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The genus Pseudomonas consists of more than 120 species that are ubiquitous in moist environments such as water and soil ecosystems and are pathogenic to animals and humans. Within the genus of Pseudomonas, P. aeruginosa is most frequently associated with human infections. The bacterium is regarded as an opportunistic pathogen, primarily causing nosocomial infections in immunocompromised patients. The existing knowledge regarding the pathogenesis of P. aeruginosa has mainly been obtained through studying clinical isolates; particularly those involved in causing chronic lung infection in cystic fibrosis patients. Nosocomial infections commonly associated with P. aeruginosa include ventilator-associated pneumonia, catheter-associated urinary tract infections, wound infections in severe burn patients and septicaemia with their pathogenesis shown to be multifactorial. The bacterium is also capable of producing a number of toxins via the type III secretion system, as well as secreting enzymes and proteins including elastase, phospholipase C and siderophores. However, P. aeruginosa is also a waterborne pathogen, commonly found in environmental waters as well as in other sources such as sewage treatment plants. The public health implication of these bacteria whilst in the environment has not been fully investigated. Here we review our present knowledge about the pathogenesis of P. aeruginosa in clinical settings and the environment. 

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Background: Pseudomonas aeruginosa is considered an opportunistic pathogen; several reports indicate that the organism can also cause infections in healthy hosts. Four effector proteins have been described in P. aeruginosa: exoU, exoS, exoT, and exoY. These genes that are translated into protein products related to type III secretion systems. Materials and Methods: A total of 134 samples were isolated, and P. aeruginosa was identified using biochemical tests. Bacterial genomic DNA was extracted, and the presence of the exoSand exoUgenes were detected by PCR. Biofilms were formed by culturing P. aeruginosaon glass slides in rich medium. Results: The exoU(73%), exoS (62%) genes were detected from infections caused by P. aeruginosa in urinary tract infection patients. Among the 119 strains isolated from patients with urinary tract infections. Conclusion: An improved understanding of virulence genes and biofilm formation in P.aeruginosa may facilitate the future development of novel vaccines and drug treatments.

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Background:  Pseudomonas aeruginosa is one of the main causes of nosocomial infections with a mortality rate up to 40-50%. Resistance to antibiotics is a global challenge in the treatment of infections caused by this bacterium.  The Class A beta-lactamases genes, including bla_SHV, bla_PER, bla_VEB, are the most common causes of resistance in this microorganism. This study was conducted to determine antibiotic resistance pattern and the presence of bla_per, bla_veb, bla_shv and bla_oxa-10 genes in clinical isolates of P. aeruginosa isolated from patients in a hospital in Bandar Abbas.
Materials and Methods:  This cross-sectional study was conducted on 72 P. aeruginosa clinical isolates. Antibiotic susceptibility testing was performed by disk diffusion method according to the clinical Laboratory Standard Institute. MIC (Minimum inhibitory concentration) of ceftazidime was performed by E-Test. Polymerase chain reaction (PCR) was performed to identify bla_shv, bla_veb-1, bla_oxa-10, and bla_per-1 genes.
Results:  Most of the isolates were detected from intensive care unit and urine samples. The highest resistance rate which was observed to sulfamethoxazole and ceftazidime, were 68 (94.44%) and 44 (61.11%), respectively.  27.8% of these isolates were multidrug resistance. Among 44 ceftazidime resistance isolates, 15 isolates (34%) showed MIC ≥32 µg.ml in the E- test. The prevalence rates of genes were 4.16, 12.5, 8.33, and 1.38% for bla_Oxa-10, bla_Shv, bla_Veb-1, and bla_Per-1 genes, respectively.
Conclusion:  The ceftazidime resistance rate and the prevalence rate of resistance genes in the present study were lower than other Iranian studies.  However, isolation of these genes is alarming that excessive use of antibiotics can lead to over expression of resistance genes and bacterial efflux pumps and the emergence of MDR phenotypes.

