Gm17 broth

All strains used in this study (Table S7) were stored at −20 or −80 °C. Streptococcus, Enterococcus, Bacillus, and Staphylococcus strains were cultivated in BHI broth (Oxoid, Hampshire, UK). Escherichia coli for protein expression was grown in Luria-Bertani (LB) broth (Fisher Scientific, Waltham, MA, USA), supplemented with 50 µg/mL kanamycin (Sigma Aldrich, Saint Louis, MO, USA). Bacteria were incubated at 37 °C and shaken at 120 rpm, if necessary. Lactococcus lactis was cultivated in GM17 broth (Oxoid, Hampshire, UK) at 30 °C. The Streptococcus infantis phage 23TH and Streptococcus anginosus phage SA01 and their host strains Streptococcus infantis 23TH and Streptococcus anginosus SA01 were saliva isolates sourced from the APC Culture Collection (APC Microbiome Ireland, Cork, Ireland).

Listeria monocytogenes F6854 strain, linked to a single case of human illness traced to contaminated turkey frankfurters in 1988 (Nelson et al., 2004 (link)), was grown in Tryptic Soy Broth (TSB) (Merck, Germany) or Tryptic Soy Agar (TSB substituted with 1.5% w/v agar) at 37°C. L. lactis strains, L. lactis NZ9700, L. lactis NZ9800-pCI372 Nisin A, L. lactis NZ9800-pCI372 M21A (Field et al., 2008 (link)), L. lactis NZ9800–pCI372 AAA (Healy et al., 2013 (link)) and L. lactis NZ9800-pCI372 Nisin V (Rouse et al., 2012 (link)), were grown on M17 supplemented with 5% glucose (GM17) broth (Oxoid, England) or GM17 agar (GM17 broth substituted with 1.5% w/v agar) at 30°C. Strains were stocked in 40% glycerol and stored at -20°C.

Different food samples (milk products; mozzarella cheese and buttermilk—pastries; commercial cakes and bread) and clinical samples (urine and stool) were collected in sterile plastic cups from Beni-Suef City, Egypt, and refrigerated for 24 h prior to processing. Urine sample precipitates (collected after centrifugation at 5000×g for 10 min) and 1 g of each of the food and stool samples were inoculated into tubes containing 5 mL of GM17 broth (Oxoid, Hampshire, UK) and incubated aerobically at 37 °C for 24 h.
Enterococci were isolated by selective culture on bile esculin agar (Oxoid), where they grow in the presence of 4% (w/v) bile and hydrolyze esculin to esculetin that reacts with Fe³⁺ to form a dark brown to black precipitate on the agar plate. The resultant black colonies were presumptively identified as Enterococcus sp. using the l-pyrrolidonyl-β-naphthylamide (PYR) test and then identified at species level using the API 50 CHL system (bioMérieux, Marcy l’Etoile, France) according to the manufacturer’s instructions.