Novel Molecular Markers Linked to Pseudomonas aeruginosa Epidemic High-Risk Clones

Carbapenem-Resistant Pseudomonas aeruginosa's Resistome: Pan-Genomic Plasticity, the Impact of Transposable Elements and Jumping Genes

Pseudomonas aeruginosa, a Gram-negative, motile bacterium, may cause significant infections in both community and hospital settings, leading to substantial morbidity and mortality. This opportunistic pathogen can thrive in various environments, making it a public health concern worldwide. P. aeruginosa's genomic pool is highly dynamic and diverse, with a pan-genome size ranging from 5.5 to 7.76 Mbp. This versatility arises from its ability to acquire genes through horizontal gene transfer (HGT) via different genetic elements (GEs), such as mobile genetic elements (MGEs). These MGEs, collectively known as the mobilome, facilitate the spread of genes encoding resistance to antimicrobials (ARGs), resistance to heavy metals (HMRGs), virulence (VGs), and metabolic functions (MGs). Of particular concern are the acquired carbapenemase genes (ACGs) and other β-lactamase genes, such as classes A, B [metallo-β-lactamases (MBLs)], and D carbapenemases, which can lead to increased antimicrobial resistance. This review emphasizes the importance of the mobilome in understanding antimicrobial resistance in P. aeruginosa.

Molecular epidemiological study of Pseudomonas aeruginosa strains isolated from hospitals in Brazil by MLST and CRISPR/Cas system analysis

The CRISPR/Cas system defends bacteria and archaea against invasive pathogens, such as phages, establishing an immunological memory from this interaction. Pseudomonas aeruginosa, an opportunistic pathogen, represents a significant public health concern due to its multidrug resistance. This study conducted a molecular epidemiological analysis of clinical isolates of Pseudomonas aeruginosa in Brazil using multilocus sequence typing (MLST) and characterization of CRISPR/Cas system. Most P. aeruginosa isolates harbored the type I-F CRISPR/Cas system (83%), with a subset also exhibiting the type I-E system. Additionally, some isolates presented incomplete CRISPR/Cas systems in their secondary loci. Notably, the isolate Pae93 exhibited a genetic composition rich in phage-related proteins proximal to the orphan CRISPR locus. The identification and characterization of spacer sequences, including previously undocumented ones, revealed a remarkable diversity of predatory mobile genetic elements (MGEs) among the P. aeruginosa isolates studied. The spacer sequences were incorporated into the MGE library. Additionally, the study identified the existence of prophages and anti-CRISPR genes. Two new sequence types (STs 3383 and 3384) were identified and added to the PubMLST database. No discernible correlation was established between the observed STs and the previously delineated CRISPR genotypes. However, the CRISPR system remains valuable for elucidating specific interactions between microorganisms and MGEs. The Brazilian population of clinical P. aeruginosa isolates was shown to be genetically heterogeneous with a non-clonal distribution, as revealed by MLST analysis. The presence of high-risk clones, such as ST 244 and ST 235, underscores the importance of robust epidemiological surveillance and infection control strategies for P. aeruginosa, especially in healthcare settings. This study significantly contributes to the understanding of the molecular epidemiology of these isolates in Brazil.

Resistance of Pseudomonas aeruginosa to Antibiotics During Long-Term Persistence in Patients with Cystic Fibrosis

Pseudomonas aeruginosa is one of the leading causes of nosocomial respiratory tract infections, significantly affecting morbidity and mortality. It can persist in the lungs of patients with cystic fibrosis (CF) for extended periods because of its adaptive capacity. The main aim of this study was to determine the phenotypic and genotypic resistance to antibiotics of clinical isolates of P. aeruginosa that persist in patients with CF receiving long-term antimicrobial therapy. The study included nine strains of P. aeruginosa isolated from the sputum of patients with CF admitted to the hospital. Susceptibility to antibiotics was determined using the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. Whole-genome sequencing was performed for phylogeny, sequence typing, and to identify antibiotic-resistant genes. The study showed that during long-term persistence in the lungs of patients receiving antibacterial therapy, the restoration of susceptibility to antibiotics occurred in some cases. Multilocus sequence typing and phylogeny revealed six sequence types. Functional annotation identified 72 genes responsible for resistance to antibacterial and chemical substances, with either chromosomal or plasmid localisation.

