Involvement of Pseudomonas aeruginosa in the occurrence of community and hospital acquired diarrhea, and its virulence diversity among the stool and the environmental samples

Transmission of Pseudomonas aeruginosa along the food chain could cause gastrointestinal infections. To show this involvement, the prevalence, putative virulence genotype, and antibiotic resistance phenotype of P. aeruginosa isolates from stool of 1482 patients with community and hospital acquired diarrhea were compared with 87 isolates from the environmental samples. The results showed infection with P. aeruginosa in 3.4% of the cases, while 57.4% of vegetable samples were contaminated. Significantly higher frequency of lasB (98%), aprA (98%), exoY (98%), and exoS (90%), but lower rate of exoT (39.2%), was detected among the stool isolates. Multi-drug resistance (MDR) phenotype was detected in 25.5% and 4% of the stool and vegetable isolates, respectively. A higher rate of studied virulence genes was detected among the MDR strains vs non-MDR strains. These results indicate P. aeruginosa as a causative agent of diarrhea either among the hospitalized patients and those with community-acquired diarrhea.

Immunoinformatics design of multivalent chimeric vaccine for modulation of the immune system in Pseudomonas aeruginosa infection

Increasing in drug-resistant Pseudomonas aeruginosa and high mortality and morbidity rate have become a health challenge worldwide; therefore, developing the novel therapeutic strategies such as immunogenic vaccine candidate are required. Despite a substantial research effort, the future of immunization against P. aeruginosa due to failure in covering two separate stages of infection, and furthermore, inducing ineffective type of immune response, still remains controversial. In this study, immunoinformatics approach was utilized to design multivalent chimeric vaccine from both stages of infection containing Lectin, HIV TAT peptide, N-terminal fragment of exotoxin A and Epi8 of outer membrane protein F (OprF) with hydrophobic linkers which have a high density of B-cell, T Lymphocytes (HTL), T Lymphocytes (CTL), and IFN-γ epitopes. The physicochemical properties, antigenicity, and allergenicity for designed vaccine were analyzed. 3D model generation and refinement further validation of the final vaccine were followed by computational docking with molecular dynamics analyses that demonstrated high- affinity interaction between vaccine and TLR-4. Finally, designed vaccine was in silico cloned in pET22b. We have expected that the designed vaccine able to elucidate innate, humoral and cellular innate immune responses and control the interaction of P. aeruginosa with host and maybe overcome to P. aeruginosa vaccines drawback.

Biochemical and computational study of an alginate lyase produced by Pseudomonas aeruginosa strain S21

OBJECTIVES

Alginates play a key role in mucoid Pseudomonas aeruginosa colonization, biofilm formation, and driving out of cationic antibiotics. P. aeruginosa alginate lyase (AlgL) is a periplasmic enzyme that is necessary for alginate synthesis and secretion. It also has a role in depolymerization of alginates. Using AlgLs in cystic fibrosis patients along with antibiotics enhances bacterial killing and host healing. In this study, we investigated the different biochemical properties of a newly isolated AlgL from P. aeruginosa S21 to complete the databank of AlgLs.

MATERIALS AND METHODS

The enzyme was extracted from the periplasmic space of the bacteria by the heat shock method. Using the TBA method, the enzyme activity and biochemical properties were assessed. The mutability of P. aeruginosa S21 AlgL to increase its thermal stability was investigated. The most favorable mutations were studied computationally. The molecular dynamics simulation (MDS) package GROMACS was used for determining the effect of S34R mutation on enzyme's thermal stability.

RESULTS

Data showed that this enzyme has the best activity at 37 ^°C and pH 7.5 and it can degrade mannuronate blocks, guluronate blocks, and sodium alginate. After 7 hr at 80 ^°C, 45% of the enzyme activity was retained. This enzyme needed 15 min to completely degrade accessible sodium alginate. Tris buffer, pH 8.5 and Britton-Robinson buffer, pH 7.0 were the preferable buffers for the enzyme activity. MDS of native and mutated enzymes showed desirable results.

