Virulence attributes in Brazilian clinical isolates of Pseudomonas aeruginosa

Pseudomonas aeruginosa Isolates from Water Samples of the Gulf of Mexico Show Similar Virulence Properties but Different Antibiotic Susceptibility Profiles than Clinical Isolates

Pseudomonas aeruginosa is an opportunistic pathogen found in a wide variety of environments, including soil, water, and habitats associated with animals, humans, and plants. From a One Health perspective, which recognizes the interconnectedness of human, animal, and environmental health, it is important to study the virulence characteristics and antibiotic susceptibility of environmental bacteria. In this study, we compared the virulence properties and the antibiotic resistance profiles of seven isolates collected from the Gulf of Mexico with those of seven clinical strains of P. aeruginosa. Our results indicate that the marine and clinical isolates tested exhibit similar virulence properties; they expressed different virulence factors and were able to kill Galleria mellonella larvae, an animal model commonly used to analyze the pathogenicity of many bacteria, including P. aeruginosa. In contrast, the clinical strains showed higher antibiotic resistance than the marine isolates. Consistently, the clinical strains exhibited a higher prevalence of class 1 integron, an indicator of anthropogenic impact, compared with the marine isolates. Thus, our results indicate that the P. aeruginosa marine strains analyzed in this study, isolated from the Gulf of Mexico, have similar virulence properties, but lower antibiotic resistance, than those from hospitals.

Exploring Oceans for Curative Compounds: Potential New Antimicrobial and Anti-Virulence Molecules against Pseudomonas aeruginosa

Although several antibiotics are already widely used against a large number of pathogens, the discovery of new antimicrobial compounds with new mechanisms of action is critical today in order to overcome the spreading of antimicrobial resistance among pathogen bacteria. In this regard, marine organisms represent a potential source of a wide diversity of unique secondary metabolites produced as an adaptation strategy to survive in competitive and hostile environments. Among the multidrug-resistant Gram-negative bacteria, Pseudomonas aeruginosa is undoubtedly one of the most important species due to its high intrinsic resistance to different classes of antibiotics on the market and its ability to cause serious therapeutic problems. In the present review, we first discuss the general mechanisms involved in the antibiotic resistance of P. aeruginosa. Subsequently, we list the marine molecules identified up until now showing activity against P. aeruginosa, dividing them according to whether they act as antimicrobial or anti-virulence compounds.

Presence of quorum sensing system, virulence genes, biofilm formation and relationship among them and class 1 integron in carbapenem-resistant clinical Pseudomonas aeruginosa isolates

Carbapenems are the most effective agents for treating clinical P. aeruginosa (PsA) infections. During an infection, a quorum-sensing (QS) system and its regulating virulence genes have a great role. The aim of the study was to detect the presence of a las and rhl QS system and related virulence genes, biofilm formation and a class 1 (Cls1) integron. A total of 52 carbapenem-resistant PsA (CRPsA) isolates obtained from Kastamonu, Turkey was analyzed. For the isolation and identification of CRPsA isolates, a conventional culture method, an automated VITEK-2 compact system, and oprL gene-based molecular technique were applied. The two QS system genes were detected in 51 (98.1%), and co-existed of four two QS system genes (lasI/R and rhIl/R genes) were determined in 41 (78.8%) of the isolates. algD, lasB, toxA and aprA genes were detected in between 46.1 and 88.5%, and co-existence of four two QS system genes with four virulence genes were detected in 40.4% of the isolates. Biofilm formation using microtiter plate assay and slime production using Congo Red Agar and Cls1 integron were determined in 84.6%, 67.3% and 51.9% of the isolates, respectively. According to statistical analyses results, there was a significant positive correlation (p < .10) between the las and the rhl systems and a strongly and positive correlation (p < .01 or p < .05) between the rhl system-three virulence genes and slime production-and among some virulence genes. In conclusion, the CRPsA isolates tested in the study are highly virulent and QS systems have a significant role in pathogenesis.

