The Microbiology of Bloodstream Infection: 20-Year Trends from the SENTRY Antimicrobial Surveillance Program

Invasive Candidiasis

Invasive candidiasis (IC) is a term that refers to a group of infectious syndromes caused by a variety of Candida species, 6 of which cause the vast majority of cases globally. Candidemia is probably the most commonly recognized syndrome associated with IC; however, Candida species can cause invasive infection of any organ, especially visceral organs, vasculature, bones and joints, eyes, and central nervous system. The optimal use of these newer diagnostics coupled with a thoughtful clinical assessment of at-risk patients and the judicious use of effective antifungal therapy is a key to achieving good antifungal stewardship and improved patient outcomes.

Prevalence and risk factors for bacteremia in community-acquired pneumonia: A systematic review and meta-analysis

BACKGROUND

Bacteremia represents a significant complication in patients with community-acquired pneumonia (CAP). Nonetheless, there is currently a dearth of systematic research that determines the precise prevalence and risk factors of bacteremia in CAP patients.

METHODS

PubMed, Cochrane Library, Embase, and Web of Science databases were searched for published studies on the prevalence or risk factors for CAP with bacteremia up to April 21, 2024. The NOS scale was utilized to appraise the study quality, and the META process was carried out in R language.

RESULTS

58,342 CAP patients were enrolled in 22 studies. Of these patients, 29,610 underwent blood culture tests, and 2332 patients had positive blood culture results. Meta-analysis pooled results showed that the incidence of bacteremia was 5.1% (95% CI: 3.6-6.8%) in CAP patients. The prevalence of co-bacteremia was 3.1% (95% CI: 1.5-5.1%) in minors and 6.9% (95% CI: 5.2%-8.8%) in adults. The most common pathogens of CAP were Streptococcus pneumoniae, Staphylococcus aureus. In addition, a summary of the original studies found that the risk factors for bacteremia in CAP patients were diverse and varied.

CONCLUSIONS

The incidence of bacteremia in CAP patients warrants significant attention. There is a pressing need to establish more specific bacterial screening protocols.

Study of interaction in dual-species biofilm of Candida glabrata and Klebsiella pneumoniae co-isolated from peripheral venous catheter using Raman characterization mapping and machine learning algorithms

Polymicrobial biofilm infections, especially associated with medical devices such as peripheral venous catheters, are challenging in clinical settings for treatment and management. In this study, we examined the mixed biofilm formed by Candida glabrata and Klebsiella pneumoniae, which were co-isolated from the same peripheral venous catheter. Our results revealed that C. glabrata can form mixed biofilms with K. pneumoniae in vitro on peripheral venous catheters and the bottom of microplate wells, as confirmed by scanning electron microscopy. Additionally, using Raman mapping, we showed the distribution of both species in mono- and dual-species biofilms and suggested the type of microbial interaction in this polymicrobial biofilm. Finally, with the assistance of appropriate machine learning (ML) algorithms, based on identified peaks of bacteria, yeast, catheter, and Microplate mapping spectra, we develop a dedicated Raman database to detect the presence of these elements in an unknown spectrum in the future.

Evaluation of Sequential Oral Versus Intravenous Antibiotic Treatment of Enterococcus faecalis Bloodstream Infections

BACKGROUND

Intravenous (IV) antibiotics have historically been considered standard of care for treatment of bloodstream infections (BSIs). Recent literature has shown sequential oral (PO) therapy to be noninferior to IV antibiotics for certain pathogens and disease states. However, a gap exists in the literature for BSI caused by Enterococcus faecalis.

OBJECTIVE

To compare outcomes of definitive sequential PO therapy to definitive IV therapy in patients with E faecalis BSI.

METHODS

Multicenter, retrospective, matched cohort study of adult patients with at least one blood culture positive for E faecalis from January 2017 to November 2022. Patients with polymicrobial BSI, concomitant infections requiring prolonged IV antibiotic therapy, those who did not receive antibiotic therapy, and those who died within 72 hours of index culture were excluded. Subjects were matched based on source of infection in a 2:1 (IV:PO) ratio. The primary outcome was a composite of all-cause mortality and treatment failure. Secondary outcomes included hospital length of stay (LOS), antibiotic duration, and 30-day readmission rate.

RESULTS

Of the 186 patients who met criteria for inclusion, there was no statistically significant difference in the primary composite outcome for PO compared to IV therapy (14.5% vs 21.8%; OR 0.53 [0.23-1.25]) or 30-day readmission (17.5% vs 29%; OR 0.53 [0.25-1.13]). Hospital LOS was significantly longer in patients receiving IV-only therapy (6 days vs 14 days; P < 0.001).

CONCLUSION AND RELEVANCE

Sequential oral therapy for E faecalis BSI had similar outcomes compared to IV-only treatment and may be considered in eligible patients.

Rapid detection of carbapenem-resistant Escherichia coli and carbapenem-resistant Klebsiella pneumoniae in positive blood cultures via MALDI-TOF MS and tree-based machine learning models

BACKGROUND

Bloodstream infection (BSI) is a systemic infection that predisposes individuals to sepsis and multiple organ dysfunction syndrome. Early identification of infectious agents and determination of drug-resistant phenotypes can help patients with BSI receive timely, effective, and targeted treatment and improve their survival. This study was based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), Decision Tree (DT), Random Forest (RF), Gradient Boosting Machine (GBM), eXtreme Gradient Boosting (XGBoost), and Extremely Randomized Trees (ERT) models were constructed to classify carbapenem-resistant Escherichia coli (CREC) and carbapenem-resistant Klebsiella pneumoniae (CRKP). Bacterial species were identified by MALDI-TOF MS in positive blood cultures isolated via the serum isolation gel method, and E. coli and K. pneumoniae in positive blood cultures were collected and placed into machine learning models to predict susceptibility to carbapenems. The aim of this study was to provide rapid detection of CREC and CRKP in blood cultures, to shorten the turnaround time for laboratory reporting, and to provide a basis for early clinical intervention and rational use of antibiotics.

RESULTS

The collected MALDI-TOF MS data of 640 E. coli and 444 K. pneumoniae were analysed by machine learning algorithms. The area under the receiver operating characteristic curve (AUROC) for the diagnosis of E. coli susceptibility to carbapenems by the DT, RF, GBM, XGBoost, and ERT models were 0.95, 1.00, 0.99, 0.99, and 1.00, respectively, and the accuracy in predicting 149 E. coli-positive blood cultures were 0.89, 0.92, 0.90, 0.92, and 0.86, respectively. The AUROC for the diagnosis of K. pneumoniae susceptibility to carbapenems by the DT, RF, GBM, XGBoost, and ERT models were 0.78, 0.95, 0.93, 0.90, and 0.95, respectively, and the accuracy in predicting 127 K. pneumoniae-positive blood cultures were 0.76, 0.86, 0.81, 0.80, and 0.76, respectively.

CONCLUSIONS

Machine learning models constructed by MALDI-TOF MS were able to directly predict the susceptibility of E. coli and K. pneumoniae in positive blood cultures to carbapenems. This rapid identification of CREC and CRKP reduces detection time and contributes to early warning and response to potential antibiotic resistance problems in the clinic.

CLINICAL TRIAL NUMBER

Not applicable.

Clinical Characteristics and Risk Factors for Multidrug-Resistant Enterobacter cloacae Complex Bacteremia in a Chinese Tertiary Hospital: A Decade Review (2013-2022)

Objective

This study aimed to analyze the antimicrobial resistance profiles, clinical characteristics and risk factors of bacteremia caused by Enterobacter cloacae complex (ECC) strains.

Methods

We retrospectively collected clinical data from patients diagnosed with ECC bacteremia between 2013 and 2022 in a tertiary hospital in Jiangsu. Subgroup analyses were performed based on multidrug resistance (MDR), nosocomial acquisition, polymicrobial bacteremia, and mortality.

Results

Among 188 ECC strains, the highest resistance was to ceftriaxone (39.9%), followed by ceftazidime (36.7%) and aztreonam (31.2%), with low resistance to carbapenems (<8.6%) and amikacin (1.6%). MDR ECC accounted for 30.9% (58/188). Previous antibiotic therapy was an independent risk factor for MDR ECC (OR = 3.193, P < 0.020), while appropriate antibiotic therapy significantly reduced the risk (OR = 0.279, P < 0.001). ICU admission was an independent risk factor for polymicrobial bacteremia, both endoscopy and blood transfusion were associated with mortality.

