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

Genomic Differences Associated with Resistance and Virulence in Pseudomonas aeruginosa Isolates from Clinical and Environmental Sites

Pseudomonas aeruginosa is a pathogen that causes healthcare-associated infections (HAIs) worldwide. It is unclear whether P. aeruginosa isolated from the natural environment has the same pathogenicity and antimicrobial resistance potential as clinical strains. In this study, virulence- and resistance-associated genes were compared in 14 genomic sequences of clinical and environmental isolates of P. aeruginosa using the VFDB, PATRIC, and CARD databases. All isolates were found to share 62% of virulence genes related to adhesion, motility, secretion systems, and quorum sensing and 72.9% of resistance genes related to efflux pumps and membrane permeability. Our results indicate that both types of isolates possess conserved genetic information associated with virulence and resistance mechanisms regardless of the source. However, none of the environmental isolates were associated with high-risk clones (HRCs). These clones (ST235 and ST111) were found only in clinical isolates, which have an impact on human medical epidemiology due to their ability to spread and persist, indicating a correlation between the clinical environment and increased virulence. The genomic variation and antibiotic susceptibility of environmental isolates of P. aeruginosa suggest potential biotechnological applications if obtained from sources that are under surveillance and investigation to limit the emergence and spread of antibiotic resistant strains.

The O-glycan is essential for the induction of protective antibodies against lethal infection by flagella A-bearing Pseudomonas aeruginosa

To address the problem of increased antimicrobial resistance, we developed a glycoconjugate vaccine comprised of O-polysaccharides (OPS) of the four most prevalent serotypes of Klebsiella pneumoniae (KP) linked to recombinant flagellin types A and B (rFlaA and rFlaB) of Pseudomonas aeruginosa (PA). Flagellin is the major subunit of the flagellar filament. Flagella A and B, essential virulence factors for PA, are glycosylated with different glycans. We previously reported that while both rFlaA and rFlaB were highly immunogenic, only the rFlaB antisera reduced PA motility and protected mice from lethal PA infection in a mouse model of thermal injury. Since recombinant flagellin is not glycosylated, we examined the possibility that the glycan on native FlaA (nFlaA) might be critical to functional immune responses. We compared the ability of nFlaA to that of native, deglycosylated FlaA (dnFlaA) to induce functionally active antisera. O glycan was removed from nFlaA with trifluoromethanesulfonic acid. Despite the similar high-titered anti-FlaA antibody levels elicited by nFlaA, rFlaA, and dnFlaA, only the nFlaA antisera inhibited PA motility and protected mice following lethal intraperitoneal bacterial challenge. Both the protective efficacy and carrier protein function of nFlaA were retained when conjugated to KP O1 OPS. We conclude that unlike the case with FlaB O glycan, the FlaA glycan is an important epitope for the induction of functionally active anti-FlaA antibodies.

Population-based genomic surveillance of Pseudomonas aeruginosa causing bloodstream infections in a large Canadian health region

PURPOSE

Population-based surveillance was undertaken to determine clinical factors, susceptibility patterns, and incidence rates (IR) of Pseudomonas aeruginosa causing bloodstream infections (BSIs) in a Canadian region (2010-2018).

METHODS

We combined clinical data with genomics to characterize P. aeruginosa (BSIs) (n = 167) in a well-defined Canadian (Calgary) human population over a 9-year period (2010-2018).

RESULTS

The annual population IR per 100,000 patient years increased from 3.4/100,000 in 2010 to 5.9/100,000 in 2018, with the highest IRs in elderly males from the hospital setting. Over a quarter of patients presented with febrile neutropenia, followed by urinary tract infections and pneumonia. Antimicrobial resistance (AMR) rates and determinants were rare. The P. aeruginosa population was polyclonal consisting of three dominant sequence types (STs), namely ST244, ST111, and ST17. Antimicrobial-susceptible ST244 was the most common clone and belonged to three clades (A, B, C). The ST244 IR/100,000 increased over time due to the expansion of clade C. Multidrug-resistant ST111 was the second most common clone and IR/100,000 decreased over time. ST111 belonged to three clades (A, B, C) with clade C containing blaVIM-2. Different serotypes were linked to various STs. The IR/100,000 of P. aeruginosa that belonged to serotypes O6 increased significantly over time.

