Insight into phylogenomic bias of blaVIM-2 or blaNDM-1 dissemination amongst carbapenem-resistant Pseudomonas aeruginosa.

OBJECTIVES: Pseudomonas aeruginosa (P. aeruginosa) are ubiquitous opportunistic pathogens that combine intrinsic and acquired multidrug resistance phenotypes. Due to different types of acquired genes, carbapenem resistance has been expanding in this species. This study hypothesised that the spread of carbapenem resistance among P. aeruginosa is influenced by phylogenomic features, being distinct for different genes. METHODS: To test this hypothesis, the genomes of P. aeruginosa harbouring blaVIM-2 or blaNDM-1 genes were compared. The blaVIM-2 gene was selected because, although frequent, it is almost restricted to this species and blaNDM-1 gene due to its wide interspecies distribution. A group of genomes harbouring the genes blaVIM-2 (n = 116) or blaNDM-1 (n = 27), available in GenBank, was characterised based on core phylogenomic analysis, functional categories in the accessory genome and mobile genetic elements flanking the selected genes. RESULTS: Most blaVIM-2 gene hosts belonged to multilocus sequence types (ST) ST111 (n = 32 of 116) and ST233 (n = 27 of 116) and were reported in Europe (n = 75 of 116). The blaNDM-1 gene hosts were distributed by different STs (ST38, ST773, ST235, ST357 and ST654), frequently from Asia (n = 11 of 27). Significant differences in the prevalence of functional protein/enzyme annotations per number of accessory genomes were observed between blaVIM-2+ and blaNDM-1+. The blaVIM-2 gene was frequently inserted in the Tn402-like and Tn21 transposons family and rarely in IS6100, while blaNDM-1 gene was preferentially flanked by ISAba125 and bleMBL genes or associated with IS91 insertion sequence. CONCLUSION: The hypothesis that carbapenem resistance gene acquisition is not random among phylogenomic lineages was confirmed, suggesting the importance of phylogeny in the dissemination of antibiotic resistance genes.

PA-MSHA Regulates PD-L1 Expression in Hepatoma Cells.

BACKGROUND: Programmed death ligand 1 (PD-L1) is expressed in hepatocellular carcinoma (HCC) cells. PD-L1 function and structure are regulated through glycosylation and various signaling pathways. However, the relationship between Pseudomonas aeruginosa mannose sensitive hemagglutinin (PA-MSHA), glycosylation and PD-L1 warrants further study. In this study, we investigated the effects of PA-MSHA on the regulation of mannosyl and N-glycosylation to identify the mechanisms underlying its function. METHODS: PD-L1, ß-catenin, c-Myc, mannosyl, MGAT1 and mannosidase II in HCC were identified by postoperative specimens from the HCC cohort with immunohistochemistry and immunofluorescence. PA-MSHA was used to suppress tumor progression. Alterations to the expression of PD-L1, ß-catenin, c-Myc, MGAT1, and mannosidase II at the gene and protein levels were detected by qRT-PCR and Western blot analysis. Soluble PD-L1 (sPD-L1) were detected using enzyme-linked immunosorbent assay. RESULTS: Mannosyl and mannosidase II expression levels increased, whereas those of MGAT1 decreased in the HCC cells. The glycosylation-related pathway proteins, namely, ß-catenin, c-Myc and PD-L1, had increased expression levels. Moreover, proliferation in the HCC cells was inhibited after PA-MSHA treatment, PD-L1 function was significantly inhibited. Transmission electron microscopy showed that PA-MSHA penetrated into the HCC cytoplasm through the cytomembrane, resulting in apoptosis. Here, PA-MSHA significantly reduced sPD-L1 expression levels in the tumor cells. CONCLUSIONS: PA-MSHA plays the role of a lectin, affecting receptors on the cytomembrane. This strain inhibits mannosyl by suppressing ß-catenin signaling. We hypothesized that PA-MSHA suppresses PD-L1 by: 1. Inhibiting the glycosylation process; and 2. Suppressing ß-catenin and c-Myc, thereby reducing the transcription of this protein.

Hackflex: low-cost, high-throughput, Illumina Nextera Flex library construction.