Conclusion

Carbapenems and amikacin are the most effective treatments for ECC bacteremia. Previous antibiotic therapy increases the risk of MDR ECC, while appropriate antibiotic therapy reduces it. ICU admission is an independent risk factor for polymicrobial bacteremia, both endoscopy and blood transfusion are linked to higher mortality. Effective control of MDR ECC bacteremia requires comprehensive strategies, including resistance detection, risk factor identification, and infection prevention.

Antimicrobial and antibiofilm activity of prepared thymol@UIO-66 and thymol/ZnONPs@UIO-66 nanoparticles against Methicillin-resistant Staphylococcus aureus: A synergistic approach

This study introduces a novel approach to enhance the antibacterial properties of UIO-66 by incorporating both Thymol and ZnO nanoparticles within its framework which represents a significant advancement like exhibiting a synergistic antibacterial effect, providing a prolonged and controlled release, and mitigating cytotoxicity associated with the release of free ZnO nanoparticles by combining these two antimicrobial agents within a single, well-defined metal-organic framework. UIO-66 frameworks are investigated as carriers for the natural antimicrobial agent, Thymol, and ZnONPs offering a novel drug delivery system for antibacterial applications. Results demonstrated 132, 90, 184, and 223 nm sizes for UIO-66, ZnONPs, UIO-66 encapsulated Thymol, and UIO-66 encapsulated both Thymol and ZnONPs, respectively. Successful encapsulation of the antibacterial drug with a high entrapment efficiency of 64 % for Thymol was approved, and 49 % in-vitro release of Thymol was achieved for 72 hours. In-vitro antibacterial assays revealed promising results, with the drug-loaded nanoparticles exhibiting significantly lower MIC values and enhanced bactericidal activity against S. Aureus bacterial strains compared to the free drug, as demonstrated by agar disk diffusion and time-kill assays. MIC values reduced from a range of 31.25-250 µg/ml for free Thymol and 12.5-100 µg/ml for free ZnONPs to 3.9-62.5 µg/ml for Thymol@UIO-66 and 1.95-15.63 µg/ml for Thymol/ZnONPs@UIO-66. According to the results, the mixture of both Thymol and ZnONPs had 41 % and 16 % more antibiofilm activities in comparison with free Thymol and free ZnONPs, respectively. Furthermore, Thymol@UIO-66 had 25 % higher antibiofilm activities relative to not-encapsulated Thymol and ZnONPs, and this improvement was even 46 % more in Thymol/ZnONPs@UIO-66 in comparison with Thymol@UIO-66. Overall, this study demonstrates the potential of Thymol/ZnONPs@UIO-66 frameworks as a promising drug delivery platform for effective antibacterial therapy. This approach to overcome antibiotic resistance and improve treatment efficacy potentially.

Patterns of Klebsiella pneumoniae bacteremic dissemination from the lung

Bacteremia, a leading cause of death, generally arises after bacteria establish infection in a particular tissue and transit to secondary sites. Studying dissemination from primary sites by solely measuring bacterial burdens does not capture the movement of individual clones. By barcoding Klebsiella pneumoniae, a leading cause of bacteremia, we track pathogen dissemination following pneumonia. Variability in organ bacterial burdens is attributable to two distinct dissemination patterns distinguished by the degree of similarity between the lung and systemic sites. In metastatic dissemination, lung bacterial clones undergo heterogeneous expansion and the dominant clones spread to secondary organs, leading to greater similarity between sites. In direct dissemination, bacterial clones exit the lungs without clonal expansion, leading to lower burdens in systemic sites and more dissimilarity from the lung. We uncover bacterial and host factors that influence the dynamics of clonal sharing and expansion. Here, our data reveal unexpected heterogeneity in Klebsiella bacteremia dynamics and define a framework for understanding within-host bacterial dissemination.

Enhancing pathogens detection in suspected geriatric bloodstream infections using Nanopore-targeted sequencing

Bloodstream infections (BSIs) are a critical concern for elderly patients, where prompt and accurate diagnosis is vital for effective treatment. Traditional blood culture methods suffer from delayed results and susceptibility to false-negatives. Nanopore-targeted sequencing (NTS) offers rapid pathogen detection and reporting, presenting a promising alternative. However, the application of NTS for diagnosing suspected BSIs in geriatric patients remains insufficiently studied. We conducted a retrospective cohort study from January 2022 to January 2024, including 198 geriatric patients suspected of BSIs. We utilized NTS to detect pathogen characteristics and compared the effectiveness and consistency of NTS with simultaneous blood culture testing for pathogen detection. NTS demonstrated a pathogen detection rate of 61.1%. The most common bacterial pathogens were Escherichia coli and Staphylococcus aureus (each 7.7%), while Candida albicans was the most prevalent fungal pathogen (30%). Mixed-bacterial infections were detected in 21.7% of NTS-positive cases, and concurrent bacterial-fungal infections were observed in 9.92% of these cases. NTS-positive patients had higher rates of comorbidities, elevated inflammatory markers, and worse prognoses compared to NTS-negative patients. NTS exhibited a significantly higher pathogen detection rate and faster turnaround time than blood culture (78.1% vs 42.2%, P < 0.001), with an agreement rate of 65.6%. The elderly BSI patients frequently involve multiple or mixed infections and correlate with poorer prognoses. NTS provides a faster and more sensitive diagnostic alternative to traditional blood culture, potentially improving clinical outcomes and guiding more effective treatment strategies. This study highlights the need for further research to validate the routine clinical integration of NTS for managing BSIs in geriatric populations.

IMPORTANCE

Bloodstream infections (BSIs) in elderly patients pose substantial diagnostic and therapeutic challenges due to the limitations of traditional blood culture methods, which are hampered by slow turnaround times and false-negatives. Nanopore-targeted sequencing (NTS) emerges as a significant advancement, offering rapid and accurate pathogen detection directly from blood samples. This study demonstrates that NTS provides a higher detection rate and faster results than conventional blood cultures, crucial for the timely management of BSIs in geriatric patients, who often present with multiple or mixed infections and have poorer clinical outcomes. The findings underscore the potential of NTS to enhance diagnostic accuracy and speed, informing more effective treatment strategies and improving overall patient outcomes. Further research is essential to establish NTS as a routine diagnostic tool in the clinical management of BSIs in the elderly.

Bacteraemia over 4 years in a Greater Western Sydney Metropolitan Local Health District: a retrospective descriptive study

BACKGROUND

Bacteraemia is associated with significant morbidity and mortality. Understanding local patterns of bacteraemia including pathogen distribution, infection source, clinical speciality team burden, susceptibility data and mortality rates can inform empiric antibiotic choices, prevention approaches and education strategies.

AIMS

To obtain descriptive data from positive blood cultures identified from Nepean Blue Mountains Local Health District in Greater Western Sydney.

METHODS

A retrospective descriptive study was performed from August 2018 to March 2023 with data extracted from electronic medical records.

RESULTS

A total of 6720 isolates were identified from positive blood cultures, of which 71.2% were clinically significant. The median age was 69 years. A total of 74.6% of clinically significant isolates were acquired in the community. The most commonly isolated pathogen was Escherichia coli (31.3%), followed by Staphylococcus aureus (14.3%), and 8.6% of patients with clinically significant positive blood cultures were neutropenic. Neutropenic patients were more likely to have Pseudomonas aeruginosa as the causative pathogen (11.4%) compared to the entire study population (3.9%). The most commonly identified source of infection was the urinary tract. The 30-day all-cause mortality rate for clinically significant positive blood cultures was 16.8%, with higher mortality rates seen with Candida species (and species previously known as Candida), P. aeruginosa and Enterococcus species. 94% of bacteraemia from Enterobacterales tested susceptible in vitro to ampicillin and/or gentamicin. The rate of methicillin resistance in S. aureus was 24%.

CONCLUSIONS

This study provides valuable insight into the local epidemiology of bacteraemia, which will allow for targeted prevention, management and educational strategies to improve outcomes.

Isoferulic acid facilitates effective clearance of hypervirulent Klebsiella pneumoniae through targeting capsule

Hypervirulent Klebsiella pneumoniae (hvKP) poses an alarming threat in clinical settings and global public health owing to its high pathogenicity, epidemic success and rapid development of drug resistance, especially the emergence of carbapenem-resistant lineages (CR-hvKP). With the decline of the "last resort" antibiotic class and the decreasing efficacy of first-line antibiotics, innovative alternative therapeutics are urgently needed. Capsule, an essential virulence determinant, is a major cause of the enhanced pathogenicity of hvKP and thus represents an attractive drug target to prevent the devastating clinical outcomes caused by hvKP infection. Here, we identified isoferulic acid (IFA), a natural phenolic acid compound widely present in traditional herbal medicines, as a potent broad-spectrum K. pneumoniae capsule inhibitor that suppresses capsule polysaccharide synthesis by increasing the energy status of bacteria. In this way, IFA remarkably reduced capsule thickness and impaired hypercapsule-associated hypermucoviscosity phenotype (HMV), thereby significantly sensitizing hvKP to complement-mediated bacterial killing and accelerating host cell adhesion and phagocytosis. Consequently, IFA facilitated effective bacterial clearance and thus remarkably protected mice from lethal hvKP infection, as evidenced by limited bacterial dissemination and a significant improvement in survival rate. In conclusion, this work promotes the development of a capsule-targeted alternative therapeutic strategy for the use of the promising candidate IFA as an intervention to curb hvKP infection, particularly drug-resistant cases.