CONCLUSION

An effective multivalent vaccine consisting of five serotypes (O1, O3, O5, O6, O11) would confer protection to > 70% of Calgary residents with P. aeruginosa BSIs. This study has provided a unique perspective of the population dynamics over time of P. aeruginosa STs, clades, and serotypes responsible for BSIs.

Molecular Analysis of Carbapenem and Aminoglycoside Resistance Genes in Carbapenem-Resistant Pseudomonas aeruginosa Clinical Strains: A Challenge for Tertiary Care Hospitals

Carbapenem-resistant Pseudomonas aeruginosa (P. aeruginosa) strains have become a global threat due to their remarkable capability to survive and disseminate successfully by the acquisition of resistance genes. As a result, the treatment strategies have been severely compromised. Due to the insufficient available data regarding P. aeruginosa resistance from Pakistan, we aimed to investigate the resistance mechanisms of 249 P. aeruginosa strains by antimicrobial susceptibility testing, polymerase chain reaction for the detection of carbapenemases, aminoglycoside resistance genes, extended-spectrum beta-lactamases (ESBLs), sequence typing and plasmid typing. Furthermore, we tested silver nanoparticles (AgNPs) to evaluate their in vitro sensitivity against antimicrobial-resistant P. aeruginosa strains. We observed higher resistance against antimicrobials in the general surgery ward, general medicine ward and wound samples. Phenotypic carbapenemase-producer strains comprised 80.7% (201/249) with 89.0% (179/201) demonstrating genes encoding carbapenemases: blaNDM-1 (32.96%), blaOXA48 (37.43%), blaIMP (7.26%), blaVIM (5.03%), blaKPC-2 (1.12%), blaNDM-1/blaOXA48 (13.97%), blaOXA-48/blaVIM (1.68%) and blaVIM/blaIMP (0.56%). Aminoglycoside-modifying enzyme genes and 16S rRNA methylase variants were detected in 43.8% (109/249) strains: aac(6')-lb (12.8%), aac(3)-lla (12.0%), rmtB (21.1%), rmtC (11.0%), armA (12.8%), rmtD (4.6%), rmtF (6.4%), rmtB/aac(3)-lla (8.2%), rmtB/aac(6')-lla (7.3%) and rmtB/armA (3.6%). In total, 43.0% (77/179) of the strains coharbored carbapenemases and aminoglycoside resistance genes with 83.1% resistant to at least 1 agent in 3 or more classes and 16.9% resistant to every class of antimicrobials tested. Thirteen sequence types (STs) were identified: ST235, ST277, ST234, ST170, ST381, ST175, ST1455, ST1963, ST313, ST207, ST664, ST357 and ST348. Plasmid replicon types IncFI, IncFII, IncA/C, IncL/M, IncN, IncX, IncR and IncFIIK and MOB types F11, F12, H121, P131 and P3 were detected. Meropenem/AgNPs and Amikacin/AgNPs showed enhanced antibacterial activity. We reported the coexistence of carbapenemases and aminoglycoside resistance genes among carbapenem-resistant P. aeruginosa with diverse clonal lineages from Pakistan. Furthermore, we highlighted AgNP's potential role in handling future antimicrobial resistance concerns.

Antimicrobial resistance survey and whole-genome analysis of nosocomial P. Aeruginosa isolated from eastern Province of China in 2016-2021

BACKGROUND

Pseudomonas aeruginosa is a major Gram-negative pathogen that can exacerbate lung infections in the patients with cystic fibrosis, which can ultimately lead to death.

METHODS

From 2016 to 2021, 103 strains of P. aeruginosa were isolated from hospitals and 20 antibiotics were used for antimicrobial susceptibility determination. Using next-generation genome sequencing technology, these strains were sequenced and analyzed in terms of serotypes, ST types, and resistance genes for epidemiological investigation.