CONCLUSION

P. aeruginosa S21 AlgL can be used in medical and industrial applications to degrade alginates.

Biosynthesised AgCl NPs using Bacillus sp. 1/11 and evaluation of their cytotoxic activity and antibacterial and antibiofilm effects on multi-drug resistant bacteria

Silver nanoparticles (AgNPs) have attracted the attention of researchers due to their properties. Biological synthesis of AgNPs is eco-friendly and cost-effective preferred to physical and chemical methods, which utilize environmentally harmful agents and large amounts of energy. Microorganisms have been explored as potential biofactories to synthesize AgNPs. Bacterial NP synthesis is affected by Ag salt concentration, pH, temperature and bacterial species. In this study, Bacillus spp., isolated from soil, were screened for AgNP synthesis at pH 12 with 5 mM Ag nitrate (AgNO3) final concentration at room temperature. The isolate with fastest color change and the best ultraviolet-visible spectrum in width and height were chosen as premier one. AgNO3 and citrate salts were compared in terms of their influence on NP synthesis. Spherical Ag chloride (AgCl) NPs with a size range of 35-40 nm were synthesized in 1.5 mM Ag citrate solution. Fourier transform infrared analysis demonstrated that protein and carbohydrates were capping agents for NPs. In this study, antimicrobial and antitumor properties of the AgNP were investigated. The resulting AgCl NPs had bacteriostatic activity against four standard spp. And multi-drug resistant strain of Pseudomonas aeruginosa. These NPs are also cytotoxic to cancer cell lines MCF-7, U87MG and T293.

A comparison of antibiotic disks from different sources on Quicolor and Mueller-Hinton agar media in evaluation of antibacterial susceptibility testing

BACKGROUND AND OBJECTIVES

Antibacterial susceptibility testing of clinical bacterial isolates through disk diffusion method plays a major role in antibacterial treatment. One of the main factors affecting the result of these tests is the type, structure and quality of the disks. The main objective of this study was to compare the agreement of antibiotic disks originated from three companies on Quicolor and Mueller-Hinton agar.

MATERIALS AND METHODS

Quicolor and Mueller-Hinton agar media were used in disk diffusion method. Seventy clinical isolates from Enterobacteriaceae family (21 Klebsiella spp., 36 Escherichia coli, 1 Enterobacter spp. and 12 Shigella spp.) were investigated in the study. After obtaining data, the results were interpreted as resistant, sensitive or intermediate. Kappa coefficient measured the agreement of two media. Coefficient of variation (CV) was also calculated for antibiotic disks.

RESULTS

The kappa agreement values for three types of antibiotic disks on Quicolor and Mueller-Hinton agar plates were good or excellent for all the examined antibiotics. CV values were also very satisfactory in the majority of cases.

CONCLUSION

Antibiotic disks from three manufacturers can successfully be used on both Quicolor and Mueller-Hinton agar plates.

Amikacin loaded PLGA nanoparticles against Pseudomonas aeruginosa

Amikacin is a very effective aminoglycoside antibiotic but according to its high toxicity, the use of this antibiotic has been limited. The aim of this study was to formulate and characterize amikacin loaded PLGA nanoparticles. Nanoparticles were synthetized using a solid-in-oil-in-water emulsion technique with different ratio of PLGA 50:50 (Resomer 502H) to drug (100:3.5, 80:3.5 and 60:3.5), two different concentrations of stabilizer (pluronic F68) (0.5% or 1%) and varied g forces to recover the final products. The most efficient formulation based on drug loading (26.0±1.3μg/mg nanoparticle) and encapsulation efficiency (76.8±3.8%) was the one obtained with 100:3.5 PLGA:drug and 0.5% luronic F68, recovered by 20,000×g for 20min. Drug release kinetic study indicated that about 50% of the encapsulated drug was released during the first hour of incubation in phospahte buffer, pH7.4, 37°C, 120rpm. Using different cell viability/cytotoxicity assays, the optimized formulation showed no toxicity against RAW macrophages after 2 and 24h of exposure. Furthermore, released drug was active and maintained its bactericidal activity against Pseudomonas aeruginosa in vitro. These results support the effective utilization of the PLGA nanoparticle formulation for amikacin in further in vivo studies.

Screening of Alginate Lyase-Producing Bacteria and Optimization of Media Compositions for Extracellular Alginate Lyase Production

Background:

Alginate is a linear polysaccharide consisting of guluronate (polyG) and mannuronate (polyM) subunits.

Methods:

In the initial screening of alginate-degrading bacteria from soil, 10 isolates were able to grow on minimal medium containing alginate. The optimization of cell growth and alginate lyase (algL) production was carried out by the addition of 0.8% alginate and 0.2-0.3 M NaCl to the culture medium. Of 10 isolates, one was selected based on its fast growth rate on minimal 9 medium containing 0.4% sodium alginate. The selected bacterium, identified based on morphological and biochemical characteristics, as well as 16S rDNA sequence data, was confirmed to be an isolate belonging to the genus Bacillus and designated as Bacillus sp. TAG8.

