A chimeric vaccine targeting Pseudomonas aeruginosa virulence factors protects mice against lethal infection.

Pseudomonas aeruginosa is an important and hazardous nosocomial pathogen in respiratory tract infections and rapidly achieves antibiotic resistance, so it is necessary to develop an effective vaccine to combat the infection. The Type III secretion system (T3SS) protein P. aeruginosa V-antigen (PcrV), outer membrane protein F (OprF), and two kinds of flagellins (FlaA and FlaB) all play important roles in the pathogenesis of P. aeruginosa lung infection and its spread into deeper tissues. In a mouse acute pneumonia model, the protective effects of a chimer vaccine including PcrV, FlaA, FlaB, and OprF (PABF) protein were investigated. PABF immunization prompted robust opsonophagocytic titer of IgG antibodies and decreased bacterial burden, and improved survival afterward intranasal challenge with ten times 50% lethal doses (LD50) of P. aeruginosa strains, indicating its broad-spectrum immunity. Moreover, these findings showed a promise chimeric vaccine candidate to treat and control P. aeruginosa infections.

Antibacterial effect of cerium oxide nanoparticle against Pseudomonas aeruginosa.

BACKGROUND: Antibiotics have been widely used for the treatment of bacterial infections for decades. However, the rapid emergence of antibiotic-resistant bacteria has created many problems with a heavy burden for the medical community. Therefore, the use of nanoparticles as an alternative for antibacterial activity has been explored. In this context, metal nanoparticles have demonstrated broad-spectrum antimicrobial activity. This study investigated the antimicrobial activity of naked cerium oxide nanoparticles dispersed in aqueous solution (CNPs) and surface-stabilized using Pseudomonas aeruginosa as a bacterial model. METHODS: Gelatin-polycaprolactone nanofibers containing CNPs (Scaffold@CNPs) were synthesized, and their effect on P. aeruginosa was investigated. The minimum inhibitory and bactericidal concentrations of the nanoparticls were determined in an ATCC reference strain and a clinical isolate strain. To determine whether the exposure to the nanocomposites might change the expression of antibiotic resistance, the expression of the genes shv, kpc, and imp was also investigated. Moreover, the cytotoxicity of the CNPs was assessed on fibroblast using flow cytometry. RESULTS: Minimum bactericidal concentrations for the ATCC and the clinical isolate of 50 µg/mL and 200 µg/mL were measured, respectively, when the CNPs were used. In the case of the Scaffold@CNPs, the bactericidal effect was 50 µg/mL and 100 µg/mL for the ATCC and clinical isolate, respectively. Interestingly, the exposure to the Scaffold@CNPs significantly decreased the expression of the genes shv, kpc, and imp. CONCLUSIONS: A concentration of CNPs and scaffold@CNPs higher than 50 µg/mL can be used to inhibit the growth of P. aeruginosa. The fact that the scaffold@CNPs significantly reduced the expression of resistance genes, it has the potential to be used for medical applications such as wound dressings.

Monoclonal antibody directed to the PilQ -PilA DSL region in Pseudomonas aeruginosa improves survival of infected mice with antibiotic combination.

The infections caused by Pseudomonas aeruginosa are related to high mortality and morbidity in critically ill patients because of multidrug resistance. Thus, we performed the efficacy of the monoclonal antibody (mAb) against PilQ -PilA DSL region (QA) in combination with antibiotics in a model of P. aeruginosa infection. In the present study, three clinically applicable antibiotics (levofloxacin, ceftazidime and gentamicin) and the anti-QA mAb were utilized for treatment of P. aeruginosa sepsis in mice. Reliably, in comparison with other treatment groups (antibody or antibiotic administration), the combination of antibiotic and anti-QA mAb essentially enhanced the survival of mice infected with P. aeruginosa PAO1. This synergistic effect was due to improved bactericidal effect, which prevented bacterial dissemination to different organs. Consequently, the antibiotic and anti-QA mAb combination gives a new effective strategy for the treatment of P. aeruginosa sepsis, particularly when large numbers of exceptionally virulent strains are present.

