smcL as a novel diagnostic marker for quantitative detection of Listeria ivanovii in biological samples

Abstract

Aims: To develop a novel molecular tool for the quantitative detection of the ruminant pathogen Listeria ivanovii in different biological matrices.

Methods and results: A real-time PCR (RTi-PCR) for the quantitative and species-specific identification of L. ivanovii was designed to target the region of the smcL gene. The assay includes an internal amplification control (IAC) to avoid false-negative results. The smcL-IAC RTi-PCR assay was 100% selective and allowed the detection of as little as one genome equivalent in 45% of reactions. The quantification accuracy was excellent, as demonstrated by its high linearity (R(2)>0·9989) and PCR efficiency (E>0·984) over a 6-log dynamic range, down to 10 genome equivalents. Finally, the applicability of this assay was evaluated with artificially contaminated biological matrices implicated in the transmission of this bacterium such as sheep raw milk, blood and amniotic fluid. The smcL-IAC RTi-PCR assay allowed the detection of as few as 50 colony forming unit numbers (CFUs) per 25 ml of raw milk, 43 CFUs per 1 ml of blood or 50 CFUs per 1 ml of amniotic fluid.

Conclusions: This method can be an adequate alternative for the identification of L. ivanovii and for complete diagnosis of animal and human listeriosis. significance and impact of the study: We present an alternative for the detection of another pathogenic member of Listeria genus, which can help to distinguish from Listeria monocytogenes and therefore facilitates the establishment of preventive and prophylactic measures in food and farm environments.