Pseudomonas aeruginosa Pneumonia: Evolution of Antimicrobial Resistance and Implications for Therapy

Pseudomonas aeruginosa (PA), a non-lactose-fermenting gram-negative bacillus, is a common cause of nosocomial infections in critically ill or debilitated patients, particularly ventilator-associated pneumonia (VAP), and infections of urinary tract, intra-abdominal, wounds, skin/soft tissue, and bloodstream. PA rarely affects healthy individuals, but may cause serious infections in patients with chronic structural lung disease, comorbidities, advanced age, impaired immune defenses, or with medical devices (e.g., urinary or intravascular catheters, foreign bodies). Treatment of pseudomonal infections is difficult, as PA is intrinsically resistant to multiple antimicrobials, and may acquire new resistance determinants even while on antimicrobial therapy. Mortality associated with pseudomonal VAP or bacteremias is high (> 35%) and optimal therapy is controversial. Over the past three decades, antimicrobial resistance (AMR) among PA has escalated globally, via dissemination of several international multidrug resistant "epidemic" clones. We discuss the importance of PA as a cause of pneumonia including health care-associated pneumonia, hospital-acquired pneumonia, VAP, the emergence of AMR to this pathogen, and approaches to therapy (both empirical and definitive).

Genetic diversity and molecular analysis of metallo beta lactamases among imipenem resistant clinical isolates of Pseudomonas aeruginosa from Peshawar, Pakistan

Objectives

Pseudomonas aeruginosa is an opportunistic pathogen with remarkable adaptation ability to thrive in diverse environmental conditions. This study aimed at phenotypic and molecular analysis of metallo beta lactamases (blaIMP, blaVIM, blaNDM-1 and blaSPM-1) and genetic diversity analysis among imipenem resistant clinical isolates of Pseudomonas aeruginosa.

Methods

This study was conducted from May 2017 to June 2018. The study included 187 Pseudomonas aeruginosa isolates collected from different clinical specimens from Peshawar, Pakistan. The isolates were analyzed for resistance to imipenem. Combined disc test (CDT) was then performed for phenotypic detection of metallo beta lactamases among imipenem resistant isolates of Pseudomonas aeruginosa. Molecular detection of metallo beta lactamases genes i.e. blaIMP, blaVIM, blaNDM-1 and blaSPM-1 was analyzed through polymerase chain reaction. Genetic diversity was determined through RAPD-PCR.

Results

MBL production was observed in 76% (n=19) isolates. The occurrence of MBL genes blaIMP, blaNDM-1 and blaVIM was 68% (n=17), 48% (n=12), and 4% (n=1) respectively. The blaSPM-1 gene was not detected. High genetic diversity was observed in current study. Out of 182 isolates 171 isolates showed different RAPD profiles (93.95% polymorphism); 160 were unique RAPD strains and based on similarity coefficient ≥ 80%, 22 isolates were clustered into 11 distinct clones.

Conclusion

A high prevalence of blaIMP and blaNDM-1 among imipenem resistant isolates of Pseudomonas aeruginosa is alarming that calls for proper control and prevention strategies. RAPD technique was found to be a good genotyping technique when limited resources are available.

Quorum sensing systems and related virulence factors in Pseudomonas aeruginosa isolated from chicken meat and ground beef

The objective of this study was to evaluate 50 [chicken meat (n = 45) and ground beef (n = 5)] Pseudomonas aeruginosa isolates to determine the expression of the lasI and rhl QS systems, related virulence factors, and the presence of N-3-oxo-dodecanoyl homoserine lactone (AHL: 3-O-C12-HSL). For the isolation and identification of P. aeruginosa, conventional culture and oprL gene-based molecular techniques were used. In relation to QS systems, eight genes consisting of four intact and four internal (lasI/R, rhlI/R) genes were analyzed with PCR assay. The two QS systems genes in P. aeruginosa isolates from ground beef (80.00%) and chicken meat (76.00%) were present at quite high levels. The 3-O-C12-HSL was detected in 14.00% of the isolates. Both biofilm formation and motility were detected in 98.00% of the isolates. Protease activity was determined in 54.00% of the isolates. Pyocyanin production was detected in 48.00% of the isolates. The las system scores strongly and positively correlated with the rhl system (p ˂ .01). PYA moderately and positively correlated with protease (p ˂ .05). In addition, there was statistically significance between lasI and protease activity (p < .10), and rhlI and twitching motility (p < .10). In conclusion, the high number of isolates having QS systems and related virulence factors are critical for public health. Pyocyanin, protease, and biofilm formation can cause spoilage and play essential role in food spoilage and food safety.

