Risk Factors for Mortality of Inpatients with Pseudomonas aeruginosa Bacteremia in China: Impact of Resistance Profile in the Mortality

Urological metabolic conditions alter regulation of quorum-sensing system and virulence genes expression in uropathogenic Pseudomonasaeruginosa

Pseudomonas aeruginosa (P. aeruginosa) is responsible for complicated urinary tract infections (UTI) acquired from different transmission routes. Quorum sensing (QS) plays an important role in the regulation of virulence factors in P. aeruginosa and is dependent on the nutritional conditions. Under pathological conditions, urine contains elevated levels of metabolites such as glucose, creatinine, albumin and haem that may alter the QS behavior in P. aeruginosa. Hence, we investigated the role of the QS system in P. aeruginosa on growth and the expression of virulence genes under altered urinary metabolic compositions. We used P. aeruginosa strains isolated from UTI patients, along with PAO1 as a reference strain and grown under simulated metabolic conditions in the synthetic urine. Growth, biofilm formation, motility, siderophore production, rhamnolipid secretion, pyocyanin production, elastase and urease activity were quantified using standard laboratory methods. The expression levels of QS genes, such as lasI/R, rhlI/R, and pqsA/R, alginate synthesis genes (algD/R), the motility-regulating gene (pilA), and urease gene (ureC), were estimated using qRT-PCR for comparison between the growth conditions. The results showed significant differences in growth, biofilm formation and virulence factors between the metabolic conditions and were significantly higher (p<0.001) in simulated glycosuria, haematuria, and creatininuria conditions compared to the control. Under albuminuria, significantly reduced growth and virulence factor production were observed. Compared to control, higher expression levels of lasI/R, rhlI/R, pqsA/R, algD/R, pilA and ureC genes were observed in all conditions except albuminuria. The results highlighted the overexpression of QS-regulating genes and virulence in strains from similar metabolic environments in patients, suggesting possible niche adaptation. Such adaptation may pose considerable challenge in the management of chronic P. aeruginosa infections in urinary tract.

Lactobacillus acidophilus (strain Scav) postbiotic metabolites reduce infection and modulate inflammation in an in vivo model of Pseudomonas aeruginosa wound infection

AIMS

This study assessed the antibacterial, antibiofilm, and immunomodulatory activity of Lactobacillus acidophilus (strain Scav) postbiotic (LaP) in a mouse model of Pseudomonas aeruginosa wound infection and evaluated the bioactive components of the LaP.

METHODS AND RESULTS

LaP was tested for Pseudomonas aeruginosa clearance and immunomodulatory activity during wound infection. We show that LaP applied 1 h after infection reduced tissue bacterial burden within 24 h, and this reduction persisted for 5 days. Ciprofloxacin given once at the exact same time did not reduce bacteria load as compared to vehicle controls. LaP reduced plasma IL-6 and MCP-1 levels after 5 days. Wound tissue IL-6 and MCP-1 levels were increased in infected vehicle mice at 5 days, but tissues from LaP-treated mice were similar to sham controls. LaP increased tissue IL-10 (antiinflammatory cytokine) levels. Ciprofloxacin decreased plasma and tissue IL-6 compared to vehicle controls but did not affect MCP-1 or IL-10 levels. To elucidate antibacterial and antibiofilm metabolite(s) in LaP, fractionation followed by Ps. aeruginosa antagonistic activity assays were performed. This was followed by liquid chromatography coupled to mass spectrometry (LCMS) analysis. Our analyses identified a low molecular weight, polar molecule, which had both antibacterial and antibiofilm activity.

CONCLUSIONS

Lactobacillus acidophilus secretes an antibacterial and antibiofilm metabolite that reduced pathogen burden and resolved systemic inflammation in a Pseudomonas aeruginosa wound infection model.

Multicenter Surveillance of Pseudomonas aeruginosa Isolates From Blood: Clinical Distribution Characteristics and Antibiotic Resistance Trends in Hebei Province, China (2016-2021)

Purpose

To analyze the clinical distribution and antimicrobial resistance of Pseudomonas aeruginosa (P. aeruginosa) isolated from blood specimens in 75 hospitals in Hebei Province from 2016 to 2021 to aid in the rational selection of antimicrobial drugs.

Patients and Methods

WHONET 5.6 and SPSS 24.0 were used to retrospectively analyze clinical distribution characteristics and variations in drug-resistance.

Results

Between 2016 and 2021, 2208 P. aeruginosa strains were detected in blood specimens from Hebei Province. The median age of the patients with isolated P. aeruginosa was 63 years, with a male-to-female ratio of 2.1:1. Predominantly, patients were in the hematology (20.7%) and critical care medicine (18.4%) departments. During the monitoring period, the resistance rate of P. aeruginosa to various antibacterial drugs, such as aminoglycosides, fluoroquinolones, and carbapenems, decreased to varying degrees, with an average resistance rate of less than 20.0% over six years. Resistance rates were notably higher in pediatric and intensive care medicine, particularly in neonatal patients, where resistance to antimicrobial drugs, such as piperacillin/tazobactam, gentamicin, ciprofloxacin, and levofloxacin, exceeded 75%.

Conclusion

The main isolates of P. aeruginosa were from elderly and intensive care patients, with a male predominance. From 2016 to 2021, the resistance rate of P. aeruginosa isolated from blood specimens in Hebei Province to various antibiotics such as aminoglycosides, fluoroquinolones, and carbapenems decreased to varying degrees. The resistance rates are high in pediatric and intensive care medicine, especially among neonatal patients. However, resistance to antibiotics varies with age and department, necessitating tailored antimicrobial administration. The issue of antibacterial drug resistance in newborn patients is concerning, and special attention is needed when during treatment.