We developed a low-cost method for the production of Illumina-compatible sequencing libraries that allows up to 14 times more libraries for high-throughput Illumina sequencing to be generated for the same cost. We call this new method Hackflex. The quality of library preparation was tested by constructing libraries from Escherichia coli MG1655 genomic DNA using either Hackflex, standard Nextera Flex (recently renamed as Illumina DNA Prep) or a variation of standard Nextera Flex in which the bead-linked transposase is diluted prior to use. In order to test the library quality for genomes with a higher and a lower G+C content, library construction methods were also tested on Pseudomonas aeruginosa PAO1 and Staphylococcus aureus ATCC 25923, respectively. We demonstrated that Hackflex can produce high-quality libraries and yields a highly uniform coverage, equivalent to the standard Nextera Flex kit. We show that strongly size-selected libraries produce sufficient yield and complexity to support de novo microbial genome assembly, and that assemblies of the large-insert libraries can be much more contiguous than standard libraries without strong size selection. We introduce a new set of sample barcodes that are distinct from standard Illumina barcodes, enabling Hackflex samples to be multiplexed with samples barcoded using standard Illumina kits. Using Hackflex, we were able to achieve a per-sample reagent cost for library prep of A$7.22 (Australian dollars) (US $5.60; UK £3.87, £1=A$1.87), which is 9.87 times lower than the standard Nextera Flex protocol at advertised retail price. An additional simple modification and further simplification of the protocol by omitting the wash step enables a further price reduction to reach an overall 14-fold cost saving. This method will allow researchers to construct more libraries within a given budget, thereby yielding more data and facilitating research programmes where sequencing large numbers of libraries is beneficial.

Distribution of serotypes and antibiotic resistance of invasive Pseudomonas aeruginosa in a multi-country collection.

BACKGROUND: Pseudomonas aeruginosa is an opportunistic pathogen that causes a wide range of acute and chronic infections and is frequently associated with healthcare-associated infections. Because of its ability to rapidly acquire resistance to antibiotics, P. aeruginosa infections are difficult to treat. Alternative strategies, such as a vaccine, are needed to prevent infections. We collected a total of 413 P. aeruginosa isolates from the blood and cerebrospinal fluid of patients from 10 countries located on 4 continents during 2005-2017 and characterized these isolates to inform vaccine development efforts. We determined the diversity and distribution of O antigen and flagellin types and antibiotic susceptibility of the invasive P. aeruginosa. We used an antibody-based agglutination assay and PCR for O antigen typing and PCR for flagellin typing. We determined antibiotic susceptibility using the Kirby-Bauer disk diffusion method. RESULTS: Of the 413 isolates, 314 (95%) were typed by an antibody-based agglutination assay or PCR (n = 99). Among the 20 serotypes of P. aeruginosa, the most common serotypes were O1, O2, O3, O4, O5, O6, O8, O9, O10 and O11; a vaccine that targets these 10 serotypes would confer protection against more than 80% of invasive P. aeruginosa infections. The most common flagellin type among 386 isolates was FlaB (41%). Resistance to aztreonam (56%) was most common, followed by levofloxacin (42%). We also found that 22% of strains were non-susceptible to meropenem and piperacillin-tazobactam. Ninety-nine (27%) of our collected isolates were resistant to multiple antibiotics. Isolates with FlaA2 flagellin were more commonly multidrug resistant (p = 0.04). CONCLUSIONS: Vaccines targeting common O antigens and two flagellin antigens, FlaB and FlaA2, would offer an excellent strategy to prevent P. aeruginosa invasive infections.

Diversity in the composition of the accessory genome of Mexican Pseudomonas aeruginosa strains.

BACKGROUND: Pseudomonas aeruginosa is an important opportunistic pathogen especially in nosocomial infections due to its easy adaptation to different environments; this characteristic is due to the great genetic diversity that presents its genome. In addition, it is considered a pathogen of critical priority due to the high antimicrobial resistance. OBJECTIVES: The aim of this study was to characterize the mobile genetic elements present in the chromosome of six Mexican P. aeruginosa strains isolated from adults with pneumonia and children with bacteremia. METHODS: The genomic DNA of six P. aeruginosa strains were isolated and sequenced using PacBio RS-II platform. They were annotated using Prokaryotic Genome Annotation Pipeline and manually curated and analyzed for the presence of mobile genetic elements, antibiotic resistances genes, efflux pumps and virulence factors using several bioinformatics programs and databases. RESULTS: The global analysis of the strains chromosomes showed a novel chromosomal rearrangement in two strains, possibly mediated by subsequent recombination and inversion events. They have a high content of mobile genetic elements: 21 genomic islands, four new islets, four different integrative conjugative elements, 28 different prophages, one CRISPR-Cas arrangements, and one class 1 integron. The acquisition of antimicrobials resistance genes into these elements are in concordance with their phenotype of multi-drug resistance. CONCLUSION: The accessory genome increased the ability of the strains to adapt or survive to the hospital environment, promote genomic plasticity and chromosomal rearrangements, which may affect the expression or functionality of the gene and might influence the clinical outcome, having an impact on the treatment.

Direct RNA Nanopore Sequencing of Pseudomonas aeruginosa Clone C Transcriptomes.