Quorum sensing systems, related virulence factors, and biofilm formation in Pseudomonas aeruginosa isolated from fish

In this study, two quorum sensing (QS) system genes, las and rhI; N-3-oxo-dodecanoyl homoserine lactone (AHL; 3-O-C₁₂-HSL); and QS-related virulence factors and correlation between them were assessed in 30 fish origin P. aeruginosa isolates. The detection of two QS system of the isolates, and eight gene regions consisting of four intact (lasI/R, rhlI/R) and four internal (lasI/R, rhlI/R) genes were tested by PCR assay. According to findings, las and rhI QS system genes were detected in 27 and 30 isolates, respectively, while 3-O-C₁₂-HSL was determined in 13 isolates. A total of 22, 27, and 18 isolates were capable of pyocyanin production, protease, and elastase activity, respectively. Biofilm formation was detected using three methods in all 30 isolates: 12 by Congo red agar, 14 by microtiter plate, and 29 by tube test. Twitching and swarming motility types were detected in 30, but the swimming motility was determined in 25 isolates. The rhI QS system genes detected in all of the isolates having three types including motility, PYA production, and protease and elastase activities. The las QS system genes were detected in 27 of the motility, 17 of PYA production, 25 of protease, and 16 of elastase activity having isolates. In conclusion, the high number of P. aeruginosa isolates from fish tested have two QS systems and related virulence factors. There was also correlation between them.

Biofilm Production and Antimicrobial Resistance of Clinical and Food Isolates of Pseudomonas spp

Due to its ubiquity, ability to form biofilms, and acquire resistance mechanisms, Pseudomonas spp. become one of the major challenge for healthcare settings and food industry. The aims of this study were to assess the biofilm production of Pseudomonas spp. recovered from clinical and food specimens and to evaluate their antimicrobial resistance. A total of 108 isolates of Pseudomonas spp. were included in the study, 48 being clinical isolates recovered from patients admitted to four tertiary care hospitals throughout Serbia and 60 were isolated from the bulk tank milk samples and meat carcasses. Biofilm production was analyzed by microtiter plate assay. Antimicrobial susceptibility was evaluated by disk diffusion method according to the CLSI guidelines, while class A and B β-lactamases encoding genes were screened by PCR. A total of 98 (90.7%) strains were biofilm producers (moderate producer: 68, 69.4%; strong producer: 8, 8.2%). Although a slightly higher percentage of clinical isolates were biofilm producers (91.7%) compared to food isolates (90%), statistical significance was not observed (P > 0.05). The proportion of carbapenem-resistant Pseudomonas aeruginosa (CRPA) isolates was significantly higher among clinical (42%) isolates compared to food (1.7%) Pseudomonads (P < 0.05). The bla_PER and bla_NDM genes were found in ESBL (seven isolates) and MBL (two isolates) production, respectively. In the present study, we confirmed that biofilm formation was highly present in both clinical and food Pseudomonas spp. irrespective of the prior existence of resistance genes. Additionally, clinical settings pose a major reservoir of MDR Pseudomonas spp. and especially CRPA isolates.

Phenazines as potential biomarkers of Pseudomonas aeruginosa infections: synthesis regulation, pathogenesis and analytical methods for their detection

Infectious diseases are still a worldwide important problem. This fact has led to the characterization of new biomarkers that would allow an early, fast and reliable diagnostic and targeted therapy. In this context, Pseudomonas aeruginosa can be considered one of the most threatening pathogens since it causes a wide range of infections, mainly in patients that suffer other diseases. Antibiotic treatment is not trivial given the incidence of resistance processes and the fewer new antibiotics that are placed on the market. With this scenario, relevant quorum sensing (QS) molecules that regulate the secretion of virulence factors and biofilm formation can play an important role in diagnostic and therapeutic issues. In this review, we have focused our attention on phenazines, as possible new biomarkers. They are pigmented metabolites that are produced by diverse bacteria, characterized for presenting unique redox properties. Phenazines are involved in virulence, competitive fitness and are an essential component of the bacterial QS system. Here we describe their role in bacterial pathogenesis and we revise phenazine production regulation systems. We also discuss phenazine levels previously reported in bacterial isolates and in clinical samples to evaluate them as putative good candidates to be used as P. aeruginosa infection biomarkers. Moreover we deeply go through all analytical techniques that have been used for their detection and also new approaches are discussed from a critical point. Graphical abstract.

