Optimization and Molecular Detection of Neuraminidase Gene in <i>Listeria monocytogenes</i>

Abstract

Background: Listeria monocytogenes is one of the human pathogenic microbes causing Listerosis and is usually found as a contaminant in many foods and dairy samples. Neuraminidases (NAs) plays a key role in many pathogenic bacteria and has the ability to block sialic acid (a virulence factor) that targets mucosal surfaces. Objectives: In the current study, NA or sialidase-producing Listeria monocytogenes were screened from different milk samples of cow. Methods: Listeria monocytogenes was identified by morphological, biochemical, and hlyA gene polymerase chain reaction (PCR) assay. Furthermore, molecular detection of 432 bp amplicon of sialidase enzyme (Neuraminidase) gene in the native isolates was noted. Results: The prevalence of Listeria species was found to be around 4.16%. Sialidase enzyme was found to be produced in high amounts in isolated L. monocytogenes. Furthermore, NA was purified by ammonium sulphate precipitation and gel filtration techniques. The partially purified sialidase enzyme possessed a molecular mass of 27.0 ± 1 with an isoelectric point of 7.6. The optimum pH and temperature were 4.6 to 8.2 and 30 to 35°C, respectively. The enzyme had no effect on metal ions, such as Mn+2, Zn+2, and Ca+2, whereas Hg+2 and Al+3 had potentially acted as inhibitors. Conclusions: This study suggests that the sialidase of L. monocytogenes plays a significant role in its pathogenesis.