flexneri Xv strain 2002017 [5]. Therefore emergence and spread of novel S. flexneri serotypes in nature poses a significant public health threat globally and in particular in developing countries where S. flexneri is the predominant cause of shigellosis. In order to reveal

possible roles played by the serotype-converting phages in the emergence of new serotypes, and potential of emergence of novel serotypes through this mechanism in nature, we performed infection assays using SfI and SfX, the 2 most common serotype-converting bacteriophages carried INK 128 manufacturer by S. flexneri based on serotype frequency data [5, 19]. We demonstrate that a novel serotype, named serotype 1 d was created in laboratory by infecting S. flexneri serotype X strains with a SfI phage or by sequential infection of serotype Y strain with SfX and SfI. Results and discussion Creation of a new serotype, serotype 1 d, through serotype conversion with phages SfI and SfX Using the procedures described by Mavris et al. [12], 2 serotype-converting phages, SfI and SfX, were induced and isolated from S. flexneri serotype 1a strain 019 and serotype Xv strain 2002017 respectively. The 2 phages were then used to sequentially infect a serotype Y strain 036 in

different order. We first performed sequential infection in the order of SfI and SfX. By infection with SfI, Copanlisib concentration the S. flexneri serotype Y strain 036 was converted into serotype 1a (036_1a), which agglutinated with both diagnostic typing sera I and grouping sera 3;4 (also known as Y-5) as shown in Table 1. Strain 036_1a was then used for infection by SfX, but surprisingly, no plaques appeared, indicating the strain cannot

be infected by SfX. Table 1 Serological characterization of S. flexneri serotype Y, X, 1a, 1b and 1c using serotyping monoclonal antibodies (MASF) Serotypes Reaction with MASF   Type antigen specific   Group antigen specific 1c   I II IV-2 V VI B 3;4* 6 7;8 IV-1   Fy – - – - – + + – - – - Fx – - – - – + – - + – - F1a + – - – - + + – - – - F1b + – - – - + – + – - – F1c – - – - – + – - – - + F1d + – - – - + – - + – - *Y-5 is a synonym of grouping 3;4 antisera Next we performed infection in the order of SfX 4��8C and SfI. The S. flexneri serotype Y strain 036 was converted to serotype X by phage SfX infection, which agglutinated only with serotype X-specific grouping sera 7;8. We named this strain as S. flexneri 036_X (Figure 1A and 1B). When 036_X was further infected with phage SfI, it was converted to a new serotype, which agglutinated with both of the diagnostic serotype 1a-specific typing sera I and serotype X-specific grouping sera 7;8, and were negative for all other type and group-specific sera (Figure 1A and 1B). The conventional serological identification results were further confirmed by Western-blot assay.