Virulence Factors Of Carbapenem-Resistant Pseudomonas aeruginosa In Hospital-Acquired Infections In Mansoura, Egypt

Purpose

The problem of carbapenem-resistant Pseudomonas aeruginosa in health-care settings is growing worse. This study was conducted to investigate the rate of carbapenemase genes, antibiotic resistance, and virulence factors in carbapenem-resistant P. aeruginosa associated with hospital-acquired infections.

Patients and methods

Isolates of P. aeruginosa were collected from patients with hospital-acquired infections at Mansoura University Hospital in Mansoura. Carbapenem susceptibility was done by broth dilution. The presence of carbapenemase genes and quorum-sensing genes was assessed by PCR. Production of protease, pyocyanin, twitching motility, hemolytic activity and biofilm formation was evaluated.

Results

Out of 80 P. aeruginosa isolates, 34 (42.5%) were resistant to carbapenem. Among carbapenem-resistant P. aeruginosa isolates, 21 (61.8%) were carbapenemase producers. The most prevalent gene detected was blaVIM. The frequency of protease, pyocyanin, twitching motility, hemolytic activity and biofilm formation was 76.2%, 58.8%, 83.8%, 93.8% and 77.5%, respectively. Biofilm formation was significantly associated with carbapenem-resistant P. aeruginosa. On the other hand, pyocyanin production was significantly lower in carbapenem-resistant isolates. No correlation existed between carbapenem resistance and any other studied virulence factors or quorum-sensing genes.

Conclusion

Association of carbapenem-resistant P. aeruginosa with other antibiotic resistance or the presence of virulence factors in hospital-acquired infection may represent a warning that enhances the need for a stringent surveillance program.

Disarming Pseudomonas aeruginosa Virulence by the Inhibitory Action of 1,10-Phenanthroline-5,6-Dione-Based Compounds: Elastase B (LasB) as a Chemotherapeutic Target

Elastase B (lasB) is a multifunctional metalloenzyme secreted by the gram-negative pathogen Pseudomonas aeruginosa, and this enzyme orchestrates several physiopathological events during bacteria-host interplays. LasB is considered to be a potential target for the development of an innovative chemotherapeutic approach, especially against multidrug-resistant strains. Recently, our group showed that 1,10-phenanthroline-5,6-dione (phendione), [Ag(phendione)₂]ClO₄ (Ag-phendione) and [Cu(phendione)₃](ClO₄)₂.4H₂O (Cu-phendione) had anti-P. aeruginosa action against both planktonic- and biofilm-growing cells. In the present work, we have evaluated the effects of these compounds on the (i) interaction with the lasB active site using in silico approaches, (ii) lasB proteolytic activity by using a specific fluorogenic peptide substrate, (iii) lasB gene expression by real time-polymerase chain reaction, (iv) lasB protein secretion by immunoblotting, (v) ability to block the damages induced by lasB on a monolayer of lung epithelial cells, and (vi) survivability of Galleria mellonella larvae after being challenged with purified lasB and lasB-rich bacterial secretions. Molecular docking analyses revealed that phendione and its Ag⁺ and Cu²⁺ complexes were able to interact with the amino acids forming the active site of lasB, particularly Cu-phendione which exhibited the most favorable interaction energy parameters. Additionally, the test compounds were effective inhibitors of lasB activity, blocking the in vitro cleavage of the peptide substrate, aminobenzyl-Ala-Gly-Leu-Ala-p-nitrobenzylamide, with Cu-phendione having the best inhibitory action (K _i = 90 nM). Treating living bacteria with a sub-inhibitory concentration (½ × MIC value) of the test compounds caused a significant reduction in the expression of the lasB gene as well as its mature protein production/secretion. Further, Ag-phendione and Cu-phendione offered protective action for lung epithelial cells, reducing the A549 monolayer damage by approximately 32 and 42%, respectively. Interestingly, Cu-phendione mitigated the toxic effect of both purified lasB molecules and lasB-containing bacterial secretions in the in vivo model, increasing the survival time of G. mellonella larvae. Collectively, these data reinforce the concept of lasB being a veritable therapeutic target and phendione-based compounds (mainly Cu-phendione) being prospective anti-virulence drugs against P. aeruginosa.