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Background: Integrons are considered as to play a significant role in the evolution and spread of antimicrobial resistance genes.
Materials and Methods: A total of 120 clinical isolates of Pseudomonas aeruginosa (collected from Zanjan hospitals between March 2015 and February 2016) were investigated for molecular characterization of MBLs and Class I and II integrons. Antimicrobial susceptibility testing was also performed based on the CLSI guidelines. The frequency of MBL producing isolates and the susceptibility to various antimicrobial agents were investigated.
Results: Based on the obtained results, Bla_IMP was the most frequently detected metallo-β-lactamase. The frequency of bla_VIM, blaSPM, and bla_SIM, in MBL producing isolates was 17.1, 57.1, and 14.1%, respectively. No bla_GIM harboring isolate was detected in our study. We detected two (5.7%) multidrug resistant P. aeruginosa strains isolated from the urine and sputum samples, which harbored bla_NDM-1. These isolates also contained bla_IMP and bla_SPM. Class I integron was detected in 94.3% of the MBL positive isolates while 8.5% of the isolates contained Class II integrons. Of five different gene cassettes identified in Class I and II integrons, cassette encoding resistance to trimethoprim (dfr) was found to be predominant.
Conclusion: These results indicate that Class I integrons are widespread among the MBL producing P. aeruginosa isolates. Therefore, appropriate surveillance and control measures are essential to prevent the further spread of MBL and integron producing P. aeruginosa in hospitals.­­

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Aims: This study aimed to determine the antibiotic resistance pattern of Pseudomonas aeruginosa clinical isolates and the frequency of blaSIM and blaAmpC genes in resistant strains.
Materials & Methods: In this cross-sectional study, 94 P. aeruginosa isolates were collected from the burn wards of Gilan province hospitals in 2018 and identified by biochemical methods. Strains producing β-lactamases and metallo-β-lactamases were detected by two methods: disk diffusion method and antibiotic resistance method in combination with disk diffusion method, respectively. The presence of blaSIM and blaAmpC genes in the resistant strains was investigated using PCR, and data analysis was performed.
Findings: Based on the obtained results, colistin was identified as the most effective antibiotic with a resistance rate of 27.7%, and the highest antibiotic resistance was observed against trimethoprim/sulfomethoxazole (83%). In the phenotypic test of 94 samples, 29 (30.9%) carbapenemase-producing isolates and 33 (35.1%) β-lactamase-producing isolates were identified. Based on the PCR results, among 44 (46.8%) samples containing β-lactamase and carbapenemase enzymes, the frequency of blaSIM gene was 9.1% (4 of 44, and 4.3% in all the studied isolates), and the frequency of blaAmpC gene was 15.9% (7 of 44, and 7.4% in the all studied isolates).
Conclusion: The results of this study indicated a high prevalence of drug resistance in clinical isolates of P. aeruginosa. In particular, there was an increasing rate of resistance to beta-lactam antibiotics, and the presence of MBL and ESBL associated genes was considerable, which limit the choice of suitable treatment for patients with severe infections.

 

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Aims: Recently, overuse and misuse of antibiotics have led to the development of multidrug-resistant bacteria and infectious diseases caused by these organisms, increasing morbidity and mortality rate in patients. Pseudomonas aeruginosa as a common Gram-negative pathogen is predominantly responsible for hospital-acquired infections. In this study, the prevalence of multidrug-resistant (MDR), extensively drug-resistant (XDR), and pandrug-resistant (PDR) P. aeruginosa strains isolated from clinical specimens of patients admitted to a teaching hospital in Gorgan, Iran, was determined.
Materials & Methods: Clinical samples of blood, urine, burn wound, eye, and secretions (pleural fluid, tracheal or bronchial aspirates and sputum) were collected from all hospitalized patients during a three-month period from April to June 2019. Using conventional biochemical methods, P. aeruginosa strains were identified, and the antibiotic resistance pattern was determined by Kirby-Bauer disc diffusion method.
Findings: A total of 40 (25.4%) P. aeruginosa strains were isolated from 377 clinical specimens. Most of the P. aeruginosa strains were isolated from wound (35%) and urine (30%) samples. Most of the P. aeruginosa positive samples were recovered from intensive care unit (32.5%) and burn ward (30%). The highest susceptibility was shown to fosfomycin (100%), and the lowest susceptibility was observed to ceftazidime (87.5%), followed by aztreonam (60%). Based on the results, 52.5 and 20% of the isolates were MDR and XDR, respectively. All of the MDR isolates exhibited susceptibility to colistin. No PDR phenotype was observed.
Conclusion: Continuous monitoring of drug resistant strains among clinical isolates of P. aeruginosa must be done to adopt effective strategies to decrease the threat of antimicrobial resistance.