Novel coenzyme Q6 genetic variant increases susceptibility to pneumococcal disease

Acute lower respiratory tract infection (ALRI) remains a major worldwide cause of childhood mortality, compelling innovation in prevention and treatment. Children in Papua New Guinea (PNG) experience profound morbidity from ALRI caused by Streptococcus pneumoniae. As a result of evolutionary divergence, the human PNG population exhibits profound genetic variation and diversity. To address unmet health needs of children in PNG, we tested whether genetic variants increased ALRI morbidity. Whole-exome sequencing of a pilot child cohort identified homozygosity for a novel single-nucleotide variant (SNV) in coenzyme Q6 (COQ6) in cases with ALRI. COQ6 encodes a mitochondrial enzyme essential for biosynthesis of ubiquinone, an electron acceptor in the electron transport chain. A significant association of SNV homozygosity with ALRI was replicated in an independent ALRI cohort (P = 0.036). Mice homozygous for homologous mouse variant Coq6 exhibited increased mortality after pneumococcal lung infection, confirming causality. Bone marrow chimeric mice further revealed that expression of variant Coq6 in recipient (that is, nonhematopoietic) tissues conferred increased mortality. Variant Coq6 maintained ubiquinone biosynthesis, while accelerating metabolic remodeling after pneumococcal challenge. Identification of this COQ6 variant provides a genetic basis for increased pneumonia susceptibility in PNG and establishes a previously unrecognized role for the enzyme COQ6 in regulating inflammatory-mediated metabolic remodeling.

Clinical characteristics and prognosis analysis of pseudomonas aeruginosa bloodstream infection in adults: a retrospective study

Pseudomonas aeruginosa bloodstream infections (PA BSIs) in adults, especially those complicated by sepsis, are associated with high rates of morbidity and mortality. Early identification of risk factors for both mortality and sepsis-induced coagulopathy (SIC) is critical to optimizing patient management and improving outcomes. We conducted a retrospective analysis of 118 adult patients diagnosed with PA BSIs at the Affiliated Hospital of Xuzhou Medical University from January 2022 to February 2024. Univariate analysis was employed to identify significant clinical factors, followed by multivariate stepwise logistic regression to determine independent predictors of mortality and SIC. Based on these findings, nomogram models were constructed and evaluated using the area under the receiver operating characteristic curve (AUC), Bootstrap resampling, and calibration plots to assess model performance. Empiric sensitive antibiotic therapy (ESAT) (OR = 0.039, P < 0.001), coronary artery disease (CAD) (OR = 10.315, P = 0.010), and invasive mechanical ventilation (OR = 3.926, P = 0.020) emerged as significant predictors of mortality. In contrast, elevated C-reactive protein (CRP) (OR = 1.011, P = 0.003), procalcitonin (PCT) (OR = 1.030, P = 0.005), and lower hemoglobin levels (OR = 0.963, P = 0.004) were independently associated with SIC. The AUC of mortality prediction model is 0.908, while the SIC prediction model yielded an AUC of 0.817. The predictive models developed in this study demonstrate early identification of mortality rates and SIC risk in PA BSI patients, which may have the potential to guide timely therapeutic interventions and improve clinical outcomes in this high-risk population.

The epidemiology of gram-negative bacteremia in Lebanon: a study in four hospitals

INTRODUCTION

Gram-negative bacteremia is a life-threatening infection with high morbidity and mortality. Its incidence is rising worldwide, and treatment has become more challenging due to emerging bacterial resistance. Little data is available on the burden and outcome of such infections in Lebanon.

METHODS

We conducted this retrospective study in four Lebanese hospitals. Data on medical conditions and demographics of 2400 patients diagnosed with a bloodstream infection based on a positive blood culture were collected between January 2014 and December 2020.

RESULTS

Most bacteremias were caused by Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii, with the more resistant organisms being hospital-acquired. Third-generation cephalosporin and quinolone resistance was steady throughout the study, but carbapenem resistance increased. Mortality with such infections is high, but carbapenem resistance or infection with Pseudomonas or Acinetobacter species were significant risk factors for poor outcomes.

CONCLUSION

This is the first multi-center study from Lebanon on gram-negative bacteremia, resistance patterns, and factors associated with a poor outcome. More surveillance is needed to provide data to guide empirical treatment for bacteremia in Lebanon.

Impact of multidrug resistance on the virulence and fitness of Pseudomonas aeruginosa: a microbiological and clinical perspective

Pseudomonas aeruginosa is one of the most common nosocomial pathogens and part of the top emergent species associated with antimicrobial resistance that has become one of the greatest threat to public health in the twenty-first century. This bacterium is provided with a wide set of virulence factors that contribute to pathogenesis in acute and chronic infections. This review aims to summarize the impact of multidrug resistance on the virulence and fitness of P. aeruginosa. Although it is generally assumed that acquisition of resistant determinants is associated with a fitness cost, several studies support that resistance mutations may not be associated with a decrease in virulence and/or that certain compensatory mutations may allow multidrug resistance strains to recover their initial fitness. We discuss the interplay between resistance profiles and virulence from a microbiological perspective but also the clinical consequences in outcomes and the economic impact.

Evaluation of fortimicin antibiotic combinations against MDR Pseudomonas aeruginosa and resistome analysis of a whole genome sequenced pan-drug resistant isolate

BACKGROUND

Multidrug-resistant (MDR) P. aeruginosa is a rising public health concern, challenging the treatment of such a ubiquitous pathogen with monotherapeutic anti-pseudomonal agents. Worryingly, its genome plasticity contributes to the emergence of P. aeruginosa expressing different resistant phenotypes and is now responsible for notable epidemics within hospital settings. Considering this, we aimed to evaluate the synergistic combination of fortimicin with other traditional anti-pseudomonal agents and to analyze the resistome of pan-drug resistant (PDR) isolate.

METHODS

Standard methods were used for analyzing the antimicrobial susceptibility tests. The checkerboard technique was used for the in vitro assessment of fortimicin antibiotic combinations against 51 MDR P. aeruginosa and whole genome sequencing was used to determine the resistome of PDR isolate.

