Silver nanoparticles have been considered as powerful antimicrobial agents recently, especially with the increasing incidence of diseases associated with biofilm and multi-drug resistant pathogens. The aim of this study was to synthesize silver nanoparticles by biological and chemical methods and combination with imipenem to eradicate biofilm-forming bacteria at phenotypic and genotypic levels. The biosynthesis of silver nanoparticles was done by using Enterobacter cloacae (cell-free suspension) while chemosynthesis was conducted using sodium borohydride. Biological and chemical silver nanoparticles were characterized by ultraviolet-visible spectrophotometry which showed absorbance peak at 400 and 390nm respectively. Fourier transformer infrared analysis revealed that carboxylic and polyphenolic groups were coated on surface of both silver nanoparticles. Scanning electron microscope and size analyser showed that the sizes of biologically and chemically silver nanoparticles were 63 nm and 25 nm, respectively. In addition, it showed the formation of cubical nanoparticles. The antimicrobial effect of synthesized silver nanoparticles were evaluated by agar well diffusion and macrodilution method to determine minimum inhibitory concentration value. The results showed that biological silver nanoparticles were more effective on biofilm forming bacteria (Serratia fonticola and Pantoea sp.) than chemical synthesized ones. In addition, the combination effect between silver nanoparticles and imipenem displayed synergistic effect. Gene expression of biofilm encoding genes (smaI and esaL) were evaluated by real-time quantitative polymerase chain reaction (RT-qPCR) before and after treatment with silver nanoparticles in both types and imipenem and in combination between them. The results revealed that biological silver nanoparticles alone or in combination with antibiotics were more effective on biofilm gene expression by down regulation than other treatments.

Staphylococcus lentus (S. lentus) is a coagulase negative gram positive cocci recognized as opportunistic pathogens and rarely forming biofilm; it has many virulence factors, but recently caused nosocomial and community infections. Biofilm formation of Staphylococcus lentus may be associated with the ability to resist antibiotics which leads to increase in mortality rate due to the difficulty in eradicate infections. To evaluate the biofilm forming capacity of Staphylococcus lentus and its susceptibility to antibiotics, phenotypic and genotypic assays were used. Among 28 biofilm bacteria, Staphylococcus lentus was isolated and identified from urine catheterized patients who were hospitalized in different departments of four Iraqi hospitals (Al-Diwaniyah Teaching, Al-Hilla Teaching, Al Qassim and Al Hashimiyah Hospitals). Staphylococcus lentus was examined for detection of biofilm formation by detecting icaA gene, the intercellular adhesion gene which expressed adhesion factor to form biofilm in staphylococci by using polymerase chain reaction (PCR) method and tested for antimicrobial susceptibility by disc diffusion method and VITEK2 system according to guidelines of the Clinical & Laboratory Standards Institute (CLSI).Three isolates of Staphylococcus lentus revealed the ability to form biofilm phenotypically which contained icaA gene with 100% antibiotics resistance to penicillin, carbenicillin, gentamicin, tobramycin, oxacillin, vancomycin, clindamycin, ciprofloxacin, and 0% antibiotics resistance to azithromycin. icaA genes are present in Staphylococcus lentus and responsible for biofilm formation which is considered as the indicator; biofilm formation is a strong cause of multidrug resistance in bacteria.

Serratia fonticola and Pantoea sp. are gram negative bacteria belonging Enterobactericeae, which were considered opportunistic pathogens and resulted in a great number of cases of nosocomial infections with serious problems of multi-drug resistance, leading to increasing morbidity and mortality rate. Recently, they were recorded as biofilm producers. There were only a few studies about the capability of these bacteria of forming biofilm. So our aim was evaluate the occurrence of Serratia fonticola and Pantoea sp. biofilm former phenotypically and genetically with the determination of their abilities to multi-drug resistance. Serratia fonticola and Pantoea sp. isolated from urine catheterized patients who were hospitalized in Iraqi hospitals. They were then examined for detection of biofilm formation phenotypically by congo red and tissue culture plate methods and genetically by detecting SmaI and EsaI genes (quarm sensing genes) in Serratia fonticola and Pantoea sp. respectively by using polymerase chain reaction method and tested for antimicrobial susceptibility by disc diffusion and VITEK2 system according to Clinical and Laboratory Standards Institute (CLSI). Serratia fonticola at 3 and Pantoea sp. at 4 isolates revealed to possess the ability of forming biofilm which contained SmaI and EsaI genes with 100% resistance to most tested antibiotics except imipenem and azithromycin. SmaI and EsaI genes are present in Serratia fonticola and Pantoea sp. respectively, and are responsible for biofilm formation and considered as indicator; biofilm formation is a strong cause of multidrug resistance in bacteria.

Staphylococcuslentus is a coagulase negative gram positive cocci recognized as opportunistic pathogens and rarely biofilm forming and have many virulence factors,but recently causes nosocomial and community infections. Biofilm formation S. lentus may be associated with ability to resistant antibiotics lead to increase in mortality rate due to difficult in eradicate infections To evaluate the biofilm forming capacity in S.lentus and its susceptibility to antibiotics by using phenotypic and genotypic assay. Twenty eight biofilm bacteria among of them S. lentus were isolated and identified from urine catheterized patients who were hospitalized in different department of four Iraqi hospitals (Al-Diwaniyah teaching,Al- Hilla teaching,Al Qassim and Al Hashimiyah hospitals) S. lentus were examined for detection biofilm formation by detecting icaA gene intercellular adhesion gene which express adhesion factor to form biofilm in staphylococci by using PCR method and tested for antimicrobial susceptibility testing by disc diffusion method and VITEK2 system CLSI guidelines. Three isolates of S. lentus revealed the ability 100% to form biofilm phenotypicallywhich contained icaA gene with clearly antibiotics resistance (100% ) to each penicillin,Carbencillin,Gentamicin,Tobramycin,Oxacillin,Vancomycin,Clindamycin and Ciprofloxacin and (0%) to Azithromycin.icaA genes present in Staphylococcuslentus and responsible for biofilm formation which consider as indicator and the biofilm formation is a strong cause of multidrug resistance in bacteria.

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