RESULTS

The age distribution of patients ranged from 10 days to 94 years with a median age of 69 years old. The strains were mainly isolated from sputum (72 strains, 69.9%) and blood (14 strains, 13.6%). The size of these genomes ranged from 6.2 Mb to 7.4 Mb, with a mean value of 6.5 Mb. In addition to eight antibiotics that show inherent resistance to P. aeruginosa, the sensitivity rates for colistin, amikacin, gentamicin, ceftazidime, piperacillin, piperacillin-tazobactam, ciprofloxacin, meropenem, aztreonam, imipenem, cefepime and levofloxacin were 100%, 95.15%, 86.41%, 72.82%, 71.84%, 69.90%, 55.34%, 52.43%, 50.49%, 50.49%, 49.51% and 47.57% respectively, and the carriage rate of MDR strains was 30.69% (31/101). Whole-genome analysis showed that a total of 50 ST types were identified, with ST244 (5/103) and ST1076 (4/103) having a more pronounced distribution advantage. Serotype predictions showed that O6 accounted for 29.13% (30/103), O11 for 23.30% (24/103), O2 for 18.45% (19/103), and O1 for 11.65% (12/103) of the highest proportions. Notably, we found a significantly higher proportion of ExoU in P. aeruginosa strains of serotype O11 than in other cytotoxic exoenzyme positive strains. In addition to this, a total of 47 crpP genes that mediate resistance to fluoroquinolones antibiotics were found distributed on 43 P. aeruginosa strains, and 10 new variants of CrpP were identified, named 1.33, 1.34, 1.35, 1.36, 1.37, 1.38, 1.39, 1.40, 1.41 and 7.1.

CONCLUSIONS

We investigated the antibiotic susceptibility of clinical isolates of P. aeruginosa and genomically enriched the diversity of P. aeruginosa for its prophylactic and therapeutic value.

Outbreak of Pseudomonas aeruginosa High-Risk Clone ST309 Serotype O11 Featuring blaPER-1 and qnrVC6

Pseudomonas aeruginosa is a leading cause of hospital-acquired infections worldwide. Biofilm production, antibiotic resistance, and a wide range of virulence factors contribute to their persistence in nosocomial environments. We describe an outbreak caused by a multidrug-resistant P. aeruginosa strain in an ICU. Antibiotic susceptibility was determined and blaPER-1 and qnrVC were amplified via PCR. Clonality was determined using PFGE and biofilm formation was studied with a static model. A combination of antibiotics was assessed on both planktonic cells and biofilms. WGS was performed on five isolates. All isolates were clonally related, resistant to ceftazidime, cefepime, amikacin, and ceftolozane-tazobactam, and harbored blaPER-1; 11/19 possessed qnrVC. Meropenem and ciprofloxacin reduced the biofilm biomass; however, the response to antibiotic combinations with rifampicin was different between planktonic cells and biofilms. WGS revealed that the isolates belonged to ST309 and serotype O11. blaPER-1 and qnrVC6 were associated with a tandem of ISCR1 as part of a complex class one integron, with aac(6')-Il and ltrA as gene cassettes. The structure was associated upstream and downstream with Tn4662 and flanked by direct repeats, suggesting its horizontal mobilization capability as a composite transposon. ST309 is considered an emerging high-risk clone that should be monitored in the Americas.

Correlation of Pseudomonas aeruginosa Phage Resistance with the Numbers and Types of Antiphage Systems

Phage therapeutics offer a potentially powerful approach for combating multidrug-resistant bacterial infections. However, to be effective, phage therapy must overcome existing and developing phage resistance. While phage cocktails can reduce this risk by targeting multiple receptors in a single therapeutic, bacteria have mechanisms of resistance beyond receptor modification. A rapidly growing body of knowledge describes a broad and varied arsenal of antiphage systems encoded by bacteria to counter phage infection. We sought to understand the types and frequencies of antiphage systems present in a highly diverse panel of Pseudomonas aeruginosa clinical isolates utilized to characterize novel antibacterials. Using the web-server tool PADLOC (prokaryotic antiviral defense locator), putative antiphage systems were identified in these P. aeruginosa clinical isolates based on sequence homology to a validated and curated catalog of known defense systems. Coupling this host bacterium sequence analysis with host range data for 70 phages, we observed a correlation between existing phage resistance and the presence of higher numbers of antiphage systems in bacterial genomes. We were also able to identify antiphage systems that were more prevalent in highly phage-resistant P. aeruginosa strains, suggesting their importance in conferring resistance.

