Finding novel and effective antibiotics for treatment of LEGIONELLA disease is a challenging field. Treatment with antibiotics usually cures LEGIONELLA infection; however, if the resultant disease is not timely recognized and treated properly, it leads to poor prognosis and high case fatality rate. LEGIONELLA pneumophila DrrA protein (Defects in Rab1 recruitment protein A) /also known as SidM affects host cell vesicular trafficking through modification of the activity of cellular small guanosine triphosphatase) GTPase (Rab (Ras-related in brain) function which facilitates intracellular bacterial replication within a supporter vacuole. Also, LEGIONELLA pneumophila LepA and LepB (LEGIONELLA effector protein A and B) proteins suppress host-cell Rab1 protein’s function resulting in the cell lysis and release of bacteria that subsequently infect neighbour cells. LEGIONELLA readily develops resistant to antibiotics and, therefore, new drugs with different modes of action and therapeutic strategic approaches are urgently required among antimicrobial drug therapies; gene therapy is a novel approach for Legionnaires disease treatment. On the contrary to the conventional treatment approaches that target bacterial proteins, new treatment interventions target DNA (Deoxyribonucleic acid), RNA (Ribonucleic acid) species, and different protein families or macromolecular complexes of these components. The above approaches can overcome the problems in therapy of LEGIONELLA infections caused by antibiotics resistance pathogens. Targeting LEGIONELLA genes involved in manipulating cellular vesicular trafficking using a dendrimer-mediated antisense therapy is a promising approach to inhibit bacterial replication within the target cells.

Introduction: L. pneumophila is the most important cause of legionaires, disease, which is currently reported either as a nosocomial or community acquired infection. Rapid and reliable diagnosis of LEGIONELLA has hampered the epidemiological studies and disease control activities. In spite of good sensitivity and specificity, the culture method encountered serious shortcomings. Polymerase chain reaction (PCR) has been used to detect the viable but non-culturable LEGIONELLA. In the present investigation, the efficacy and accuracy of mip gene based primers were tested in PCR for culture-negative samples. Materials and Methods: The samples used in this investigation were previously reported as negative by means of conventional culture methods. DNA extraction was carried out by freezing-boiling method. The small fragment of mip gene (of L. pneumophila) was used for the primer set (LEG 1 and LEG-2) in PCR, and also for specific probe LEG-3 in southern blot.Results: From 32 culture-negative samples subjected to these primer sets, L. pneumophila DNA was detected in 6 samples. System accuracy was then checked by dot blot hybridization.Conclusion: The results of this investigation indicated that the PCR method, with suitable primer set and probe, detects the viable but non-culturable LEGIONELLA in clinical and environmental samples.