Non-Antibiotic Immunomodulatory Combination Treatment for Staphylococcus aureus Infections: In vitro Preliminary Studies I

Abstract

Despite advancements in prevention measures, infectious mastitis is a common disease of economic significance in cattle. Clinical mastitis affects 20 to 25% of cows each year. Staphylococcus aureus (S. aureus) causes an estimated 10-11.7% of clinical bovine infectious mastitis cases in the US. Antibiotic therapy tends to fail 50% of the time and nature and vaccine immunity usually fails, due to S. aureus’ evasion mechanisms, leading to significant morbidity, chronic mastitis, and culling of such cows. Specific IgYs have been found to inhibit the growth of S. aureus in vitro, but such IgYs have been produced especially for such experiments, commercially available presentations have not been compared to the IgY produced by naturally exposed chickens. In the present study, we compare the impact of two sources of IgY. IgY was obtained commercially and purified from the eggs of chickens naturally exposed to S. aureus (RIR IgY). Their effect on the in vitro growth of S. aureus was compared and the commercial chicken anti-SpA IgY (IgY). This was done by mixing tryptic soy broth cultures of S. aureus with 5, 25, or 125 µg/mL of IgY or RIR IgY (3 tubes per concentration). The result was evaluated by the plate count method. Next, the treated and control broths were sampled and plated at 4, 8, and 12 h. IgY (commercial) showed a powerful inhibitory effect over S. aureus. This effect was sustained for over 12 h when compared to RIR IgY and two respectively to the control. Though the RIR IgY effect was significant; however, it subsided after 8 h. Based on our findings, IgY may have an effective component against S. aureus growth which is more observed in the IgY commercially obtained than the IgY purified chickens which are naturally exposed to S. aureus (RIR IgY).