The transcriptomes of Pseudomonas aeruginosa clone C isolates NN2 and SG17M during the mid-exponential and early stationary phases of planktonic growth were evaluated by direct RNA sequencing on the nanopore platform and compared with established short-read cDNA sequencing on the Illumina platform. Fifty to ninety percent of the sense RNAs turned out to be rRNA molecules, followed by similar proportions of mRNA transcripts and noncoding RNAs. The two platforms detected similar proportions of uncharged tRNAs and 29 yet-undescribed antisense tRNAs. For example, the rarest arginine codon was paired with the most abundant tRNAArg, and the tRNAArg gene is missing for the most frequent arginine codon. More than 90% of the antisense RNA molecules were complementary to a coding sequence. The antisense RNAs were evenly distributed in the genomes. Direct RNA sequencing identified more than 4,000 distinct nonoverlapping antisense RNAs during exponential and stationary growth. Besides highly expressed small antisense RNAs less than 200 bases in size, a population of longer antisense RNAs was sequenced that covered a broad range (a few hundred to thousands of bases) and could be complementary to a contig of several genes. In summary, direct RNA sequencing identified yet-undescribed RNA molecules and an unexpected composition of the pools of tRNAs and sense and antisense RNAs. IMPORTANCE Genome-wide gene expression of bacteria is commonly studied by high-throughput sequencing of size-selected cDNA fragment libraries of reverse-transcribed RNA preparations. However, the depletion of rRNAs, enzymatic reverse transcription, and the fragmentation, size selection, and amplification during library preparation lead to inevitable losses of information about the initial composition of the RNA pool. We demonstrate that direct RNA sequencing on the Nanopore platform can overcome these limitations. Nanopore sequencing of total RNA yielded novel insights into the Pseudomonas aeruginosa transcriptome that-if replicated in other species-will change our view of the bacterial RNA world. The discovery of sense-antisense pairs of transfer-messenger RNA (tmRNA), tRNAs, and mRNAs indicates a further and unknown level of gene regulation in bacteria.

A comparative study on biological activities of different solvent extracts from whole seed, seed coat and cotyledon of two Lathyrus species

Abstract The present study was conducted to assess the phenolic content, and antibacterial and antioxidant activities of Lathyrus L. species. The extraction of phenolic compounds from whole seeds, seed coat and cotyledon of Lathyrus hierosolymitanus Boiss. and Lathyrus annuus L. seeds was performed employing different solvents. Total phenolic content (TPC) was measured by Folin- Ciocalteau assay, while the antioxidant activity was determined by DPPH radical scavenging activity, and reducing power assay. It was found that TPC of extracts ranged from 0.12 mg to 6.53 mg GAE/gdw. For each solvent, seed coat extracts were generally observed to render higher TPC and antioxidant activities. There was a correlation between TPC and antioxidant activity. In addition, all extracts were also examined for their antimicrobial activity against Bacillus cereus, Escherichia coli and Pseudomonas aeruginosa. Methanol extracts showed the highest antibacterial activity which is consistent with TPC, but there was no correlation between TPC and antibacterial activity. Solvents were observed to have effects on gallic acid, caffeic acid, and epicatechin extractions. HPLC analysis results of extracts confirmed methanol and ethanol as preferred solvents for phenolic extraction from Lathyrus sp. Phenolic content in the extracts could be suggested to contribute to their antioxidant and antibacterial activity.

Expressão e localização celular da diguanilato ciclase DgcP em Pseudomonas aeruginosa / Expression and cell localization of the diguanylate cyclase DgcP in Pseudomonas aeruginosa

A bactéria Gram-negativa Pseudomonas aeruginosa é um patógeno oportunista frequentemente associado a vítimas de queimaduras graves ou indivíduos com fibrose cística, sendo os isolados resistentes a carbepenêmicos dessa espécie considerados pela OMS como uma das maiores ameaças ao controle de infecções. O estabelecimento da infecção por esse patógeno é dependente de uma série de fatores de virulência, entre eles o pilus tipo IV (T4P), que possui papel importante na adesão a superfícies e motilidade do tipo twitching, essenciais para a colonização do hospedeiro. Uma das moléculas importantes na diferenciação entre as formas séssil e planctônica de P. aeruginosa é o segundo mensageiro bis-(3,5)-di-guanosina monofosfato cíclico (c-di-GMP), cuja síntese é feita enzimaticamente por diguanilato ciclases (DGCs). DgcP é uma DGC localizada nos polos da célula, que tem sua atividade de síntese de c-di-GMP aumentada na presença da proteína FimV, essencial para a montagem do T4P em P. aeruginosa. Neste trabalho, ensaios de microscopia de fluorescência, organização e expressão gênica foram realizados com o objetivo de aumentar a compreensão sobre o papel de DgcP em relação a sua expressão e aos fatores que regulam o T4P de P. aeruginosa. A proteína DgcP em fusão com mNeonGreen no C-terminal, expressa a partir do locus cromossômico, se localiza de maneira predominantemente bipolar tanto na linhagem selvagem quanto nos mutantes ΔpilA, ΔpilR e ΔchpA, evidenciando que seu padrão de localização não depende dos sistemas de regulação Pil-Chp e PilS-PilR. Ensaios de RT-PCRmostraram que dgcP se encontra em operon com PA14_72430 e dsbA1, indicando um papel celular conjunto entre esses genes, até o momento, desconhecido. Por fim, ensaios de qRT-PCR revelaram que os níveis de mRNA de dgcP são invariáveis nas linhagens WT, ΔpilA, ΔpilR, ΔchpA e ΔfimV, cultivadas em meio líquido ou meio sólido. Os resultados aqui mostrados, combinados com trabalhos prévios do nosso e de outros grupos, sugerem que DgcP é uma diguanilato ciclase responsável por geração constante de c-di-GMP nos polos da célula, possivelmente, atuando na sinalização local dependente do dinucleotídeo cíclico, cuja localização e atividade não são dependentes dos sistemas de regulação que atuam sobre o T4P

