In vitro activities of antibiotics and antimicrobial cationic peptides alone and in combination against methicillin resistance Staphylococcus aureus biofilms.
Oct 2012
Source
Department of Pharmaceutical Microbiology Faculty of Pharmacy, Istanbul University, 34116, Beyazit-Istanbul, Turkiye.
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) strains are most often found in hospital and community-acquired infections. The danger of MRSA infections results from not only the emergence of multi-drug resistance but also the occurrence of strong biofilm forming bacteria. We investigated the in-vitro activities of antibiotics (daptomycin, linezolid, teichoplanine, azithromycin and ciprofloxacin) and antimicrobial cationic peptides (AMPs; indolicidin, CAMA: cecropin (1-7)-melittin A (2-9) amide, and nisin) alone or in combination against MRSA ATCC 43300 biofilms. The minimum inhibitory concentrations (MIC) and minimum biofilm eradication concentrations (MBEC) were determined by microbroth dilution technique. Antibiotic and AMP combinations were assessed using the chequerboard technique. For MRSA planktonic cells, MICs of antibiotics and AMPs were ranged between 0.125-512 and 8-16 mg/L, and the MBEC values of them were 512-5120 and 640 mg/L, respectively. With a fractional inhibitory concentration of ≤ 0.5 as borderline, synergistic interactions againstMRSA biofilms were frequent with almost all antibiotic-antibiotic and antibiotic-AMP combinations. Against planktonic cells, they generally had an additive effect. No antagonism was observed. All of the antibiotics, AMPs, and their combinations were able to inhibit the attachment of bacteria at the 1/10xMIC and biofilm formation at 1xMIC. Biofilm-associated MRSA was not affected by therapeutically achievable concentrations of antimicrobial agents. Using a combination of antimicrobial agents can provide a synergistic effect, which rapidly enhances anti-biofilm activity and may help prevent or delay the emergence of resistance. AMPs seem to be a good candidate for further investigations in the treatment of MRSA biofilms, alone or in combination with antibiotics.