Results:

The results showed the ability of Bacillus sp. TAG8 in utilizing alginate as a sole carbon source. Bacillus sp. TAG8 growth and algL production were augmented with an increase in sodium alginate concentration and also by the addition of 0.2-0.3 M NaCl. Molecular analysis of TAG8 algL gene showed 99% sequence identity with algL of Pseudomonasaeruginosa PAO1. The algL produced by Bacillus sp. TAG8 cleaved both polyM and polyG blocks in alginate molecule, as well as acetylated alginate residues, confirming the bifunctionality of the isolated lyase.

Conclusion:

The identification of novel algL genes from microbial communities constitutes a new approach for exploring lyases with specific activity against bacterial alginates and may thus contribute to the eradication of persistent biofilms from clinical samples.

IgA nephropathy with early kidney disease is associated with increased arterial stiffness and renin-angiotensin system activity

BACKGROUND

IgA nephropathy is associated with increased cardiovascular risk, though whether this is due to loss of kidney function or proteinuria is unclear.

METHODS

For this study 10 normotensive IgA nephropathy subjects with early kidney disease (41±5 yrs, glomerular filtration rate (GFR) 87±9 ml/min, proteinuria 720±300 mg/d) and 10 gender- and blood pressure-matched healthy controls (36±1 yrs, estimated GFR 102±5 ml/min, proteinuria 70±6 mg/d) were studied in high-salt balance. Blood pressure and arterial stiffness, expressed as pulse wave velocity and aortic augmentation index, were measured at baseline and in response to 60 min of angiotensin II (AngII) infusion.

RESULTS

At baseline, IgA nephropathy subjects demonstrated similar pulse wave velocity (8.6±0.7 vs. 8.0±0.4 m/s, p=0.5) but increased aortic augmentation index (12.6±3.1 vs. 1.8±4%, p=0.04) and a trend towards increased circulating renin-angiotensin system (RAS) components (plasma renin activity, 0.55±0.18 vs. 0.21±0.05 ng/l/s, p=0.08; angiotensin II, 25±5 vs. 16±1 ng/l, p=0.08) compared with controls. However, despite similar baseline blood pressure values (p=0.8), IgA nephropathy was associated with reduced arterial sensitivity to AngII challenge (Δmean arterial pressure: 19±4 vs. 29±1 mm Hg, p=0.05; Δpulse wave velocity: -0.06±0.6 vs. 1.5±0.3 m/s, p=0.07) compared with controls, even after multivariate analysis.

CONCLUSION

Even in the setting of early kidney disease, IgA nephropathy is associated with increased arterial stiffness and decreased angiotensin II responsiveness, a marker of increased RAS activity.

Assessment of Biofilm Formation and Resistance to Imipenem and Ciprofloxacin among Clinical Isolates of Acinetobacter baumannii in Tehran

Background:

Biofilms are communities of bacteria attached to the surfaces in an extracellular polymeric matrix which are associated with many chronic infections in humans. Acinetobacter spp. are emerging as a major cause of nosocomial infections and Acinetobacterbaumannii is the predominant species associated with this kind of infections.

Objectives:

In the present study, the potential of biofilm formation of clinical isolates, A. baumannii, was assessed by using crystal violet method. Furthermore, susceptibility pattern of these strains to ciprofloxacin and imipenem was determined.

Methods and Materials:

Biofilm formation by 75 A. baumannii isolates was evaluated by using microtiter plate and tube methods and crystal violet staining. Tube method was carried out under static and shaking conditions. Then, the susceptibility of isolates to ciprofloxacin and imipenem was determined.

Results:

Results showed that in tube method under shaking, 22% of clinical isolates were strong biofilm producers while 23% of them were not able to form biofilms. In this experiment, 18% and 42% of isolates were considered as moderate and weak biofilm-forming strains, respectively. In microtiter plate tests, 18% of strains were strong-biofilm producers and 25% of them were notable biofilm producers. In this assessment, 10% and 47% were considered as moderate and weak biofilm-forming isolates, respectively. The susceptibility tests, using microdilution method, confirmed that 92% of these isolates were resistant and 6.6% were susceptible to ciprofloxacin, although these results for imipenem were 68% and 24%, respectively.