 

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Background: This study aimed to determine antibacterial activity of ethanolic extract of Matricaria chamomilla (chamomile) against methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant (MDR) Pseudomonas aeruginosa strains isolated from clinical specimens.
Materials & Methods: The plant samples were collected, and the flowers and leaves were separated and dried completely in the shade. After grinding, extraction was performed using the maceration method. The extracts of both flowers and leaves were dried at 37°C for 24 hrs. About 500 mg of the dried plant extract was dissolved in 10 mL of 5% dimethyl sulfoxide and sterilized by filtration through a 0.45 µm membrane filter. For the antibacterial assay, agar well diffusion and broth microdilution methods were used.
Findings: No inhibitory effect was observed for both extracts against MDR P. aeruginosa isolates in agar well diffusion method. In broth microdilution method, the leaves extract showed inhibitory effect, and its MIC and MBC were determined at 12.5 and 25 mg/mL concentrations, respectively. The flowers extract showed antibacterial activity against most MRSA isolates. The extract of leaves demonstrated inhibitory effect on 7 MRSA isolates. The MIC and MBC of flowers extract were determined at concentrations of 6.25 and 12.5 mg/mL for most MRSA isolates, while MIC and MBC of leaves extract were 12.5 and 25 mg/mL for a few MRSA isolates, respectively.
Conclusion: In this study, the ethanolic extract of chamomile leaves showed antibacterial activity against MDR P. aeruginosa isolates; meanwhile, the flowers extract showed better activity against MRSA isolates.

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Backgrounds: Metallo-β-Lactamase (MBL) enzymes-producing Pseudomonas aeruginosa strains are one of the most important causes of nosocomial infections and are very difficult to treat, leading to high mortality rate. Therefore, control of these cases is very important, especially in burns. This study aimed to systematically review published data on MBL genes prevalence among P. aeruginosa strains isolated from burn patients.
Materials & Methods: ISI Web of Science, Scopus, PubMed, and Google Scholar were searched using appropriate key terms as follows: P. aeruginosa, metallo-β-lactamase, burn patients, imipenem resistant, and Iran. Antibiotic susceptibility tests were conducted by Kirby-Bauer disc diffusion and broth microdilution methods according to the CLSI guidelines. The MBL producers was evaluated by the combination disk diffusion test (CDDT), and detection of genes such as blaIMP, blaVIM, blaSPM and blaNDM was performed with polymerase chain reaction (PCR). In this review statistical analyses were performed using STATA statistical software Ver.13.
Results: Out of 410 retrieved articles, 18 articles were eligible to be included in this systematic review and meta-analysis. These studies were carried out in Tehran, Shiraz, Yazd, Zahedan, and other locations. Pooled estimation of all P. aeruginosa strains included in 18 studies showed that the prevalence of MBL-producing P. aeruginosa strains in Iranian population was about 49% (95% CI: 33-65). The present study findings also revealed that in Iranian population, the most prevalent MBL genes were blaIMP with 17% (95% CI) and blaVIM with 13% (95% CI), respectively.
Conclusion: Detection of these bacterial resistance genes should be performed nationally, and strict control measures should be put on the agenda to reduce the incidence of these cases.

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Purpose: In this study the inhibitory effect of Eucalyptus extracts as a natural and herbal antibacterial substance was evaluated against Pseudomonas aeruginosa strains (8821M and ATCC27853). Material and Methods: The MIC (Minimal Inhibitory Concentration) of alcoholic and aquatic extracts of Eucalyptus was determined using the tube and agar dilution methods. The growth rate of Pseudomonas aeruginosa in sub-MIC concentration of extracts was compared with the controls. Phenol coefficients of extracts were determined by the Ridal- Walker method. Result and Discussion: The MIC was 1:8(3.2 mg/ml) fold of the alcoholic extracts and 1:4(17.5 mg/ml) fold of the aquatic extracts. In the sub-MIC concentration of extracts, by increasing the Eucalyptus extract concentration, the growth rate was decreased. Phenol coefficients of the alcoholic and aquatic extracts were evaluated to be 0.0381 and 0.019, respectively. Conclusion: Results of this study indicated that crude aquatic and alcoholic extracts of Eucalyptus have inhibitory effects on the growth of Pseudomonas aeruginosa and in the sub- MIC concentration of extracts this value decreases. Overall, the plants indicated a wide range of antimicrobial activities which can lead to the detection of new antibiotics against resistant bacteria.