Heterogeneous production of proteases from Brazilian clinical isolates of Pseudomonas aeruginosa

BACKGROUND

Pseudomonas aeruginosa is an important human pathogen that causes severe infections in a wide range of immunosuppressed patients. Herein, we evaluated the proteolytic profiles of 96 Brazilian clinical isolates of P. aeruginosa recovered from diverse anatomical sites.

METHODS

Cell-associated and extracellular proteases were evidenced by gelatin-SDS-PAGE and by the cleavage of soluble gelatin. Elastase was measured by using the peptide substrate N-succinyl-Ala-Ala-Ala-p-nitroanilide. The prevalence of elastase genes (lasA and lasB) was evaluated by PCR.

RESULTS

Bacterial extracts were initially applied on gelatin-SDS-PAGE and the results revealed four distinct zymographic profiles as follows: profile I (composed by bands of 145, 118 and 50kDa), profile II (118 and 50kDa), profile III (145kDa) and profile IV (118kDa). All the proteolytic enzymes were inhibited by EDTA, identifying them as metalloproteases. The profile I was the most detected in both cellular (79.2%) and extracellular (84.4%) extracts. Overall, gelatinase and elastase activities measured in the spent culture media were significantly higher (around 2-fold) compared to the cellular extracts and the production level varied according to the site of bacterial isolation. For instance, tracheal secretion isolates produced elevated amount of gelatinase and elastase measured in both cellular and extracellular extracts. The prevalence of elastase genes revealed that 100% isolates were lasB-positive and 85.42% lasA-positive. Some positive/negative correlations were showed concerning the production of gelatinase, elastase, isolation site and antimicrobial susceptibility.

CONCLUSION

The protease production was highly heterogeneous in Brazilian clinical isolates of P. aeruginosa, which corroborates the genomic/metabolic versatility of this pathogen.

Transient Proteotoxicity of Bacterial Virulence Factor Pyocyanin in Renal Tubular Epithelial Cells Induces ER-Related Vacuolation and Can Be Efficiently Modulated by Iron Chelators

Persistent infections of biofilm forming bacteria, such as Pseudomonas aeruginosa, are common among human populations, due to the bacterial resistance to antibiotics and other adaptation strategies, including release of cytotoxic virulent factors such as pigment pyocyanin (PCN). Urinary tract infections harbor P. aeruginosa strains characterized by the highest PCN-producing capacity, yet no information is available on PCN cytotoxicity mechanism in kidney. We report here that renal tubular epithelial cell (RTEC) line NRK-52E responds to PCN treatments with paraptosis-like activity features. Specifically, PCN-treated cells experienced dilation of endoplasmic reticulum (ER) and an extensive development of ER-derived vacuoles after about 8 h. This process was accompanied with hyper-activation of proteotoxic stress-inducible transcription factors Nrf2, ATF6, and HSF-1. The cells could be rescued by withdrawal of PCN from the culture media before the vacuoles burst and cells die of non-programmed necrosis after about 24–30 h. The paraptosis-like activity was abrogated by co-treatment of the cells with metal-chelating antioxidants. A microscopic examination of cells co-treated with PCN and agents aiming at a variety of the cellular stress mediators and pathways have identified iron as a single most significant co-factor of the PCN cytotoxicity in the RTECs. Among biologically relevant metal ions, low micromolar Fe²⁺specifically mediated anaerobic oxidation of glutathione by PCN, but catechol derivatives and other strong iron complexing agents could inhibit the reaction. Our data suggest that iron chelation could be considered as a supplementary treatment in the PCN-positive infections.

Clinical and Molecular Epidemiology of Multidrug-Resistant P. aeruginosa Carrying aac(6')-Ib-cr, qnrS1 and blaSPM Genes in Brazil