Hospital environment as reservoir of Pseudomonas aeruginosa in human cases: a molecular epidemiology investigation in a hospital setting in central Italy

Pseudomonas aeruginosa is one of the main causes of hospital infections that are difficult to manage because of multidrug resistance (MDR). The aim of this study was to describe a molecular investigation on 19 clinical and 14 isolates from the environment in the Hub hospital of the Molise region, central Italy. Antimicrobial susceptibility was evaluated using BD Phoenix™ Automated Microbiology System. Pulsed-field gel electrophoresis (PFGE) with SpeI, enterobacterial repetitive intergenic consensus (ERIC-PCR), and random amplified polymorphic DNA-PCR were performed for genotyping. All 33 P. aeruginosa showed MDR phenotype. PFGE had 0.99 discriminatory power, underlining high heterogeneity among the strains. The genetic relatedness between two human isolates (H12 and H15) from neonatal intensive care (NICU) and one environmental strain (E1) collected from siphon of sink in the delivery room was noticeable, as well as between one strain from faucet in NICU (E2) and siphon sink (E5) from delivery room. The link between H12, H15, and E1 strains was corroborated by ERIC-PCR showing epidemiological concordance, although with a lower discriminatory power. The study findings strengthened the critical correlation between clinical P. aeruginosa and environment, according to previous molecular surveys on outbreaks occurred in Italy.

Assessing the role of environment in Pseudomonas aeruginosa healthcare-associated bloodstream infections: a one-year prospective survey

BACKGROUND

Deciphering precise sources and patterns of healthcare-associated Pseudomonas aeruginosa colonization/infection is crucial in defining strategies of prevention and control.

AIM

To prospectively investigate the role of hospital environment in P. aeruginosa nosocomial bloodstream infections (Pa-BSIs) during one year in a tertiary-care hospital.

METHODS

Clinical records of patients presenting Pa-BSIs after >48 h of hospitalization were investigated to confirm the nosocomial character of BSIs and identify the routes of entry and risk factors. Environmental investigations were performed to track P. aeruginosa source/reservoir along the care pathway. Clinical and environmental strains were compared by whole-genome sequencing to identify the route of contamination from hospital environment to patients.

FINDINGS

Fifty-three BSIs episodes in 49 patients were considered as nosocomial, mostly involving men (73%), with an average age of 62.4 years, immunosuppressed in >40% of cases, and after previous antibiotic therapy in almost 92% of cases. BSIs occurred after 27 days of hospitalization on average. The main routes of entry were urinary (30%, on indwelling catheters for two-thirds of cases) and cutaneous (17%, catheter-related in almost 80% of cases). P. aeruginosa was found in 16 out of 49 investigations, representing 34 positive samples, including 54% of sink traps, 23% of water, and 20% of tap aerators. An epidemiological link was established between environmental and clinical strains only for eight patients, representing 15% of nosocomial BSIs.

CONCLUSION

The hospital environment usually considered as the main source of P. aeruginosa healthcare-associated infections was identified as responsible for nosocomial BSIs in only 15% of patients. Since the implementation of water and hospital environment management, one may hypothesize that P. aeruginosa has become a community-acquired pathogen with a nosocomial expression in infection.

High-risk Pseudomonas aeruginosa clones harboring β-lactamases: 2024 update

Carbapenem-resistant Pseudomonas aeruginosa is defined by the World Health Organization as a "high priority" in developing new antimicrobials. Indeed, the emergence and spread of multidrug-resistant (MDR) or extensively drug-resistant (XDR) bacteria increase the morbidity and mortality risk of infected patients. Genomic variants of P. aeruginosa that display phenotypes of MDR/XDR have been defined as high-risk global clones. In this mini-review, we describe some international high-risk clones that carry β-lactamase genes that can produce chronic colonization and increase infected patients' morbidity and mortality rates.