RESULTS

Out of 51 MDR P. aeruginosa, the highest synergistic effect was recorded for a combination of fortimicin with β-lactam group as meropenem, ceftazidime, and aztreonam at 71%, 59% and 43%, respectively. Of note, 56.8%, 39.2%, and 37.2% of the tested MDR isolates that had synergistic effects were also resistant to meropenem, ceftazidime, and aztreonam, respectively. The highest additive effects were recorded for combining fortimicin with amikacin (69%) and cefepime (44%) against MDR P. aeruginosa. Resistome analysis of the PDR isolate reflected its association with the antibiotic resistance phenotype. It ensured the presence of a wide variety of antibiotic-resistant genes (β-lactamases, aminoglycosides modifying enzymes, and efflux pump), rendering the isolate resistant to all clinically relevant anti-pseudomonal agents.

CONCLUSION

Fortimicin in combination with classical anti-pseudomonal agents had shown promising synergistic activity against MDR P. aeruginosa. Resistome profiling of PDR P. aeruginosa enhanced the rapid identification of antibiotic resistance genes that are likely linked to the appearance of this resistant phenotype and may pave the way to tackle antimicrobial resistance issues shortly.

Taming Pseudomonas aeruginosa AM26 the barbarian: Targeting the PQS quorum sensing network using crude mandarin extract

Pseudomonas aeruginosa, one of the most notorious organisms, causes fatal diseases like-, meningitis, pneumonia as well as worsens the prognosis of cystic fibrosis patients. It is also multi-drug resistant and resists a wide range of antibiotics. Attempts have been made to reduce its virulence/pathogenic potential using a number of organic compounds. For this purpose, the Quorum sensing (QS) system of P. aeruginosa was targeted, which regulates its virulence. Pseudomonas Quinolone System (PQS), one of the four quorum sensing systems, producing pyocyanin pigment was chosen. 2-heptyl-3-hydroxy-4-quinolone (HHQ) is a ligand which binds to PQS protein is responsible for pyocyanin pigment production. Attempts were made to find a compound analogous to HHQ which could bind to PQS active site and inhibit the pigment formation. In-silico analysis was performed to estimate possible interactions and to find/predict the possible PQS inhibitors.

14-Year Epidemiologic study of Pseudomonas aeruginosa bloodstream infection incidence and resistance in the Veterans Health Administration system, 2009-2022

Background

Multidrug resistant Pseudomonas aeruginosa (PA) represents a serious threat to hospitalized patients. Characterizing the incidence of PA infection and degree of resistance can inform empiric treatment and preventative measures.

Objectives

We sought to describe trends in incidence and resistance characteristics of PA bloodstream infections (BSI) observed within the Veterans Health Administration (VHA) system and identify factors contributing to higher observed mortality within this population.

Methods

We characterized demographic and clinical features of unique patients among the VHA population presenting with their first episode of PA-BSI between 2009 and 2022 and summarized trends related to mortality and resistance phenotype based on year and geographical location. We additionally used logistic regression analysis to identify predictors of 30-day mortality among this cohort.

Results

We identified 8039 PA-BSIs during the study period, 32.7% of which were hospital onset. Annual PA-BSI cases decreased by 35.8%, and resistance among all antimicrobial classes decreased during the study period, while the proportion of patients receiving early active treatment based on susceptibility testing results increased. Average 30-day mortality rate was 23.3%. Higher Charlson Comorbidity Index, higher mAPACHE score, VHA facility complexity 1b and hospital-onset cases were associated with higher mortality, and early active treatment was associated with lower mortality.

Conclusions

PA-BSI resistance decreased across the VHA system during the study period. Further investigation of antimicrobial stewardship measures possibly contributing to the observed decreased resistance in this cohort and identification of measures to improve on the high mortality associated with PA-BSI in the VHA population is warranted.

Gingival Necrosis Related to Sepsis-Induced Agranulocytosis Due to Pseudomonas aeruginosa Bacteraemia: A Case Report

Background: There have been no reports of sepsis-induced agranulocytosis causing gingival necrosis in otherwise medically healthy patients to the authors' best knowledge. Even though there are several case reports of gingival necrosis secondary to medication-induced agranulocytosis, they have not systematically described the natural progression of agranulocytosis-related gingival necrosis. Methods: This paper presents a case report of a 29-year-old female Indian patient with generalised gingival necrosis and constitutive signs of intermittent fever, nausea, and vomiting. She also complained of abdominal pains. Blood counts showed agranulocytosis, and the patient was admitted for a workup of the underlying cause. Parenteral broad-spectrum antibiotics were administered, which brought about clinical resolution. Results: Her gingival necrosis was attributed to sepsis-induced agranulocytosis triggered by Pseudomonas aeruginosa bacteraemia, and upon clinical recovery, spontaneous exfoliation left behind exposed bone. Secondary healing over the exposed alveolar bone was noted after a year-long follow-up, albeit with some residual gingival recession. Conclusions: Oral manifestations of gingival necrosis, when present with concomitant constitutive symptoms, could indicate a serious underlying systemic condition that could be potentially life-threatening if left untreated. Dentists should be cognizant of this possibility so that timely intervention is not delayed.

Registry-Based Retrospective Cohort Study of Mortality among Adults Admitted to Intensive Care Units in Istanbul with Hospital Acquired Pseudomonas aeruginosa Bloodstream-Infection between 2014-2021

BACKGROUND

Managing Pseudomonas aeruginosa bloodstream infections (BSIs) is challenging due to increasing antimicrobial resistance, limited therapeutic options, and high mortality rates. In this study, we aimed to identify 30-day mortality risk factors and assess infectious diseases consultants' preferences for combination or monotherapy.

METHODS

The study was conducted in four hospitals in Istanbul, Turkey, involving 140 adult ICU beds and 336,780 ICU-bed-days between 1 January 2014, and 31 December 2021. A total of 157 patients were included in the study. Cox proportional hazard regression was performed to assess the factors on 30-day mortality.

RESULTS

The 30-day mortality rate was 44.6% (70/157). Higher Charlson Comorbidity Index (CCI) score, severe sepsis, primary bloodstream infection, being in COVID-19 pandemic period, and infection caused by MDR strain were associated with higher hazard of 30-day mortality. Combination therapy was more commonly used in patients with BSIs with MDR or DTR (difficult-to-treat) strains but did not significantly improve the hazard of 30-day mortality.

