Molecular characterization of the pilS2 gene and its association with the frequency of Pseudomonas aeruginosa plasmid pKLC102 and PAPI-1 pathogenicity island

Antibacterial and antibiofilm activity of silver nanoparticles stabilized with C-phycocyanin against drug-resistant Pseudomonas aeruginosa and Staphylococcus aureus

Background

Biofilms are bacterial communities that can protect them against external factors, including antibiotics. In this study, silver nanoparticles (AgNPs) were formed by modifying AgNPs with C-phycocyanin (Ag-Pc) to inhibit the growth of carbapenem-resistant Pseudomonas aeruginosa (CR P. aeruginosa) and methicillin-resistant Staphylococcus aureus (MRSA) and destroy biofilm of these bacteria.

Methods

The AgNPs were prepared with the green synthesis method, and Pc was used to stabilize the AgNPs. The Ag-Pc's antibacterial and antibiofilm effects were evaluated using the Microbroth dilution method and microtiter plate assay. The inhibitory effect of Ag-Pc on the expression of biofilm-related genes was evaluated by real-time PCR. Moreover, the MTT assay was used to assess the Ag-Pc toxicity.

Results

The Ag-Pc minimum inhibitory concentration (MIC) was 7.4 μg/mL for CR P. aeruginosa and MRSA. Pc did not show antibacterial effects against any of the strains. Ag-Pc suppressed biofilm formation and destroyed matured biofilm in both bacteria more efficiently than the AgNPs (P< 0.05). The expression of all genes was not significantly reduced in the presence of synthesized nanoparticles. Finally, the MTT assay results did not show toxicity against a murine fibroblast cell line (L929) at MIC concentration.

Conclusion

The present study showed the promising potential of Pc for improving the antibacterial and antibiofilm function of AgNPs and inhibiting drug-resistant bacteria. Therefore, Ag-Pc nanoparticles can be considered a promising therapeutic approach for the managing of the bacterial biofilm.

Exploiting immunopotential PAPI-1 encoded type IVb major pilin targeting Pseudomonas aeruginosa

Pseudomonas aeruginosa (P. aeruginosa) significantly contributes to nosocomial infections and necessitates research into novel treatment methods. For the first time, this research evaluated the immunoprotective potential of recombinant PAPI-1 encoded type IV pili targeting P. aeruginosa in BALB/C mice. The target sequence was identified, and a PilS2-encoding vector was constructed. The vector was then expressed and purified in E. coli BL21 (DE3). The PilS2 protein was inoculated into BALB/C mice in four groups, with or without alum, to measure total IgG, its subclasses, and cytokines. MTT and opsonophagocytosis tests were used to examine the immunological response. PilS2, especially when paired with alum, boosts the humoral immune response by enhancing IgG and IL-4 levels. However, PilS2 did not affect IL-17 or IFN-γ and only increased lymphocyte proliferation. Antibodies targeting PilS2 increased phagocytic cell death of P. aeruginosa by over 95 %, indicating possible therapies for P. aeruginosa infections. Our study on the immunopotentiation of P. aeruginosa PilS2 paves the way for pilin-based vaccines and immunotherapy targeting this pathogen.

Inhibitory effect of natural compounds on quorum sensing system in Pseudomonas aeruginosa: a helpful promise for managing biofilm community

Pseudomonas aeruginosa biofilm is a community of bacteria that adhere to live or non-living surfaces and are encapsulated by an extracellular polymeric substance. Unlike individual planktonic cells, biofilms possess a notable inherent resistance to sanitizers and antibiotics. Overcoming this resistance is a substantial barrier in the medical and food industries. Hence, while antibiotics are ineffective in eradicating P. aeruginosa biofilm, scientists have explored alternate strategies, including the utilization of natural compounds as a novel treatment option. To this end, curcumin, carvacrol, thymol, eugenol, cinnamaldehyde, coumarin, catechin, terpinene-4-ol, linalool, pinene, linoleic acid, saponin, and geraniol are the major natural compounds extensively utilized for the management of the P. aeruginosa biofilm community. Noteworthy, the exact interaction of natural compounds and the biofilm of this bacterium is not elucidated yet; however, the interference with the quorum sensing system and the inhibition of autoinducer production in P. aeruginosa are the main possible mechanisms. Noteworthy, the use of different drug platforms can overcome some drawbacks of natural compounds, such as insolubility in water, limited oral bioavailability, fast metabolism, and degradation. Additionally, drug platforms can deliver different antibiofilm agents simultaneously, which enhances the antibiofilm potential of natural compounds. This article explores many facets of utilizing natural compounds to inhibit and eradicate P. aeruginosa biofilms. It also examines the techniques and protocols employed to enhance the effectiveness of these compounds.

