Molecular Study of Acinetobacter baumannii that Lacking Some Essentials Genes Responsible of Toxin-Antitoxin System

Acinetobacter genus has various species that are widespread in different environments and can exist in non-living environment samples as well. Acinetobacter baumannii (A. baumannii) is known to be one of the main causes of nosocomial infection. Few studies have examined the possibility of the presence of this opportunistic pathogen in nonliving environment samples. In this study, A. baumannii strain cl-2 was isolated from dishwasher basket samples and it was identified by 16S ribosomal RNA sequencing analysis. The present study also investigated the presence of some important genes responsible for toxin-antitoxin (TA) systems necessary for the resistance of this bacterium in improper environmental conditions. Additionally, attempts were made to study some essential virulence factors, such as hemolysin, lipase, protease, and lecithinase production, as well as biofilm formation and surface motility. The findings revealed that the isolate belongs to the A. baumannii strain cl-2. The isolate was deposed in the National Center for Biotechnology Information, (NCBI) and the data can be accessed via the NCBI accession number (MW642251). The results of screening the TA system by higBA, mazEF, and relBE genes showed the isolate did not contain these genes. The hemolysin toxin activity (phenotypic test) was performed by using the streaking and spot methods on blood agar. It was found that the A. baumannii strain cl-2 had the ability to hemolyze red blood cells and produce lecithinase and protease enzymes. Finally, it was revealed that the A. baumannii strain cl-2 had surface motility based on the concentric diffusion ring of growth observed on Luria Broth agar (0.3%). In conclusion, the isolates under study showed association patterns between their ability to produce hemolysin, lipase, lecithinase, as well as protease, and other virulence factors, including surface motility and biofilm formation.