Antibiotic-Resistant Pseudomonas aeruginosa from Market Meat in Peru

Unconsidered microorganisms, such as Pseudomonas aeruginosa, may be often recovered from food samples. This study aimed to characterize seven P. aeruginosa recovered from traditional market chicken meat in Lima, Peru. Antimicrobial susceptibility to 18 antimicrobial agents as well as the presence of amino acid changes in fluoroquinolone targets, 10 mediated colistin resistance (mcr) genes and integrons were analyzed. Clonal relationships were determined through pulsed-field gel electrophoresis (PFGE). Serotype by agglutination, multilocus sequence typing and the presence of 14 virulence factors (VFs) were established. Two isolates were multidrug-resistant, all being fluoroquinolone-resistant and exhibited the amino acid changes GyrA T83I and ParC S87L. No mcr gene was detected in the colistin-resistant isolates. The isolates showed identical PFGE patterns, and the selected P6 isolate belonged to the serotype O:4 and the sequence type 1800, and presented 12 VFs (all but exoU and exlA). The present study highlights the presence of multidrug and virulent P. aeruginosa in market chicken meat, and suggests cross-contamination during meat manipulation.

Decoding Pseudomonas aeruginosa: Genomic insights into adaptation, antibiotic resistance, and the enigmatic role of T6SS in interbacterial dynamics

Pseudomonas aeruginosa demonstrates a remarkable capacity for adaptation and survival in diverse environments. Furthermore, its clinical importance is underscored by its intrinsic and acquired resistance to a wide range of antimicrobial agents, posing a substantial challenge in healthcare settings. Amidst this complex landscape of resistance, the Type VI Secretion System (T6SS) in P. aeruginosa adds yet another layer of intricacy and allows bacteria to engage in interbacterial competition, potentially influencing their resilience and pathogenicity. Whole genome sequencing (WGS) was conducted on the five isolates under investigation, enabling the identification of antibiotic resistance genes (ARGs) and mutations associated with resistance. All isolates exhibit class C and D β-lactamases, displaying variant differences. The Resistance-nodulation-division (RND) antibiotic efflux pumps, crucial for multidrug resistance, have been encoded chromosomally. When exploring the role of the T6SS in urinary tract infections involving other bacteria, it was noted that P. aeruginosa isolates exhibited reduced counts when co-cultivated with other bacteria. The downregulation of the tssJ gene, associated with the T6SS under bacterial stress, and the exclusion of several cluster genes in this study suggest the hypothesis of a basal state rather than an attack/defence mechanism in the initial contact.

Residual risk of Pseudomonas aeruginosa waterborne contamination in an intensive care unit despite the presence of filters at all water points-of-use

OBJECTIVE

To assess the residual risk of waterborne contamination by Pseudomonas aeruginosa from a water network colonized by a single genotype [sequence type (ST) 299] despite the presence of antimicrobial filters in a medical intensive care unit (ICU).

METHODS

During the first 19-month period since the ICU opened, contamination of the water network was assessed monthly by collecting water upstream of the filters. Downstream water was also sampled to assess the efficiency of the filters. P. aeruginosa isolates from patients were collected and compared with the waterborne ST299 P. aeruginosa by multiplex-rep polymerase chain reaction (PCR), pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing. Cross-transmission events by other genotypes of P. aeruginosa were also assessed.

RESULTS

Overall, 1.3% of 449 samples of filtered water were positive for P. aeruginosa in inoculum, varying between 1 and 104 colony-forming units/100 mL according to the tap. All P. aeruginosa hydric isolates belonged to ST299 and displayed fewer than two single nucleotide polymorphisms (SNPs). Among 278 clinical isolates from 122 patients, 10 isolates in five patients showed identical profiles to the hydric ST299 clone on both multiplex-rep PCR and PFGE, and differed by an average of fewer than five SNPs, confirming the water network reservoir as the source of contamination by P. aeruginosa for 4.09% of patients. Cross-transmission events by other genotypes of P. aeruginosa were responsible for the contamination of 1.75% of patients.