The Gram-negative bacterium Pseudomonas aeruginosa is an opportunistic pathogen often associated with severe burn victims or individuals with cystic fibrosis, which carbapenem-resistant isolates were classified by th World Health Organization classified one of the greatest threats to infection control. The establishment of infection by this pathogen is dependent on a series of virulence factors, including the type IV pilus (T4P), which plays an important role in adhesion to surfaces and twitching motility, essential features for host colonization. Bis-(3',5')-cyclic dimeric guanosine monophosphate (c-di-GMP) is a second messenger that involved in processes of biofilm formation, motility, and virulence. The diguanylate cyclase DgcP synthetizes cdi-GMP and it is located at the cell poles, and its activity depends on the scaffold protein FimV, essential for T4P assembly in P. aeruginosa. By increasing c-di-GMP levels, DgcP decreases flagellum-dependent motility and increases biofilm formation. In this work, fluorescence microscopy, gene organization and expression assays were performed to understand the whether DgcP localization and expression are under the control of T4P regulatory proteins. Fluorescence microscopy analysis showed that DgcP localizes predominantly at both cell poles in ΔpilA, ΔpilR, and ΔchpA mutants, showing that its localization pattern does not depend on the Pil-Chp and PilS-PilR systems. Furthermore, RT-PCR assays showed that dgcP is found in an operon with PA14_72430 and dsbA1, indicating an unknown putative related cellular role for these genes. Finally, qRT-PCR assays indicated that DgcP expression is invariant in ΔpilA, ΔpilR, ΔchpA, and ΔfimV mutants, either in liquid or solid medium. The results shownhere, combined with previous work by ours and other groups, suggest that DgcP is a diguanylate cyclase responsible for constant generation of c-di-GMP at the cell poles, possibly acting in local signaling dependent on the cyclic dinucleotide, but that is not under the control of the known T4P regulatory systems

Worldwide distribution and environmental origin of the Adelaide imipenemase (AIM-1), a potent carbapenemase in Pseudomonas aeruginosa.

Carbapenems are potent broad-spectrum ß-lactam antibiotics reserved for the treatment of serious infections caused by multidrug-resistant bacteria such as Pseudomonas aeruginosa. The surge in P. aeruginosa resistant to carbapenems is an urgent threat, as very few treatment options remain. Resistance to carbapenems is predominantly due to the presence of carbapenemase enzymes. The assessment of 147 P. aeruginosa isolates revealed that 32 isolates were carbapenem non-wild-type. These isolates were screened for carbapenem resistance genes using PCR. One isolate from wastewater contained the Adelaide imipenemase gene (blaAIM-1) and was compared phenotypically with a highly carbapenem-resistant clinical isolate containing the blaAIM-1 gene. A further investigation of wastewater samples from various local healthcare and non-healthcare sources as well as river water, using probe-based qPCR, revealed the presence of the blaAIM-1 gene in all the samples analysed. The widespread occurrence of blaAIM-1 throughout Adelaide hinted at the possibility of more generally extensive spread of this gene than originally thought. A blast search revealed the presence of the blaAIM-1 gene in Asia, North America and Europe. To elucidate the identity of the organism(s) carrying the blaAIM-1 gene, shotgun metagenomic sequencing was conducted on three wastewater samples from different locations. Comparison of these nucleotide sequences with a whole-genome sequence of a P. aeruginosa isolate revealed that, unlike the genetic environment and arrangement in P. aeruginosa, the blaAIM-1 gene was not carried as part of any mobile genetic elements. A phylogenetic tree constructed with the deduced amino acid sequences of AIM-1 suggested that the potential origin of the blaAIM-1 gene in P. aeruginosa might be the non-pathogenic environmental organism, Pseudoxanthomonas mexicana.

Phylogenetic Analysis with Prediction of Cofactor or Ligand Binding for Pseudomonas aeruginosa PAS and Cache Domains.