The therapeutic effect of engineered phage, derived protein and enzymes against superbug bacteria

Defending against antibiotic-resistant infections is similar to fighting a war with limited ammunition. As the new century unfolded, antibiotic resistance became a significant concern. In spite of the fact that phage treatment has been used as an effective means of fighting infections for more than a century, researchers have had to overcome many challenges of superbug bacteria by manipulating phages and producing engineered enzymes. New enzymes and phages with enhanced properties have a significant impact on the ability to fight antibiotic-resistant infections, which is considered a window of hope for the future. This review, therefore, illustrates not only the challenges caused by antibiotic resistance and superbug bacteria but also the engineered enzymes and phages that are being developed to solve these issues. Our study found that engineered phages, phage proteins, and enzymes can be effective in treating superbug bacteria and destroying the biofilm caused by them. Combining these engineered compounds with other antimicrobial substances can increase their effectiveness against antibiotic-resistant bacteria. Therefore, engineered phages, proteins, and enzymes can be used as a substitute for antibiotics or in combination with antibiotics to treat patients with superbug infections in the future.

Unraveling the immunopotentiation of P. aeruginosa PAPI-1 encoded pilin: From immunoinformatics survey to active immunization

For protection against Pseudomonas aeruginosa strains, a number of vaccine candidates have been introduced thus far. However, despite significant attempts in recent years, there are currently no effective immunogenic Bacteria components against this pathogen on the market. P. aeruginosa encoding a number of different virulence characteristics, as well as the rapid growth in multiple drug-resistant forms, has raised numerous health issues throughout the world. This pathogen expresses three different subtypes of T4P, including IVa, IVb, and Tad which are involved in various cellular processes. Highly virulent strains of P. aeruginosa can encode well-conserved PAPI-1 associated PilS2 pilus. Designing an efficient pili-based immunotherapy approach targeting P. aeruginosa pilus has remained controversial due to the variability heterogeneousness and hidden well-preserved binding site of T4aP and no approved human study is commercially based on IVa pilin. In this investigation, for the first time, through analytical immunoinformatics, we designed an effective chimeric PilS2 immunogen against numerous clinically important P. aeruginosa strains. Through active immunization against the extremely conserved region of the chimeric PilS2 pilin, we showed that PilS2 chimeric pilin whether administered alone or formulated with alum as an adjuvant could substantially stimulate humoral immunological responses in BALB/c mice. Based on these findings, we conclude that PilS2 pilin is therapeutically effective against a variety of highly virulent strains of P. aeruginosa and can act as a new immunogen for more research towards the creation of efficient immunotherapy techniques against the P. aeruginosa as a dexterous pathogen.

Virtual Screening of Potential RoxS Inhibitors and Evaluation of Their Antimicrobial Activity in Combination with Antibiotics against Clinically Resistant Bacteria

Pseudomonas aeruginosa with difficult-to-treat resistance has been designated as an urgent or serious threat by the CDC in the United States; therefore, novel antibacterial drugs and combination strategies are urgently needed. The sensor kinase RoxS is necessary for the aerobic growth of Pseudomonas aeruginosa. This study aimed to screen candidate RoxS inhibitors and evaluate their efficacy in treating multi-drug-resistant and extensively drug-resistant Pseudomonas aeruginosa in combination with meropenem and amikacin to identify promising combination strategies. RoxS protein structures were constructed using homology modeling and potential RoxS inhibitors, including Ezetimibe, Deferasirox, and Posaconazole, were screened from the FDA-approved ZINC drug database using molecular docking and molecular dynamics simulations. MIC and checkerboard assays were used to determine the in vitro antimicrobial efficacy of the three drugs in combination with antibiotics. The results of in vitro experiments showed an additive effect of 100 μg/mL Deferasirox or 16 μg/mL Posaconazole in combination with meropenem and a synergistic effect of 1.5 μg/mL Deferasirox and amikacin. In summary, these three drugs are potential inhibitors of RoxS, and their combination with meropenem or amikacin is expected to reverse the resistance of P. aeruginosa, providing new combination strategies for the treatment of clinically difficult-to-treat Pseudomonas aeruginosa.