Inhibitory Effects of Lactococcus lactis and its Supernatant on Listeria monocytogenes.

BACKGROUND: The application of biological compounds generated by lactic acid bacteria, especially Lactococcus lactis, is recently considered to be a natural preservative for improving quality and health of food. The purpose of this study is to investigate the inhibitory potential of L. lactis supernatant on the expression of inlA, plc, and hly genes related to L. monocytogenes virulence capacity. METHODS: L. lactis was cultured under anaerobic conditions for 16 - 18 hours. The supernatant and live bacteria were then separated by centrifuge. The antilisteria effects of L. lactis and supernatant were measured using the agar diffusion technique, and the effect on the expression of the virulence-related genes was calculated by real-time PCR. Also, the effects of live bacteria and its supernatant on the microbial count of milk and sausage infected by L. monocytogenes was evaluated by the colony count assay. RESULTS: After 24 hours, the highest non-growing hole diameter was obtained in the presence of acidic supernatant (pH = 3.5). The microbial count showed the inhibitory effect on the eighth day after incubation with L. lactis. qPCR data revealed a down-regulation of virulence-related genes of inlA (8 fold), hly (6 fold), and plc (1 fold) in L. monocytogenes after 24-hour incubation with the supernatant. CONCLUSIONS: Our findings showed that the supernatant of L. lactis has an effective inhibitory role in the growth of L. monocytogenes. In the presence of supernatant, among plc, inlA and hly genes, the expression of inlA and hly genes decreased after 2 hours, which could indicate the molecular inhibitory mechanism of L. lactis in L. monocytogenes.

Analysis of virulence genes and molecular typing of Listeria monocytogenes isolates from human, food, and livestock from 2008 to 2016 in Iran.

The frequency of Listeria monocytogenes isolates collected from a total of 1150 samples including food (n = 300), livestock (n = 50), and human clinical (n = 800) was evaluated during 2008-2016. Antimicrobial resistance patterns, virulence factors, and molecular characteristics of these isolates were analyzed using disk diffusion method, sequencing, serotyping, and pulsed-field gel electrophoresis (PFGE). The analysis of 44 L. monocytogenes isolates showed that 72.7% (32 of 44) of all the isolates belonged to Serotype 1/2c, and 15.9% (7 of 44) belonged to Serotype 3c. All 44 isolates were resistant to one or more antimicrobial agents with the most frequent resistance to penicillin (75%) and tetracycline (47.7%). Of the 44 L. monocytogenes strains, 100, 69.2, and 62.5% of livestock, human, and food strains were resistant to penicillin, respectively. Using pulsed-field gel electrophoresis (PFGE) technique, the isolates' genetic diversity was determined, and 28 PFGE patterns with 8 common (CT) and 20 single types (ST) were identified. This study highlights the high prevalence of Serotype 1/2c in clinical and livestock samples, while different serotypes were observed in food samples. The presence of rare serotypes such as 4c, belonging to the Lineage III, as well as 4e and 1/2c which are infrequent in Iran indicates that paying attention to uncommon serotypes, especially 1/2c, during the listeriosis outbreaks is necessary.

A trivalent vaccine consisting of "flagellin A+B and pilin" protects against Pseudomonas aeruginosa infection in a murine burn model.