PAS domains are omnipresent building blocks of multidomain proteins in all domains of life. Bacteria possess a variety of PAS domains in intracellular proteins and the related Cache domains in periplasmic or extracellular proteins. PAS and Cache domains are predominant in sensory systems, often carry cofactors or bind ligands, and serve as dimerization domains in protein association. To aid our understanding of the wide distribution of these domains, we analyzed the proteome of the opportunistic human pathogen Pseudomonas aeruginosa PAO1 in silico. The ability of this bacterium to survive under different environmental conditions, to switch between planktonic and sessile/biofilm lifestyle, or to evade stresses, notably involves c-di-GMP regulatory proteins or depends on sensory pathways involving multidomain proteins that possess PAS or Cache domains. Maximum likelihood phylogeny was used to group PAS and Cache domains on the basis of amino acid sequence. Conservation of cofactor- or ligand-coordinating amino acids aided by structure-based comparison was used to inform function. The resulting classification presented here includes PAS domains that are candidate binders of carboxylic acids, amino acids, fatty acids, flavin adenine dinucleotide (FAD), 4-hydroxycinnamic acid, and heme. These predictions are put in context to previously described phenotypic data, often generated from deletion mutants. The analysis predicts novel functions for sensory proteins and sheds light on functional diversification in a large set of proteins with similar architecture. IMPORTANCE To adjust to a variety of life conditions, bacteria typically use multidomain proteins, where the modular structure allows functional differentiation. Proteins responding to environmental cues and regulating physiological responses are found in chemotaxis pathways that respond to a wide range of stimuli to affect movement. Environmental cues also regulate intracellular levels of cyclic-di-GMP, a universal bacterial secondary messenger that is a key determinant of bacterial lifestyle and virulence. We study Pseudomonas aeruginosa, an organism known to colonize a broad range of environments that can switch lifestyle between the sessile biofilm and the planktonic swimming form. We have investigated the PAS and Cache domains, of which we identified 101 in 70 Pseudomonas aeruginosa PAO1 proteins, and have grouped these by phylogeny with domains of known structure. The resulting data set integrates sequence analysis and structure prediction to infer ligand or cofactor binding. With this data set, functional predictions for PAS and Cache domain-containing proteins are made.

Influence of Simplified Microbial Community Biofilms on Bacterial Retention in Porous Media under Conditions of Stormwater Biofiltration.

Porous media filters are used widely to remove bacteria from contaminated water, such as stormwater runoff. Biofilms that colonize filter media during normal function can significantly alter performance, but it is not clear how characteristics of individual populations colonizing porous media combine to affect bacterial retention. We assess how four bacterial strains isolated from stormwater and a laboratory strain, Pseudomonas aeruginosa PAO1, alter Escherichia coli retention in experimental sand columns under conditions of stormwater filtration relative to a clean-bed control. Our results demonstrate that these strains differentially affect E. coli retention, as was previously shown for a model colloid. To determine whether E. coli retention could be influenced by changes in relative abundance of strains within a microbial community, we selected two pairs of biofilm strains with the largest observed differences in E. coli retention and tested how changes in relative abundance of strain pairs in the biofilm affected E. coli retention. The results demonstrate that E. coli retention efficiency is influenced by the retention characteristics of the strains within biofilm microbial community, but individual strain characteristics influence retention in a manner that cannot be determined from changes in their relative abundance alone. This study demonstrates that changes in the relative abundance of specific members of a biofilm community can significantly alter filter performance, but these changes are not a simple function of strain-specific retention and the relative abundance. Our results suggest that the microbial community composition of biofilms should be considered when evaluating factors that influence filter performance. IMPORTANCE The retention efficiency of bacterial contaminants in biofilm-colonized biofilters is highly variable. Despite the increasing number of studies on the impact of biofilms in filters on bacterial retention, how individual bacterial strains within a biofilm community combine to influence bacterial retention is unknown. Here, we studied the retention of an E. coli K-12 strain, as a model bacterium, in columns colonized by four bacterial strains isolated from stormwater and P. aeruginosa, a model biofilm-forming strain. Simplified two-strain biofilm communities composed of combinations of the strains were used to determine how relative abundance of biofilm strains affects filter performance. Our results provide insight into how biofilm microbial composition influences bacterial retention in filters and whether it is possible to predict bacterial retention efficiency in biofilm-colonized filters from the relative abundance of individual members and the retention characteristics of cultured isolates.

National surveillance pilot study unveils a multicenter, clonal outbreak of VIM-2-producing Pseudomonas aeruginosa ST111 in the Netherlands between 2015 and 2017.

