Characterization of the Fermentation Process and the Inhibition Effect of Lactobacillus lactis in Staphylococcus aureus and Staphylococcus epidermidis

Abstract

The fermentative process and <em>in vitro</em> inhibition of <em>L. lactis in Staphylococcus aureus</em> and <em>Staphylococcus epidermidis</em> were assessed. The growth of <em>L. lactis</em> at three pH (2.5, 4.5 and 7), bile salts (0.5, 1 and 2 %), bovine bile (1 and 1.2 %) and two temperatures (38 and 45 °C) were evaluated. Peptides and organic acids in supernatant of <em>L. lactis</em> by HPLC were determined. Fermentation kinetics was carried out, evaluating: pH, total sugar, protein and lactic acid. An antibiogram of dicloxacilin, cefepime, penilicin and cefalotin was made. The inhibition of <em>L. lactis</em> and its supernatant were defined in pathogenic strains. The best growth was at a pH of 2.5 (3 × 10¹² UFC/ml) of 1 × 10¹⁰ and 4 × 10⁹ UFC/ml for 0.5 % of bile salts and 1.2 % of bovine bile, respectively of 3.5 × 10¹³ and 3.4 × 10¹³ UFC/ml for 38 and 45 °C, respectively. The HPLC determined the peptides VAR-TIR-VAR and lactic acid (83.11 %). The fermentation kinetics determined the exponential phase at 14:24 h with a value of 77 × 10¹⁰ UFC/ ml, pH values of 4.284, 2.33 mg/ml sugar, 1.44 mg/ml protein and acidity of 0.79 %. It was found that <em>S. aureus</em> and <em>S. epidermidis</em> were sensitive to all antibiotics. The pathogenic bacteria were resistant to the lactic strain, but <em>S. epidermidis</em> was sensitive to the supernatant of <em>L. lactis</em>. The conclusion is that <em>Lactobacillus lactis</em> showed adequate growth capacity, good fermentation parameters and inhibitory effect in strains of <em>S. aureus</em> and <em>S. epidermidis</em> in <em>in vitro</em> conditions.