Pseudomonas aeruginosa is a common nosocomial pathogen in burn patients, and rapidly achieves antibiotic resistance, and thus, developing an effective vaccine is critically important for combating P. aeruginosa infection. Flagella and pili play important roles in colonization of P. aeruginosa at the burn wound site and its subsequent dissemination to deeper tissue and organs. In the present study, we evaluated protective efficacy of a trivalent vaccine containing flagellins A and B (FlaA + FlaB) + pilin (PilA) in a murine burn model of infection. "FlaA + FlaB + PilA" induced greater protection in P. aeruginosa murine burn model than the single components alone, and it showed broad immune protection against P. aeruginosa strains. Immunization with "FlaA + FlaB + PilA" induced strong opsonophagocytic antibodies and resulted in reduced bacterial loads, systemic IL-12/IL-10 cytokine expression, and increased survival after challenge with three times lethal dose fifty (LD50) of P. eruginosa strains. Moreover, the protective efficacy of "FlaA + FlaB + PilA" vaccination was largely attributed to specific antibodies. Taken together, these data further confirm that the protective effects of "FlaA + FlaB + PilA" vaccine significantly enhance efficacy compared with antibodies against either mono or divalent antigen, and that the former broadens the coverage against P. eruginosa strains that express two of the three antigens.

Evaluation of cell-penetrating peptide-peptide nucleic acid effect in the inhibition of cagA in Helicobacter pylori.

Helicobacter pylori is the most common cause of chronic infection in human and is associated with gastritis, peptic ulcer disease, and adenocarcinoma of mucosa-associated lymphoid tissue cells. Peptide nucleic acid (PNA) is a synthetic compound, which can inhibit the production of a particular gene. This study aimed to investigate the effect of PNA on inhibiting the expression of cagA. After confirmation of the desired gene by polymerase chain reaction (PCR), the antisense sequence was designed against cagA gene. The minimum inhibitory concentrations of conjugated PNA against H. pylori was determined. The effect of the compound on the expression level of the cagA was investigated in HT29 cell culture using real-time PCR. The results showed 2 and 3 log reduction in bacterial count after 8- and 24-h treatment with 4 and 8 µM of the compound, respectively. The lowest expression level of the cagA gene was observed at a concentration of 8 µM after 6 h. The results of this study showed that cell-penetrating peptide antisense can be employed as effective tools for inhibiting the target gene mRNA for various purposes. Moreover, further research is necessary to assess the potency, safety, and pharmacokinetics of CPP-PNAs for clinical prevention and treatment of infections due to H. pylori.

Targeting Listeria monocytogenes consensus sequence of internalin genes using an antisense molecule.

As an intracellular pathogen, Listeria monocytogenes can enter host cells where it can replicate and escape detection and eradication by the host immune response making the clearance of infection very challenging. Furthermore, with the advent of antimicrobial resistance, the need for alternative targets is inevitable. Internalin proteins are crucial to this bacterium as they contribute to bacterial entry to the systemic circulation. In this study, we targeted a highly conserved region of these proteins by an antisense sequence that was covalently conjugated to the cell penetrating peptides (CPP) to overcome the challenging delivery barriers. Then, we evaluated the efficiency of this construct in vitro. We also assessed the antigenicity, cytotoxicity, and probability of apoptosis induction by this construct. The studied CPP-PNA inhibited bacterial growth and suppressed the mRNA expression of internalins in a dose-dependent manner. In addition, at all studied concentrations, CPP-PNA significantly reduced the invasion rate of L. monocytogenes in the examined cell lines. Moreover, different concentrations of CPP-PNA did not have a significant antigenic, cytotoxic, and apoptotic properties compared to the control. These results suggest the effectiveness of CPP-antisense in targeting the mRNAs of internalins for various research, therapeutic and preventive purposes. However, additional research is required to evaluate the potency, safety, and pharmacokinetics of this compound for the prevention and treatment of listeriosis.

Putative type II toxin-antitoxin systems in Listeria monocytogenes isolated from clinical, food, and animal samples in Iran.