A. castellanii and P. aeruginosa mutually exacerbate damage to corneal cells during coinfection

IMPORTANCE

At the National Cheng Kung University Hospital, numerous cases of amoebic keratitis had been identified with concurrent bacterial infections. Among these bacterial coinfections, Pseudomonas aeruginosa accounted for 50% of the reported cases. However, the impact of pathogenic bacteria on amoeba-induced corneal damage remains unclear. In our study, we successfully demonstrated that P. aeruginosa accumulated on the Acanthamoeba castellanii surface and caused more severe corneal damage. We also indicated that the exposure of P. aeruginosa to amoeba-soluble antigens enhanced its adhesion ability, promoted biofilm formation, and led to more severe corneal cell damage. These findings significantly contributed to our understanding of the risk associated with P. aeruginosa coinfection in the progression of amoeba keratitis.

Efficacy of a Pseudomonas aeruginosa serogroup O9 vaccine

There are currently no approved vaccines against the opportunistic pathogen Pseudomonas aeruginosa. Among vaccine targets, the lipopolysaccharide (LPS) O antigen of P. aeruginosa is the most immunodominant protective candidate. There are 20 different O antigens composed of different repeat sugar structures conferring serogroup specificity, and 10 are found most frequently in infection. Thus, one approach to combat infection by P. aeruginosa could be to generate immunity with a vaccine cocktail that includes all these serogroups. Serogroup O9 is 1 of the 10 serogroups commonly found in infection, but it has never been developed into a vaccine, due in part to the acid-labile nature of the O9 polysaccharide. Our laboratory has previously shown that intranasal administration of an attenuated Salmonella strain expressing the P. aeruginosa serogroup O11 LPS O antigen was effective in clearing bacteria and preventing mortality in mice following intranasal challenge with serogroup O11 P. aeruginosa. Consequently, we set out to develop a P. aeruginosa serogroup O9 vaccine using a similar approach. Here, we show that Salmonella expressing serogroup O9 triggered an antibody-mediated immune response following intranasal administration to mice and that it conferred protection from P. aeruginosa serogroup O9 in a murine model of acute pneumonia.

Comparative De Novo and Pan-Genome Analysis of MDR Nosocomial Bacteria Isolated from Hospitals in Jeddah, Saudi Arabia

Multidrug-resistant (MDR) bacteria are one of the most serious threats to public health, and one of the most important types of MDR bacteria are those that are acquired in a hospital, known as nosocomial. This study aimed to isolate and identify MDR bacteria from selected hospitals in Jeddah and analyze their antibiotic-resistant genes. Bacteria were collected from different sources and wards of hospitals in Jeddah City. Phoenix BD was used to identify the strains and perform susceptibility testing. Identification of selected isolates showing MDR to more than three classes on antibiotics was based on 16S rRNA gene and whole genome sequencing. Genes conferring resistance were characterized using de novo and pan-genome analyses. In total, we isolated 108 bacterial strains, of which 75 (69.44%) were found to be MDR. Taxonomic identification revealed that 24 (32%) isolates were identified as Escherichia coli, 19 (25.3%) corresponded to Klebsiella pneumoniae, and 17 (22.67%) were methicillin-resistant Staphylococcus aureus (MRSA). Among the Gram-negative bacteria, K. pneumoniae isolates showed the highest resistance levels to most antibiotics. Of the Gram-positive bacteria, S. aureus (MRSA) strains were noticed to exhibit the uppermost degree of resistance to the tested antibiotics, which is higher than that observed for K. pneumoniae isolates. Taken together, our results illustrated that MDR Gram-negative bacteria are the most common cause of nosocomial infections, while MDR Gram-positive bacteria are characterized by a wider antibiotic resistance spectrum. Whole genome sequencing found the appearance of antibiotic resistance genes, including SHV, OXA, CTX-M, TEM-1, NDM-1, VIM-1, ere(A), ermA, ermB, ermC, msrA, qacA, qacB, and qacC.

