3 Molecular Detection of SpnI/SpnR and AHL‐Mediated Quorum Sensing Signals Genes in Serratia Marcescens

Abstract

Quorum sensing process, bacteria connect with each other using secreted chemical signaling molecules called autoinducers. a quorum-sensing signaling molecule suggested to be involved in related species communication. Twelve isolates Serratia marcescens were collected from Baghdad hospitals. Of the 12 S. marcescens isolates examined, only 8 (66.66%) produced prodigiosin pigment. This work describes a high frequency of isolation of pigmented S. marcescens from clinical specimens, indicating that pigmented strains become clinically significant. The antibiotic sensitivity test showed multi drug resistant against (8- 18) antibiotics, all isolates were resistant (%100) against Beta lactam group, an indication of the comprehensive resistance to beta-lactam antibiotics, as a result of the irresponsible use of these antibiotics, which made them lose the effective therapeutic role that they previously required. In another hand S. marcescens 100% sensitive for to Meropenem and Imipenem and varied in their response to other antibiotics used in this study. The results showed a different distribution in S. marcescens (AI-2 kinase, Tsq, rpoS and SpnI/SpnR) genes. Eleven out of (92%) isolates namely were negative for AI-2 kinase gene, while (100%) 12/12 isolates observed positive for Tsq gene. 1\12 (8%) were positive for the presence of rpoS gene, whereas 12/12 isolates were positive, spnI/spnR gene was found with the highest percentage ratio (100%) when only one isolate were harboring all sets of genes. Our study suggested that expression of spnI/spnR by S. marcescens is independent of AHL signals synthesis.