# Randomized, Negative-Controlled Pilot Study on the Treatment of Intramammary Staphylococcus aureus Infections in Dairy Cows with a Bacteriophage Cocktail

## TL;DR

A pilot study found that a phage cocktail safely and effectively treated S. aureus infections in dairy cows, outperforming controls.

## Contribution

Demonstrated the safety and preliminary efficacy of a phage cocktail for treating antibiotic-resistant S. aureus mastitis in dairy cows.

## Key findings

- Phage treatment achieved an 81.3% bacteriological cure rate compared to 28.6% in the control group.
- No systemic side effects were observed in the treatment group.
- Results suggest phage therapy could be a viable alternative to antibiotics for S. aureus mastitis.

## Abstract

Background/Objectives: Staphylococcus (S.) aureus is a major pathogen causing bovine mastitis and is often refractory to antibiotic therapies due to virulence factors and resistance mechanisms. In this pilot study, the safety and efficacy of an intramammary phage cocktail, in naturally S. aureus-infected dairy cows, were investigated. Methods: The initial part of the study on farm 1 confirmed tolerability and safety, as there were no observed systemic side effects of treatment. The subsequent efficacy study on farm 2 included 23 with S. aureus infected udder quarters, which were randomly divided into a treatment group (n = 16) and a control group (n = 7). The quarters in the treatment group received five intramammary infusions of the phage cocktail at 12-h intervals. Results: This resulted in a bacteriological cure rate of 81.3% (13/16) for the treatment group, compared to 28.6% (2/7) in the control group (p = 0.026). Conclusions: These results indicate that phage therapy is well-tolerated and may be a promising alternative to antibiotics for treating S. aureus mastitis, although confirmation in larger-scale, multicenter studies is required.