Hit 'em Where It Hurts: Gram-Negative Bacterial Lipopolysaccharide as a Vaccine Target

Infections with antimicrobial-resistant (AMR) bacteria pose an increasing threat to the ability to perform surgical procedures, organ transplantation, and treat cancer among many other medical conditions. There are few new antimicrobials in the development pipeline. Vaccines against AMR Gram-negative bacteria may reduce the use of antimicrobials and prevent bacterial transmission. This review traces the origins of lipopolysaccharide (LPS)-based vaccines against Gram-negative bacteria, the role of O polysaccharides and LPS core regions as potential vaccine targets, the development of new vaccine technologies, and their application to vaccines in current development.

Investigation of virulence factors in Pseudomonas aeruginosa isolates by phenotypic and genotypic methods

INTRODUCTION

Pseudomonas aeruginosa possesses a variety of virulence factors that may contribute to its pathogenicity, and relationship has been determined between antibiotic resistance and biofilm. The aim of this study was to investigate the virulence factors of Pseudomonas aeruginosa isolates by genotypic and phenotypic methods, as well as whether there is a relationship between other virulence factors and antibiotic resistance.

METHODS

A total of 80 Pseudomonas aeruginosa strains were sent from various clinics included in the study. Identification and antibiotic resistance profile of isolates were determined by Vitek 2 (Biomerioux, France) automated system. Pseudomonas P agar, Pseudomonas F agar, and motility test medium were used for phenotyping tests. Tox A, Exo S, Plc N, and Las B were evaluated with Real-time PCR (Anatolia, Geneworks, Turkey).

RESULTS

The highest rates of antibiotic resistance were observed against imipenem (42.5%) and meropenem (40%). Among the isolates, 81.3% tested positive for Tox A, 30% for Exo S, 32.5% for Plc N, and 42.5% for Las B. Additionally, 70.4% of the isolates tested positive for pyocyanin, 41.3% for pyoverdine, 1.8% for pyorubin, and 8.9% tested negative for pyorubin. No statistically significant difference was found between antibiotic resistance and the presence of virulence factors (p > 0.005).

CONCLUSIONS

The relationship between antibiotic resistance and virulence factors is controversial. There are studies demonstrating the relationship between virulence factors and antibiotic resistance, as well as studies that indicate the absence of such a relationship. Investigating virulence and antibiotic resistance rates may be important for identifying potential drug targets for subsequent research.

Endemic High-Risk Clone ST277 Is Related to the Spread of SPM-1-Producing Pseudomonas aeruginosa during the COVID-19 Pandemic Period in Northern Brazil

Pseudomonas aeruginosa is a high-priority bacterial agent that causes healthcare-acquired infections (HAIs), which often leads to serious infections and poor prognosis in vulnerable patients. Its increasing resistance to antimicrobials, associated with SPM production, is a case of public health concern. Therefore, this study aims to determine the antimicrobial resistance, virulence, and genotyping features of P. aeruginosa strains producing SPM-1 in the Northern region of Brazil. To determine the presence of virulence and resistance genes, the PCR technique was used. For the susceptibility profile of antimicrobials, the Kirby-Bauer disk diffusion method was performed on Mueller-Hinton agar. The MLST technique was used to define the ST of the isolates. The exoS+/exoU- virulotype was standard for all strains, with the aprA, lasA, toxA, exoS, exoT, and exoY genes as the most prevalent. All the isolates showed an MDR or XDR profile against the six classes of antimicrobials tested. HRC ST277 played a major role in spreading the SPM-1-producing P. aeruginosa strains.