DISCUSSION/CONCLUSION

Antimicrobial filters are not sufficient to protect patients from waterborne pathogens when the water network is highly contaminated. A microbiological survey of filtered water may be needed in units hosting patients at risk of P. aeruginosa infections, even when all water points-of-use are fitted with filters.

Spread of Pseudomonas aeruginosa ST274 Clone in Different Niches: Resistome, Virulome, and Phylogenetic Relationship

Pseudomonas aeruginosa ST274 is an international epidemic high-risk clone, mostly associated with hospital settings and appears to colonize cystic fibrosis (CF) patients worldwide. To understand the relevant mechanisms for its success, the biological and genomic characteristics of 11 ST274-P. aeruginosa strains from clinical and non-clinical origins were analyzed. The extensively drug-resistant (XDR/DTR), the non-susceptible to at least one agent (modR), and the lasR-truncated (by ISPsp7) strains showed a chronic infection phenotype characterized by loss of serotype-specific antigenicity and low motility. Furthermore, the XDR/DTR and modR strains presented low pigment production and biofilm formation, which were very high in the lasR-truncated strain. Their whole genome sequences were compared with other 14 ST274-P. aeruginosa genomes available in the NCBI database, and certain associations have been primarily detected: blaOXA-486 and blaPDC-24 genes, serotype O:3, exoS+/exoU- genotype, group V of type IV pili, and pyoverdine locus class II. Other general molecular markers highlight the absence of vqsM and pldA/tleS genes and the presence of the same mutational pattern in genes involving two-component sensor-regulator systems PmrAB and CreBD, exotoxin A, quorum-sensing RhlI, beta-lactamase expression regulator AmpD, PBP1A, or FusA2 elongation factor G. The proportionated ST274-P. aeruginosa results could serve as the basis for more specific studies focused on better antibiotic stewardship and new therapeutic developments.

Antimicrobial resistance and genotyping of Pseudomonas aeruginosa isolated from the ear canals of dogs in Japan

The strong bond between dogs and their owners creates a close association that could result in the transfer of antibiotic-resistant bacteria from canines to humans, potentially leading to the spread of antimicrobial resistance genes. Pseudomonas aeruginosa, a common causative agent of persistent ear infections in dogs, is often resistant to multiple antibiotics. Assessing the antimicrobial resistance profile and genotype of P. aeruginosa is crucial for the appropriate use of veterinary pharmaceuticals. However, in recent years, few studies have been conducted on this bacterium in Japan. We determined the antimicrobial resistance profile and genotype of P. aeruginosa isolated from the ear canal of dogs in Japan in 2020. Analysis of antimicrobial resistance using disk diffusion tests indicated a high frequency of resistance to most antimicrobial agents. Particularly, 29 isolates from the ear canals of the 29 affected dogs (100%) were resistant to cefovecin, cefpodoxime, and florfenicol; however, they were susceptible to cefepime and piperacillin/tazobactam. Only 3.4, 10.3, and 10.3% of the isolates were resistant to ceftazidime, tobramycin, and gentamicin, respectively. Furthermore, upon analyzing the population structure using multilocus sequence typing, a considerably large clonal complex was not observed in the tested isolates. Three isolates, namely ST3881, ST1646, and ST532, were clonally related to the clinically isolated sequence types in Japan (such as ST1831, ST1413, ST1812, and ST1849), which is indicative of dog-to-human transmission. Considering the variation in antibiotic resistance compared to that reported by previous studies and the potential risk of dog-to-human transmission, we believe that the survey for antimicrobial resistance profile and population structure should be continued regularly. However, the prevalence of multidrug-resistant P. aeruginosa in dogs in Japan is not a crisis.

