The two viruses remained stable under several storage and temperature conditions, but the findings so far come from laboratory and UHT-milk tests.
Researchers isolated 19 viruses that infect Staphylococcus aureus from wastewater and raw milk. They selected two, named SAKAY1298 and SAKAY1306, for further testing and combined them into a cocktail.
The cocktail reduced bacterial counts by up to 4.31 log CFU/mL in laboratory tests at 37 °C and by up to 1.44 log CFU/mL in UHT milk held at 4 °C. It also fully inhibited production of staphylococcal enterotoxin A in one in vitro assay.
The researchers isolated 19 lytic bacteriophages—viruses that infect and destroy bacteria—from wastewater and raw milk. They selected SAKAY1298 and SAKAY1306 based on their ability to kill S. aureus, the range of strains they infected and their growth characteristics.
Both had small, complete genomes of about 17.5 kilobases, with 18 phage-related genes. The genome analyses found no virulence or antibiotic-resistance determinants. The viruses remained stable at pH 4, at temperatures up to 50 °C, and for more than one year at 4 °C and −80 °C in the tested storage solutions.
In a laboratory assay at 37 °C, the cocktail reduced S. aureus counts by up to 4.31 log CFU/mL. In UHT milk at 4 °C, it reduced counts by up to 1.44 log CFU/mL, with p < 0.001 reported for the reductions. The cocktail also fully inhibited production of staphylococcal enterotoxin A in the in vitro assay.
Staphylococcus aureus can be a concern in dairy applications, and some strains produce toxins. These results indicate that the two-virus cocktail could help reduce the bacterium in milk and block production of staphylococcal enterotoxin A under the tested laboratory conditions. The study therefore provides evidence for possible dairy uses, while leaving its performance in real-world milk processing and production to be tested.
The study reports laboratory experiments using isolated bacteriophages, which are viruses that infect bacteria. The cocktail reduced Staphylococcus aureus in laboratory conditions and in UHT milk, but the abstract does not report tests in commercial dairy production, animals or people. The complete inhibition of toxin production was reported for one in vitro assay, so its relevance to milk products outside that test remains uncertain.
International Microbiology · 2026 · DOI: 10.1007/s10123-026-00862-9
Authors: Naim Deniz Ayaz, Gizem Çufaoğlu, Görkem CENGİZ, BAHAR ONARAN ACAR, Nurhan Ertaş Onmaz, Gultekin Unal, Muammer Goncuoglu, İrfan Erol, TÜBİTAK-121Z447 project scholars and consultants, Ayse Nur Erdinc, Ahmet BESTİL, Ayçe Fadime Düzenli, Tansu Yıldız, Bilge Alpaslan Kocamemi
Institutions: Ankara University, Lokman Hekim Üniversitesi, Erciyes University, Instituto de Nutricion e Higiene de los Alimentos
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