Immortelle (Helichrysum italicum (Roth) G. Don) Essential Oil Showed Antibacterial and Biofilm Inhibitory Activity against Respiratory Tract Pathogens

The biofilm formation of bacteria in different parts of the human body can influence the success of antibiotic therapy. Essential oils (EOs) and their components are becoming increasingly popular in point of view of medicinal applications, because of their antibacterial efficacy. The immortelle EO has been used traditionally as an expectorant; however, there are no studies summarizing its antibacterial effect against respiratory tract bacteria. Our aim was to investigate the antibacterial and biofilm inhibitory activity of immortelle (Helichrysum italicum) EO against respiratory tract pathogens such as Haemophilus influenzae, H. parainfluenzae, Pseudomonas aeruginosa and Streptococcus pneumoniae. In order to prove the antibacterial effect of the immortelle EO, broth microdilution and biofilm inhibition tests, and membrane damage assay were investigated. Scanning electron microscopy was used to identify the structural modifications in bacterial cells. Our results showed that immortelle EO has antibacterial and anti-biofilm effects against respiratory tract bacteria used in this study. H. parainfluenzae was the most sensitive to each treatment, however, P. aeruginosa was the most resistant bacteria. In conclusion, the studied EO may have a role in the treatment of respiratory tract infections due to their antibacterial and anti-biofilm activity.

Molecular determination of O25b/ST131 clone type among extended spectrum β-lactamases production Escherichia coli recovering from urinary tract infection isolates

Background

Escherichia coli (E. coli) O25b/ST131 clone causes urinary tract infection (UTI) and is associated with a broad spectrum of other infections, such as intra-abdominal and soft tissue infections, that can be affecting bloodstream infections. Therefore, since O25b/ST131 has been reported in several studies from Iran, in the current study, we have investigated the molecular characteristics, typing, and biofilm formation of O25b/ST131 clone type E. coli collected from UTI specimens.

Methods

A total of 173 E. coli isolates from UTI were collected. The susceptibility to all fourth generations of cephalosporins (cefazolin, cefuroxime, ceftriaxone, cefotaxime, ceftazidime, cefepime) and ampicillin, ampicillin-sulbactam and aztreonam was determined. Class A ESBLs, class D ESBL and the presence of pabB gene screenings to detect of O25b/ST131 clone type were performed by using of PCR. Biofilm formation was compared between O25b/ST131 isolates and non-O25b/ST131 isolates. Finally, ERIC-PCR was used for typing of ESBL positive isolates.

Results

Ninety-four ESBL positive were detected of which 79 of them were O25b/ST131. Antimicrobial susceptibility test data showed that most antibiotics had a higher rate of resistance in isolates of the O25b/ST131 clonal type. Biofilm formation showed that there was a weak association between O25b/ST131 clone type isolates and the level of the biofilm formation. ERIC-PCR results showed that E. coli isolates were genetically diverse and classified into 14 groups.

Conclusion

Our results demonstrated the importance and high prevalence of E. coli O25b/ST131 among UTI isolates with the ability to spread fast and disseminate antibiotic resistance genes.

Antibacterial efficacy of lytic phages against multidrug-resistant Pseudomonas aeruginosa infections in bacteraemia mice models

BACKGROUND

Pseudomonas aeruginosa is an opportunistic pathogen that can cause a variety of infections in humans, such as burn wound infections and infections of the lungs, the bloodstream and surgical site infections. Nosocomial spread is often concurrent with high degrees of antibiotic resistance. Such resistant strains are difficult to treat, and in some cases, even reserved antibiotics are ineffective. A particularly promising therapy to combat infections of resistant bacteria is the deployment of bacteriophages, known as phage therapy. In this work, we evaluated the in vivo efficacy of two Pseudomonas phages in bacteremia mice models. For this study, non-neutropenic mice (BalB/C) were infected with P. aeruginosa AB030 strain and treated using two bacteriophages, AP025 and AP006.

RESULTS

The results showed that a single dose of phages at higher concentrations, bacteria: phage at 1:10 and 1:100 were effective in eliminating the bloodstream infection and achieving 100% mice survival.

CONCLUSION

This study highlights the efficacy of using a single dose of phages to restore mice from bacteremia.