We described a comprehensive analysis of the molecular epidemiology of multidrug-resistant (MDR) P. aeruginosa. Molecular analysis included typing by Pulsed Field Gel Electrophoresis, identification of genes of interest through PCR-based assays and sequencing of target genes. Case-control study was conducted to better understand the prognostic of patients and the impact of inappropriate therapy in patients with bacteremia, as well as the risk factors of MDR infections. We observed a high rate of MDR isolates (40.7%), and 51.0% of them was independently associated with inappropriate antibiotic therapy. Bacteremia was detected in 66.9% of patients, and prolonged hospital stay was expressive in those resistant to fluoroquinolone. Plasmid-mediated quinolone resistance genes (PMQR), qnrS1 and aac(6')Ib-cr, were detected in two different nosocomial isolates (5.3%), and the aac(6')-Ib7 variant was detected at a high frequency (87.5%) in those negative to PMQR. The presence of mutations in gyrA and parC genes was observed in 100% and 85% of selected isolates, respectively. Isolates harboring PMQR genes or mutations in gyrA and parC were not closely related, except in those containing SPM (São Paulo metallo-β-lactamase) clone. In addition, there is no study published in Brazil to date reporting the presence of Pseudomonas aeruginosa isolates harboring both qnrS1 and aac(6')Ib-cr genes, with alarming frequency of patients with inappropriate therapy.

Clonal Relatedness among Imipenem-Resistant Pseudomonas aeruginosa Isolated from ICU-Hospitalized Patients

Imipenem-resistant Pseudomonas aeruginosa (P. aeruginosa) has become an increasingly important problem in healthcare settings worldwide. The aim of the present study was to evaluate clonal spread among imipenem-resistant P. aeruginosa isolated from ICU-hospitalized patients. Totally, 150 wound specimens were analyzed. Antibiotic resistance profiles and clonal diversity were evaluated using Kirby-Bauer's disk diffusion method and Random Amplified Polymorphic DNA- (RAPD-) PCR, respectively. The isolates showed a high frequency of antibiotic resistance against meropenem, and imipenem (100%) followed by ciprofloxacin, and ceftazidime (90%); meanwhile resistance to polymyxin B was not observed. Eighteen (40%) of P. aeruginosa isolates were MBL-positive via ethylenediaminetetraacetic acid (EDTA) combined disk test. Our findings showed high genetic diversity, with 37 different RAPD types detected. RAPD typing results showed cross-acquisition of P. aeruginosa in investigated hospital, suggesting failure in infection control practices. Incidence of MBL-positive isolates is high and should be regarded as a threat to hospitalized patients.

Anti-Pseudomonas aeruginosa activity of 1,10-phenanthroline-based drugs against both planktonic- and biofilm-growing cells

OBJECTIVES

The beneficial antimicrobial properties of 1,10-phenanthroline (phen)-based drugs, together with the imperative need to develop new chemotherapeutic options for prevention/treatment of infections caused by MDR Gram-negative bacteria, led us to evaluate the effects of phen, 1,10-phenanthroline-5,6-dione (phendione), [Ag(phendione)2]ClO4 and [Cu(phendione)3](ClO4)2·4H2O on planktonic- and biofilm-growing Pseudomonas aeruginosa.

METHODS

Thirty-two non-duplicated Brazilian clinical isolates of P. aeruginosa with distinct genetic backgrounds were used in all experiments. The effect of test compounds on planktonic bacterial proliferation was determined as recommended by CLSI protocol. The effect on biofilm formation was evaluated by crystal violet incorporation (biomass determination) and XTT (viability assay). Mature biofilm disorganization was evidenced by staining with crystal violet.

RESULTS

Phen-based compounds presented anti-P. aeruginosa activity, but with different potencies concerning the geometric mean MIC: [Cu(phendione)3](2+) (7.76 μM) > [Ag(phendione)2](+) (14.05 μM) > phendione (31.15 μM) > phen (579.28 μM). MICs of each compound were similar irrespective of whether the P. aeruginosa isolates were susceptible or resistant to classical antimicrobials (ceftazidime, meropenem and imipenem). The pretreatment of bacteria with phen, phendione and phendione's metal derivatives at 0.5 × MIC value inhibited biofilm formation, particularly the use of [Cu(phendione)3](2+) and [Ag(phendione)2](+), which significantly reduced both biomass (48% and 44%, respectively) and viability (78% and 77%, respectively). The compounds studied also disrupted mature biofilm in a dose-dependent manner, especially [Ag(phendione)2](+) and [Cu(phendione)3](2+) (IC50, 9.39 and 10.16 μM, respectively).

CONCLUSIONS

Coordination of phendione to Ag(+) and Cu(2+) represents a new promising group of anti-infective agents, which revealed a potent anti-P. aeruginosa action against both planktonic- and biofilm-growing cells.