Is intestinal colonization with multidrug-resistant Enterobacterales associated with higher rates of nosocomial Enterobacterales bloodstream infections?

OBJECTIVES

Intestinal colonization with multidrug-resistant Enterobacterales (MDRE-IC) increases the risk of MDRE bloodstream infection (BSI). However, its impact on the overall risk of nosocomial Enterobacterales bloodstream infections (nE-BSIs) remains unclear. This study aimed to determine this risk and identify associated factors in hospitalized patients.

DESIGN

This retrospective cohort study at a 3200-bed tertiary institution including patients hospitalized in 2019 who underwent MDRE rectal swab (RS) screening. Inclusion criteria were age ≥18 years, first RS in 2019, follow-up ≥7 days, and Enterobacterales BSIs >48 hours after RS. The primary outcome was the first nE-BSI during the follow-up period, analyzed using a Cox model.

RESULTS

Among 7006 patients, 817 (11.9%) had MDRE-IC. Most were male and primarily hospitalized in acute wards. nE-BSIs occurred in 433 (6.1%) patients and were more frequent in patients with MDRE-IC than the non-colonized group (adjusted hazard ratio [aHR] = 1.78, 95% confidence interval [CI]: 1.40-2.26). Intestinal colonization with extended-spectrum β-lactamase-producing and carbapenemase-resistant Enterobacterales showed similar risks for Enterobacterales BSI onset: aHR = 1.73 (95% CI: 1.33-2.24) and aHR = 2.02 (95% CI: 1.27-3.22), respectively.

CONCLUSIONS

In hospitalized patients, MDRE-IC is associated with a higher rate of nE-BSI than those without MDRE-IC, underscoring the urgent need for improved infection prevention and control measures, as well as optimized antibiotic use to mitigate this risk.

Investigating the time to blood culture positivity: why does it take so long?

Introduction. Bloodstream infections (BSIs) are one of the most serious infections investigated by microbiologists. However, the time to detect a BSI fails to meet the rapidity required to inform clinical decisions in real time.Gap Statement. Blood culture (BC) is considered the gold standard for diagnosing bloodstream infections. However, the time to blood culture positivity can be lengthy. Underpinning this is the reliance on bacteria replicating to a high concentration, which is necessary for the detection using routine blood culture systems. To improve the diagnosis and management of patients with BSIs, more sensitive detection methods are required.Aim. The study aimed to answer key questions addressing the delay in BSI detection and whether the time to BSI detection could be expedited using a Scattered Light Integrated Collection (SLIC) device.Methodology. A proof-of-concept study was conducted to compare the time to positivity (TTP) of Gram-negative BCs flagging positive on BacT/ALERT with an SLIC device. An SLIC device was utilized to compare the TTP of the most prevalent BSI pathogens derived from nutrient broth and BC, the influence of bacterial load on TTP and the TTP directly from whole blood. Additionally, the overall turnaround time (TAT) of SLIC was compared with that of a standard hospital workflow.Results. Most pathogens tested took significantly longer to replicate when derived from BC than from nutrient medium. The median TTP of Gram-negative BC on BacT/ALERT was 13.56 h with a median bacterial load of 6.4×109 c.f.u. ml-1. All pathogens (7/7) derived from BC at a concentration of 105 c.f.u. ml-1 were detectable in under 70 min on SLIC. Decreasing Escherichia coli BC concentration from 105 to 102 c.f.u. ml-1 increased the TTP of SLIC from 15 to 85 min. Direct BSI detection from whole blood on SLIC demonstrated a 76% reduction in TAT when compared with the standard hospital workflow.Conclusion. An SLIC device significantly reduced the TTP of common BSI pathogens. The application of this technology could have a major impact on the detection and management of BSI.

Integration of MALDI-TOF MS and machine learning to classify enterococci: A comparative analysis of supervised learning algorithms for species prediction

This research focused on distinguishing distinct matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) spectral signatures of three Enterococcus species. We evaluated and compared the predictive performance of four supervised machine learning algorithms, K-nearest neighbor (KNN), support vector machine (SVM), and random forest (RF), to accurately classify Enterococcus species. This study involved a comprehensive dataset of 410 strains, generating 1640 individual spectra through on-plate and off-plate protein extraction methods. Although the commercial database correctly identified 76.9% of the strains, machine learning classifiers demonstrated superior performance (accuracy 0.991). In the RF model, top informative peaks played a significant role in the classification. Whole-genome sequencing showed that the most informative peaks are biomarkers connected to proteins, which are essential for understanding bacterial classification and evolution. The integration of MALDI-TOF MS and machine learning provides a rapid and accurate method for identifying Enterococcus species, improving healthcare and food safety.

The role of rapid multiplex molecular syndromic panels in the clinical management of infections in critically ill patients: an experts-opinion document

Rapid multiplex molecular syndromic panels (RMMSP) (3 or more pathogens and time-to-results < 6 h) allow simultaneous detection of multiple pathogens and genotypic resistance markers. Their implementation has revolutionized the clinical landscape by significantly enhancing diagnostic accuracy and reducing time-to-results in different critical conditions. The current revision is a comprehensive but not systematic review of the literature. We conducted electronic searches of the PubMed, Medline, Embase, and Google Scholar databases to identify studies assessing the clinical performance of RMMSP in critically ill patients until July 30, 2024. A multidisciplinary group of 11 Spanish specialists developed clinical questions pertaining to the indications and limitations of these diagnostic tools in daily practice in different clinical scenarios. The topics covered included pneumonia, sepsis/septic shock, candidemia, meningitis/encephalitis, and off-label uses of these RMMSP. These tools reduced the time-to-diagnosis (and therefore the time-to-appropriate treatment), reduced inappropriate empiric treatment and the length of antibiotic therapy (which has a positive impact on antimicrobial stewardship and might be associated with lower in-hospital mortality), may reduce the length of hospital stay, which could potentially lead to cost savings. Despite their advantages, these RMMSP have limitations that should be known, including limited availability, missed diagnoses if the causative agent or resistance determinants are not included in the panel, false positives, and codetections. Overall, the implementation of RMMSP represents a significant advancement in infectious disease diagnostics, enabling more precise and timely interventions. This document addresses relevant issues related to the use of RMMSP on different critically ill patient profiles, to standardize procedures, assist in making management decisions and help specialists to obtain optimal outcomes.

Antimicrobial Resistance in Enterobacterales, Acinetobacter spp. and Pseudomonas aeruginosa Isolates From Bloodstream Infections in Australian Children, 2013-2021

BACKGROUND

Gram-negative bloodstream infections are associated with significant morbidity and mortality in children. Increasing antimicrobial resistance (AMR) is reported globally, yet efforts to track pediatric AMR at a national level over time are lacking.

METHODS

The Australian Group on Antimicrobial Resistance (AGAR) surveillance program captures clinical and microbiological data of isolates detected in blood cultures across Australia. EUCAST 2022 was used for MIC interpretation and the AMR package in R for data analysis.

RESULTS

Over a 9-year period, there were 3145 bloodstream infections with 3266 gram-negative isolates reported in hospitalized children aged <18 years; 21.0% were from neonates. The median length of stay was 9 days, and 30-day all-cause mortality was 5.2%. A greater odds of death was observed in those with a multi-drug resistant organism (aOR: 2.1, 95% CI: 1.3, 3.3, p: 0.001). Escherichia coli (44.5%) and Klebsiella pneumoniae complex (12.6%) were the two most frequently reported organisms. Overall resistance in Enterobacterales to gentamicin/tobramycin was 11.6%, to ceftazidime/ceftriaxone was 12.9%, and 13.2% to ciprofloxacin. Resistance increased over time. Of the 201 Pseudomonas aeruginosa isolates reported, 19.7% were resistant to piperacillin-tazobactam, 13.1% resistant to cefepime/ceftazidime, and 9.8% to ciprofloxacin. Of 108 Acinetobacter spp. isolates, one was resistant to meropenem, and two were resistant to ciprofloxacin. Resistance did not increase over time.