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Backgrounds: The ever-increasing incidence of multidrug resistance in ESBL-producing Pseudomonas aeruginosa is one of the most serious public health threats. This study aimed to investigate the antibiotic resistance profile and molecular characteristics of ESBL-producing P. aeruginosa isolates.
Materials & Methods: Antimicrobial susceptibility testing was performed for 120 P. aeruginosa clinical isolates using the Kirby-Bauer disk diffusion and broth microdilution assays. Combined disk test (CDT) was applied to screen for ESBL production among P. aeruginosa isolates. PCR assays determined the presence of bla_GES, bla_PER, and bla_VEB genes in all isolates.
Findings: The clinical isolates of P. aeruginosa showed the highest resistance to cefotaxime (86.7%) and gentamicin (65.8%). Of 120 P. aeruginosa isolates, 60.8% were MDR, and 53.3% were XDR. The prevalence of these strains was significantly higher in hospitalized patients than in out-patients (p<.001). Also, 58 P. aeruginosa strains (48.3%) were considered as phenotypic ESBL producers. Furthermore, 15, 35, and 24.2% of P. aeruginosa isolates harbored bla_GES, bla_VEB, and bla_PER, respectively. The incidence of MDR (71.4% vs. 41.9%, p= .001) and XDR (63.6% vs. 34.9%, p= .002) was significantly higher in ESBL-producing P. aeruginosa isolates compared to non-ESBL producers. The highest incidence rate of MDR was reported in bla_VEB gene-positive P. aeruginosa isolates (95.2%), followed by isolates harboring bla_PER (79.3%) and bla_GES (55.6%) genes.
Conclusion: This study findings show a high prevalence of MDR ESBL-producing P. aeruginosa isolates, indicating the importance of correct identification of these superbugs and judicious use of various antibiotics to prevent their spread.

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Backgrounds: Carbapenem resistance among Pseudomonas aeruginosa strains is alarming. This study aimed to investigate the relative frequency of carbapenem-resistant P. aeruginosa strains by phenotypic and genotypic methods.
Materials & Methods: The antibiotic susceptibility pattern of 60 P. aeruginosa isolates was determined by disk diffusion method (Kirby-Bauer). BD Phoenix automated microbiology system was used to identify carbapenem-resistant isolates, and the minimum inhibitory concentration (MIC) was determined using E-Test. In addition, mCIM (modified carbapenem inactivation method) phenotypic test was performed to evaluate carbapenem resistance genes in P. aeruginosa isolates. The prevalence of metallo-beta-lactamase (MβL) genes in carbapenem-resistant P. aeruginosa isolates was determined using conventional polymerase chain reaction (PCR).
Findings: The frequency of carbapenem-resistant P. aeruginosa isolates was 36% (22 of 60). The highest resistance was observed to imipenem and meropenem (36.6%), and the highest sensitivity was observed to amikacin (75%). All carbapenem-resistant P. aeruginosa isolates were confirmed by the BD Phoenix automated system (MIC> 8 µg/mL for imipenem and meropenem), E-test (MIC ˂32 µg/mL), and mCIM assay (the growth inhibition zone diameter was 6-8 mm).  In carbapenem-resistant P. aeruginosa isolates, the frequency of bla_VIM, bla_IMP, and bla_SPM genes was 9.1% (2 of 22), 4.5% (1 of 22), and 4.5% (1 of 22), respectively. Bla_KPC and bla_NDM genes were not found in any of the isolates.
Conclusion: Based on the present study results, all phenotypic tests used to identify carbapenemase-producing isolates had the same sensitivity (100%) and specificity (100%).

