Mastitis pathogens

The infection process and disease development process can be related to a range of factors that affect various udder tissues (localisations). There are also a range of interactions between the udder tissues and mastitis pathogens. These were recently reviewed by Hamann 2001 (see also Table 11.1). 

Sensitivity of mastitis pathogens to an antibiotic iri vitro merely indicates potential therapeutic efficacy. The data from clinical trials reflect a lesa encouraging reality, in which both pathogen and host characteristics influence the outcome ( ). Some pathogens are highly tissue-invasive. Once sequestered and metabolically inactive within infection foci they are unaffected by antibiotics that act by disruption of cell wall synthesis, such as penicillins and cephalosporins. ... 

Aiemsaard J, Aiumlamai S, Aromdee C, Taweechaisupapong S, Khunkitti W (2011) The effect of lemongrass oil and its major components on clinical isolate mastitis pathogens and their mechanisms of action on Staphylococcus aureus DMST 4745. Res Vet Sci 91(3) e31-e37... 

M. W. Woolford, J. H. Williamson, H. V. Henderson. Changes in electrical conductivity and somatic cell count between milk fractions from quarters subcUnicaUy infected with particular mastitis pathogens. J Dairy Res 65 187, 1998. 

Nair, M. K., Joy, J., Vasudevan, P., Hinckley, L., Hoagland, T. A. Venkitanarayanan, K. S. (2005b). Antibacterial effect of caprylic acid and monocaprylin on major bacterial mastitis pathogens. J. Dairy Sci., 88, 3488-3495. 

The objective of mastitis treatments is to cure the infected udders from the infection, but cure is defined in very different ways. For example, in economic terms, the farmer needs to achieve a level of udder health that allows expected milk yields and quality parameters specified by processors/ national regulations to be achieved. On the other hand, cure with respect to antibiotic treatments, is often defined in terms of absence of bacterial pathogens in milk (bacterial cure), with the proportion of cows without detectable pathogen presence following treatment being defined as the bacterial cure rate (BCR). The main problem with using BCR as the main indicator of cure is that it was frequently shown to include a proportion of cows with drastically elevated SCC values (indicative of sub-clinical mastitis) after treatment, but without clinical (sensory) symptoms. 

The objective of antibiotic treatments is to reduce the density of microbial pathogen in infected udder tissues and thereby improve the capacity of the animal s immune system to deal with the infection. The effect of a successful antibiotic treatment is therefore self-cure of mastitis (Hamann and Kromker, 1999). However, some antibiotics (e.g. tetracycline and gentamycine) may also have negative side effects on the animal s immune response to udder infection, as they have been shown to inhibit/reduce phagocytosis of the animal s own defence cells (Nickerson et al 1986). 

Given the diversity of disease-causing organisms, the interactions between farm-specific environmental factors and the types of mastitis causing pathogens found, the potential efficacy of antibiotic treatments can only be assessed accurately in the context of the specific on-farm conditions. Furthermore, many recent investigations concluded that, except for some specific infections caused by streptococci, a prophylactic and or longer-term use of antibiotics for chronic and sub-clinical mastitis should not recommended in the future (Deluyker et al., 2005). 

However, in case of acute clinical mastitis, it is widely accepted that animal welfare considerations should take prevalence. If both farmer and veterinarian are not familiar with non-antibiotic treatments, they should be advised to use broad-spectrum antibiotics immediately, because any delay (e.g. the 2-3 days it often takes between diagnosis and the return of microbiological test results) may seriously harm the animal. This approach should, however, only be taken after a sound clinical diagnosis, since antibiotic treatments themselves may lead to dramatic aggravation of the condition. For example, E. coli inflammations are able to develop into severe toxaemia, because increased levels of toxins are released into the animal tissues when E. coli cells are killed or stressed by antibiotic treatments. Also, if yeasts are the main cause or form part of the pathogen complex that causes mastitis, their growth and proliferation may be supported by the administration of anti-bacterial antibiotics (Crawshaw et al., 2005). 

Guterbock, W.M., Van Eenennaam, A.L., Anderson, R.J., Gardner, I.A., Cullor, J.S. and Holmberg, C.A. (1993), Efficacy of intramammary antibiotic therapy for treatment of clinical mastitis caused by environmental pathogens . Journal of Dairy Science, 76, 3437-3444. 

Mastitis is a complex of infections, caused by a variety of microorganisms with inherent differences in sensitivity to antimicrobial agents. Furthermore, sensitivity vitro does not assure efficacy vivo. Additionally, pathogens have the capacity to gain resistance to antibiotics, particularly under conditions of heavy and poorly controlled use. 

Early detection of mastitis and immediate treatment reduces pathologic damage and increases the likelihood of eliminating the infection. Because therapy is given without identification of the pathogen involved, a product with a broad antibacterial spectrum is essential (4. The desirable kinetic and other properties of an intramammary antibiotic product for treatment in lactation have been summarized by Ziv (23). 

In addition to DCT, recommended mastitis control in the U.S. includes the dipping of the cow s teats in a germicide immediately after each milking. This strategy commonly results in a lowered prevalence of IMI in a dairy herd, but also a shift in pathogen... 

Sischo W.M., L.E. Hieder, G.Y. Miller, and D.A. Moore (1993). Prevalence of contagious pathogens of borne mastitis and use of mastitis control practices. Journal of the American Veterinary Medical Association 202 595-500. 

Kanamycin is an aminoglycoside complex produced by Streptomyces ka-namyceticus. It is comprised of three components, kanamycin A being the major component and kanamycins B and C minor congeners. Kanamycin is active against many pathogenic bacteria and has been used parenterally for treatment of bovine respiratory disease, mastitis, and other infectious conditions. A popular combination used in horses and cattle with respiratory disease is kanamycin and penicillin G. It is also used orally for treatment of bacterial enteritis because limited absorption occurs after oral administration. 

Enrofloxacin is another fluoroquinolone antibacterial developed exclusively for animals (146). It is administered either by parenteral route to cattle, swine, sheep and rabbits, or by the oral route to cattle, swine, rabbits, chickens, and turkeys (147). Although it is not allowed for use in dairy cows, enrofloxacin is also used in some countries for treatment of coliform mastitis in lactating cows. In addition, enrofloxacin has received growing attention during the last years for its potential against several fish pathogens (148). 

Novobiocin (Fig. 3.9) is a narrow-spectrum antibiotic with antibacterial activity against many gram-positive pathogens. It is frequently used, in combination with penicillin, for treatment of bovine mastitis by intramammary infusion of 200 mg/ quarter in two quarters, and to control fowl cholera and staphylococcal infections in chickens and turkeys at a level of 200-350 g/ton in feed. 

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