CONCLUSIONS

AMR in gram-negative organisms causing bloodstream infections in Australian children is increasing, which should be considered when updating guidelines and empiric treatment regimens. Ongoing pediatric-specific national surveillance with pediatric reporting must remain a priority to strengthen antimicrobial stewardship and infection control programs.

Essential oils from Colombian Croton spp. exhibit antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and ampicillin- and streptomycin-resistant Escherichia coli

Bacterial resistance, a global public health concern prioritized by the World Health Organization, is particularly alarming in Staphylococcus aureus and Escherichia coli. Urgently addressing this, the search for new antibiotics has turned to plant essential oils. Our study focused essential oils derived from Colombian plants Croton killipianus, Croton smithianus, Croton leptostachyus, Croton hondensis, and Croton gossypiifolius. We performed antimicrobial susceptibility tests targeting Staphylococcus aureus, methicillin-resistant Staphylococus aureus, sensitive Escherichia coli, and ampicillin- and streptomycin-resistant Escherichia coli. Simultaneosly, citotoxic assays and chemical analysis were carried out. The essential oil derived from C. hondensis demonstrated superior inhibitory efficacy, effectively targeting methicillin-resistant S. aureus, susceptible S. aureus, and both sensitive and ampicillin- and streptomycin-resistant strains of E. coli. Furthermore, it exhibited notable potential for protective activity in Chinese hamster ovary cells. C. killipianus manifested inhibitory effects against MRSA and susceptible S. aureus, whereas C. smithianus specifically affected susceptible strains of S. aureus. Chemical analysis of the essential oils revealed rich content in phenolic compounds, flavonoids, tannins, and steroids. Gas-coupled mass spectrometry identified key compounds like γ-muurolene, α-humulene, (E)-caryophyllene, α-copaene, curcumene, and (E)-nerolidol. These findings underscore C. hondensis, C. killipianus, and C. smithianus as potential natural sources for antibacterial agent development.

Treatment Options for Nosocomial Ventriculitis/Meningitis: A Case Report and Review of the Literature

Ventriculo-meningitis or nosocomial meningitis/ventriculitis is a severe nosocomial infection that is associated with devastating neurological sequelae. The cerebrospinal fluid isolates associated with the infection can be Gram-positive or -negative, while the Enterococcus spp. is rarely identified. We report a case of a 68-year-old woman with a past medical history of insulin-dependent diabetes mellitus, hypertension, and coronary artery disease. She was admitted to the intensive care unit following a scheduled sphenoid wing meningioma resection. Her course was complicated with left middle cerebral artery pseudoaneurysm and hemispheric hemorrhage, and an arterial stent and external ventricular drainage catheter were placed. Neurological evaluation showed a minimal conscious state. She presented high fever on the 35th intensive care unit day. Cerebrospinal fluid was sampled and the external ventricular catheter was removed. Enterococcus faecalis was isolated from the culture specimen. The patient received targeted treatment with an ampicillin plus ceftriaxone combination, and a follow-up culture confirmed the pathogen's eradication. Although she was considered cured, she had a prolonged intensive care unit stay and finally died in the ward two months after the completion of treatment. This case highlights the first reported use of this combination in a severe, non-endocarditis, invasive enterococcal infection, while the review discusses treatment options for nosocomial ventriculitis/meningitis.

Global and regional burden of bloodstream infections caused by carbapenem-resistant Gram-negative bacteria in 2019: A systematic analysis from the MICROBE database

OBJECTIVES

To quantify the global and regional burden of bloodstream infections associated with and attributable to carbapenem-resistant Gram-negative bacteria.

METHODS

We extracted data from the Measuring Infectious Causes and Resistance Outcomes for Burden Estimation database, which includes the estimated burden of 23 pathogens and 88 pathogen-drug combinations across 12 major infectious syndromes globally in 2019. The number and rate of deaths, as well as disability-adjusted life-years linked to bloodstream infections, were systematically analyzed.

RESULTS

In 2019, bloodstream infections accounted for approximately 2.91 (95% UI, 1.74-4.53) million deaths globally, with Gram-negative bacteria responsible for 51.1% of these fatalities. An estimated 391,800 (95% UI 221,500-631,400) deaths were associated with carbapenem resistance, constituting 26.3% of all bloodstream infection-related deaths. The highest burden of carbapenem resistance was seen in South Asia, East Asia, and Eastern Europe, while the lowest burden was in Sub-Saharan Africa. Notably, Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa were the leading carbapenem-resistant pathogens contributing to mortality.

CONCLUSIONS

Our findings underscore the significant global burden of bloodstream infections caused by carbapenem-resistant Gram-negative bacteria, with notable regional disparities. There is an urgent need for enhanced surveillance, improved infection prevention and control measures, and better access to first-line antibiotics, particularly in high-burden regions.

Pathogenic Burden, Antimicrobial Resistance Pattern and Clinical Outcome of Nosocomial Bloodstream Infections in Intensive Care Unit

Purpose: Nosocomial bloodstream infections with multidrug-resistant microorganisms have become a common health threat in intensive care settings worldwide. Understanding antimicrobial resistance and the outcomes of these infections is crucial for addressing this issue. This study aimed to investigate the burden, antimicrobial resistance, and 28-day outcomes of nosocomial bloodstream infections in the intensive care unit. Materials and Methods: This retrospective study was conducted in a multispecialty intensive care unit at a tertiary care hospital in western India. Adult patients aged ≥18 years with bloodstream infections acquired after 48 h of admission were included in the analysis. Results: A total of 245 patients suspected of having nosocomial infections in the intensive care unit were evaluated, and 179 were included in the study. Gram-negative bacteremia was identified in the majority of cases, affecting 111 (62%) patients. Carbapenem-resistant Acinetobacter baumannii was the most prevalent pathogen, found in 21.2% (38/179) of patients. Candida species were detected in 37 (20.6%) cases, and gram-positive cocci were identified in 31 (17.3%) patients, with vancomycin-sensitive Enterococci being the most common gram-positive cocci isolated from blood. The central venous catheter was the most frequent source of bloodstream infection, identified in 66 (36.9%) patients. Among all patients, 28-day mortality was observed in 102 (57%) patients. Higher quick sepsis-related organ failure (qSOFA) scores at the onset of bloodstream infection, central venous catheters as a source of infection, inability to initiate early appropriate therapy and septic shock at the onset of bloodstream infection were identified as independent predictors of mortality in patients with nosocomial bloodstream infections. Conclusion: An increased burden of gram-negative bacilli and Candida was found to cause nosocomial bloodstream infections, with very high rates of antimicrobial resistance. Early appropriate diagnosis and treatment play a critical role in improving survival. Additionally, enhanced infection prevention and control practices are necessary to mitigate the heavy burden of infections caused by multidrug-resistant organisms in critical care settings.

Evaluation of elderly patients with bacteremia in the cardiology intensive care unit

In this study, the blood culture results of patients aged >65 years who were admitted to the cardiology intensive care unit in a training and research hospital and who had positive blood cultures within the first 48 hours were evaluated. This was a retrospective, observational and nonrandomized study. Patient data at the time of the blood culture were included in the study. Sex, age, length of hospital stay, mortality, Acute Physiology Chronic Health Evaluation II score, laboratory values, and microorganisms grown in blood culture included in the study. Two hundred forty-seven patients, 43.3% of whom were female (n = 107), were included in the study. The median age of the patients was 75 (range 70-83). The mean hospital stay was 5 days (range 3-8). All patients had a median Acute Physiology Chronic Health Evaluation II score of 21 (range 19-23). The overall mortality rate 48.2% (n = 119). The results showed that 49.8% of those died and 50.2% of survivors had positive blood culture results. The most common gram-positive cocci in those died were Staphylococcus hominis (15.6%), Staphylococcus epidermis (14.8%), Enterococcus faecium (9.6%). The most common gram-negative cocci were Escherichia coli (9.6%), Klebsiella pneumoniae (9.6%), Acinetobacter baummanii (1.6%). With an increase in the elderly population, infection management in elderly patients hospitalized in cardiology intensive care units has become increasingly critical.

Mandatory surveillance of bacteremia conducted by automated monitoring

Except for a few countries, comprehensive all-cause surveillance for bacteremia is not part of mandatory routine public health surveillance. We argue that time has come to include automated surveillance for bacteremia in the national surveillance systems, and explore diverse approaches and challenges in establishing bacteremia monitoring. Assessed against proposed criteria, surveillance for bacteremia should be given high priority. This is based on severity, burden of illness, health gains obtained by improved treatment and prevention, risk of outbreaks (including health care associated infections), the emergence of antimicrobial drug resistance as well as the changing epidemiology of bacteremia which is seen along with an aging population and advances in medical care. The establishment of comprehensive surveillance for bacteremia was until recently conceived as an insurmountable task. With computerized systems in clinical microbiology, surveillance by real-time data capture has become achievable. This calls for re-addressing the question of including bacteremia among the conditions under mandatory surveillance. Experiences from several countries, including Denmark, show that this is feasible. We propose enhanced international collaboration, legislative action, and funding to address the challenges and opportunities.