Acquisition of T6SS Effector TseL Contributes to the Emerging of Novel Epidemic Strains of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen with multiple strategies to interact with other microbes and host cells, gaining fitness in complicated infection sites. The contact-dependent type VI secretion system (T6SS) is one critical secretion apparatus involved in both interbacterial competition and pathogenesis. To date, only limited numbers of T6SS-effectors have been clearly characterized in P. aeruginosa laboratory strains, and the importance of T6SS diversity in the evolution of clinical P. aeruginosa remains unclear. Recently, we characterized a P. aeruginosa clinical strain LYSZa7 from a COVID-19 patient, which adopted complex genetic adaptations toward chronic infections. Bioinformatic analysis has revealed a putative type VI secretion system (T6SS) dependent lipase effector in LYSZa7, which is a homologue of TseL in Vibrio cholerae and is widely distributed in pathogens. We experimentally validated that this TseL homologue belongs to the Tle2, a subfamily of T6SS-lipase effectors; thereby, we name this effector TseL (TseLPA in this work). Further, we showed the lipase-dependent bacterial toxicity of TseLPA, which primarily targets bacterial periplasm. The toxicity of TseLPA can be neutralized by two immunity proteins, TsiP1 and TsiP2, which are encoded upstream of tseL. In addition, we proved this TseLPA contributes to bacterial pathogenesis by promoting bacterial internalization into host cells. Our study suggests that clinical bacterial strains employ a diversified group of T6SS effectors for interbacterial competition and might contribute to emerging of new epidemic clonal lineages. IMPORTANCE Pseudomonas aeruginosa is one predominant pathogen that causes hospital-acquired infections and is one of the commonest coinfecting bacteria in immunocompromised patients and chronic wounds. This bacterium harbors a diverse accessory genome with a high frequency of gene recombination, rendering its population highly heterogeneous. Numerous Pa lineages coexist in the biofilm, where successful epidemic clonal lineage or strain-specific type commonly acquires genes to increase its fitness over the other organisms. Current studies of Pa genomic diversity commonly focused on antibiotic resistant genes and novel phages, overlooking the contribution of type VI secretion system (T6SS). We characterized a Pa clinical strain LYSZa7 from a COVID-19 patient, which adopted complex genetic adaptations toward chronic infections. We report, in this study, a novel T6SS-lipase effector that is broadly distributed in Pa clinical isolates and other predominant pathogens. The study suggests that hospital transmission may raise the emergence of new epidemic clonal lineages with specified T6SS effectors.

The predictive potential of different molecular markers linked to amikacin susceptibility phenotypes in Pseudomonas aeruginosa

Informed antibiotic prescription offers a practical solution to antibiotic resistance problem. With the increasing affordability of different sequencing technologies, molecular-based resistance prediction would direct proper antibiotic selection and preserve available agents. Amikacin is a broad-spectrum aminoglycoside exhibiting higher clinical efficacy and less resistance rates in Ps. aeruginosa due to its structural nature and its ability to achieve higher serum concentrations at lower therapeutic doses. This study examines the predictive potential of molecular markers underlying amikacin susceptibility phenotypes in order to provide improved diagnostic panels. Using a predictive model, genes and variants underlying amikacin resistance have been statistically and functionally explored in a large comprehensive and diverse set of Ps. aeruginosa completely sequenced genomes. Different genes and variants have been examined for their predictive potential and functional correlation to amikacin susceptibility phenotypes. Three predictive sets of molecular markers have been identified and can be used in a complementary manner, offering promising molecular diagnostics. armR, nalC, nalD, mexR, mexZ, ampR, rmtD, nalDSer32Asn, fusA1Y552C, fusA1D588G, arnAA170T, and arnDG206C have been identified as the best amikacin resistance predictors in Ps. aeruginosa while faoAT385A, nuoGA890T, nuoGA574T, lptAT55A, lptAR62S, pstBR87C, gidBE126G, gidBQ28K, amgSE108Q, and rplYQ41L have been identified as the best amikacin susceptibility predictors. Combining different measures of predictive performance together with further functional analysis can help design new and more informative molecular diagnostic panels. This would greatly inform and direct point of care diagnosis and prescription, which would consequently preserve amikacin functionality and usefulness.