Background:            The ability to form biofilms by microorganisms is one of the virulence factors used by bacteria to cause disease and is measured by measuring optical density (O.D), which is a measure to estimate the concentration of bacterial species growing in the culture media. Materials and Methods:           The bacterial cultures of six different bacterial isolates of S. marcescens and Klebsilla    pnemoniae , Enterococcus cloacea , Eshcherchia coli , Staphylococcus aureus, Psedomonas aeruginosa were reconstituted from frozen stock, which diagnosed by using VITEK 2 Densi screening tool, then plant extracts  of Allium sativum and Alhagi maurorum were prepared to test the effect of these extracts on the bacterial isolates under study.Optical density was measured using a spectrophotometer at a wavelength of 490 nm before and after treatment of the bacterial isolates with the two extracts A.sativum and A. maurorum . Results:          The ability of K. pnemoniae , S. marcescens and E. cloacea, to form biofilm reduced with absorption value 0.52±0.01, 0.66±0.03, 0.8±0.01 respectively, and the ability to form biofilm from E. cloacea , E. coli after adding A. maurorum extract was decreased and the absorbance value reached 0.66±0.01,0.66±0.005 respectively after being treated with A. maurorum extract. Conclusion:        Biofilm formation is one of the virulence factors that helps microorganisms resist the environment in which they exist and resist antibiotics. Therefore, medicinal plant extracts are used as an alternative, which have been shown to inhibit the growth of some pathogenic bacterial species.

Pseudomonas aeruginosa is an opportunistic pathogen. Quorum sensing (QS) is one of processes that are responsible for biofilm formation. P. aeruginosa can live in different environments, some of which are pathogenic (clinical isolates) and some that are found outside the body (environmental isolates). The present study aimed to determine the presence of a number of genes responsible for QS in clinical and environmental isolates of P. aeruginosa. In the present study full DNA was separated from all environmental and clinical isolates that contained seven genes (rhlA, rhlR, rhlI, lasR, lasI, lasB, phzA1) associated with QS occurrence. The total DNA was separated from all environmental and clinical isolates (PAE1, PAE2, PAE3, PAE4, PAE5, PAE6, PAE7, PAE8, PAE10, PAE11, PAE12, PAE14, PAC1, PAC2, PAC5, PAC7, PAC8, PAC9 and PAC10). This study found that all studied environmental and clinical isolates contained the seven genes rhlA, rhlR, rhlI, lasR, lasI, lasB, phzA1, which was associated with QS occurrence.

Helicobacter pylori is believed to be a main reason of stomach diseases in addition to the occurrence of infections that may end in cancer, there may be new virulence factors and as a result of the genetic analysis of this bacteria, which shows a wide view of the genome of this bacteria, so we hope to discover a new generation of genetic sequencers to verify the presence of new virulence agents. Studying the function of virulence factors possessed by H. pylori that increase its susceptibility to disease will lead to the possibility of developing treatments and vaccines. This review focuses on virulence factors and their role within pathogenesis of H. pylori contagion. This review contributes for development about new prevention and treatment methods based on an understanding of the role of cagA, vacA, ureE-H, and ureI proteins in increasing the susceptibility of bacteria to colonize the host digestive system in addition cause damage of host tissue.