Background and purpose: Antibiotics resistance is one of the biggest challenges facing human health and the cost of the treatment has led to the development of new and effective antimicrobial reagents. Several investigations have been carried out concerning the use of biodegradable polymers as antibacterial agents in combination with conventional antimicrobial drugs. The aim of this study was to investigate the influence of poly(styrene-alt-maleic anhydride, PSMA)- spermine conjugate on the antimicrobial activity of ceftazidime and ciprofloxacin antibiotics against Enterococcus faecalis and Acinetobacter baumannii in acidic conditions. Materials and Methods: Antibacterial activity of PMSA- spermine conjugate alone and in combination with ciprofloxacin or ceftazidime against clinical Enterococcus faecalis and Acinetobacter baumannii in acidic conditions were evaluated by broth microdilution. For this purpose, serial two-fold dilutions of each antibacterial agents were prepared in liquid culture medium. The growth of bacteria in the presence of PMSA- spermine conjugate and each antibiotic, alone and combined, were measured as the optical density at 630 nm every 2 h for 24 h. Results: The most growth inhibitory effect of PMSA-spermine conjugate against Enterococcus faecalis was observed at 12.5 mg/ml concentration with percent growth inhibition of 40%. PMSA-spermine conjugate had not shown any antibacterial activity against Acinetobacter baumannii. Enterococcus faecalis and Acinetobacter baumannii were resistant to ciprofloxacin and ceftazidime antibiotics. PMSA-spermine conjugate significantly increased the growth inhibitory effect of both antibiotics against Enterococcus faecalis. Conclusion: These findings suggest that PMSA-spermine conjugate enhances the antimicrobial activity of ciprofloxacin and ceftazidime antibiotics against Enterococcus faecalis in acidic conditions.

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