Conclusions:

It can be concluded that most of A. baumannii isolates can form biofilm in microtiter plate and tube. The results also verified that most of these isolates were resistant to ciprofloxacin and imipenem.

Role of serum erythropoietin, erythropoietin-independent erythroid colony formation, and bone marrow assessment in the diagnosis of polycythemia vera in patients with JAK2 V617F mutation

7085

Background: The discovery of the JAK2 V617F mutation in over 95% of polycythemia vera (PV) patients has led to the development of the new 2008 World Health Organization diagnostic criteria for PV. These specify a requirement for an elevated hemoglobin (Hb, males: >185 g/L, females: >165 g/L) and either evidence of JAK2-mutant cells plus any one of the following minor criteria: a below normal level of serum erythropoietin (Epo), detectable Epo-independent erythroid colony (EEC) formation in vitro, or panmyelosis in the bone marrow, or two of the latter in the absence of detectable JAK2-mutant cells. However, in patients with an elevated Hb and JAK2V617F positivity, there are few data to determine whether any of the 3 minor criteria actually add an independent contribution to the diagnosis of PV. Methods: We performed a retrospective chart review of 77 patients who had an elevated Hb and were positive for the JAK2 V617F mutation and who also had a test for at least one of the 3 minor criteria (serum Epo level: n = 53; EEC formation: n = 66; bone marrow examination: n = 16) to determine the frequency of cases who might lack one or more of these. Results: Although the number of patients with a complete set of data was limited, the results, nevertheless, were sufficient to show that all 3 minor criteria were highly represented and all 77 of the patients analyzed (100%) were positive for at least one of them; i.e., 47 of 53 tested (89%) had a reduced serum Epo level; 65 of 66 tested (98%) had EECs and 15 of 16 tested (94%) had evidence of bone marrow panmyelosis. Conclusions: Neither the Epo level, nor the presence of EECs nor evidence of bone marrow panmyelosis provided additional diagnostic specificity in a population of 77 patients with both JAK2 V617F-positive cells and an elevated Hb. Consideration should be given to limiting serum Epo, EEC, and bone marrow assessments to JAK2 mutant-negative patients.

No significant financial relationships to disclose.

Study of antibiotic resistance by efflux in clinical isolates of Pseudomonas aeruginosa

Twenty three multidrug resistant (MDR) strains were selected from 104 clinical isolates of P. aeruginosa and screened for resistance to ceftazidim, ceftriaxone, ciprofloxacin, ofloxacin and ethidium bromide by determining MICs. The MICs of EtBr and antibiotics were also measured in presence of proton conductor, carbonyl cyanide m-chlorophenyl hydrazone (CCCP). The presence of proton gradient-dependent efflux mechanism was assessed using ethidium bromide accumulation assays. Drug accumulation studies for these antibiotics were performed to determine the drug specificity of efflux. PCR was used to identify the mexAB-oprM gene as a major factor in MDR intrinsic resistance of clinical isolates of P. aeruginosa. In absence of CCCP, the MICs of these antimicrobial agents were > or = 4 microg L(-1). CCCP reduced the MICs of them at least in 1 dilution. Ethidium bromide accumulation assays confirmed the presence of proton gradient-dependent efflux mechanism in clinical isolates of P. aeruginosa and results of accumulation assays of drugs demonstrate that, active efflux in this bacterium are due to broadly-specific multidrug efflux system(s). PCR products demonstrate the presence of mexAB-oprM operon in 4 strains from 23 clinical isolates. These results confirmed the presence of proton gradient-dependent efflux mechanism in all of the clinical isolates of P. aeruginosa and demonstrate that, efflux pumps in this bacterium are broadly-specific multidrug efflux systems. In this study we show that MexAB-OprM multidrug efflux system was expressed in only 17% of clinical isolates of P. aeruginosa. These results confirmed the presence of other multidrug efflux pumps in clinical isolates of P. aeruginosa.

Pulsed field gel electrophoresis & plasmid profile of Pseudomonas aeruginosa at two hospitals in Tehran, Iran

BACKGROUND & OBJECTIVE

Pseudomonas aeruginosa is a common cause of nosocomial infections and exhibits innate resistance to a wide range of antibiotics. This study was undertaken to determine the resistance patterns of P. aeruginosa isolates recovered from patients at two hospitals in Tehran, to investigate the presence of plasmids and to genetically characterize them by pulsed field gel electrophoresis (PFGE).

