With respect to sequence type 155, recent studies published in the literature show that it has a specific mutation in the prfA gene which determines the synthesis of a longer version of the master transcriptional activator of the virulence gene and consequently a lower expression of inlA, inlB, and prfA and no expression of hly and actA, causing a reduction in the virulence potential of these strains and an inability to cause meningitis [37]. The gene discussed is ACTA1; the disease is infectious meningitis.