Verona Integron-encoded Metallo-beta-lactamase (VIM) is the most frequently-encountered carbapenemase in the healthcare-related pathogen Pseudomonas aeruginosa. In the Netherlands, a low-endemic country for antibiotic-resistant bacteria, no national surveillance data on the prevalence of carbapenemase-producing P. aeruginosa (CPPA) was available. Therefore, in 2016, a national surveillance pilot study was initiated to investigate the occurrence, molecular epidemiology, genetic characterization, and resistomes of CPPA among P. aeruginosa isolates submitted by medical microbiology laboratories (MMLs) throughout the country. From 1221 isolates included in the study, 124 (10%) produced carbapenemase (CIM-positive); of these, the majority (95, 77%) were positive for the blaVIM gene using PCR. Sequencing was performed on 112 CIM-positive and 56 CIM-negative isolates (n = 168), and genetic clustering revealed that 75/168 (45%) isolates were highly similar. This genetic cluster, designated Group 1, comprised isolates that belonged to high-risk sequence type ST111/serotype O12, had similar resistomes, and all but two carried the blaVIM-2 allele on an identical class 1 integron. Additionally, Group 1 isolates originated from around the country (i.e. seven provinces) and from multiple MMLs. In conclusion, the Netherlands had experienced a nationwide, inter-institutional, clonal outbreak of VIM-2-producing P. aeruginosa for at least three years, which this pilot study was crucial in identifying. A structured, national surveillance program is strongly advised to monitor the spread of Group 1 CPPA, to identify emerging clones/carbapenemase genes, and to detect transmission in and especially between hospitals in order to control current and future outbreaks.

Differential Surface Competition and Biofilm Invasion Strategies of Pseudomonas aeruginosa PA14 and PAO1.

Pseudomonas aeruginosa strains PA14 and PAO1 are among the two best-characterized model organisms used to study the mechanisms of biofilm formation while also representing two distinct lineages of P. aeruginosa. Previous work has shown that PA14 and PAO1 use different strategies for surface colonization; they also have different extracellular matrix composition and different propensities to disperse from biofilms back into the planktonic phase surrounding them. We expand on this work here by exploring the consequences of these different biofilm production strategies during direct competition. Using differentially labeled strains and microfluidic culture methods, we show that PAO1 can outcompete PA14 in direct competition during early colonization and subsequent biofilm growth, that they can do so in constant and perturbed environments, and that this advantage is specific to biofilm growth and requires production of the Psl polysaccharide. In contrast, P. aeruginosa PA14 is better able to invade preformed biofilms and is more inclined to remain surface-associated under starvation conditions. These data together suggest that while P. aeruginosa PAO1 and PA14 are both able to effectively colonize surfaces, they do so in different ways that are advantageous under different environmental settings. IMPORTANCE Recent studies indicate that P. aeruginosa PAO1 and PA14 use distinct strategies to initiate biofilm formation. We investigated whether their respective colonization and matrix secretion strategies impact their ability to compete under different biofilm-forming regimes. Our work shows that these different strategies do indeed impact how these strains fair in direct competition: PAO1 dominates during colonization of a naive surface, while PA14 is more effective in colonizing a preformed biofilm. These data suggest that even for very similar microbes there can be distinct strategies to successfully colonize and persist on surfaces during the biofilm life cycle.

A LAMP-based system for rapid detection of eight common pathogens causing lower respiratory tract infections.

Lower respiratory tract infections (LRTIs) are a leading cause of morbidity and mortality worldwide and lack a rapid diagnostic method. To improve the diagnosis of LRTIs, we established an available loop-mediated isothermal amplification (LAMP) assay for the detection of eight common lower respiratory pathogens, including Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, Staphylococcus aureus, Escherichia coli, Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis. The whole process can be achieved within 1 h (sample to results read out). We established an extraction free isothermal system. 528 sputum samples collected from patients suspected to have LRTIs were analyzed by the system (8 tests in each sample, a total of 4224 tests) and compared with the standard culture method (SCM). The samples with inconsistent results were further verified by Sanger sequencing and High-throughput sequencing (NGS). The detection limits of the LAMP assay for the 8 pathogens ranged from 103 to 104 CFU/mL. Upon testing 528 samples, the Kappa coefficients of all pathogens ranged between 0.5 and 0.7 indicated a moderate agreement between the LAMP assay and the SCM. All inconsistent samples were further verified by Sanger sequencing, we found that the developed LAMP assay had a higher consistency level with Sanger sequencing than the SCM for all pathogens. Additionally, when the NGS was set to a diagnostic gold standard, the specificity and sensitivity of the LAMP assay for LRTIs were 94.49% and 75.00%. The present study demonstrated that the developed LAMP has high consistency with the sequencing methods. Meanwhile, the LAMP assay has a higher detection rate compared to the SCM. It may be a powerful tool for rapid and reliable clinical diagnosis of LRTIs in primary hospitals.

Glycerol or crude glycerol as substrates make Pseudomonas aeruginosa achieve anaerobic production of rhamnolipids.