Efficacy of a Pseudomonas aeruginosa Serogroup O9 Vaccine

There are currently no approved vaccines against the opportunistic pathogen Pseudomonas aeruginosa. Among vaccine targets, the lipopolysaccharide (LPS) O antigen of P. aeruginosa is the most immunodominant protective candidate. There are twenty different O antigens composed of different repeat sugars structures conferring serogroup specificity, and ten are found most frequently in infection. Thus, one approach to combat infection by P. aeruginosa could be to generate immunity with a vaccine cocktail that includes all these serogroups. Serogroup O9 is one of the ten serogroups commonly found in infection, but it has never been developed into a vaccine, likely due, in part, to the acid labile nature of the O9 polysaccharide. Our laboratory has previously shown that intranasal administration of an attenuated Salmonella strain expressing the P. aeruginosa serogroup O11 LPS O antigen was effective in clearing and preventing mortality in mice following intranasal challenge with serogroup O11 P. aeruginosa. Consequently, we set out to develop a P. aeruginosa serogroup O9 vaccine using a similar approach. Here we show that Salmonella expressing serogroup O9 triggered an antibody-mediated immune response following intranasal administration to mice and that it conferred protection from P. aeruginosa serogroup O9 in a murine model of acute pneumonia.

Monoclonal antibodies against lipopolysaccharide protect against Pseudomonas aeruginosa challenge in mice

Pseudomonas aeruginosa is a common cause of hospital-acquired infections, including central line-associated bloodstream infections and ventilator-associated pneumonia. Unfortunately, effective control of these infections can be difficult, in part due to the prevalence of multi-drug resistant strains of P. aeruginosa. There remains a need for novel therapeutic interventions against P. aeruginosa, and the use of monoclonal antibodies (mAb) is a promising alternative strategy to current standard of care treatments such as antibiotics. To develop mAbs against P. aeruginosa, we utilized ammonium metavanadate, which induces cell envelope stress responses and upregulates polysaccharide expression. Mice were immunized with P. aeruginosa grown with ammonium metavanadate and we developed two IgG2b mAbs, WVDC-0357 and WVDC-0496, directed against the O-antigen lipopolysaccharide of P. aeruginosa. Functional assays revealed that WVDC-0357 and WVDC-0496 directly reduced the viability of P. aeruginosa and mediated bacterial agglutination. In a lethal sepsis model of infection, prophylactic treatment of mice with WVDC-0357 and WVDC-0496 at doses as low as 15 mg/kg conferred 100% survival against challenge. In both sepsis and acute pneumonia models of infection, treatment with WVDC-0357 and WVDC-0496 significantly reduced bacterial burden and inflammatory cytokine production post-challenge. Furthermore, histopathological examination of the lungs revealed that WVDC-0357 and WVDC-0496 reduced inflammatory cell infiltration. Overall, our results indicate that mAbs directed against lipopolysaccharide are a promising therapy for the treatment and prevention of P. aeruginosa infections.

The antibacterial activity of LL-37 peptide against multidrug-resistant Pseudomonas aeruginosa isolated from burn infections

Multidrug-resistant Pseudomonas aeruginosa has emerged as a significant problem worldwide, posing a severe hazard to burn-infected patients. Antimicrobial peptides produced from humans or animals and synthetic peptides have received interest as antibiotic options for treating resistant bacteria, particularly those obtained from burn patients. The current work evaluated the role of antimicrobial peptide LL-37 as an antibacterial agent against multidrug P. aeruginosa isolates from burn infections. The study samples were collected between November 2021 and the end of February 2022 and included 157 clinical specimens as burn swabs from patients with burn infections admitted to four Baghdad hospitals in Baghdad, Iraq. The results of selective media, biochemical tests, and the ITEK2 system identified 39 isolates (24.8%) as p. aeruginosa from all collected bacterial cultures. The findings of the antimicrobial susceptibility test by disc diffusion method for the isolates under investigation revealed that P. aeruginosa clinical isolates were moderately resistant to antibiotics tested. Most P. aeruginosa isolates were highly resistant to Tetracycline (89.7%), Azithromycin (71.7%), and Amikacin, Cefepime, and Gentamycin. Also, the highest sensitivity was recorded for Ciprofloxacin, Piperacillin/tazobactam, C ceftazidime and Levofloxacin. The results of minimum inhibitory concentrations (MICs) of LL-37 against (8) multidrug-resistant P. aeruginosa isolates revealed that the concentration range of LL-37 was (15.6-1000 µg/ml), indicating that LL-37 has a significant effect on P. aeruginosa growth at low concentrations. In conclusion, t using the antimicrobial peptides LL-37 in treating life-threaded infections could lead to developing a new generation of antimicrobials that can overcome bacterial resistance mechanisms. Keywords: Antibacterial, Burns, LL-37, Pseudomonas aeruginosa

