Isolate independent molecular typing improves the yield of O typing of infections due to Shiga toxin producing Escherichia coli

Abstract

Molecular screening has increased detection of Shiga-toxin producing Escherichia coli (STEC). However, it is difficult to isolate the organism for epidemiological typing. We applied a molecular method for direct detection of nine O types from 110 stx positive faeces samples and compared the results with conventional isolate based methods. Using conventional methods 55/110 (50%) samples were O typed. Using the molecular method, 72/110 (65%) were O typed, including 23/38 (61%) culture negative samples. Combining both techniques typed 88/110 (80%) of samples. Molecular typing increased detection of O128 (2-25%, p<0.001), O26 (11-16%) O45 (0-6%) and O103 (1-6%) infections. Molecular typing of STEC direct from faecal samples improved O type yield; risk of bias in epidemiological and surveillance activities may be reduced by inclusion of culture independent typing methods.