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Backgrounds: Multidrug-resistant Pseudomonas aeruginosa is known as a major opportunistic pathogen in burn patients with hospital-acquired infections. The aim of this study was to investigate antibiotic resistance and the capability of (GTG) 5-PCR (polymerase chain reaction) assay for molecular typing of P. aeruginosa strains isolated from clinical samples of hospitalized burn patients in southern Iran.
Materials & Methods: This cross-sectional research was carried out on 70 P. aeruginosa isolates collected from hospitalized burn patients in southern Iran from June 2020 to January 2021. Antimicrobial susceptibility patterns of the isolates were determined using disk diffusion method. Additionally, repetitive extragenic palindromic-PCR (rep-PCR) method was used to examine the genetic similarities among the strains.
Findings: Antimicrobial susceptibility patterns revealed that the highest antibiotic resistance was against gentamicin (95.8%), followed by imipenem (94.3%) and piperacillin–tazobactam (92.8%), while colistin was the most effective antimicrobial agent. Rep-PCR typing revealed that 60 P. aeruginosa strains were classified into 49 GTG5 types (G1-G49), which were then grouped into 12 clusters (A-L) and 10 isolates with unique banding patterns according to the 80% cut off point.
Conclusion: The present study data indicated a substantial resistance to the studied antimicrobial agents, especially the last-resort antimicrobial agents. In addition, rep-PCR analysis revealed that most of the evaluated strains had partial genetic diversity; therefore, infection control activities should be carried out to decrease the colonization of MDR P. aeruginosa isolates in the hospital setting.

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Aims: Pseudomonas aeruginosa is considered as an important opportunistic bacterial pathogen associated with nosocomial infections. Therefore, it is important to identify this bacterium in clinical samples and report the results to health authorities. The aim of this study was the molecular identification of some virulence factors and fosfomycin resistance genes in P. aeruginosa strains.
Materials & Methods: A total of 100 P. aeruginosa strains were isolated from clinical samples of patients with eye infections in three distinct laboratories in Tehran hospitals (Pars, Milad, and Motahari). The antibiogram of all isolates against eight antibiotics was determined by standard Kirby-Bauer disk diffusion method. Then DNA was extracted from the isolates, and the frequency of exoY, exoT, exoU, exoS, fosC, fosB, and fosA genes was evaluated by multiplex PCR (polymerase chain reaction).
Findings: The highest resistance was observed to cotrimoxazole (85%), ceftazidime (83%), cefotaxime (79%), and cefepime (72%), and the highest sensitivity was observed to ciprofloxacin (55%), gentamicin (52%), and piperacillin (41%), respectively. Out of 60 investigated isolates, 58 isolates were positive for exoY, exoT, and exoU, while only four isolates were exoS positive. In addition, one strain (1.66%) had the fosC gene, two strains (3.33%) had the fosB gene, and 12 strains (20.02%) had the fosA gene.
Conclusion: The results showed that the frequency of fosfomycin resistance genes, whose protein product modifies the epoxide group of fosfomycin and reduces the effectiveness of this antibiotic, was significantly low in the investigated strains.

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Background: Biofilm is described as an accumulation of microbial organisms connected to a living or unmoving surface mainly through self-secreted polymeric materials. With a complete understanding of biofilm behaviors and the role of rhamnolipids in its stability or dispersion, a new path could be designed in the treatment of infections like Pseudomonas aeruginosa (P. aeruginosa). The purpose of this study was to investigate the role and function of rhamnolipids in P. aeruginosa velocity and biofilm formation ability.
Materials & Methods: In this study, 68 P. aeruginosa clinical samples were isolated from February 2022 to 2023 and confirmed based on culture and molecular methods. The presence of genes associated with di-rhamnolipid (rhlC) and mono-rhamnolipid (rhlA and rhlB) biosynthesis was detected by PCR method. For velocity assay, bacterial cultures on Bushnell Haas medium were monitored for 24 and 72 hours (0.5%).
Findings: The results showed that the distribution of biofilm strength among P. aeruginosa strains was normal. The frequency of rhlC was significantly different from those of rhlA and rhlB (p= .01). In the first 24 hours, the velocity of P. aeruginosa on Bushnell Haas with glucose was 2 µm/min and decreased during 72 hours. But after 72 hours, the velocity of moderate and weak biofilm-producing strains on solid medium with glycerol was constant.
Conclusion: In this study, rhamnolipids produced from different carbon sources showed different behaviors on colony shape, velocity, and strength of bacterial biofilms.