In Vivo Activity Profiling of Biosynthetic Darobactin D22 against Critical Gram-Negative Pathogens

In recent years, naturally occurring darobactins have emerged as a promising compound class to combat infections caused by critical Gram-negative pathogens. In this study, we describe the in vivo evaluation of derivative D22, a non-natural biosynthetic darobactin analogue with significantly improved antibacterial activity. We found D22 to be active in vivo against key critical Gram-negative human pathogens, as demonstrated in murine models of Pseudomonas aeruginosa thigh infection, Escherichia coli peritonitis/sepsis, and urinary tract infection (UTI). Furthermore, we observed the restored survival of Acinetobacter baumannii-infected embryos in a zebrafish infection model. These in vivo proof-of-concept (PoC) in diverse models of infection against highly relevant pathogens, including drug-resistant isolates, highlight the versatility of darobactins in the treatment of bacterial infections and show superiority of D22 over the natural darobactin A. Together with a favorable safety profile, these findings pave the way for further optimization of the darobactin scaffold toward the development of a novel antibiotic.

Genomic virulence markers are associated with severe outcomes in patients with Pseudomonas aeruginosa bloodstream infection

BACKGROUND

Pseudomonas aeruginosa (PA) bloodstream infection (BSI) is a common healthcare-associated complication linked to antimicrobial resistance and high mortality. Ongoing clinical trials are exploring novel anti-virulence agents, yet studies on how bacterial virulence affects PA infection outcomes is conflicting and data from real-world clinical populations is limited.

METHODS

We studied a multicentre cohort of 773 adult patients with PA BSI consecutively collected during 7-years from sites in Europe and Australia. Comprehensive clinical data and whole-genome sequencing of all bacterial strains were obtained.

RESULTS

Based on the virulence genotype, we identify several virulence clusters, each showing varying proportions of multidrug-resistant phenotypes. Genes tied to biofilm synthesis and epidemic clones ST175 and ST235 are associated with mortality, while the type III secretion system is associated with septic shock. Adding genomic biomarkers to machine learning models based on clinical data indicates improved prediction of severe outcomes in PA BSI patients.

CONCLUSIONS

These findings suggest that virulence markers provide prognostic information with potential applications in guiding adjuvant sepsis treatments.

Characterization of two lytic bacteriophages infecting carbapenem-resistant clinical Klebsiella pneumoniae in Dhaka, Bangladesh

Bacteriophages or bacteria infecting viruses are genetically diverse. Due to the emergence of antimicrobial-resistant bacteria, lytic bacteriophages are gaining enormous attention for treating superbug infections. Klebsiella pneumoniae is one of the eight most significant nosocomial pathogens and is addressed as a critical priority pathogen by WHO, requiring alternative treatment options. We reported two highly lytic bacteriophages, Klebsiella phage Kpn BM7 and the novel Klebsiella phage Kpn BU9, isolated from hospital wastewater and exhibiting lytic activity against different clinical isolates. Whole-genome analysis revealed that phages BM7 and BU9 belong to class Caudoviricetes. Phage BM7, with a genome length of 170,558 bp, is a member of the genus Marfavirus and the species Marfavirus F48. While phage BU9, with a genome length of 60,450 bp, remains unclassified. Neither phage harbors any lysogenic, toxin, or antimicrobial resistance genes. Both phages can steadily survive up to 40 °C and at pH 5-7. The optimal MOI was 0.1 for BM7 and 1 for BU9, with short latent periods of 10 and 25 min and burst sizes of 85 PFU/cell and 12 PFU/cell, respectively. This is the first carbapenem-resistant K. pneumoniae targeting lytic phages to be reported from Bangladesh. This study suggests that BM7 and BU9 are potential candidates for targeting carbapenem-resistant K. pneumoniae.

Targeting bacterial growth in biofilm conditions: rational design of novel inhibitors to mitigate clinical and food contamination using QSAR

Antimicrobial resistance (AMR) is a pressing global issue exacerbated by the abuse of antibiotics and the formation of bacterial biofilms, which cause up to 80% of human bacterial infections. This study presents a computational strategy to address AMR by developing three novel quantitative structure-activity relationship (QSAR) models based on molecular topology to identify potential anti-biofilm and antibacterial agents. The models aim to determine the chemo-topological pattern of Gram (+) antibacterial, Gram (-) antibacterial, and biofilm formation inhibition activity. The models were applied to the virtual screening of a commercial chemical database, resulting in the selection of 58 compounds. Subsequent in vitro assays showed that three of these compounds exhibited the most promising antibacterial activity, with potential applications in enhancing food and medical device safety.

Gut Microbiota Dysbiosis Facilitates Susceptibility to Bloodstream Infection

To study the role of intestinal flora in the development of bloodstream infections (BSIs). 42 patients and 19 healthy controls (HCs) were screened into the study and their intestinal flora was measured by 16S rRNA gene sequencing. The bacterial diversity was significantly lower in the BSI group compared with that in the HCs (P < 0.001), and beta diversity was significantly differentiated between the two groups (PERMANOVA, P = 0.001). The four keystone species [Roseburia, Faecalibacterium, Prevotella, and Enterococcus (LDA > 4)] differed significantly between the two groups. Dysbiosis of fecal microbial ecology is a common condition present in patients with BSI. The proliferation of certain pathogens or reduction of SCFA-producing bacteria would cause susceptibility to BSI.

Klebsiella pneumoniae capsular polysaccharide: Mechanism in regulation of synthesis, virulence, and pathogenicity

Hypervirulent Klebsiella pneumoniae exhibits strong pathogenicity and can cause severe invasive infections but is historically recognized as antibiotic-susceptible. In recent years, the escalating global prevalence of antibiotic-resistant hypervirulent K. pneumoniae has raised substantial concerns and created an urgent demand for effective treatment options. Capsular polysaccharide (CPS) is one of the main virulence determinants contributing to the hypervirulent phenotype. The structure of CPS varies widely among strains, and both the structure and composition of CPS can influence the virulence of K. pneumoniae. CPS possesses various immune evasion mechanisms that promote the survival of K. pneumoniae, as well as its colonization and dissemination. Given the proven viability of therapies that target the capsule, improving our understanding of the CPS structure is critical to effectively directing treatment strategies. In this review, the structure and typing of CPS are addressed as well as genes related to synthesis and regulation, relationships with virulence, and pathogenic mechanisms. We aim to provide a reference for research on the pathogenesis of K. pneumoniae.

Multivariate statistical analysis of surface water quality in the capibaribe river (Pernambuco state, Northeast Brazil): Contributions to water management

Assessing the quality of surface waters is essential for identifying changes in freshwater ecosystems and supporting the planning/proposing of measures to mitigate polluting sources. However, many studies involving the identification of pathogenic bacteria and/or their resistance profile to antimicrobial agents need a more holistic approach to conditioning or modulating factors. Thus, we apply different multivariate statistical techniques to the data set from the Capibaribe River's surface water, one of the most important in the Northeast of Brazil. Our data, taken together, suggest that the waters of the Capibaribe River have been suffering impacts associated with different human activities. Due to its flow crossing a large urban area, different sources are contributing to the contamination/pollution of its aquatic ecosystem, whose multivariate analysis allowed us to identify site-dependent characteristics that reflect the degree and type of human influence. The study of physical-chemical and chemical parameters reveals the influence of the high load of effluents (industrial and domestic) on the chemical and microbiological quality of the waters sampled at the SS4 site. On the other hand, the antimicrobial resistance profile of the isolates evaluated, especially at SS1, SS2, and SS3 sites, provides a comprehensive sample of the "resistome" present in the fecal content of thousands of people living in the region surrounding the Capibaribe River. The presence of enterobacteria in water indicates contamination of fecal origin. It represents a public health problem since the waters of the Capibaribe River can be a source of dissemination and persistence of bacteria resistant to humans and the environment. In conclusion, our study provides a more comprehensive understanding of the relationships between surface water, basic sanitation, antibiotic exposure, bacterial gene transfer, and human colonization, whether in the context of the region studied or other locations.

Gram-negative bloodstream infections in six German university hospitals, 2016-2020: clinical and microbiological features

PURPOSE

To analyze the longitudinal epidemiology and antimicrobial resistance (AMR) patterns of Gram-negative bloodstream infections (BSI) in Germany.

