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Objective: Increased resistance rate to macrolides used as empirical treatment of pneumococcal infections is a major problem in our country and all over the world. In our study, we aimed to determine macrolide resistance mechanisms of the erythromycin-resistant Streptococcus pneumonia isolated from clinical samples and to investigate serotype and resistance relationship within our region with the high macrolide resistance rates among pneumococci. Methods: Fifty isolates were studied for erythromycin, azithromycin, clarithromycin, clindamycin susceptibilities with disk diffusion, and liquid microdilution methods. Genetic determinants of macrolide resistance, mef(A), mef(E), erm(B), erm(TR) genes were investigated by PCR using specific primers for each gene, multiplex PCR was used to determine the serotypes. Results: Constitutive and inducible MLSB phenotypes and M phenotype were expressed in 86%, 4% and 10% of the isolates, respectively. Total of 42% of the isolates (n=21) were positive for erm(B), 12% (n=6) for mef(E) gene, in 46% (n=23) of the isolates both genes were detected. Serotype distribution was as follows: 28 (56%) 19F, 6 (12%) 6A/B, 5 (10%) 23F, 1 (2%) 39, 2 (4%) 15A-F, 1 (2%) 14, 1 (% 2) 23B and 6 (%12) isolates were nontypeable. 12 isolates carry erm(B), and 16 isolates carry both erm(B) and mef(E) in serotype 19F. One isolate carries erm(B), and 5 isolates carry both erm(B) and mef(E) in serotype 6A/B. Four isolates carry erm(B) and one isolate carries both erm(B) and mef(E) in serotype 23F. Conclusion: The most striking results of this study are the presence of macrolide efflux pump coding mef(E) gene in 58% of our isolates, the presence of additional erm(B) gene in %46 of isolates, and high rate of erm(B)+ mef(E) genes combination (56%) in predominant serotype 19F isolates. [ABSTRACT FROM AUTHOR]

• Vancomycin was conjugated with antimicrobial cationic polymers via cross metathesis pathways. • Poly(ethylene glycol) was used as linker between vancomycin and antibacterial cationic polymers. • The conjugates showed activity and selectivity towards Gram positive S. aureus and E. feacalis. • This study affords a pathway to synthesize a new non-toxic and non-hemolytic antibiotic-candidate. In this study, a Gram positive bacteria effective antibiotic, vancomycin (VAN), was conjugated with antimicrobial cationic polymers (ACPs) that were found to be active against both Gram positive and Gram negative bacteria previously, and the antibacterial activity of newly synthesized VAN-PEG-ACP conjugates were investigated. VAN was first PEGylated using Michael Addition method, then the ACPs, which were synthesized using ring-opening metathesis polymerization (ROMP), were bound covalently to the VAN-PEG structure using cross metathesis pathways and thus cationic polymer-vancomycin conjugates (VAN-PEG-ACPs) were obtained. The antimicrobial activity of the conjugates were investigated against Gram negative strain E. coli and Gram positive strains S. aureus and E. feacalis. Con_1_10k_1, Con_2a_3k_1, and Con_2b_3k_1 were found to be active towards S. aureus (MIC = 64 µg/ml, 32 µg/mL, and 32 µg/mL, respectively) and Con_2a_3k_1, and Con_2b_3k_1 were found to be active also towards E. feacalis (MIC = 16 µg/ml and 32 µg/mL, respectively), however they did not show activity towards E. coli. All the conjugates were found to be non-hemolytic towards red blood cells (HC 50 = >1024 µg/mL). MTS assay results also showed that the conjugates did not lyse viable HUVEC cells within 72 h. The membrane deformation of S. aureus was monitored using scanning electron microscopy (SEM) techniques in the presence of the polymers and the conjugates. [ABSTRACT FROM AUTHOR]