Cinnamomum: The New Therapeutic Agents for Inhibition of Bacterial and Fungal Biofilm-Associated Infection

Due to the potent antibacterial properties of Cinnamomum and its derivatives, particularly cinnamaldehyde, recent studies have used these compounds to inhibit the growth of the most prevalent bacterial and fungal biofilms. By inhibiting flagella protein synthesis and swarming motility, Cinnamomum could suppress bacterial attachment, colonization, and biofilm formation in an early stage. Furthermore, by downregulation of Cyclic di‐guanosine monophosphate (c‐di‐GMP), biofilm-related genes, and quorum sensing, this compound suppresses intercellular adherence and accumulation of bacterial cells in biofilm and inhibits important bacterial virulence factors. In addition, Cinnamomum could lead to preformed biofilm elimination by enhancing membrane permeability and the disruption of membrane integrity. Moreover, this substance suppresses the Candida species adherence to the oral epithelial cells, leading to the cell wall deformities, damage, and leakages of intracellular material that may contribute to the established Candida’s biofilm elimination. Therefore, by inhibiting biofilm maturation and destroying the external structure of biofilm, Cinnamomum could boost antibiotic treatment success in combination therapy. However, Cinnamomum has several disadvantages, such as poor solubility in aqueous solution, instability, and volatility; thus, the use of different drug-delivery systems may resolve these limitations and should be further considered in future investigations. Overall, Cinnamomum could be a promising agent for inhibiting microbial biofilm-associated infection and could be used as a catheter and other medical materials surface coatings to suppress biofilm formation. Nonetheless, further in vitro toxicology analysis and animal experiments are required to confirm the reported molecular antibiofilm effect of Cinnamomum and its derivative components against microbial biofilm.

PLGA-Based Nanoplatforms in Drug Delivery for Inhibition and Destruction of Microbial Biofilm

The biofilm community of microorganisms has been identified as the dominant mode of microbial growth in nature and a common characteristic of different microorganisms such as Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis. The biofilm structure helps in the protection from environmental threats including host immune system and antimicrobial agents. Thus, the biofilm community has led to a higher prevalence of multidrug-resistant (MDR) strains in recent years. In this regard, the use of a new class of antibiotics, natural compounds, and anti-biofilm enzymes has been considered for the destruction of the microbial biofilm. However, different drawbacks such as low penetration, high susceptibility to degradation, instability, and poor solubility in aqueous solutions limit the use of anti-biofilm agents (ABAs) in a clinical setting. As such, recent studies have been using poly lactic-co-glycolic acid (PLGA)-based nanoplatforms (PLGA NPFs) for delivery of ABAs that have reported promising results. These particles, due to proper drug loading and release kinetics, could suppress microbial attachment, colonization, and biofilm formation for a long time. Additionally, PLGA NPFs, because of the high drug-loading efficiencies, hydrophilic surface, negative charge, and electrostatic interaction, lead to effective penetration of antibiotics to the deeper layer of the biofilm, thereby eliminating the microbial biofilm. Thus, PLGA NPFs could be considered as a potential candidate for coating catheters and other medical material surfaces for inhibition and destruction of the microbial biofilm. However, the exact interaction of PLGA NPFs and the microbial biofilm should be evaluated in animal studies. Additionally, a future goal will be to develop PLGA formulations as systems that can be used for the treatment of the MDR microbial biofilm, since the exact interactions of PLGA NPFs and these biofilm structures are not elucidated. In the present review article, we have discussed various aspects of PLGA usage for inhibition and destruction of the microbial biofilm along with different methods and procedures that have been used for improving PLGA NPF efficacy against the microbial biofilm.

Isolation of a lytic bacteriophage against extensively drug-resistant Acinetobacter baumannii infections and its dramatic effect in rat model of burn infection

Objectives

Acinetobacter Baumannii is an opportunistic nosocomial pathogen belonging to the Moraxellaceae family. The emergence of multidrug resistant strains of this pathogen caused many problems for hospitals and patients. The aim of the current study was to isolate, identify, and morphologically, physiologically, and in vivo analyze a new lytic bacteriophage targeting extensively drug‐resistant (XDR) A. baumannii.

Materials and Methods

Different wastewater samples were tested for isolation of lytic bacteriophage against 19 A. baumannii isolates obtained from patients hospitalized in a hospital in Arak, Iran, from January 2019 to March 2019. The phenotypic and genotypic characteristics of A. baumannii strains (resistance genes including: adeA, adeB, adeC, adeR, adeS, ISAba1, blaOXA‐23, blaOXA‐24) were analyzed. The isolated phage characteristics including adsorption time, pH and thermal stability, host range, one‐step growth rate, electron microscopy examination, and therapeutic efficacy of the phage were also investigated. Therapeutic efficacy of the phage was evaluated in a rat model with burn infection of XDR A. baumannii. The lesion image was taken on different days after burning and infection induction and was compared with phage untreated lesions.