METHODS

Post-hoc analysis of prospectively documented BSI due to Escherichia coli, Klebsiella spp., Enterobacter spp., Pseudomonas aeruginosa and Acinetobacter baumannii from six university hospitals between 2016 and 2020. In a subanalysis 1228 episodes of BSI (E. coli N = 914, Klebsiella spp. N = 314) were analyzed for clinical endpoints and risk factors.

RESULTS

E. coli was the most prevalent cause of BSI, with 5412 cases, followed by Klebsiella spp. (2148 cases), P. aeruginosa (789 cases), Enterobacter spp. (696 cases), and A. baumannii (31 cases). BSI incidence rates were particularly high in haematology/oncology, with E. coli BSI reaching 13.9 per 1000 admissions. Most (58%) of the BSI episodes were community-acquired. A notable finding was the moderate increase of third-generation cephalosporin resistant Enterobacterales (3GCREB) for E. coli from 13.9% in 2016 to 14.4% in 2020 and a decrease for Klebsiella spp. from 16.5% in 2016 to 11.1% in 2020 corresponding to extended-spectrum betalactamase (ESBL) phenotype. In our analysis, the 3GCREB phenotype was not associated with a higher risk of death or discharge with sequelae for E. coli and Klebsiella spp.

CONCLUSION

Our study provides longitudinal data on Gram-negative BSI in Germany on a clinical basis for the first time. These data underscores the critical need for ongoing surveillance and more pathogen-related clinical data.

Gram-Negative Bloodstream Infections in a Medical Intensive Care Unit: Epidemiology, Antibiotic Susceptibilities, and Risk Factors for in-Hospital Death

Purpose

Gram-negative bloodstream infection (GNBI) poses a serious threat to critically ill patients. This retrospective study aimed to uncover drug resistance of pathogens and the GNBI effect on in-hospital death and distinguish death risk factors in a medical intensive care unit (ICU).

Patients and Methods

A retrospective study of all GNBI patients in the medical ICU of the Third Xiangya Hospital over 9 nine years was conducted. Blood samples were performed by a BACTEC 9240 system, MALDI-TOF MS, Bruker and Vitek-2 system. Logistic regression was used for analyzing risk factors for death.

Results

Seventy-five episodes of GNBI developed in 68 (1.4%) out of 4954 patients over a span of 9 years. The most frequently isolated bacterium was Klebsiella pneumoniae, with the lungs as the predominant source of GNBI. The resistance rate of Gram-negative bacteria to polymyxin B was 11.6% after excluding those intrinsically resistant non-fermentative bacteria. All Enterobacter spp. were susceptible to ceftazidime/avibactam. Thirty-three (48.5%) patients underwent inappropriate empirical antibiotic treatment and 48 (70.6%) patients died during the hospitalization. Multivariate logistic regression analysis identified that lymphocyte count at GNBI onset ≤0.5×109/L, invasive mechanical ventilation, and septic shock were related to in-hospital death. Body mass index ≥23 and appropriate empirical antibiotic use after GNBI were negatively associated with in-hospital death.

Conclusion

GNBI was a frequent complication among patients in the medical ICU. This study underscored the presence of diverse factors that either heightened or attenuated the risk of in-hospital death.

Clinical characteristics and bloodstream infection pathogens by gram-negative bacteria in different aged adults: A retrospective study

This study aims to determine the characteristics and distribution of pathogenic bacteria in bloodstream infections (BSIs) by gram-negative bacteria in adults. One hundred seventy-one adult patients with BSIs who were treated at the Affiliated Hospital of Chengde Medical College between January 2018 and January 2020 were included in this study. The patients were assigned to the young- and middle-aged group and elderly group based on age. General patient data were analyzed. More elderly patients had BSIs and gram-negative bacteria than young- and middle-aged patients. The incidence of underlying diseases in elderly patients was significantly higher than the young- and middle-aged patients (P < .01). The composition of Brucella spp. was significantly different between the elderly group and young- and middle-aged group (P < .05). There were significantly more gallbladder infections in the elderly group than the young- and middle-aged group, and significantly fewer elderly patients had no definite infection sites than the young- and middle-aged group (P < .05). The incidence of complications and in-hospital mortality in the elderly group was higher than the young- and middle-aged group (P < .05). BSIs caused by gram-negative bacteria mainly involved elderly patients. BSIs were characterized by complications and a poor prognosis, as well as pathogenic bacteria and primary infection sites.

Geneticand phenotypic characterization of a novel ST45-K43 carbapenem-resistant Klebsiella pneumoniae strain causing bloodstream infection: a potential clinical threat

Klebsiella pneumoniae is a common pathogen of nosocomial infection, which can cause pneumonia, urinary tract infection, cystitis, and bloodstream infections (BSIs). Here, we genetically characterize a novel carbapenem-resistant K. pneumoniae (CRKP) strain recovered from the blood of a 44-year-old male patient with severe acute necrotizing pancreatitis and septic shock in China. The strain is a ST45 K. pneumoniae with a novel serotype of K43, named 18SHX166. The susceptibility testing results showed that 18SHX166 was resistant to cephalosporin and carbapenems but still susceptible to ceftazidime-avibactam, quinolones, colistin, and amikacin. Genomic sequencing revealed that 18SHX166 contains three plasmids, namely pSHX166-Hv, pSHX166-KPC, and pSHX166-3. pSHX166-Hv harbored the iucABCD operon, encoding the siderophore of aerobactin. pSHX166-KPC harbored blaKPC-2 gene and possessed complete conjugative regions. The conjugation experiment verified pSHX166-KPC as a self-transmissible plasmid mediating the dissemination of antibiotic resistance, with a conjugation rate of 2.21 × 10-5. Additionally, the growth curve showed that 18SHX166 demonstrates a higher growth rate than the control strains. The characteristics of 18SHX166 indicate a potential high risk of clinical transmission.IMPORTANCEST45-K43 carbapenem-resistant Klebsiella pneumoniae isolate, 18SHX166, carries a carbapenem resistance plasmid and virulence plasmid. It has the characteristics of multidrug resistance, high transmissibility, and a fast growth rate, which could pose a threat to the control of antimicrobial resistance and clinical transmission, causing a severe challenge to public health.

Missed Opportunities for Early De-Escalation of Antipseudomonal Beta-Lactam Antimicrobial Therapy in Enterobacterales Bloodstream Infection

Background: Antipseudomonal β-lactams (APBL) are commonly used for empirical therapy of Gram-negative bloodstream infections (BSI). This retrospective cohort study examines risk factors for prolonged APBL use (≥48 h) in patients with Enterobacterales BSI and compares 28-day mortality between early de-escalation of APBL and prolonged APBL therapy. Methods: Adult patients admitted to two community hospitals in South Carolina with Enterobacterales BSI from January 2010 to June 2015 were included in this study. Data were extracted manually from medical records. Multivariate logistic regression and Cox proportional hazards analyses were used to examine predictors of prolonged APBL therapy and mortality, respectively. Results: Among 993 patients with Enterobacterales BSI, 491 (49%) underwent early de-escalation of APBL and 502 (51%) received prolonged APBL therapy. Cancer, immune compromised status, residence at a skilled nursing facility, a high Pitt bacteremia score, non-urinary source of infection, and BSI due to AmpC-producing Enterobacterales were independently associated with prolonged use of APBL. Antimicrobial stewardship interventions were inversely associated with prolonged APBL use. Early de-escalation of APBL was not associated with increased mortality. Conclusions: This study exemplifies the safety and effectiveness of early de-escalation of APBL in Enterobacterales BSI. Antimicrobial stewardship strategies should be implemented to encourage the practice of early de-escalation of antimicrobial therapy, including in high-risk populations.

Proteomic approach to identify host cell attachment proteins provides protective Pseudomonas aeruginosa vaccine antigen FtsZ

Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen that causes severe nosocomial infections in susceptible individuals due to the emergence of multidrug-resistant strains. There are no approved vaccines against P. aeruginosa infections nor candidates in active clinical development, highlighting the need for novel candidates and strategies. Using a cell-blot proteomic approach, we reproducibly identified 49 proteins involved in interactions with human lung epithelial cells across four P. aeruginosa strains. Among these were cell division protein FtsZ and outer membrane protein OpmH. Escherichia coli BL21 cells overexpressing recombinant FtsZ or rOpmH showed a 66- and 15-fold increased ability to attach to 16HBE14o- cells, further supporting their involvement in host cell attachment. Both antigens led to proliferation of NK and CD8+ cytotoxic T cells, significant increases in the production of IFN-γ, IL-17A, TNF and IL-4 in immunised mice and elicited strong antigen-specific serological IgG1 and IgG2c responses. Immunisation with FtsZ significantly reduced bacterial burden in the lungs by 1.9-log CFU and dissemination to spleen by 1.8-log CFU. The protective antigen candidate, FtsZ, would not have been identified by traditional approaches relying on either virulence mechanisms or sequence-based predictions, opening new avenues in the development of an anti-P. aeruginosa vaccine.