Genome-Based Analysis of Virulence Factors and Biofilm Formation in Novel P. aeruginosa Strains Isolated from Household Appliances

In household washing machines, opportunistic pathogens such as Pseudomonas aeruginosa are present, which represent the household as a possible reservoir for clinical pathogens. Here, four novel P. aeruginosa strains, isolated from different sites of household appliances, were investigated regarding their biofilm formation. Only two isolates showed strong surface-adhered biofilm formation. In consequence of these phenotypic differences, we performed whole genome sequencing using Oxford Nanopore Technology together with Illumina MiSeq. Whole genome data were screened for the prevalence of 285 virulence- and biofilm-associated genes as well as for prophages. Linking biofilm phenotypes and parallelly appearing gene compositions, we assume a relevancy of the las quorum sensing system and the phage-encoded bacteriophage control infection gene bci, which was found on integrated phi297 DNA in all biofilm-forming isolates. Additionally, only the isolates revealing strong biofilm formation harbored the ϕCTX-like prophage Dobby, implicating a role of this prophage on biofilm formation. Investigations on clinically relevant pathogens within household appliances emphasize their adaptability to harsh environments, with high concentrations of detergents, providing greater insights into pathogenicity and underlying mechanisms. This in turn opens the possibility to map and characterize potentially relevant strains even before they appear as pathogens in society.

Isolation of an Extensively Drug-Resistant Pseudomonas aeruginosa exoS+/O4 Strain Belonging to the "High-Risk" Clone ST654 and Coproducer of NDM-1 and the Novel VIM-80

The aim of this study was to investigate the genomic features of an extensively drug-resistant (XDR) Pseudomonas aeruginosa isolate (P-469) emerging in Chile. Antibiotic susceptibility was determined by disk diffusion and "colistin agar" test. Whole-genome sequencing (WGS) was performed by the Illumina NextSeq 2000 platform, and epidemiologically and clinically relevant data (i.e., sequence-type, serotype, mobile genetic elements, virulome, resistome, plasmidome, prophages, and CRISPR-Cas systems) were retrieved using multiple bioinformatic tools. The P-469 strain displayed an XDR profile, remaining susceptible to colistin. Genomic analysis revealed that this isolate belonged to the "high-risk" clone ST654 (CC654), serotype O4, and genotype exoS⁺. Strikingly, two CRISPR-Cas systems, five intact prophages sequences, and a broad resistome that included bla_NDM-1 and the novel bla_VIM-80 carbapenemase genes were predicted. Our results revealed the genomic characteristics of P. aeruginosa belonging to the high-risk clone ST654/O4 coproducing NDM-1 and VIM-80 in Chile, supporting that genomic surveillance is necessary to track the emergence and spread of epidemiologically successful WHO's critical priority pathogens in order to prevent their rapid dissemination.

Genome characterization of a uropathogenic Pseudomonas aeruginosa isolate PA_HN002 with cyclic di-GMP-dependent hyper-biofilm production

Pseudomonas aeruginosa can cause various types of infections and is one of the most ubiquitous antibiotic-resistant pathogens found in healthcare settings. It is capable of adapting to adverse conditions by transforming its motile lifestyle to a sessile biofilm lifestyle, which induces a steady state of chronic infection. However, mechanisms triggering the lifestyle transition of P. aeruginosa strains with clinical significance are not very clear. In this study, we reported a recently isolated uropathogenic hyper-biofilm producer PA_HN002 and characterized its genome to explore genetic factors that may promote its transition into the biofilm lifestyle. We first showed that high intracellular c-di-GMP content in PA_HN002 gave rise to its attenuated motilities and extraordinary strong biofilm. Reducing the intracellular c-di-GMP content by overexpressing phosphodiesterases (PDEs) such as BifA or W909_14950 converted the biofilm and motility phenotypes. Whole genome sequencing and comprehensive analysis of all the c-di-GMP metabolizing enzymes led to the identification of multiple mutations within PDEs. Gene expression assays further indicated that the shifted expression profile of c-di-GMP metabolizing enzymes in PA_HN002 might mainly contribute to its elevated production of intracellular c-di-GMP and enhanced biofilm formation. Moreover, mobile genetic elements which might interfere the endogenous regulatory network of c-di-GMP metabolism in PA_HN002 were analyzed. This study showed a reprogrammed expression profile of c-di-GMP metabolizing enzymes which may promote the pathoadaption of clinical P. aeruginosa into biofilm producers.