Results

The results showed unique characteristics of the isolated phage (vB‐AbauM‐Arak1) including high specificity for Acinetobacter baumannii, stability at a relatively wide range of temperatures and pH values, short adsorption time, short latent period, and large burst size. In relation to the therapeutic efficacy of the phage, the lesion area decreased in phage‐treated groups over 14 days than in those untreated, significantly (p < 0.05).

Conclusion

Our findings demonstrated that isolated lytic phage was able to eliminate burn infections caused by XDR A. baumannii in a rat model. So, it may be recommended as alternative options toward to developing a treatment for extensively drug resistant Acinetobacter infections.

Prevalence of algD, pslD, pelF, Ppgl, and PAPI-1 Genes Involved in Biofilm Formation in Clinical Pseudomonas aeruginosa Strains

Introduction

Biofilm formation is one of the main virulence factors in Pseudomonas aeruginosa infections. This study is aimed at investigating the presence of genes involved in biofilm formation in clinical P. aeruginosa isolates. Material and Methods. A cross-sectional study was conducted on 112 P. aeruginosa isolates. The biofilm formation assay was performed on all isolates. Antimicrobial resistance was determined by the disk diffusion method, and the presence of genes was detected by polymerase chain reaction. Isolates were typed with Rep-PCR.

Results

The results of biofilm formation demonstrated that 85 strains (75.9%) were biofilm producers, and 27 strains (24.1%) were nonproducer isolates. Antibiotic susceptibility pattern in biofilm-positive and biofilm-negative isolates obtained from hospitalized patients showed a high rate of antibiotic resistance to amoxicillin with 95.7% and 92.3%, respectively. Based on PCR amplification results, the frequency of genes involved in biofilm formation among all isolates was as follows: algD (78.6%), pelF (70.5%), pslD (36.6%), Ppgl (0%), and PAPI-1 (77.6%). Rep-PCR typing demonstrated that 112 P. aeruginosa isolates were classified into 57 types according to 70% cut-off. The predominant type was A which contained 15 isolates. Moreover, 7 isolates were clustered in genotype B, followed by C type (6), D (4), E (4), F (4), G (4), H (3), I (3), J (3 isolates), and 12 genotypes, each containing two isolates. Also, 35 isolates were distributed in scattered patterns and showed single types.

Conclusion

Study results showed significant association between biofilm formation and resistance to antibiotics such as ceftazidime and meropenem. Analysis of Rep-PCR patterns indicated that the evaluated isolates were heterogeneous, relatively.

Evaluation of phenotypic and genotypic patterns of aminoglycoside resistance in the Gram-negative bacteria isolates collected from pediatric and general hospitals

The purpose of the current study was to evaluate the phenotypic and genotypic patterns of aminoglycoside resistance among the Gram-negative bacteria (GNB) isolates collected from pediatric and general hospitals in Iran. A total of 836 clinical isolates of GNB were collected from pediatric and general hospitals from January 2018 to the end of December 2019. The identification of bacterial isolates was performed by conventional biochemical tests. Susceptibility to aminoglycosides was evaluated by the disk diffusion method (DDM). The frequency of genes encoding aminoglycoside-modifying enzymes (AMEs) was screened by the PCR method via specific primers. Among all pediatric and general hospitals, the predominant GNB isolates were Acinetobacter spp. (n = 327) and Escherichia coli (n = 144). However, E. coli (n = 20/144; 13.9%) had the highest frequency in clinical samples collected from pediatrics. The DDM results showed that 64.3% of all GNB were resistant to all of the tested aminoglycoside agents. Acinetobacter spp. and Klebsiella pneumoniae with 93.6%, Pseudomonas aeruginosa with 93.4%, and Enterobacter spp. with 86.5% exhibited very high levels of resistance to gentamicin. Amikacin was the most effective antibiotic against E. coli isolates. In total, the results showed that the aac (6')-Ib gene with 59% had the highest frequency among genes encoding AMEs in GNB. The frequency of the surveyed aminoglycoside-modifying enzyme genes among all GNB was found as follows: aph (3')-VIe (48.7%), aadA15 (38.6%), aph (3')-Ia (31.3%), aph (3')-II (14.4%), and aph (6) (2.6%). The obtained data demonstrated that the phenotypic and genotypic aminoglycoside resistance among GNB was quite high and it is possible that the resistance genes may frequently spread among clinical isolates of GNB.

