Only one isolate was resistant to ceftriaxone, and resistance to imipenem, ertapenem, levofloxacin, moxifloxacin, gatifloxacin, rifampin, and vancomycin was not found. Therefore, only ciprofloxacin resistance was GSK2118436 order not related to the dual presence of the erm(B) and mef(A) genes. Fluoroquinolone resistance including ciprofloxacin is mainly due to point mutations of

the genes encoding DNA gyrase or topoisomerase IV (Jones et al., 2000). Thus, ciprofloxacin resistance may not be related to the uptake of foreign materials, as is the case with erythromycin resistance from the acquisition of erm(B) or mef(A) genes. As only the erm(B) gene bestows a high-level resistance against erythromycin, the dual presence of erm(B) and mef(A) may not be advantageous, and may pose a burden for growth. However, we have shown that pneumococcal isolates with both erm(B) and mef(A) genes may have originated from isolates possessing only the mef(A) gene and acquiring the erm(B) gene in a certain clonal complex, CC271 (Ko & Song, 2004). Compared with isolates that possess only the mef(A) gene, and which exhibit low-level erythromycin resistance, pneumococcal isolates with both erm(B) and mef(A) genes may have some advantages in certain environments, such as antibiotic pressure. Pneumococcal strains show differences in recombination Stem Cell Compound Library nmr frequency (Samrakandi & Pasta, 2000; Hsieh et al., 2006). Hsieh et al. (2006) reported that certain serotypes such as 6B, 14, 19F, 9V, 23F, 3, and

18C showed a high competence for plasmid uptake. It is noteworthy that these serotypes are included in the seven-valent pneumococcal conjugate vaccine (PCV7) because Cell press of public health concerns due to high

antimicrobial resistance and prevalence. The dual presence of erm(B) and mef(A) genes and uptake of foreign resistance determinants in certain pneumococcal isolates may be due to the same traits, such as their high competency and recombination rates. Thus, certain isolates with high potency to transform and recombine foreign genes have a strong possibility of acquiring antimicrobial resistance determinants and to become MDR. The present results demonstrate that the dual presence of erm(B) and mef(A) genes in some pneumococcal isolates may be associated with a high recombination frequency, high antimicrobial resistance, and even a high prevalence of those isolates. This study was partly supported by a grant from the Samsung Biomedical Research Institute (SBRI, Seoul, Korea). J.-Y.L. and J.-H.S. contributed equally as joint first authors. “
“The quality and yield of extracted DNA are critical for the majority of downstream applications in molecular biology. Moreover, molecular techniques such as quantitative real-time PCR (qPCR) are becoming increasingly widespread; thus, validation and cross-laboratory comparison of data require standardization of upstream experimental procedures. DNA extraction methods depend on the type and size of starting material(s) used.