Treating Mastitis

The treatment of mastitis is most often via the administration of antibiotics. An antibiotic may have a systemic effect - by injection into the muscle or under the skin of the animal - or it may be infused into the teat through the teat canal. Often both routes are used to treat a case of mastitis.

Broad-spectrum antibiotics can be effective against a wide variety of bacterial varieties, and are useful where the causative bacterium is unknown. However, for maximum targeted effectiveness and to limit future antibiotic resistance, a narrow-spectrum antibiotic is likely to be more useful, but this requires knowing which variety of bacterium is causing the infection.

In general terms, there are two large groups of bacteria, known as either Gram-positive or Gram-negative bacteria, differentiated by their Gram staining characteristics. Gram staining was developed by Hans Christian Gram and is used to differentiate bacterial species based on the physical properties of their cell walls. Bacterial cell wall structure plays an important role in determining a bacterium's susceptibility to different antibiotics and thus is an essential factor in selecting the most effective antibiotic for treatment.

The literature provided with an antibiotic will state whether it is effective against Gram-positive bacteria, Gram-negative bacteria or both.

Many of the bacterial species associated with causing mastitis in dairy cattle are classified as Gram-positive, such as Staphylococcus and Streptococcus. This group has been expanded to include mastitis-causing bacteria like Mycoplasma that lack cell walls and so cannot be stained by the Gram method.

In general, Gram-positive bacteria show a better response to treatment with antibiotics than Gram-negative species.