Subinhibitory Concentrations of Biogenic Silver Nanoparticles Affect Motility and Biofilm Formation in Pseudomonas aeruginosa

Biogenic silver nanoparticles (bio-AgNPs) are increasingly recognized as an antibiofilm and antivirulence strategy against P. aeruginosa, a bacterium that causes chronic infections in immunocompromised and cystic fibrosis patients. This study aimed to investigate the effects of subinhibitory concentrations of bio-AgNPs on motility and biofilm formation in P. aeruginosa. Bio-AgNPs were synthesized via reduction of ionic silver catalyzed by cell-free culture filtrate from Fusarium oxysporum. A total of 17 P. aeruginosa isolates and strains were evaluated for swarming, swimming, and twitching motility in the presence and absence (control) of bio-AgNPs, including 10 clinical isolates from patients with and without cystic fibrosis, 5 environmental isolates obtained from the public water supply system, and 2 reference strains (PAO1 and PA14). Isolates were identified by biochemical and molecular methods. Minimum inhibitory concentrations (MICs) were determined by the broth microdilution method. Swarming, swimming, and twitching motility assays were performed in Petri dishes. Biofilm formation capacity was assessed quantitatively by the crystal violet method. MIC values ranged from 15.62 to 62.50 µM. The results showed that subinhibitory concentrations of bio-AgNPs (½ MIC, 7.81-31.25 µM) significantly increased (p < 0.05) swarming, swimming, and twitching motility in 40.0, 40.0, and 46.7% of isolates, respectively. Subinhibitory bio-AgNP treatment enhanced (p < 0.05) biofilm formation capacity in PA14 and a cystic fibrosis isolate (P11). It is concluded that subinhibitory concentrations of bio-AgNPs increased biofilm formation and swarming, swimming, and twitching motility in PA14 and some P. aeruginosa isolates. These virulence factors are directly involved with quorum-sensing systems. Further research should investigate the effects of AgNPs on P. aeruginosa quorum sensing to help elucidate their mechanism of action at subinhibitory concentrations.

Synergistic Effect of Tazobactam on Amikacin MIC in Acinetobacter baumannii Isolated from Burn Patients in Tehran, Iran

BACKGROUND

Burn is still an important global public health challenge. Wound colonization of antibiotic resistant bacteria such as Acinetobacter baumannii can lead to high morbidity and mortality in burn patients. The aim of this study was to evaluate the inhibitory effect of tazobactam on efflux pump, which can cause aminoglycoside resistant in A. baumannii isolated from burn patients.

METHODS

In this study, 47 aminoglycoside resistant A. baumannii spp. were obtained from burn patients, admitted to the Shahid Motahari Burns Hospital in Tehran, Iran, during June-August 2018. The inhibitory effect of tazobactam against adeB such as efflux pump was evaluated by Minimum Inhibitory Concentration (MIC) determination of amikacin alone and in combination with tazobactam. Fractional Inhibitory Concentration index (FIC) was used to determine the efficacy of tazobactam/ amikacin combination. Further, semi-quantitative Real- Time PCR was performed to quantify the expression rates of the adeB gene before and after addition of tazobactam/amikacin.

RESULTS

The MIC values were significantly reduced when a combined amikacin and tazobactam was utilized. The most common interaction observed was synergistic (78.2%), followed by.additive effects (21.8%), as per FIC results. The adeB mRNA expression levels were found to be downregulated in 60.7% of isolates treated with tazobactam.

CONCLUSION

Tazobactam can have impact on resistance to aminoglycoside by inhibiting efflux pump. Thus, the combination of tazobactam with amikacin can be used as an alternative treatment approach in multidrug resistant A. baumannii infections.