Listeria monocytogenes is known as a major food-borne pathogen causing a severe life-threatening disease, listeriosis, in susceptible patients. This bacterium has special features that facilitate its survival in different conditions and cause resistance to antibacterial agents and biocides. Toxin-antitoxin (TA) system has a potential to be introduced as an antibacterial target because of its participation in cell physiology, including stress response, antiphage activity, biofilm formation, and resistance to antibiotics. In this study, after the identification of 6 genes of 3 TA pairs (lM/E-lM/F, lM/S-lM/B and ydc/D-ydc/E) via existing databases, the presence and expression level of these genes were investigated by PCR and q-PCR techniques, respectively. The result of RT-qPCR revealed that identified genes were expressed in different strains and ydc (maz) increased under thermal stress. It seems that the products of these genes play an important role in the physiology and survival of the bacterium especially in heat stress. Presence of 6 detected TA genes in all of the tested isolates demonstrated that TA system could be an antibacterial target in L. monocytogenes; however, more research is needed to explain the actual role of these genes.

Bivalent flagellin immunotherapy protects mice against Pseudomonas aeruginosa infections in both acute pneumonia and burn wound models.

Pseudomonas aeruginosa infections are a serious challenge to therapy because of the complex pathogenesis and paucity of new effective antibiotics, thus renewing interest in antibody-based therapeutic strategies. Immunotherapy strategies typically target selected virulence factors that are expressed by the majority of clinical strains of P. aeruginosa, particularly because virulence factors mediate infection. Type a and b flagellins (flagellin a+b) of P. aeruginosa are acute virulence factors that play a major role in the establishment of infection. Here we evaluate the protective efficacy of antibodies raised against "flagellin a+b" in both acute pneumonia and burn models. A combination strategy using antibodies against "flagellin a+b" provided greater protection against cell invasion and enhanced opsono-phagocytosis and decreased motility of P. aeruginosa strains, compared to strategies using antibodies against a single flagellin. Antibodies against "flagellin a+b"-protected mice infected with P. aeruginosa strains significantly reduced bacterial dissemination from the site of infection to the liver and spleen. Passive immunization with antibodies against "flagellin a+b" led to an efficacious protection against P. aeruginosa infection in both acute pneumonia and burn models.

Antibodies raised against divalent type b flagellin and pilin provide effective immunotherapy against Pseudomonas aeruginosa infection of mice with burn wounds.

Burn wound infections caused by multidrug-resistant Pseudomonas aeruginosa strains are a serious challenge to therapy because of the complex pathogenesis and paucity of new effective antibiotics. Therefore, there is renewed interest in developing antibody-based therapeutic strategies. Immunotherapy strategies typically target selected virulence factors that are expressed by the majority of clinical strains of P. aeruginosa, particularly because virulence factors mediate infection. Here we used a murine model of burn wound infection to evaluate the efficacy of antibodies raised against the divalent type b flagellin and PilA (flagellin b + PilA), as acute virulence factors, to prevent and treat infection. Antibodies to flagellin b + PilA exhibited superior synergistic effects that improved opsono-phagocytosis and cell invasion compared with antibodies to each monovalent flagellin b or PilA. Further, when used for prophylaxis, the antibodies against flagellin b + PilA and combined therapeutic and prophylactic regimens markedly improved the survival of mice infected with disparate P. aeruginosa strains from 91.6% to 100% compared with treatment using imipenem. Therefore, antibodies against flagellin b + PilA interfere with the activities of their respective cognate individual target antigens and enhance coverage against clinical strains of P. aeruginosa that may not express one of these two virulence factors.

Passive immunization against Pseudomonas aeruginosa recombinant PilA in a murine burn wound model.