CONCLUSIONS

Targeted interventions and vigilant management strategies are crucial for patients with defined risk factors. While infectious disease consultants tended to favor combination therapy, particularly for drug-resistant strains, our analysis revealed no significant impact on 30-day mortality hazard. The increased incidence of P. aeruginosa BSIs during the pandemic emphasizes the need for infection control measures and appropriate antibiotic prescribing practices.

Incidence, antimicrobial resistance and mortality of Pseudomonas aeruginosa bloodstream infections among hospitalized patients in China: a retrospective observational multicenter cohort study from 2017 to 2021

Background

Pseudomonas aeruginosa (P. aeruginosa) accounts for high antimicrobial resistance and mortality rates of bloodstream infections (BSIs). We aim to investigate incidence, antimicrobial resistance and risk factors for mortality of P. aeruginosa BSIs among inpatients.

Methods

A retrospective cohort study were conducted at two tertiary hospitals in 2017-2021. Medical and laboratory records of all inpatients diagnosed with P. aeruginosa BSIs were reviewed. A generalized linear mixed model was used to identify risk factors for mortality.

Results

A total of 285 patients with P. aeruginosa BSIs were identified. Incidence of P. aeruginosa BSIs fluctuated between 2.37 and 3.51 per 100,000 patient-days over the study period. Out of 285 P. aeruginosa isolates, 97 (34.04%) were carbapenem-resistant (CR) and 75 (26.32%) were multidrug-resistant (MDR). These isolates showed low resistance to aminoglycosides (9.51-11.62%), broad-spectrum cephalosporins (17.19-17.61%), fluoroquinolones (17.25-19.43%), and polymyxin B (1.69%). The crude 30-day mortality rate was 17.89% (51/285). Healthcare costs of patients with MDR/CR isolates were significantly higher than those of patients with non-MDR/CR isolates (P < 0.001/=0.002). Inappropriate definitive therapy [adjusted odds ratio (aOR) 4.47, 95% confidence interval (95% CI) 1.35-14.77; P = 0.014], ICU stay (aOR 2.89, 95% CI: 1.26-6.63; P = 0.012) and corticosteroids use (aOR 2.89, 95% CI: 1.31-6.41; P = 0.009) were independently associated with 30-day mortality.

Conclusion

Incidence of P. aeruginosa BSIs showed an upward trend during 2017-2020 but dropped in 2021. MDR/CR P. aeruginosa BSIs are associated with higher healthcare costs. Awareness is required that patients with inappropriate definitive antimicrobial therapy, ICU stay and corticosteroids use are at higher risk of death from P. aeruginosa BSIs.

Changing Genotypic Distribution, Antimicrobial Susceptibilities, and Risk Factors of Urinary Tract Infection Caused by Carbapenemase-Producing Pseudomonas aeruginosa

Background

Carbapenem-resistant Pseudomonas aeruginosa (CrPA) is a leading cause of healthcare-associated urinary tract infections (UTIs). Carbapenemase production is an important mechanism that significantly alters the efficacy of frequently used anti-pseudomonal agents. Reporting the current genotypic distribution of carbapenemase-producing P. aeruginosa (CPPA) isolates in relation to antimicrobial susceptibility, UTI risk factors, and mortality is necessary to increase the awareness and control of these strains.

Methods

In total, 1,652 non-duplicated P. aeruginosa strains were isolated from hospitalized patients between 2015 and 2020. Antimicrobial susceptibility, carbapenemase genotypes, risk factors for UTI, and associated mortality were analyzed.

Results

The prevalence of carbapenem-non-susceptible P. aeruginosa isolates showed a decreasing trend from 2015 to 2018 and then increased in the background of the emergence of New Delhi metallo-β-lactamase (NDM)-type isolates since 2019. The CPPA strains showed 100.0% non-susceptibility to all tested antibiotics, except aztreonam (94.5%) and colistin (5.9%). Carbapenems were identified as a risk and common predisposing factor for UTI (odds ratio [OR]=1.943) and mortality (OR=2.766). Intensive care unit (ICU) stay (OR=2.677) and white blood cell (WBC) count (OR=1.070) were independently associated with mortality.

Conclusions

The changing trend and genetic distribution of CPPA isolates emphasize the need for relentless monitoring to control further dissemination. The use of carbapenems, ICU stay, and WBC count should be considered risk factors, and aggressive antibiotic stewardship programs and monitoring may serve to prevent worse outcomes.

Characterization of Virulence Genes Associated with Type III Secretion System and Biofilm Formation in Pseudomonas aeruginosa Clinical Isolates

Pseudomonas aeruginosa is a common pathogen with an increasing multidrug resistance (MDR) phenotype. Its virulence determinants include many factors such as antimicrobial resistance, biofilm formation, and type III secretion system (T3SS) which correlate with disease severity. There are no reports regarding the virulence features of P. aeruginosa in Cyprus. The aim of this study was to investigate the frequency and distribution of selected virulence-encoding genes and evaluate the biofilm formation potential as well as antibiotic resistance rates of isolates in the region. One hundred clinical P. aeruginosa isolates were obtained from clinical specimens and were identified using standard microbiological techniques. Antimicrobial susceptibility was assessed using the VITEK-2 system and biofilm quantification was performed by the microtiter plate assay with crystal violet staining. The presence of algD, exoU, exoT, and exoS was evaluated using polymerase chain reaction (PCR). Among all isolates, 35% were strong biofilm former, 28% were moderate biofilm former, 19% were weak biofilm former, and 18% were non-biofilm former. The rates of MDR and extensive drug resistance (XDR) were 26% and 1%. PCR analysis indicated that 93% of the isolates were algD positive. T3SS genes exoT, exoS, and exoU were detected in 91%, 63%, and 32% of the isolates, respectively. There was a high frequency of exoT + /exoS + genotype (61%), whereas exoT + /exoU + (32%) and exoS + /exoU + (2%) genotypes were relatively uncommon. This study reports the first dataset on the molecular profile of P. aeruginosa in Cyprus. Our results demonstrated that most strains have the biofilm-forming capacity with an algD-positive genotype and the majority carry exoT and exoS with a high frequency of exoT + /exoS + genotype.