Bacteriophage therapy against Pseudomonas aeruginosa biofilms: a review

Multi-Drug Resistant (MDR) Pseudomonas aeruginosa is one of the most important bacterial pathogens that causes infection with a high mortality rate due to resistance to different antibiotics. This bacterium prompts extensive tissue damage with varying factors of virulence, and its biofilm production causes chronic and antibiotic-resistant infections. Therefore, due to the non-applicability of antibiotics for the destruction of P. aeruginosa biofilm, alternative approaches have been considered by researchers, and phage therapy is one of these new therapeutic solutions. Bacteriophages can be used to eradicate P. aeruginosa biofilm by destroying the extracellular matrix, increasing the permeability of antibiotics into the inner layer of biofilm, and inhibiting its formation by stopping the quorum-sensing activity. Furthermore, the combined use of bacteriophages and other compounds with anti-biofilm properties such as nanoparticles, enzymes, and natural products can be of more interest because they invade the biofilm by various mechanisms and can be more effective than the one used alone. On the other hand, the use of bacteriophages for biofilm destruction has some limitations such as limited host range, high-density biofilm, sub-populate phage resistance in biofilm, and inhibition of phage infection via quorum sensing in biofilm. Therefore, in this review, we specifically discuss the use of phage therapy for inhibition of P. aeruginosa biofilm in clinical and in vitro studies to identify different aspects of this treatment for broader use.

Bacteriophages, a New Therapeutic Solution for Inhibiting Multidrug-Resistant Bacteria Causing Wound Infection: Lesson from Animal Models and Clinical Trials

Wound infection kills a large number of patients worldwide each year. Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa are the most important colonizing pathogens of wounds that, with various virulence factors and impaired immune system, causes extensive tissue damage and nonhealing wounds. Furthermore, the septicemia caused by these pathogens increases the mortality rate due to wound infections. Because of the prevalence of antibiotic resistance in recent years, the use of antibiotics to inhibit these pathogens has been restricted, and the topical application of antibiotics in wound infections increases antibiotic resistance. Therefore, finding a new therapeutic strategy against wound infections is so essential since these infections have a destructive effect on the patient’s mental health and high medical costs. In this review, we discussed the use of phages for the prevention of multidrug-resistant (MDR) bacteria, causing wound infection and their role in wound healing in animal models and clinical trials. The results showed that phages have a high ability to inhibit different wound infections caused by MDR bacteria, heal the wound faster, have lower side effects and toxicity, destroy bacterial biofilm, and they are useful in controlling immune responses. Many studies have used animal models to evaluate the function of phages, and this study appears to have a positive impact on the use of phages in clinical practice and the development of a new therapeutic approach to control wound infections, although there are still many limitations.

Cyclin-dependent kinases and CDK inhibitors in virus-associated cancers

The role of several risk factors, such as pollution, consumption of alcohol, age, sex and obesity in cancer progression is undeniable. Human malignancies are mainly characterized by deregulation of cyclin-dependent kinases (CDK) and cyclin inhibitor kinases (CIK) activities. Viruses express some onco-proteins which could interfere with CDK and CIKs function, and induce some signals to replicate their genome into host's cells. By reviewing some studies about the function of CDK and CIKs in cells infected with oncoviruses, such as HPV, HTLV, HERV, EBV, KSHV, HBV and HCV, we reviewed the mechanisms of different onco-proteins which could deregulate the cell cycle proteins.

Wound healing properties and antimicrobial activity of platelet-derived biomaterials

We analyzed the potential antibacterial effects of two different PdB against methicillin-resistant S. aureus and P. aeruginosa. The third-degree burn wound healing effects of PdB was also studied. Blood samples were obtained from 10 healthy volunteers and biological assays of the PdB were performed and the antimicrobial activity against MRSA and P. aeruginosa was determined using disk diffusion (DD), broth microdilution (BMD), and time-kill assay methods. 48 Wistar albino rats were burned and infected with MRSA. Two groups were injected PdB, the control groups were treated with plasma and received no treatment respectively. In the next step, the rats were euthanized and skin biopsies were collected and histopathologic changes were examined. The results of DD and BMD showed that both PdB performed very well on MRSA, whereas P. aeruginosa was only inhibited by F-PdB and was less susceptible than MRSA to PdBs. The time-kill assay also showed that F-PdB has an antibacterial effect at 4 hours for two strains. Histopathological studies showed that the treated groups had less inflammatory cells and necrotic tissues. Our data suggest that PdB may possess a clinical utility as a novel topical antimicrobial and wound healing agent for infected burn wounds.