The impact of the COVID-19 pandemic on pediatric bloodstream infections and alteration in antimicrobial resistance phenotypes in Gram-positive bacteria, 2020-2022

BACKGROUND

Alteration in the etiology of pediatric bloodstream infections (BSIs) and antimicrobial resistance (AMR) is not well known during the Coronavirus disease 2019 (COVID-19) pandemic. This study aimed to investigate the impact of the COVID-19 pandemic on pediatric BSIs and alteration in antimicrobial resistance phenotypes in Gram-positive bacteria.

METHODS

The frequency of BSIs among children under 18 years old was retrospectively recorded in a tertiary children's hospital in Tehran, Iran from February 2020 to December 2022. The status of COVID-19 infection using reverse transcription polymerase chain reaction, bacteremia/fungemia according to BACTEC 9120 Culture System results, characterization of bacteria using biochemical tests, and antimicrobial susceptibility patterns for Gram-positive bacterial isolates using disk diffusion method were determined. Statistical analysis was done to measure the correlation of COVID-19 infection with BSIs and AMR.

RESULTS

Out of 13,345 COVID-19 tests and 4,194 BACTEC blood culture requests, bacteremia/fungemia were confirmed in 10.37% (435/4,194) of the patients who requested both tests simultaneously. The COVID-19 infection was confirmed in 25.3% (110/435) of the patients with bacteremia/fungemia. The infection with characterized Gram-positive bacteria (GPB) and fungi was detected in 32.3% (140/433) and 8.31% (36/433) of the cases, respectively. Coagulase-negative Staphylococcus (CNS, 72, 16.62%), S. aureus (36, 8.3%), and Enterococcus spp. (22, 5%) were among the common isolates. Candida spp. and non-Candida yeasts were detected in 6.7% and 13.4% of the cases, respectively. A positive correlation was shown between the CNS bacteremia and COVID-19 infection (p-value = 0.019). Antibiotic susceptibility testing results showed the highest frequency of resistance to azithromycin among CNS, azithromycin and tetracycline among S. aureus and tetracycline among Enterococcus spp. Methicillin-resistance phenotype in the S. aureus (MRSA) and coagulase-negative Staphylococcus spp. (MR-CNS) was detected in 40% and 61.5% of the strains, respectively and the Enterococci were resistant to vancomycin in 33.3% of the isolates.

CONCLUSION

A decline in the trend of BSIs by GPB and an increase in AMR was shown in children during the COVID-19 pandemic. Increasing antibiotic resistance is a concern; however, chloramphenicol, linezolid, and vancomycin remain active against common causes of GPB-BSIs.

A paradigm shift in the detection of bloodborne pathogens: conventional approaches to recent detection techniques

Bloodborne pathogens (BBPs) pose formidable challenges in the realm of infectious diseases, representing significant risks to both human and animal health worldwide. The review paper provides a thorough examination of bloodborne pathogens, highlighting the serious worldwide threat they pose and the effects they have on animal and human health. It addresses the potential dangers of exposure that healthcare workers confront, which have affected 3 million people annually, and investigates the many pathways by which these viruses can spread. The limitations of traditional detection techniques like PCR and ELISA have been criticized, which has led to the investigation of new detection methods driven by advances in sensor technology. The objective is to increase the amount of knowledge that is available regarding bloodborne infections as well as effective strategies for their management and detection. This review provides a thorough overview of common bloodborne infections, including their patterns of transmission, and detection techniques.

Bloodstream infections: mechanisms of pathogenesis and opportunities for intervention

Bloodstream infections (BSIs) are common in hospitals, often life-threatening and increasing in prevalence. Microorganisms in the blood are usually rapidly cleared by the immune system and filtering organs but, in some cases, they can cause an acute infection and trigger sepsis, a systemic response to infection that leads to circulatory collapse, multiorgan dysfunction and death. Most BSIs are caused by bacteria, although fungi also contribute to a substantial portion of cases. Escherichia coli, Staphylococcus aureus, coagulase-negative Staphylococcus, Klebsiella pneumoniae and Candida albicans are leading causes of BSIs, although their prevalence depends on patient demographics and geographical region. Each species is equipped with unique factors that aid in the colonization of initial sites and dissemination and survival in the blood, and these factors represent potential opportunities for interventions. As many pathogens become increasingly resistant to antimicrobials, new approaches to diagnose and treat BSIs at all stages of infection are urgently needed. In this Review, we explore the prevalence of major BSI pathogens, prominent mechanisms of BSI pathogenesis, opportunities for prevention and diagnosis, and treatment options.

Prevalence of Extended-Spectrum Beta-Lactamase (ESBL)-Producing Escherichia coli in Humans, Food, and Environment in Kathmandu, Nepal: Findings From ESBL E. coli Tricycle Project

The need to address antimicrobial resistance (AMR) through a One Health (OH) approach is now well recognized. There is, however, limited guidance on how AMR surveillance should be implemented across sectors to generate meaningful AMR and AMU data for decision-making. Using a sympatric approach to cross-sector sample collection, Nepal adopted the WHO extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (E. coli) Tricycle Project as a step toward OH surveillance for assessing the prevalence of ESBL-producing E. coli across human, veterinary, and environment sectors. This involved a three-stage approach: identification of human hotspots (Stage 1) and sample collection sites for poultry (Stage 2) and wastewater (Stage 3). A total of 53 blood cultures from patients with bloodstream infections (BSIs), 100 stool samples from healthy pregnant women, 220 poultry ceca from slaughterhouses and live markets, and 48 wastewater samples were processed for bacterial culture and analyzed for the presence of ESBL-producing E. coli. The prevalence of ESBL-producing E. coli among isolated E. coli was the highest in wastewater samples (91%) followed by human BSIs (49%), poultry (38.6%), and fecal carriage isolates from healthy pregnant females (15%). A statistically significant association was seen in the prevalence of multidrug resistance among ESBL producers (52%) and nonproducers (26%). ESBL-producing E. coli was detected in all wastewater samples tested except for the upstream river. The findings of the study showed a high prevalence of ESBL-producing E. coli in samples from all three sectors and provided baseline data based upon which strategies for the safe disposal of communal and hospital waste, integrated AMR surveillance, and control strategies could be planned and implemented.

Changing epidemiology and antimicrobial susceptibility of bloodstream infections at a Vietnamese infectious diseases hospital (2010-2020)

Bloodstream infection (BSI) poses a global health problem, with diverse organisms and rising antimicrobial resistance (AMR). Here, we characterized trends in BSI prevalence, AMR, and antibiotic use at a Vietnamese infectious diseases hospital from 2010 to 2020. Among 108,303 cultured blood samples, 8.8% were positive, yielding 7995 pathogens. Of 7553 BSI cases, 86.4% were community-acquired. BSI prevalence varied from 17 to 35 cases/1000 admissions/year, highest in HIV/hepatitis wards and patients >60. The in-hospital mortality or hospice discharge outcome was 21.3%. The top three pathogens, E. coli (24%), K. pneumoniae (8.7%) and S. aureus (8.5%) exhibited increasing prevalence and multidrug resistance. Pathogens like Cryptococcus neoformans (8.4%), Talaromyces marneffei (6.7%), and Salmonella enterica (6.5%) declined. E. coli and K. pneumoniae were prevalent in older adults with community-acquired BSIs. Antibiotic use reached 842.6 DOT/1000 PD and significantly reduced after an antibiotic control policy. Enhanced surveillance and antimicrobial stewardship are crucial for managing BSIs in Vietnam.

Association Between Infectious Diseases Consultation and Mortality in Hospitalized Patients With Gram-negative Bloodstream Infection: A Retrospective Population-wide Cohort Study

OBJECTIVES

Data supporting routine infectious diseases (ID) consultation in gram-negative bloodstream infection (GN-BSI) are limited. We evaluated the association between ID consultation and mortality in patients with GN-BSI in a retrospective population-wide cohort study in Ontario using linked health administrative databases.

METHODS

Hospitalized adult patients with GN-BSI between April 2017 and December 2021 were included. The primary outcome was time to all-cause mortality censored at 30 days, analyzed using a mixed effects Cox proportional hazards model with hospital as a random effect. ID consultation 1-10 days after the first positive blood culture was treated as a time-varying exposure.

