Aims: To investigate the main genotypic virulence markers and the phenotypic features of an environmental Helicobacter pylori strain, named MDC1. Methods and Results: The H. pylori MDC1 genotypic status was evaluated by PCR amplification. The mosaicism in vacA alleles was expressed by the s1m1 allelic combination, as found in strains which are strong vacuolating cytotoxin producers; the number of cagA variable EPIYA motifs displayed P1P2P3P3 pattern and the iceA1 was recorded between the iceA allelic types and the babA2 gene found in strains causing more severe disease. The biofilm formation was evaluated on a polystyrene surface in static conditions by scanning electron microscopy and confocal scanning laser microscopy. Helicobacter pylori MDC1 displayed a dense mature biofilm with cells in a coccoid morphology persistent in time in which the expression of the luxS gene, related to the quorum-sensing signalling, was always detected. Conclusions: Helicobacter pylori MDC1 strain had the main virulence markers closely related to gastric pathogenesis and displayed a well-structured biofilm which allowed this bacterium to be more protected in the environment. Significance and Impact of the Study: The persistence of the environmental virulent H. pylori strain in a clustered state suggests a long-term survival of this bacterial community outside of the host, enabling the bacterial transmission with important clinical repercussions.