How Phages Overcome the Challenges of Drug Resistant Bacteria in Clinical Infections

Nowadays the most important problem in the treatment of bacterial infections is the appearance of MDR (multidrug-resistant), XDR (extensively drug-resistant) and PDR (pan drug-resistant) bacteria and the scarce prospects of producing new antibiotics. There is renewed interest in revisiting the use of bacteriophage to treat bacterial infections. The practice of phage therapy, the application of phages to treat bacterial infections, has been around for approximately a century. Phage therapy relies on using lytic bacteriophages and purified phage lytic proteins for treatment and lysis of bacteria at the site of infection. Current research indicates that phage therapy has the potential to be used as an alternative to antibiotic treatments. It is noteworthy that, whether phages are used on their own or combined with antibiotics, phages are still a promising agent to replace antibiotics. So, this review focuses on an understanding of challenges of MDR, XDR, and PDR bacteria and phages mechanism for treating bacterial infections and the most recent studies on potential phages, cocktails of phages, and enzymes of lytic phages in fighting these resistant bacteria.

Evaluation of Nano-curcumin effects on expression levels of virulence genes and biofilm production of multidrug-resistant Pseudomonas aeruginosa isolated from burn wound infection in Tehran, Iran

Background

P. aeruginosa is considered as one of the most important pathogens, and high antibiotic resistance to P. aeruginosa has become an alarming concern. This study attempts to further improve curcumin solubility and stability by producing the involved nanoparticle and investigate the effect of this nanoparticle on those virulence genes of P. aeruginosa in pathogenicity and biofilm formation.

Methods

In this study, the curcumin nanoparticles were synthesized and characterized, and the antibacterial and antibiofilm effects of Nano-curcumin and curcumin were investigated by microdilution broth and microtiter plate, respectively. In addition, cytotoxic effect of Nano-curcumin on human epithelial cell lines (A549) was determined. The effects of Nano-curcumin on P. aeruginosa virulence genes, mexD, mexB, and mexT (efflux pumps), lecA (adhesion), nfxB (negative regulator of MexCD-OprJ), and rsmZ (biofilm formation) were determined using real-time quantitative PCR.

Results

Synthesized Nano-curcumins were soluble in water, which inhibited the growth of multidrug-resistant (MDR) P. aeruginosa at 128 µg/mL, whereas it was inhibited at 256 µg/mL for soluble curcumin in DMSO. Sub-inhibitory concentrations of Nano-curcumin reduced biofilm formation and, at 64 μg/mL, disrupted 58% of the established bacterial biofilms. In addition, curcumin nanoparticle downregulated the transcription of virulence genes except nfxB and exerted no cytotoxic effect on human epithelial cell lines (A549).

Conclusions

Results suggest that Nano-curcumin could be potentially used to reduce P. aeruginosa virulence and biofilm. However, in vivo studies with respect to an animal model are necessary to validate these results.

Evaluating the antimicrobial resistance patterns among major bacterial pathogens isolated from clinical specimens taken from patients in Mofid Children's Hospital, Tehran, Iran: 2013-2018

BACKGROUND

This study evaluates the epidemiology and antimicrobial resistance profile of Gram-negative bacteria (GNB) and Gram-positive bacteria (GPB) isolated from clinical specimens in children admitted to Mofid Children's Hospital.

METHODS

This was a retrospective study of the patients' clinical specimens collected from January 2013 until the end of December 2018. All specimens were evaluated to determine the presence of infection-causing agents using a BACTEC 9120 blood culture. Isolation and identification of bacterial strains were performed using conventional biochemical tests. Antibiotic resistance was determined using Kirby-Bauer disk diffusion and broth microdilution methods. Results were interpreted according to CLSI and EUCAST.

RESULTS

A total of 1130 different pathogenic bacteria were detected from 14,690 different clinical specimens and the overall detection rate was 7.7% (1130/14,690). Among bacterial pathogen isolated from clinical specimens, 55% (n=622) were GNB and 45% (n=508) were GPB. The predominant GNB isolates were Pseudomonas aeruginosa, Klebsiella spp., Acinetobacter baumannii, Escherichia coli, Enterobacter spp., Citrobacter spp., respectively. Among GPB, CoNS was the most frequent and Enterococcus spp. was found to have low levels of resistance to linezolid. In GNB, most A. baumannii and P. aeruginosa were ceftriaxone resistant. P. aeruginosa was found to have low levels of resistance to levofloxacin and ciprofloxacin.

CONCLUSIONS

Our findings revealed that the resistance rate among GNB and GPB associated with different infections in children is very high. These results suggest a constant screening and follow-up programs for the detection of antibiotic resistance, and it also suggests to develop antimicrobial stewardship programs in Tehran, Iran.