Pseudomonas aeruginosa type IV pili have an essential role in twitching motility, colonization and biofilm formation. In this study, we investigated the efficacy of intraperitoneal administration of rabbit anti-recombinant PilA (anti-r-PilA) immunoglobulin G (IgG) against P. aeruginosa infection in a mouse burn-wound model. After burn and infection, mortality rate was assessed in all mice, and that of mice passively immunized with rabbit anti-r-PilA IgG was compared to non-immunized mice. Bacterial quantities in the skin and internal organs were measured to determine the level of systemic infection. Results showed that passive immunotherapy with anti-r-PilA IgG protected the burned mice infected with P. aeruginosa strains, PAO1 and the clinical isolate (CI). Anti-r-PilA antibodies enhanced the opsonophagocytosis of these strains. Moreover, the administration of anti-r-PilA IgG was also successful in reducing the bacterial burden in infected mice. The reduction of systemic bacterial spread increased the survival rate of passively immunized mice. Findings of this study revealed an improved survival rate of 62.5%, thus confirming the protective effect of anti-r-PilA IgG.

Antimicrobial resistance of Listeria monocytogenes isolated from seafood and humans in Iran.

Fourteen Listeria monocytogenes isolates previously collected from seafood (n = 7) and human patients (n = 7) were studied for their antimicrobial susceptibility against eight common antimicrobials (ampicillin, penicillin, gentamicin, streptomycin, tetracycline, trimethoprim-sulfamethoxazole, chloramphenicol, and cefotaxime). A high resistance level to ampicillin, cefotaxime (100%), and pencillin (57% in seafood isolates and 71.4% in clinical isolates) was observed in this study. However, all of the isolates were susceptible to trimethoprim-sulfamethoxazole, chloramphenicol, and tetracycline. Simultaneous resistance was identified in 4 clinical isolates (57.1%). Genotypic characterization of fish isolates (isolated from three fish species) was performed by pulsed-field gel electrophoresis (PFGE). A high diversity among fish isolates was observed. PFGE analyses distinguished the 4 isolates into 4 reproducible pulsotypes. There was no correlation between the antibiograms with pulsotypes. In conclusion, the resistance of seafood isolates to the antibiotics commonly used to treat listeriosis could be a potential health hazard for consumers.

Effectiveness of photodynamic therapy on the treatment of chronic periodontitis: a systematic review during 2008-2023.

Objective: This study investigated the effect of photodynamic therapy on chronic periodontitis patients and then evaluated the microbial, immunological, periodontal, and clinical outcomes. The significant effects of photodynamic therapy obtained by in vitro and in vivo studies have made it a popular treatment for periodontal diseases in recent years. Photodynamic therapy is a novel bactericidal strategy that is stronger, faster, and less expensive than scaling and root planing. Method: This study registered on PROSPERO (CRD42021267008) and retrieved fifty-three randomized controlled trials by searching nine databases (Medline, Embase, Scopus, Open Gray, Google Scholar, ProQuest, the Cochrane Library, Web of Science, and ClinicalTrials.gov) from 2008 to 2023. Of 721 records identified through database searches following title and full-text analysis, and excluding duplicate and irrelevant publications, 53 articles were included in this systematic review. Fifty of the 53 eligible studies fulfilled all the criteria in the Joanna Briggs Institute's (JBI's) Checklist for RCTs; the remaining articles met 9-12 criteria and were considered high quality. Results: The present study showed that photodynamic therapy in adjunct to scaling and root planing has the potential to improve periodontal parameters such as clinical attachment loss or gain, decrease in bleeding on probing, and probing pocket depth. In addition, photodynamic therapy decreases the rate of periodontal pathogens and inflammation markers, which, in turn, reduces the progression of periodontitis. Conclusion: Photodynamic therapy is considered a promising, adjunctive, and low-cost therapeutic method that is effective in tissue repair, reducing chronic periodontitis, reducing inflammation, and well-tolerated by patients.

A hope for ineffective antibiotics to return to treatment: investigating the anti-biofilm potential of melittin alone and in combination with penicillin and oxacillin against multidrug resistant-MRSA and -VRSA.

