This study was performed to characterize 35 L. monocytogenes isolates from animals, foods, environmental samples collected between 1997 and 2007 with no apparent epidemiological relations, and five reference isolates using serotypic, genotypic and molecular typing methods to understand the pattern of strain distribution in Korea. For this study, we used serotyping and detected 6 different virulence-associated genes (inlA, inlB, plcA, plcB, hlyA, and actA) and 16s rRNA using multiplex-PCR. We also compared RAPD and PFGE to determine genetic characterization of L. monocytogenes strains to define the genetic diversity. Serotype patterns of the 30 L. monocytogenes strains was as follows; 9 isolates (30.0 %) belonged to serotype, 7 isolates (23.3%) belonged to serotype 4b, 4 isolates (13.3%) belonged to serotype 1/2b, 3 isolates (10.0%) belonged to serotype 1/2c, 2 (6.7%) isolates belonged to 4c, 2 (6.7%) isolates belonged to NT (Non Type), one isolate (3.2%) belonged to 3a and 3b, and 4a, respectively. Although, a limited number of isolates were analyzed in this study, molecular typing with RAPD and PFGE indicated that PFGE is more discriminatory for the subtyping L. monocytogenes than RAPD. Some L. monocytogenes isolates by RAPD and PFGE types are associated with specific sources. And, combining data obtained by these methods will increases the likelihood of strain discrimination.

Biological filtration refers to the process of removing both particulate matter and biodegradable organic matter (BOM) from water [1]. Biological filters can remove organic compounds through the fixed biofilm that develops on various media such as sand, anthracite, granular activated carbon (GAC), or membranes [2]. The biologically active rapid filter and the biological activated carbon (BAC) filter have been widely used for decades in drinking water treatment plants [1-3]. The rapid filter is usually filled with sand or anthracite, and is considered the most economical way to remove particles and BOM with the same filter unit [1]. However, many previous studies have demonstrated that the BAC filter is a more appropriate process to remove BOM than the rapid filter [4, 5]. Generally, the combination of ozonation and GAC filter is referred to as the BAC process [3]. Ozonation converts high-molecular-weight refractory organic matter into low-molecular-weight BOM, and this increased BOM can be effectively removed by the bacteria attached to the BAC filter [1, 4, 6-8]. Biological filtration has many advantages for drinking water treatments. First of all, it is important to increase the biostability of drinking water by reducing the quantity of BOM which can cause bacterial regrowth in distribution systems [1, 3-5]. It can reduce the disinfection by-product