BACKGROUND: The anaerobic production of rhamnolipids is significant in research and application, such as foamless fermentation and in situ production of rhamnolipids in the anoxic environments. Although a few studies reported that some rare Pseudomonas aeruginosa strains can produce rhamnolipids anaerobically, the decisive factors for anaerobic production of rhamnolipids were unknown. RESULTS: Two possible hypotheses on the decisive factors for anaerobic production of rhamnolipids by P. aeruginosa were proposed, the strains specificity of rare P. aeruginosa (hypothesis 1) and the effect of specific substrates (hypothesis 2). This study assessed the anaerobic growth and rhamnolipids synthesis of three P. aeruginosa strains using different substrates. P. aeruginosa strains anaerobically grew well using all the tested substrates, but glycerol was the only carbon source that supported anaerobic production of rhamnolipids. Other carbon sources with different concentrations still failed for anaerobic production of rhamnolipids by P. aeruginosa. Nitrate was the excellent nitrogen source for anaerobic production of rhamnolipids. FTIR spectra analysis confirmed the anaerobically produced rhamnolipids by P. aeruginosa using glycerol. The anaerobically produced rhamnolipids decreased air-water surface tension to below 29.0 mN/m and emulsified crude oil with EI24 above 65%. Crude glycerol and 1, 2-propylene glycol also supported the anaerobic production of rhamnolipids by all P. aeruginosa strains. Prospects and bottlenecks to anaerobic production of rhamnolipids were also discussed. CONCLUSIONS: Glycerol substrate was the decisive factor for anaerobic production of rhamnolipids by P. aeruginosa. Strain specificity resulted in the different anaerobic yield of rhamnolipids. Crude glycerol was one low cost substrate for anaerobic biosynthesis of rhamnolipids by P. aeruginosa. Results help advance the research on anaerobic production of rhamnolipids, deepen the biosynthesis theory of rhamnolipids and optimize the anaerobic production of rhamnolipids.

The rise and the fall of a Pseudomonas aeruginosa endemic lineage in a hospital.

The biological features that allow a pathogen to survive in the hospital environment are mostly unknown. The extinction of bacterial epidemics in hospitals is mostly attributed to changes in medical practice, including infection control, but the role of bacterial adaptation has never been documented. We analysed a collection of Pseudomonas aeruginosa isolates belonging to the Besançon Epidemic Strain (BES), responsible for a 12year nosocomial outbreak, using a genotype-to-phenotype approach. Bayesian analysis estimated the emergence of the clone in the hospital 5 years before its opening, during the creation of its water distribution network made of copper. BES survived better than the reference strains PAO1 and PA14 in a copper solution due to a genomic island containing 13 metal-resistance genes and was specifically able to proliferate in the ubiquitous amoeba Vermamoeba vermiformis. Mutations affecting amino-acid metabolism, antibiotic resistance, lipopolysaccharide biosynthesis, and regulation were enriched during the spread of BES. Seven distinct regulatory mutations attenuated the overexpression of the genes encoding the efflux pump MexAB-OprM over time. The fitness of BES decreased over time in correlation with its genome size. Overall, the resistance to inhibitors and predators presumably aided the proliferation and propagation of BES in the plumbing system of the hospital. The pathogen further spread among patients via multiple routes of contamination. The decreased prevalence of patients infected by BES mirrored the parallel and convergent genomic evolution and reduction that affected bacterial fitness. Along with infection control measures, this may have participated in the extinction of BES in the hospital setting.

Genomic characterization of carbapenem-non-susceptible Pseudomonas aeruginosa in Singapore.

Pseudomonas aeruginosa is a clinically important pathogen implicated in many hospital-acquired infections. Its propensity to acquire broad-spectrum resistance has earned the organism its status as a severe public health threat requiring urgent control measures. While whole-genome sequencing-based genomic surveillance provides a means to track antimicrobial resistance, its use in molecular epidemiological surveys of P. aeruginosa remains limited, especially in the Southeast Asian region. We sequenced the whole genomes of 222 carbapenem-non-susceptible P. aeruginosa (CNPA) isolates collected in 2006-2020 at the largest public acute care hospital in Singapore. Antimicrobial susceptibilities were determined using broth microdilution. Clonal relatedness, multi-locus sequence types, and antimicrobial resistance determinants (acquired and chromosomal) were determined. In this study, CNPA exhibited broad-spectrum resistance (87.8% multi-drug resistance), retaining susceptibility only to polymyxin B (95.0%) and amikacin (55.0%). Carbapenemases were detected in 51.4% of the isolates, where IMP and NDM metallo-ß-lactamases were the most frequent. Carbapenem resistance was also likely associated with OprD alterations or efflux mechanisms (ArmZ/NalD mutations), which occurred in strains with or without carbapenemases. The population of CNPA in the hospital was diverse; the 222 isolates grouped into 68 sequence types (ST), which included various high-risk clones. We detected an emerging clone, the NDM-1-producing ST308, in addition to the global high-risk ST235 clone which was the predominant clone in our population. Our results thus provide a "snapshot" of the circulating lineages of CNPA locally and the prevailing genetic mechanisms contributing to carbapenem resistance. This database also serves as the baseline for future prospective surveillance studies.