In Vivo Development of Aztreonam Resistance in Meropenem-Resistant Pseudomonas aeruginosa Owing to Overexpression of the blaPDC-16

The rapid acquisition of antibiotic resistance of Pseudomonas aeruginosa has been a complex problem in clinics. Two meropenem-resistant P. aeruginosa isolates were collected from the same patient on May 24, 2021, and June 4, 2021, respectively. The first was susceptible to aztreonam, while the second displayed resistance. This study aimed to identify the genetic differences between two P. aeruginosa isolates and uncover alterations formed by the within-host bacterial evolution leading to aztreonam resistance during therapy. Strains were subjected to antimicrobial susceptibility testing using the broth microdilution method. Genomic DNAs were obtained to identify their genetic differences. The relative mRNA levels of β-lactam-resistance genes were determined by real-time PCR. Both isolates belonged to ST 773 high-risk clones with the same antibiotic resistance genes, eliminating the possibility of horizontally obtaining resistance genes. Reverse transcription (RT)-PCR results showed that the blaPDC-16 mRNA level in the second one was about 1,500 times higher than that in the first one. When 3-aminophenyl boronic acid was added, the second strain recovered its susceptibility to aztreonam, which confirmed that the overexpression of blaPDC-16 was the main reason for the isolate's resistance to aztreonam. Compared to the first strain, the second showed a single amino acid substitution in AmpR located upstream of blaPDC-16, which may contribute to the upregulation of blaPDC-16 and lead to aztreonam resistance. AmpR plays an essential role in regulating antibiotic resistance in P. aeruginosa, and there is a need to be alert to clinical treatment failures associated with mutations in ampR. IMPORTANCE Pseudomonas aeruginosa is notorious for being highly resistant to antimicrobial agents. In this study, two P. aeruginosa strains isolated from the same patient with different susceptibility to aztreonam were used to illustrate the within-host resistance evolution process of P. aeruginosa. Both isolates, which belonged to a ST773 high-risk clone, had the same β-lactam resistance genes (blaPDC-16, blaIMP-45, blaOXA-1, and blaOXA-395), which means the second isolate might have been derived from the first isolate by gaining aztreonam resistance via mutations associated with aztreonam resistance relative genes. Subsequently, we found that mutation in ampR may be the cause of aztreonam resistance in the second isolate. Mutation in ampR leads to its loss of control over blaPDC-16, allowing overexpression of blaPDC-16 and further resistance to aztreonam. This study revealed that ampR plays an essential role in regulating antibiotic resistance in P. aeruginosa. There is a need to be alert to clinical treatment failures associated with mutations in ampR.

The dilemma of antibiotic susceptibility and clinical decision-making in a multi-drug-resistant Pseudomonas aeruginosa bloodstream infection

Objective: How to choose the appropriate antibiotics and dosage has always been a difficult issue during the treatment of multi-drug-resistant bacterial infections. Our study aims to resolve this difficulty by introducing our multi-disciplinary treatment (MDT) clinical decision-making scheme based on rigorous interpretation of antibiotic susceptibility tests and precise therapeutic drug monitoring (TDM)-guided dosage adjustment. Method: The treatment course of an elderly patient who developed a multi-drug-resistant Pseudomonas aeruginosa (MDRPA) bloodstream infection from a brain abscess was presented. Results: In the treatment process, ceftazidime-avibactam (CAZ-AVI) was used empirically for treating the infection and clinical symptoms improved. However, the follow-up bacterial susceptibility test showed that the bacteria were resistant to CAZ-AVI. Considering the low fault tolerance of clinical therapy, the treatment was switched to a 1 mg/kg maintenance dose of susceptible polymyxin B, and TDM showed that the AUC_{24h, ss} of 65.5 mgh/L had been achieved. However, clinical symptoms were not improved after 6 days of treatment. Facing the complicated situation, the cooperation of physicians, clinical pharmacologists, and microbiologists was applied, and the treatment finally succeeded with the pathogen eradicated when polymyxin B dose was increased to 1.4 mg/kg, with the AUC_{24h, ss} of 98.6 mgh/L. Conclusion: MDT collaboration on the premise of scientific and standardized drug management is helpful for the recovery process in patients. The empirical judgment of doctors, the medication recommendations from experts in the field of TDM and pharmacokinetics/pharmacodynamics, and the drug susceptibility results provided by the clinical microbiology laboratory all provide the direction of treatment.

Development of a combination antibiogram for empirical treatments of Pseudomonas aeruginosa at a university-affiliated teaching hospital

INTRODUCTION

The significantly higher mortality rate in the critical illness patients with Pseudomonas aeruginosa (PA) infection is linked to inappropriate selecting of empirical treatment. Traditional local antibiogram provides clinicians the resistant rate of a single antimicrobial agent to the pathogen in the specific setting. The information is valuable to the clinicians in selecting suitable empirical antibiotic therapy. However, traditional local antibiogram can only provide information for single agent empirical antibiotic not combination regimens. The combination antibiogram should be developed to facilitate the selection of appropriate antibiotics to broader the coverage rate of resistant PA.

METHODS

The susceptibility to the β-lactam antibiotics (piperacillin/tazobactam (PTZ), ceftazidime, cefepime, imipenem, or meropenem) or to those administered in combination with an aminoglycoside (gentamicin or amikacin) or fluoroquinolone (ciprofloxacin or levofloxacin) was calculated. The chi-square test was used to compare the differences of combination coverage rates between non-ICU and ICU isolates.

RESULTS

880 PA isolates were isolated during study period. The susceptibility of single agents ranged from 83.1% to 89.7%. The combination regimens containing amikacin provide the highest cover rate (98.9%-99.1%) and those containing levofloxacin provide less coverage rate (92.3%-93.9%). The susceptibility to five β-lactam single agents in ICU isolates significantly lower than non-ICU isolates. The non-ICU isolates exhibited significantly higher susceptibility to the PTZ-gentamicin (p = 0.002) and ceftazidime-gentamicin (p = 0.025) than ICU isolates.