Background: The emergence and rapid spread of multi-drug resistant (MDR) bacterial strains, such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant S. aureus (VRSA), have posed a significant challenge to the medical community due to their ability to form biofilm and develop resistance to common antibiotics. Traditional antibiotics that were once effective in treating bacterial infections are now becoming increasingly ineffective, leading to severe consequences for patient outcomes. This concerning situation has called for urgent research to explore alternative treatment strategies. Recent studies have shown that antimicrobial peptides (AMPs) hold promise as effective agents against biofilm-associated drug-resistant infections as well as to enhance the efficacy of conventional antibiotics. Accordingly, we aimed to investigate the antimicrobial and antibiofilm effects of melittin AMP, both alone and in combination with penicillin and oxacillin, against biofilm-forming MDR-MRSA and -VRSA. Methods: In this study, we investigated the kinetics of biofilm formation and assessed various parameters related to the antimicrobial and antibiofilm efficacy of melittin and antibiotics, both alone and in combination, against MDR-MRSA and -VRSA. The antimicrobial parameters included the Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Fractional Inhibitory Concentration Index (FICi), Fractional Bactericidal Concentration Index (FBCi), and the antibiofilm activity of melittin and antibiotics indicated by the Minimum Biofilm Inhibitory Concentration (MBIC), Minimal Biofilm Eradication Concentration (MBEC), Fractional Biofilm Inhibitory Concentration Index (FBICi), and Fractional Biofilm Eradication Concentration Index (FBECi). Results: The MIC results showed that all S. aureus isolates were resistant to penicillin (≥0.25 µg/mL), and 66% of isolates were resistant to oxacillin. The geometric means of the MIC values for penicillin, oxacillin, and melittin were 19.02, 16, and 1.62 µg/ml, respectively, and the geometric means of the MBC values for penicillin, oxacillin, and melittin were 107.63, 49.35, and 5.45 µg/ml, respectively. The study revealed that the combination indexes of melittin-penicillin and melittin-oxacillin, as determined by FIC values against all isolates, were 0.37 and 0.03, respectively. Additionally, melittin-penicillin and melittin-oxacillin exhibited combination indexes based on FBC values against all isolates at 1.145 and 0.711, respectively. Besides, melittin inhibited the biofilm formation of all S. aureus isolates, with MBIC values ranging from 10 to 1.25 µg/mL, and MBEC values ranging from 40 to 10 µg/mL. Generally, the combination indexes of melittin-penicillin and melittin-oxacillin, determined using FBIC values against all isolates, were 0.23 and 0.177, respectively. Moreover, melittin-penicillin and melittin-oxacillin typically had combination indexes based on FBEC values against all isolates at 5 and 2.97, respectively. Conclusion: In conclusion, our study provides evidence that melittin is effective against both planktonik and biofilm forms of MRSA and VRSA and exhibits significant synergistic effects when combined with antibiotics. These results suggest that melittin and antibiotics could be a potential candidate for further investigation for in vivo infections caused by MDR S. aureus. Furthermore, melittin has the potential to restore the efficacy of penicillin and oxacillin antibiotics in the treatment of MDR infections. Applying AMPs, like melittin, to revive beta-lactam antibiotics against MRSA and VRSA is an innovative approach against antibiotic-resistant bacteria. Further research is needed to optimize dosage and understand melittin mechanism and interactions with beta-lactam antibiotics for successful clinical applications.

Emerging role of microbiota derived outer membrane vesicles to preventive, therapeutic and diagnostic proposes.

The role of gut microbiota and its products in human health and disease is profoundly investigated. The communication between gut microbiota and the host involves a complicated network of signaling pathways via biologically active molecules generated by intestinal microbiota. Some of these molecules could be assembled within nanoparticles known as outer membrane vesicles (OMVs). Recent studies propose that OMVs play a critical role in shaping immune responses, including homeostasis and acute inflammatory responses. Moreover, these OMVs have an immense capacity to be applied in medical research, such as OMV-based vaccines and drug delivery. This review presents a comprehensive overview of emerging knowledge about biogenesis, the role, and application of these bacterial-derived OMVs, including OMV-based vaccines, OMV adjuvants characteristics, OMV vehicles (in conjugated vaccines), cancer immunotherapy, and drug carriers and delivery systems. Moreover, we also highlight the significance of the potential role of these OMVs in diagnosis and therapy.

