Silver nanoparticles have been considered a powerful antimicrobial agents recently especially after increasing incidence of diseases associated with biofilm and multi-drug resistant pathogens required to find a novel path to eradicate that challenge. The present study aims to evaluate the antibacterial activity of biosynthesized silver nanoparticles (AgNPs) using a cell-free extract of Enterobacter cloacae and chemo synthesis by sodium borohydride (NaBH₄) on biofilm-forming Pseudomonas oryzihabitans. Antimicrobial effect of silver nanoparticles in both types and in combination with imipenem were evaluated by agar well diffusion method. The results revealed a good response to inhibit biofilm-forming Pseudomonas oryzihabitans growth by silver nanoparticles antibacterial activity in both types (biological and chemical) and in combination with imipenem; the antimicrobial effect was increased and enhanced. In the present study, it was found that the biological and chemical silver nanoparticles were considered a novel and decisive solution against biofilm and multi- drug resistance bacteria with a preference of biological silver nanoparticles.

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.

Pseudomonas oryzihabitans is uncommon pathogen, but recently there may be warning of this bacterium to be dangerous, highly virulence, and may cause increase in morbidity and mortality rate, especially if there are multi-drug resistance and biofilm former. Biofilm forming bacteria display resistance to antibiotics, reaching to 1000 time higher than planktonic bacteria. The aim of the current study was to detect Pseudomonas oryzihabitans as biofilm producer and determine the susceptibility to the tested antibiotics. Pseudomonas oryzihabitans was isolated from urine of catheterized patients in Iraqi hospitals and diagnosed as biofilm former phenotypically by congo red and tissue culture plate methods, and genetically by polymerase chain reaction analysis to detect lasR gene (quarm sensing gene) as biofilm indicator and determine its susceptibility to antibiotics by disc diffusion and VITEK AST method. The results revealed that Pseudomonas oryzihabitans was present at 3 isolates; all of them had lasR gene and were resistant to most tested antibiotics at 100%, except that it showed sensitivity rate reaching to 100% to imipenem. From the present study, it was concluded that Pseudomonas oryzihabitans was isolated for the first time as biofilm producer from urinary catheter which possessed lasR gene as biofilm formation indicator, and the multi-drug resistance was considered as a distinctive feature of biofilm formation 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.

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.