CONCLUSION

Our results support the use of aminoglycosides instead of fluoroquinolones as additive agents in empirical combination treatments for patients with critical infections caused by PA.

Assessing and Reassessing the Association of Comorbidities and Coinfections in COVID-19 Patients

Coronavirus disease 2019 (COVID-19) has posed an enormous global health and economic burden. To date, 324 million confirmed cases and over 5.5 million deaths have been reported. Several studies have reported comorbidities and coinfections associated with complicated and serious COVID-19 infections. Data from retrospective, prospective, case series, and case reports from various geographical locations were assessed, which included ~ 2300 COVID-19 patients with varying comorbidities and coinfection. We report that Enterobacterales with Staphylococcus aureus was the most while Mycoplasma pneumoniae was the least prevalent coinfection in COVID-19 patients with a comorbidity. In this order, hypertension, diabetes, cardiovascular disease, and pulmonary disease were the prevalent comorbidities observed in COVID-19 patients. There was a statistically significant difference in the prevalent comorbidities observed in patients coinfected with Staphylococcus aureus and COVID-19 and a statistically non-significant difference in the prevalent comorbidities in patients coinfected with Mycoplasma pneumoniae and COVID-19 as compared to similar infections in non-COVID-19 coinfection. We report a significant difference in the prevalent comorbidities recorded in COVID-19 patients with varying coinfections and varying geographic study regions. Our study provides informative data on the prevalence of comorbidities and coinfections in COVID-19 patients to aid in evidence-based patient management and care.

Risk Factors and Outcomes of Patients with Carbapenem-Resistant Pseudomonas aeruginosa Bloodstream Infection

Purpose

The rising incidence of carbapenem-resistant Pseudomonas aeruginosa (PA) bloodstream infection (BSI) has made the selection of antibiotic therapy more difficult and caused high mortality. This study was aimed at exploring the risk factors for carbapenem-resistant Pseudomonas aeruginosa (CRPA) bloodstream infection and identifying the risk factors for the outcomes of patients with PA-BSI.

Methods

We performed a retrospective cohort study of patients with PA-BSI in a tertiary hospital from January 2017 to December 2021 in China. Epidemiological, clinical, and microbiological characteristics were described. Risk factors for CRPA-BSI and the outcomes of PA-BSI inpatients were identified, using multivariate logistic regression analysis.

Results

A total of 198 PA-BSI inpatients were included. The negative outcome rate was significantly higher in patients infected with CRPA (15/34, 44.12%) than with carbapenem-susceptible Pseudomonas aeruginosa (CSPA) (35/164, 21.34%), and the difference was statistically significant (P=0.005). Multivariate logistic regression analysis showed that previous exposure to carbapenem (OR 3.519, 95% CI 1.359-9.110, P=0.010) was an independent risk factor for CRPA-BSI. In addition, CRPA (OR 1.615, 95% CI 0.626-4.171, P=0.32) was not an independent risk factor for negative outcome among PA-BSI inpatients.

Conclusion

Our study showed that previous exposure to carbapenem was an independent risk factor for CRPA-BSI. CRPA was not an independent risk factor for a negative outcome in PA-BSI inpatients.

Clinical predictors of mortality in patients with pseudomonas aeruginosa infection

BACKGROUND

Infections caused by Pseudomonas aeruginosa are difficult to treat with a significant cost and burden. In Lebanon, P. aeruginosa is one of the most common organisms in ventilator-associated pneumonia (VAP). P. aeruginosa has developed widespread resistance to multiple antimicrobial agents such as fluoroquinolones and carbapenems. We aimed at identifying risk factors associated for P. aeruginosa infections as well as identifying independent risk factors for developing septic shock and in-hospital mortality.

METHODS

We used a cross-sectional study design where we included patients with documented P. aeruginosa cultures who developed an infection after obtaining written consent. Two multivariable regression models were used to determine independent predictors of septic shock and mortality.

RESULTS

During the observed period of 30 months 196 patients were recruited. The most common predisposing factor was antibiotic use for more than 48 hours within 30 days (55%). The prevalence of multi-drug resistant (MDR) P. aeruginosa was 10%. The strongest predictors of mortality were steroid use (aOR = 3.4), respiratory failure (aOR = 7.3), identified respiratory cultures (aOR = 6.0), malignancy (aOR = 9.8), septic shock (aOR = 18.6), and hemodialysis (aOR = 30.9).

CONCLUSION

Understanding resistance patterns and risk factors associated with mortality is crucial to personalize treatment based on risk level and to decrease the emerging threat of antimicrobial resistance.

Relationship between Biofilm-Formation, Phenotypic Virulence Factors and Antibiotic Resistance in Environmental Pseudomonas aeruginosa

The formation of a protective biofilm by Pseudomonas aeruginosa (PA) is one of the hallmarks of their survival both in vivo and in harsh environmental conditions, thus, biofilm-eradication has relevance from therapeutic perspectives and for infection control. The aim of our study was to investigate the possible relationship between antibiotic resistance, biofilm-forming capacity and virulence factors in n = 166 PA isolates of environmental origin. Antimicrobial susceptibility testing and the phenotypic detection of resistance determinants were carried out using standard protocols. The biofilm-forming capacity of PA was tested using a standardized crystal violet microtiter plate-based method. Motility (swimming, swarming, and twitching) and siderophore production of the isolates were also assessed. Resistance rates were highest for ciprofloxacin (46.98%), levofloxacin (45.18%), ceftazidime (31.92%) and cefepime (30.12%); 19.28% of isolates met the criteria to be classified as multidrug-resistant (MDR). Efflux pump overexpression, AmpC overexpression, and modified Hodge-test positivity were noted in 28.31%, 18.07% and 3.61%, respectively. 22.89% of isolates were weak/non-biofilm producers, while 27.71% and 49.40% were moderate and strong biofilm producers, respectively. Based on MDR status of the isolates, no significant differences in biofilm-production were shown among environmental PA (non-MDR OD570 [mean ± SD]: 0.416 ± 0.167 vs. MDR OD570: 0.399 ± 0.192; p > 0.05). No significant association was observed between either motility types in the context of drug resistance or biofilm-forming capacity (p > 0.05). 83.13% of isolates tested were positive for siderophore production. The importance of PA as a pathogen in chronic and healthcare-associated infections has been described extensively, while there is increasing awareness of PA as an environmental agent in agriculture and aquaculture. Additional studies in this field would be an important undertaking to understand the interrelated nature of biofilm production and antimicrobial resistance, as these insights may become relevant bases for developing novel therapeutics and eradication strategies against PA.