Highly Synergistic Effects of Melittin With Vancomycin and Rifampin Against Vancomycin and Rifampin Resistant Staphylococcus epidermidis.

Methicillin-resistant Staphylococcus epidermidis (MRSE) strains are increasingly emerging as serious pathogens because they can be resistant to many antibiotics called multidrug resistance (MDR) that limit the therapeutic options. In the case of vancomycin- and rifampin-resistant MDR-MRSE, the physicians are not allowed to increase the doses of antibiotics because of severe toxicity. Accordingly, we investigated the synergistic activity of melittin antimicrobial peptide with vancomycin and rifampin against vancomycin-resistant, and rifampin-resistant MDR-MRSE isolates. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), fractional inhibitory concentration index (FICi), and fractional bactericidal concentration index (FBCi) of antimicrobial agents against isolates were determined. Coagulate activities and serum and salt stability as well as melittin cytotoxicity on the human embryonic kidney (HEK) 293 cells and human red blood cells (RBCs) at their synergistic concentrations. MIC and MBC values for melittin were in the range of 0.312-2.5 and 0.312-5, respectively. Results also showed that the interaction of melittin with drugs was highly synergistic in which the geometric means of FICi and FBCi were < 0.5. Induced synergism led to a decrease in melittin, rifampin, and vancomycin concentrations by 8-1,020, 2-16, and 4-16-folds, respectively. This phenomenon caused a reduction in melittin toxicity by which the synergistic concentration of melittin needed to kill bacteria did not show cytotoxicity and hemolytic activity. Besides, no coagulation activity was found for the synergistic and alone concentrations of melittin in both Prothrombin Time (PT) and Partial Thromboplastin Time (PTT). Interestingly, the antibacterial activity of melittin in Mueller Hinton Broth (MHB) containing human serum did no significant differences between MIC and MBC values of melittin in MHB and MHB containing 10% human serum. The present findings showed that the therapeutic index of melittin was improved by 32.08- and 12.82-folds when combined with vancomycin and rifampin, respectively. Taken together, the obtained data show that melittin alone was effective against MDR-MRSE isolates and this antimicrobial peptide showed highly synergistic effects with vancomycin and rifampin without causing toxicity. Therefore, the combination of melittin and traditional antibiotics could be a promising strategy for the treatment of infections caused by MDR-MRSE.

Passive immunization with anti- chimeric protein PilQ/PilA -DSL region IgY does not protect against mortality associated with Pseudomonas aeruginosa sepsis in a rabbit model.

BACKGROUND: Pseudomonas aeruginosa sepsis is associated with unacceptably high mortality and, for many of those who survive, long-term morbidity. The aims of this study were to production of IgY against chimeric protein pilQ-pilA-DSL region and killed- whole cell Pseudomonas aeruginosa O1 (PAO1) strain and their efficacy for immunoprophylaxis of sepsis caused by P. aeruginosa in a rabbit model. METHODS: Specific IgY was obtained by immunization of hens. The purity of IgY was determined by SDS-PAGE analysis. The effect of IgY on growth and hydrophobicity of P. aeruginosa were performed through time-kill assay and microbial adhesion to hydrocarbons test (MATH), respectively. The efficacy of specific IgYs was examined against P. aeruginosa sepsis in a rabbit model. The rabbits were monitored for 72 h to record physiological characters and survival. Hematologic factors, C-reactive protein, pro-inflammatory cytokines, and bacterial count from blood and solid organs were measured, periodically. RESULTS: We found that the growth inhibitory effect of the anti- killed whole cell IgY was higher than anti-pilQ-pilA IgY (P < 0.001). The hydrophobicity effect of PAO1 increased when bacteria were opsonized by anti- killed whole cell IgY while the hydrophobicity activity was decreased following incubation of PAO1 with anti-pilQ-pilA IgY in a broth medium (P < 0.001). Following intravenous (IV) administration of produced IgYs, no significant difference was observed in the survival, decrease in inflammatory mediators and clinical symptoms between the groups 48h post infection (P > 0.05). Moreover, no considerable decrease was observed in the bacterial load of blood, lungs and kidneys in rabbits treated with specific IgYs and control groups (P > 0.05). No bacteria were found in the spleen and liver samples from infected rabbits. CONCLUSION: Although produced IgYs had a good immunoreactivity, IV immunization of IgYs was not protective against P. aeruginosa sepsis in the rabbit model. Further studies are needed to assess the immune response and decreasing mortality rate using the rabbit sepsis model.