METHODS

The susceptibility of 104 isolates of P. aeruginosa to 13 different antibiotics was determined by agar disk diffusion method. The alkaline lysis method was used for plasmid extraction. PFGE technique was optimized for DNA fingerprinting of isolates.

RESULTS

The isolates showed resistance to 13 different antibiotics ceftizoxime (99%), lomefloxacin (94.3%), ceftazidime (59.6%), ticarcillin (50%), ceftriaxone (44.3%), cefoperazone (37.5%), tobramycin (34.6%), piperacillin and gentamicin (33.7%), carbenicillin (25%), amikacin (22%), ciprofloxacin (15.4%) and imipenem (2.9%). Plasmids were detected in 31 isolates (29.8%) that produced 15 different patterns. In total, 84 DNA banding patterns were detected by PFGE. The dominant PFGE type, Pattern A with 14 isolates was found at both hospitals. The remaining isolates were grouped in B, C, D and PF1-PF80. The majority of isolates with the identical plasmid profiles and resistance patterns produced closely related DNA fingerprints by PFGE.

INTERPRETATION & CONCLUSION

Isolates in pattern A were distributed widely at both hospitals and the environment. Absence of plasmids in majority of isolates indicated low typeability and discriminatory power of this technique.

Bactericidal activity of various antibiotics against biofilm-producing Pseudomonas aeruginosa

Clinical isolates of Pseudomonas aeruginosa were collected from hospitals in Tehran, Iran, and identified using biochemical tests. A modified microtitre plate test was used to determine the biofilm-forming capacity of the isolates, measured with an enzyme-linked immunosorbent assay (ELISA) reader. Results showed that P. aeruginosa strain 214 was the most efficient at producing biofilm compared with the other strains. Observation of the bacterial biofilm on Teflon sheets and on a catheter using a scanning electron microscope showed greater biofilm formation on the catheter than on Teflon sheets. In this study, we investigated the bactericidal activity of fluoroquinolones, beta-lactams, macrolides and aminoglycoside. The results showed differences in the antibiotic susceptibility of planktonic and biofilm cell populations. Fluoroquinolones showed more potent activity than the other antibiotics, and biofilms were completely eradicated by treatment with 16 x the minimum inhibitory concentration (MIC) of ciprofloxacin and 64 x MIC of ofloxacin, whereas all biofilms survived 2560 microg/mL of imipenem and ceftazidime. Production of an exopolysaccharide matrix is one of the distinguishing characteristics of biofilms. It has been suggested that this matrix prevents access of antibiotics to the bacterial cells embedded in the community. In this study, we also evaluated the permeation of antibiotics through alginate of P. aeruginosa strain 214 using a sandwich cup method. Macrolides were most efficient, showing 100% penetration; fluoroquinolones and beta-lactams had a high permeation rate > 75%, whereas the rates for aminoglycosides were low (amikacin = 59%; gentamicin = 73%).

Cytotoxic effects of pyocin S2 produced by Pseudomonas aeruginosa on the growth of three human cell lines

Pyocin typing of 82 Pseudomonas aeruginosa strains, collected from different Iranian clinical sources, revealed that one isolate, P. aeruginosa 42A, produced pyocin S2, a protease-sensitive bacteriocin. Pyocin S2 production was induced by mitomycin C (2 µg/mL) in the pyocin S2 producer P. aeruginosa 42A. Pyocin S2 was purified using ion exchange chromatography with CM-Sepharose CL-6B and sodium phosphate buffer (pH 8) from an 80% ammonium sulfate precipitate of whole-cell lysates. Pyocin activity of the fractions was detected using the Govan spot testing method. The purity of the active fraction was confirmed by SDS–PAGE, where a single band with a molecular mass of 74 kDa was detected. Cytotoxic effects of purified pyocin S2 and partially purified pyocin from P. aeruginosa 42A on the human tumor cell lines HepG2 and Im9 and the normal human cell line HFFF (Human Foetal Foreskin Fibroblast) were studied by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The results demonstrated that partially purified pyocin and pyocin S2 exhibited substantial inhibitory effects on the growth of the tumor cell lines HepG2 and Im9, while no inhibitory effects were observed on the normal cell line HFFF. Pure lipopolysaccharide was used as a control and was found to have no inhibitory effect on any of the cell lines tested.Key words: Pseudomonas aeruginosa, pyocin, cytotoxicity, MTT assay.