. agalactiae, S. dysgalactiae e S. uberis normalmente causam maiores danos ao úbere que outros patógenos causadores de mastite, e por isto são denominados patógenos principais ou maiores (Reyher et al, 2012). Entre os agentes causadores da mastite mais frequentemente isolados, são S. aureus e S. agalactiae, responsáveis por, aproximadamente, 90% das infecções intramamárias dos rebanhos de bovinos leiteiros.…”