Infectious Disease Consults of Pseudomonas aeruginosa Bloodstream Infection and Impact on Health Outcomes

BACKGROUND

Infectious diseases (ID) consultation improves health outcomes for certain infections but has not been well described for Pseudomonas aeruginosa (PA) bloodstream infection (BSI). Therefore, the goal of this study was to examine ID consultation of inpatients with PA BSI and factors impacting outcomes.

METHODS

This was a retrospective cohort study from January 1, 2012, to December 31, 2018, of adult hospitalized veterans with PA BSI and antibiotic treatment 2 days before through 5 days after the culture date. Multidrug-resistant (MDR) cultures were defined as cultures with resistance to at least 1 agent in ≥3 antimicrobial categories tested. Multivariable logistic regression models were fit to assess the impact of ID consults and adequate treatment on mortality.

RESULTS

A total of 3256 patients had PA BSI, of whom 367 (11.3%) were multidrug resistant (MDR). Most were male (97.5%), over 65 years old (71.2%), and White (70.9%). Nearly one-fourth (n = 784, 23.3%) died during hospitalization, and 870 (25.8%) died within 30 days of their culture. Adjusted models showed that ID consultation was associated with decreased in-hospital (odds ratio [OR], 0.47; 95% CI, 0.39-0.56) and 30-day mortality (OR, 0.51; 95% CI, 0.42-0.62).

CONCLUSIONS

Consultation with ID physicians improves clinical outcomes such as in-hospital and 30-day mortality for patients with PA BSI. ID consultation provides value and should be considered for patients with PA BSI.

Risk factors for mortality in hospitalized patients infected with carbapenem-resistant Pseudomonas aeruginosa in Iran

Introduction

Mortality due to carbapenem-resistant Pseudomonas aeruginosa (CRPA) infection has increased worldwide in recent years. The risk factors associated with hospital settings in Iran and the role of strain resistance mechanisms in many studies are unclear.

Methods

A retrospective study was conducted on consecutive non-repetitive patients with CRPA infections isolated from seven major hospitals from northwest of Iran. We evaluated different risk factors and characteristics of bacteria for the death or survival of patients.

Results

In this study, 116 CRPA isolates were obtained from patients admitted to seven hospitals. Forty-one (35.3%) patients were enrolled in the study of mortality risk factors. Significant risk factors associated with mortality included the site of infection, hospitalization in different wards, the use of invasive devices, and the type of carbapenem resistance mechanisms.

Conclusions

ICU admission, the use of mechanical ventilation and chest tube and infection with pandrug-resistant strains were the most important factors in increasing mortality due to CRPA infection. These results suggested that the clinicians should emphasize the proper use of antibiotic and invasive procedures.

A unique antigen against SARS-CoV-2, Acinetobacter baumannii, and Pseudomonas aeruginosa

The recent outbreak of COVID-19 has increased hospital admissions, which could elevate the risk of nosocomial infections, such as A. baumannii and P. aeruginosa infections. Although effective vaccines have been developed against SARS-CoV-2, no approved treatment option is still available against antimicrobial-resistant strains of A. baumannii and P. aeruginosa. In the current study, an all-in-one antigen was designed based on an innovative, state-of-the-art strategy. In this regard, experimentally validated linear epitopes of spike protein (SARS-CoV-2), OmpA (A. baumannii), and OprF (P. aeruginosa) were selected to be harbored by mature OmpA as a scaffold. The selected epitopes were used to replace the loops and turns of the barrel domain in OmpA; OprF_311–341 replaced the most similar sequence within the OmpA, and three validated epitopes of OmpA were retained intact. The obtained antigen encompasses five antigenic peptides of spike protein, which are involved in SARS-CoV-2 pathogenicity. One of these epitopes, viz. QTQTNSPRRARSV could trigger antibodies preventing super-antigenic characteristics of spike and alleviating probable autoimmune responses. The designed antigen could raise antibodies neutralizing emerging variants of SARS-CoV-2 since at least two epitopes are consensus. In conclusion, the designed antigen is expected to raise protective antibodies against SARS-CoV-2, A. baumannii, and P. aeruginosa.

Carbapenem Resistant Pseudomonas aeruginosa Infections in Elderly Patients: Antimicrobial Resistance Profiles, Risk Factors and Impact on Clinical Outcomes

Objective

The prevalence and clinical impact on mortality of carbapenem-resistant Pseudomonas aeruginosa (CRPA) infection are unclear in elderly patients. Here, we aimed to clarify the prevalence, the clinical manifestations, antimicrobial resistance, risk factors and outcomes of elderly inpatients with CRPA infection.

Methods

A retrospective study of 600 elderly inpatients infected with P. aeruginosa was conducted at Yueyang Hospital of Integrated Traditional Chinese and Western Medicine from January 1st 2018 to December 31st 2020. All 155 patients with CRPA infection were designated as a case group. Patients with carbapenem-susceptible Pseudomonas aeruginosa (CSPA) were randomly selected from remaining 445 cases in a 1:1 ratio to case group as a control group.