Transcriptome analysis of biofilm formation under aerobic and microaerobic conditions in clinical isolates of Campylobacter spp.

It has been well documented that Campylobacter is the leading cause of foodborne infections and bacterial enteritis in high-income countries. The gastrointestinal tract of most warm-blooded animals, such as mammals and poultry, is prone to this pathogen. Infections caused by this bacterium in humans have usually been associated with the consumption of contaminated poultry meat. The important point about Campylobacter is that this bacterium has adapted to harsh environmental conditions along the food chain (poultry digestive tract to the consumer's plate) and developed an adapted mechanism to those conditions. This study aimed to compare the ability of Campylobacter jejuni and Campylobacter coli strains to form biofilms under aerobic and microaerobic conditions. The presence and expression of flab, FliS, DnaK, luxs, CsrA, Cj0688, and cosR genes involved in biofilm formation were investigated. Finally, the correlation between the biofilm forming ability of Campylobacter isolates and the presence/expression of selected genes has been explored. A significant correlation was observed between the presence and expression of some genes and the degree of biofilm formation in C. jejuni and C. coli isolates. A strong biofilm production was detected in strains harboring all selected genes with greater expression levels. The ability of C. jejuni and C. coli strains in biofilm formation is associated with the coordinated function and convergent expression of the selected genes. Seemingly, stress response- and motility-related genes have the most involvement in biofilm formation of C. jejuni and C. coli strains, while other genes have an accessory role in this phenomenon.

Characterization of Antimicrobial Resistance Patterns of Klebsiella pneumoniae Isolates Obtained from Wound Infections.

CDATA[Background: Multidrug resistance among ESBL producing isolates has limited the administration of proper antibiotics. It is, therefore, important to monitor the resistance patterns of Klebsiella pneumoniae isolates and provide infection control strategies to prevent nosocomial outbreaks. This study was aimed to determine antimicrobial resistance patterns of K. pneumoniae isolates obtained from wound infections of patients in Tehran, Iran. METHODS: A total of 102 K. pneumoniae isolates were obtained from wound infections of patients in Tehran, Iran. The production of phenotypic ESBL and carbapenemase was assessed using the double-disc synergy test (DDST) and modified Hodge test (MHT), respectively. PCR was performed for the detection of ESBL, carbapenemase, quinolone and aminoglycoside resistance genes. RESULTS: Forty-six (45.1%) and 23 (22.5%) isolates, out of the 102 isolates, were phenotypically detected as ESBL and carbapenemase producers, respectively. The PCR results showed that 80/102 (78.4%) and 51/102 (50%) isolates possessed at least one of the assessed ESBL and carbapenemase genes, respectively. Quinolone resistance determinants (QRDs) and aac(6')-Ib genes were found amongst 50 (49%) and 67 (65.7%) isolates, respectively. Four isolates carried blaTEM, blaSHV, blaCTX-M, qnrB, qnrS and aac(6')-Ib genes, simultaneously. CONCLUSION: Due to the presence of multiple resistance genes among some K. pneumoniae strains, antibiotic agents should be used with caution to preserve their efficacy in case of life-threatening infections.