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Objective: Pseudomonas aeruginosa is the major cause of septicemia and wound infection in burned patients. Immunotraphy is the best practical way for prevention and treatment of these infections. Flagella as one of the most important bacterial virulence factors has important role in attachment, motility, chemotaxis and TLR-5-dependent immune response so that it propounded as a vaccine candidate. Production of anti-flagellar antibodies and evaluation of its protective effects in burned induced infection of mice was the main aim of this study. Materials and Methods: In the first step, flagellar antigen prepared by ultra-centrifugation. Anti-flagellar antibodies produced in rabbit and its impurity separated by absorption technique. Specification of the obtained antibodies for flagellar antigen was investigated via agglutination test. After determination of LD50 in a known strain, different dilutions of anti-flagellar antibodies injected in burned mice for passive immunization. The rate of bacterial spread from burn site was determined by quantification assay of bacteria in skin and liver. In this study, clinical isolate and PA103 in addition to ATCC 27853 strain were used for agglutination test. Results: H-antiserum reduced mortality of burned mice challenged with ATCC 27853 strains about 80%. Counting of bacteria in the skin and liver showed that the number of bacteria in immunized mice, in contrast with control group, was significantly low. Conclusion: The results of this study showed that anti-flagellar antibodies of Pseudomonas can inhibit invasion of Pseudomonas and facilitate its opsonization, so these antibodies have protective effects in burned wound infections.

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This study aimed to produce a smart infection warning film based on chitosan and gum arabic containing anthocyanin (0.5, 0.75, and 1 g) as a wound infection warning. Chitosan/gum film was prepared in a ratio of 1:2 with different doses of anthocyanin pigment (0.5, 0.75, and 1 g), and the control sample was considered without anthocyanin. The prepared film was evaluated on Pseudomonas and Mannitol salt agar media. To evaluate the functional properties of the prepared film, the amount of moisture, solubility, thickness, and water absorption of the treatments were measured. The lowest and highest film moisture content were in the control treatment, and the treatment contained 0.75% anthocyanins, respectively. As the percentage of anthocyanin increased, the thickness and solubility of the samples decreased significantly. Regarding the water absorption test, the highest amount was related to the treatment containing 1% anthocyanin, and the lowest amount belonged to the control treatment. To evaluate the effect of chitosan or gum film containing anthocyanin on the culture medium when the bacteria were well grown, chitosan or gum biofilms containing different concentrations of anthocyanin were cut to 1.1 cm and cut into It was placed on the culture medium for 60 minutes, and the color change of the films was checked with a colorimeter. The highest rate of color change of films in culture medium containing Pseudomonas aeruginosa was obtained in the treatment containing 0.5%; however, in the case of Pseudomonas aureus, the highest color change was observed in the treatment containing 1%. Finally, the best film in terms of physical characteristics is the 1% treatment, and in terms of color change in response to the growth of Pseudomonas, it is 0.5%, and for Staphylococcus aureus, it is 1%.

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Pseudomonas aeruginosa is one of the most important causes of infection in medicine, which in recent years is known as an antibiotic resistant bacterium. One of the antibiotic resistance strategies of this bacterium is algD and PpyR genes expression for biofilm formation.

 In recent years, it has been shown that using microorganisms, such as probiotics, is a method of pathogen bacterium harnessing, hence, in this study, for preventing biofilm formation of P. aeruginosa, E.coli Nissle 1917(EcN) probiotic bacterium is used, as a new treatment choice.

Due to direct relationship between antibiotic resistance and biofilm formation, strains with the    

highest antibiotic resistance was chosen by antibiogram test. Then, in order to determine the inhibition rate of EcN bacterium in the formation of biofilm caused by P. aeruginosa bacterium, a biofilm formation test was performed.

At the end, to evaluate algD and PpyR genes expression, which were key parts of biofilm formation, in the presence of probiotic EcN bacterium, Real- time PCR method was used.

Based on the results of the biofilm formation test, EcN bacterium showed a high inhibitory effect on the formation of biofilm caused by P. aeruginosa bacterium.

.Also, in assessment of algD and PpyR genes expression in presence of EcN probiotic, a significant reduction in PpyR gene expression has been seen, in comparison with control group. The results of this study showed that EcN probiotic can act as a suitable new treatment option, to reduce P. aeruginosa biofilm formation.