Results

Of 600 P. aeruginosa isolates, the overall rates of CRPA, MDR PA (multidrug-resistance Pseudomonas aeruginosa) were 25.8% (155), 22.3% (134), respectively. The rankings of the top five resistant rates of CRPA to tested antimicrobial drugs were imipenem (87.7%), meropenem (70.3%), ciprofloxacin (51.0%), levofloxacin (48.4%), cefoperazone (43.2%). Independent risk factors for patients with CRPA infection were cerebrovascular disease (OR = 3.517, P < 0.001), foley catheter (OR = 2.073, P = 0.018), length of hospital stay ≥ 14 days (OR = 1.980, P = 0.013), albumin < 35 g/L (OR = 2.049, P = 0.020), previous antibiotic exposure to carbapenems (OR = 7.022, P = 0.004), previous antibiotic exposure to third- or fourth-generation cephalosporins (OR = 12.649, P = 0.002). Of 155 patients with CRPA infection, the mortality rate was 16.8% (26/155). Independent risk factors for mortality were receiving mechanical ventilation (OR = 3.671, P = 0.007) and neutrophil percentage ≥ 80% (OR = 2.908, P = 0.024).

Conclusion

The study revealed high rates of CRPA, MDR PA among the hospitalized elderly patient with P. aeruginosa infection. The analysis of antimicrobial susceptibility emphasizes the necessity for antimicrobial stewardship and infection control in hospitals. These findings of risk factors are practical significant to identify patients at high risk for CRPA infection and mortality that may benefit from alternate empiric treatment.

No Correlation between Biofilm Formation, Virulence Factors, and Antibiotic Resistance in Pseudomonas aeruginosa: Results from a Laboratory-Based In Vitro Study

Pseudomonas aeruginosa (P. aeruginosa) possesses a plethora of virulence determinants, including the production of biofilm, pigments, exotoxins, proteases, flagella, and secretion systems. The aim of our present study was to establish the relationship between biofilm-forming capacity, the expression of some important virulence factors, and the multidrug-resistant (MDR) phenotype in P. aeruginosa. A total of three hundred and two (n = 302) isolates were included in this study. Antimicrobial susceptibility testing and phenotypic detection of resistance determinants were carried out; based on these results, isolates were grouped into distinct resistotypes and multiple antibiotic resistance (MAR) indices were calculated. The capacity of isolates to produce biofilm was assessed using a crystal violet microtiter-plate based method. Motility (swimming, swarming, and twitching) and pigment-production (pyoverdine and pyocyanin) were also measured. Pearson correlation coefficients (r) were calculated to determine for antimicrobial resistance, biofilm-formation, and expression of other virulence factors. Resistance rates were the highest for ceftazidime (56.95%; n = 172), levofloxacin (54.97%; n = 166), and ciprofloxacin (54.64%; n = 159), while lowest for colistin (1.66%; n = 5); 44.04% (n = 133) of isolates were classified as MDR. 19.87% (n = 60), 20.86% (n = 63) and 59.27% (n = 179) were classified as weak, moderate, and strong biofilm producers, respectively. With the exception of pyocyanin production (0.371 ± 0.193 vs. non-MDR: 0.319 ± 0.191; p = 0.018), MDR and non-MDR isolates did not show significant differences in expression of virulence factors. Additionally, no relevant correlations were seen between the rate of biofilm formation, pigment production, or motility. Data on interplay between the presence and mechanisms of drug resistance with those of biofilm formation and virulence is crucial to address chronic bacterial infections and to provide strategies for their management.

Bloodstream Infections Caused by Carbapenem-Resistant Enterobacterales: Risk Factors for Mortality, Antimicrobial Therapy and Treatment Outcomes from a Prospective Multicenter Study

Purpose

Carbapenem-resistant Enterobacterales bloodstream infections (CRE BSIs) have a high mortality. However, an optimal antimicrobial treatment has not been determined. This study was conducted to evaluate the risk factors for mortality and provided potential therapeutic options for treatment of CRE infection.

Patients and Methods

We investigated patients with CRE BSIs from 18 hospitals across nine Chinese provinces from January to December 2019. Data were collected from the medical records according to a pre-established questionnaire. Antimicrobial susceptibility testing and DNA sequencing were performed to investigate the characteristics of isolates.

Results

A total of 208 patients enrolled; the overall 30-day mortality rate was 46.2%. The causative pathogen was carbapenem-resistant Klebsiella pneumoniae (CRKP) (85.6%). Patients infected by ST11-KL64 CRKP had a high sepsis/septic shock incidence rate (p < 0.05). Sepsis/septic shock, short duration of antimicrobial therapy and empirical using tigecycline were independent risk factors for mortality (p < 0.05 for each risks). Appropriate therapy had better survival benefit than inappropriate therapy (p = 0.003). No difference was identified between monotherapy and combination therapy (p = 0.105). Tigecycline as a frequently used antimicrobial had poor therapeutic effect on BSI patients (p < 0.001). Carbapenem-based treatment had a better therapeutic effect on patients infected by isolates with meropenem MIC ≤ 8 mg/L (p = 0.022). The patients who received short duration of antimicrobial therapy had poorer prognosis (p < 0.001) than the patients who received long duration of antimicrobial therapy.

Conclusion

Reducing the mortality of CRE BSIs need to comprehensively consider whether the antimicrobials were used appropriately, together with infection severity and CRE strains.

It's Not Easy Being Green: A Narrative Review on the Microbiology, Virulence and Therapeutic Prospects of Multidrug-Resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is the most frequent cause of infection among non-fermenting Gram-negative bacteria, predominantly affecting immunocompromised patients, but its pathogenic role should not be disregarded in immunocompetent patients. These pathogens present a concerning therapeutic challenge to clinicians, both in community and in hospital settings, due to their increasing prevalence of resistance, and this may lead to prolonged therapy, sequelae, and excess mortality in the affected patient population. The resistance mechanisms of P. aeruginosa may be classified into intrinsic and acquired resistance mechanisms. These mechanisms lead to occurrence of resistant strains against important antibiotics-relevant in the treatment of P. aeruginosa infections-such as β-lactams, quinolones, aminoglycosides, and colistin. The occurrence of a specific resistotype of P. aeruginosa, namely the emergence of carbapenem-resistant but cephalosporin-susceptible (Car-R/Ceph-S) strains, has received substantial attention from clinical microbiologists and infection control specialists; nevertheless, the available literature on this topic is still scarce. The aim of this present review paper is to provide a concise summary on the adaptability, virulence, and antibiotic resistance of P. aeruginosa to a readership of basic scientists and clinicians.