Biofilm Subtyping of Stx and 16s rRNA Gene Analysis of Some Bulgarian Shiga Toxin Producing Escherichia coli Isolates

In this study, among five positive isolates of stx1 isolated from raw milk and chicken meat, one isolate showed a positive result for subtype stx1d and the other four isolates were positive for subtypes stx1d and stx1a. An isolate positive for stx2 isolated from pork was found to carry an stx2g subtype. Besides subtyping, we performed phylogenetic analysis based on 16s RNA gene sequencing data. Based on the mutations identified in the isolates, we sought for restriction enzymes to distinguish the strains from one another. The results for the combination of stx1 subtypes are in agreement with other reports, being the most common combination in Escherichia coli isolates with an origin from pigs. Interestingly, the pork isolate subtyped as stx2g by us is in contrast with studies according to which the most common subtype of this source is stx2e.