Mitigating antibiotic resistance against S. aureus and E. coli in combination with organic acids under in-vitro studies

In the context of the escalating challenge of antibiotic resistance, the efficacy of organic acids, including lactic acid and acetic acid, has proven to be promising. Strains of Staphylococcus aureus and Escherichia coli (n=2), recovered from clinical isolates of mastitis, were tested using the broth-dilution method to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for lactic acid and acetic acid in combination with antibiotics such as ampicillin, cefotaxime, and imipenem, with triplicate samples for accuracy. The MIC values for ampicillin, cefotaxime, and imipenem against S. aureus were 1.04±0.26, 1.67±0.41, and 7.80±0, respectively, while against E. coli, they were 4.16±1.04, 0.05±0.01, and 10.40±2.6, respectively. Notably, these MICs were significantly reduced when combined with lactic acid, reaching 0.52±0.13, 0.83±0.21, and 5.20±1.3 against S. aureus, and 2.08±0.52, 0.02±0.01, and 5.20±1.3 against E. coli. Similarly, combinations with acetic acid yielded MICs of 0.65±0.13, 1.03±0.21, and 6.50±1.3 against S. aureus, and 2.60±0.52, 0.03±0.01, and 6.50±1.3 against E. coli. The MBC values for ampicillin, cefotaxime, and imipenem were 1.56±0.00, 2.91±1.10, and 13.00±2.60 against S. aureus, and 7.29±2.75, 0.11±0.02, and 18.20±6.87 against E. coli. When combined with lactic acid, the MBCs were 0.91±0.34, 1.67±0.41, and 6.50±1.30 against S. aureus, and 3.64±1.37, 0.05±0.01, and 10.40±2.60 against E. coli. The acetic acid combinations yielded MBCs of 1.30±0.26, 2.08±0.41, and 10.40±2.60 against S. aureus, and 5.20±1.04, 0.06±0.01, and 13.00±2.60 against E. coli. These findings provide valuable insights into the potential synergistic effects of antibiotics combined with organic acids, which could enhance antibacterial efficacy and aid in overcoming the growing issue of antimicrobial resistance.