Comparative genome analysis of multidrug-resistant Pseudomonas aeruginosa JNQH-PA57, a clinically isolated mucoid strain with comprehensive carbapenem resistance mechanisms.

BACKGROUND: The prevalence of clinical multidrug-resistant (MDR) Pseudomonas aeruginosa has been increasing rapidly worldwide over the years and responsible for a wide range of acute and chronic infections with high mortalities. Although hundreds of complete genomes of clinical P. aeruginosa isolates have been sequenced, only a few complete genomes of mucoid strains are available, limiting a comprehensive understanding of this important group of opportunistic pathogens. Herein, the complete genome of a clinically isolated mucoid strain P. aeruginosa JNQH-PA57 was sequenced and assembled using Illumina and Oxford nanopore sequencing technologies. Genomic features, phylogenetic relationships, and comparative genomics of this pathogen were comprehensively analyzed using various bioinformatics tools. A series of phenotypic and molecular-genetic tests were conducted to investigate the mechanisms of carbapenem resistance in this strain. RESULTS: Several genomic features of MDR P. aeruginosa JNQH-PA57 were identified based on the whole-genome sequencing. We found that the accessory genome of JNQH-PA57 including several prophages, genomic islands, as well as a PAPI-1 family integrative and conjugative element (ICE), mainly contributed to the larger genome of this strain (6,747,067 bp) compared to other popular P. aeruginosa strains (with an average genome size of 6,445,223 bp) listed in Pseudomonas Genome Database. Colony morphology analysis and biofilm crystal staining assay respectively demonstrated an enhanced alginate production and a thicker biofilm formation capability of JNQH-PA57. A deleted mutation at nt 424 presented in mucA gene, resulted in the upregulated expression of a sigma-factor AlgU and a GDP mannose dehydrogenase AlgD, which might explain the mucoid phenotype of this strain. As for the carbapenem resistance mechanisms, our results revealed that the interplay between impaired OprD porin, chromosomal ß-lactamase OXA-488 expression, MexAB-OprM and MexXY-OprM efflux pumps overexpression, synergistically with the alginates-overproducing protective biofilm, conferred the high carbapenem resistance to P. aeruginosa JNQH-PA57. CONCLUSION: Based on the genome analysis, we could demonstrate that the upregulated expression of algU and algD, which due to the truncation variant of MucA, might account for the mucoid phenotype of JNQH-PA57. Moreover, the resistance to carbapenem in P. aeruginosa JNQH-PA57 is multifactorial. The dataset presented in this study provided an essential genetic basis for the comprehensive cognition of the physiology, pathogenicity, and carbapenem resistance mechanisms of this clinical mucoid strain.

Persistent Bacterial Coinfection of a COVID-19 Patient Caused by a Genetically Adapted Pseudomonas aeruginosa Chronic Colonizer.

Pseudomonas aeruginosa is a biofilm-forming opportunistic pathogen which causes chronic infections in immunocompromised patients and leads to high mortality rate. It is identified as a common coinfecting pathogen in COVID-19 patients causing exacerbation of illness. In our hospital, P. aeruginosa is one of the top coinfecting bacteria identified among COVID-19 patients. We collected a strong biofilm-forming P. aeruginosa strain displaying small colony variant morphology from a severe COVID-19 patient. Genomic and transcriptomic sequencing analyses were performed with phenotypic validation to investigate its adaptation in SARS-CoV-2 infected environment. Genomic characterization predicted specific genomic islands highly associated with virulence, transcriptional regulation, and DNA restriction-modification systems. Epigenetic analysis revealed a specific N6-methyl adenine (m6A) methylating pattern including methylation of alginate, flagellar and quorum sensing associated genes. Differential gene expression analysis indicated that this isolate formed excessive biofilm by reducing flagellar formation (7.4 to 1,624.1 folds) and overproducing extracellular matrix components including CdrA (4.4 folds), alginate (5.2 to 29.1 folds) and Pel (4.8-5.5 folds). In summary, we demonstrated that P. aeuginosa clinical isolates with novel epigenetic markers could form excessive biofilm, which might enhance its antibiotic resistance and in vivo colonization in COVID-19 patients.

Chemotaxis Toward Crude Oil by an Oil-Degrading Pseudomonas aeruginosa 6-1B Strain.

The chemotactic properties of an oil-degrading Pseudomonas aeruginosa strain 6-1B, isolated from Daqing Oilfield, China, have been investigated. The strain 6-1B could grow well in crude oil with a specific rhamnolipid biosurfactant production. Furthermore, it exhibits chemotaxis toward various substrates, including glycine, glycerol, glucose, and sucrose. Compared with another oil-degrading strain, T7-2, the strain 6-1B presented a better chemotactic response towards crude oil and its vital component, n-alkenes. Based on the observed distribution of the strain 6-1B cells around the oil droplet in the chemotactic assays, the potential chemotaxis process of bacteria toward crude oil could be summarized in the following steps: searching, moving and consuming.