Extensive in vitro activity of guanidine hydrochloride polymer analogs against antibiotics-resistant clinically isolated strains

Polyhexamethylene guanidine hydrochloride (PHMG) possesses great potential in the development of covalently bound permanent sterile-surface materials for hospital infection control. This study aimed at evaluating the extensive activity of PHMG and its three novel analogs, including polybutamethylene guanidine hydrochloride, polyoctamethylene guanidine hydrochloride (POMG) and poly(m-xylylene guanidine hydrochloride), against 370 clinical strains, especially 96 isolates of which were antibiotics-resistant. Their in vitro antimicrobial activities were determined by testing the minimal inhibitory concentration (MIC) and time-killing curves. POMG, the novel oligoguanidine had significantly lower MIC values (0.5–16 mg/L) against 370 antibiotics-susceptible and -resistant clinical strains compared to PHMG (1–64 mg/L) and chlorhexidine digluconate (2–64 mg/L). Interestingly, POMG displayed excellent activity against meticillin resistant-Staphylococcus aureus (1–8 mg/L) and -coagulase-negative staphylococci (1–2 mg/L), vancomycin resistant Enterococcus faecium (2–4 mg/L), multidrug resistant Pseudomonas aeruginosa (8–16 mg/L), ceftazidime resistant-Citrobacter spp. (1–4 mg/L) and -Enterobacter spp. (2–4 mg/L). PHMG was especially efficient against methicillin resistant-S. aureus and -coagulase-negative staphylococci (1–8 mg/L). The presented extensive activity of POMG and PHMG against antibiotic-resistant bacteria provides encouraging reference information for the using and further development of cationic guanidine-based polymers in the biomedical material field.