Detection of Pseudomonas aeruginosa Serogroup G Using Real-Time PCR for Novel Target Genes Identified Through Comparative Genomics

Accurate serotyping is essential for effective infection control. Pseudomonas aeruginosa serogroup G is one of the most common serogroups found in water. Conventional serotyping methods are not standardized and have several shortcomings. Therefore, a robust method for rapidly identifying P. aeruginosa serotypes is required. This study established a real-time PCR method for identifying P. aeruginosa serogroup G strains using novel target gene primers based on comparative genomic analysis. A total of 343 genome sequences, including 16 P. aeruginosa serogroups and 67 other species, were analyzed. Target genes identified were amplified using real-time PCR for detecting P. aeruginosa serogroup G strains. Eight serogroup G genes, PA59_01276, PA59_01887, PA59_01888, PA59_01891, PA59_01894, PA59_04268, PA59_01892, and PA59_01896, were analyzed to determine specific targets. A real-time fluorescence quantitative PCR method, based on the novel target PA59_01276, was established to detect and identify serogroup G strains. The specificity of this method was confirmed using P. aeruginosa serogroups and non-P. aeruginosa species. The sensitivity of this real-time PCR method was 4 × 10² CFU/mL, and it could differentiate and detect P. aeruginosa serogroup G in the range of 4.0 × 10³–4.0 × 10⁸ CFU/mL in artificially contaminated drinking water samples without enrichment. The sensitivity of these detection limits was higher by 1–3 folds compared to that of the previously reported PCR methods. In addition, the G serum group was accurately detected using this real-time PCR method without interference by high concentrations of artificially contaminated serum groups F and D. These results indicate that this method has high sensitivity and accuracy and is promising for identifying and rapidly detecting P. aeruginosa serogroup G in water samples. Moreover, this research will contribute to the development of effective vaccines and therapies for infections caused by multidrug-resistant P. aeruginosa.

Photodynamic Inactivation of Antibiotic-Resistant and Sensitive Aeromonas hydrophila with Peripheral Pd(II)- vs. Zn(II)-Phthalocyanines

The antimicrobial multidrug resistance (AMR) of pathogenic bacteria towards currently used antibiotics has a remarkable impact on the quality and prolongation of human lives. An effective strategy to fight AMR is the method PhotoDynamic Therapy (PDT). PDT is based on a joint action of a photosensitizer, oxygen, and light within a specific spectrum. This results in the generation of singlet oxygen and other reactive oxygen species that can inactivate the pathogenic cells without further regrowth. This study presents the efficacy of a new Pd(II)- versus Zn(II)-phthalocyanine complexes with peripheral positions of methylpyridiloxy substitution groups (pPdPc and ZnPcMe) towards Gram-negative bacteria Aeromonas hydrophila (A.hydrophila). Zn(II)-phthalocyanine, ZnPcMe was used as a reference compound for in vitro studies, bacause it is well-known with a high photodynamic inactivation ability for different pathogenic microorganisms. The studied new isolates of A.hydrophila were antibiotic-resistant (R) and sensitive (S) strains. The photoinactivation results showed a full effect with 8 µM pPdPc for S strain and with 5 µM ZnPcMe for both R and S strains. Comparison between both new isolates of A.hydrophila (S and R) suggests that the uptakes and more likely photoinactivation efficacy of the applied phthalocyanines are independent of the drug sensitivity of the studied strains.