RESULTS

Of 30 159 patients with GN-BSI across 53 hospitals, 11 013 (36.5%) received ID consultation. Median prevalence of ID consultation for patients with GN-BSI across hospitals was 35.0% with wide variability (range 2.7%-76.1%, interquartile range 19.6%-41.1%). In total, 1041 (9.5%) patients who received ID consultation died within 30 days, compared to 1797 (9.4%) patients without ID consultation. In the fully adjusted multivariable model, ID consultation was associated with mortality benefit (adjusted hazard ratio [HR] 0.82, 95% confidence interval [CI] .77-.88, P < .0001; translating to absolute risk reduction of -3.8% or number needed to treat [NNT] of 27). Exploratory subgroup analyses of the primary outcome showed that ID consultation could have greater benefit in patients with high-risk features (nosocomial infection, polymicrobial or non-Enterobacterales infection, antimicrobial resistance, or non-urinary tract source).

CONCLUSIONS

Early ID consultation was associated with reduced mortality in patients with GN-BSI. If resources permit, routine ID consultation for this patient population should be considered to improve patient outcomes.

[A single-center analysis of pathogenic bacteria distribution and drug resistance in bacterial bloodstream infections among patients with hematological diseases]

Objective: To analyze the distribution and drug resistance of pathogens of bacterial bloodstream infection in patients with hematological diseases in the Department of Hematology of Tianjin Medical University General Hospital, and to provide etiological data for clinical empirical anti-infection treatment. Methods: A retrospective analysis was conducted on the general clinical information, pathogenic bacteria and drug susceptibility test results of patients with hematological diseases diagnosed with bacterial bloodstream infection by menstrual blood culture in our center from January 2016 to December 2022. Results: Patients included 498 inpatients, with a total of 639 bacterial strains. Among the patients, 86.9% patients had malignancies, and 76.7% had agranulocytosis. Symptoms of concurrent infections, including those of the respiratory tract, oral mucosa, skin and soft tissues, and abdominal sources were observed in 68.3% patients. Gram-negative bacteria (G(-)) accounted for 79.0% of the isolated bacteria, and gram-positive bacteria (G(+)) accounted for 21.0%. The top five isolated pathogens were Klebsiella pneumoniae (22.5%), Escherichia coli (20.8%), Pseudomonas aeruginosa (15.0%), Enterococcus faecium (5.5%), and Stenotrophomonas maltophilum (5.0%). Escherichia coli exhibited a decreasing trend of resistance to quinolones, cephalosporins, and carbapenems. Klebsiella pneumoniae exhibited increasing rates of resistance to quinolones and cephalosporins between 2016 and 2018, but the rated decreased after 2019. The resistance rate to carbapenems exhibited by Pseudomonas aeruginosa was approximately 20%. Carbapenem-resistant strains of Pseudomonas aeruginosa strains were first detected in 2017, with a peak resistance rate of 35.7%, detected in 2019. A 60.0% resistance rate to methicillin was observed in methicillin-resistant coagulase-negative staphylococci (MRCNS), and one case of linezolid-resistant MRCNS was detected. Conclusions: Pathogenic bacteria of bacterial bloodstream infections were widely distributed in our center, and precautions are warranted against carbapenem resistant P. aeruginosa and Klebsiella pneumoniae.

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.

Demographics, Epidemiology, Mortality, and Difficult-To-Treat Resistance Patterns of Bacterial Bloodstream Infections in the Global United States Military Health System from 2010-2019: A Retrospective Cohort Study

Objective

To describe demographics, causative pathogens, hospitalization, mortality, and antimicrobial resistance of bacterial bloodstream infections (BSIs) among beneficiaries in the global U.S. Military Health System (MHS), a single-provider healthcare system with 10-year longitudinal follow-up.

Design

Retrospective cohort study.

Setting

Clinical and demographic data collected from the MHS Data Repository and collated with microbiological data obtained from the Defense Centers for Public Health-Portsmouth.

Participants

12,748 MHS beneficiaries diagnosed with 15,357 bacterial BSIs (2010-2019).

Main Outcomes and Measures

Demographic data and diagnosis codes preceding BSI episodes and during hospitalizations were collected. Inpatient admission data identified acute clinical diagnoses, intensive care unit (ICU) admission, and mortality. BSI pathogens were evaluated for antimicrobial resistance, including difficult-to-treat resistance (DTR). Crude mortality trends were assessed.

Results

The decade analyzed included 15,357 BSI episodes in 12,748 patients; 6,216 patients (48.8%) were ≥65 years and 83.7% of episodes had ≥1 comorbidity (12,856 of 15,357). Approximately 29% of episodes with hospitalization required ICU admission and ~34% had concurrent urinary tract infections. Pathogen distribution was 53% and 47% for Gram-positive bacteria and Gram-negative bacilli (GNB), respectively. Inpatient mortality was 4.4%, and at one year was 23.4%; 0.5% (16 of 2,977) of deaths were associated with DTR GNB. Among an average 8,145,778 individuals receiving care annually in the MHS, annual rates of overall BSI, methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus spp., and DTR GNB BSI were 18.9, 1.30, 0.25, and 0.05 per 100,000 beneficiaries, respectively. Over the decade, annual mortality did not significantly increase for any pathogen and decreased by ~3% for lactose-fermenting GNB BSI (p=0.048).

Conclusions

In the global U.S. MHS, mortality burden associated with BSI was substantial (approximately 1 in 4 dying at 1 year), relatively unchanged over a decade, and associated with older age and comorbidities. First-line treatment options remained available for 99.7% of BSIs. Population-level improvements in BSI survival might be maximally influenced by focusing on prevention, early detection, prompt antibiotics, and other novel therapies not contingent on in vitro activity.

Epidemiological trends and susceptibility patterns of bloodstream infections caused by Enterococcus spp. in six German university hospitals: a prospectively evaluated multicentre cohort study from 2016 to 2020 of the R-Net study group

PURPOSE

To analyse recent epidemiological trends of bloodstream infections (BSI) caused by Enterococcus spp. In adult patients admitted to tertiary care centres in Germany.

METHODS

Epidemiological data from the multicentre R-NET study was analysed. Patients presenting with E. faecium or E. faecalis in blood cultures in six German tertiary care university hospitals between October 2016 and June 2020 were prospectively evaluated. In vancomycin-resistant enterococci (VRE), the presence of vanA/vanB was confirmed via molecular methods.

RESULTS

In the 4-year study period, 3001 patients with BSI due to Enterococcus spp. were identified. E. faecium was detected in 1830 patients (61%) and E. faecalis in 1229 patients (41%). Most BSI occurred in (sub-) specialties of internal medicine. The pooled incidence density of enterococcal BSI increased significantly (4.0-4.5 cases per 10,000 patient days), which was primarily driven by VRE BSI (0.5 to 1.0 cases per 10,000 patient days). In 2020, the proportion of VRE BSI was > 12% in all study sites (range, 12.8-32.2%). Molecular detection of resistance in 363 VRE isolates showed a predominance of the vanB gene (77.1%).

CONCLUSION

This large multicentre study highlights an increase of BSI due to E. faecium, which was primarily driven by VRE. The high rates of hospital- and ICU-acquired VRE BSI point towards an important role of prior antibiotic exposure and invasive procedures as risk factors. Due to limited treatment options and high mortality rates of VRE BSI, the increasing incidence of VRE BSI is of major concern.

Discovery of Arylpiperazines with Broad-Spectrum Antimicrobial Activity and Favorable Pharmacokinetic Profiles

Microorganisms can induce diseases with significant clinical implications for human health. Multidrug-resistant microorganisms have been on the rise worldwide over the past few decades, and no new antibiotics have been introduced to the market in a considerable amount of time. Such situation highlights the urgency of discovering new antimicrobial drugs to address this pressing issue. Therefore, the objective of this study was to identify bioactive compounds against 15 species of bacteria and 5 species of fungi of clinical relevance through in vitro screening of 58 synthetic compounds from four chemical classes of our internal library of synthetic compounds. Our findings highlight arylpiperazines 18, 20, 26, 27, and 29, and the aminothiazole 50, as potent broad-spectrum antimicrobials (MICs=12.5-15.6 μg mL-1) against clinically relevant bacteria and fungi. Additionally, these compounds displayed low cytotoxicity against various host cells and a favorable in vitro pharmacokinetic profile for oral administration. Indeed, all six showed adequate lipophilicity, high gastrointestinal permeability, metabolic stability in human and mouse liver microsomes, and satisfactory aqueous solubility. Thus, they emerge as promising starting points for hit-to-lead studies towards new antibacterial and antifungal agents, especially against Staphylococcus epidermidis, Staphylococcus aureus, Lactobacillus paracasei and Candida orthopsilosis.

Enterococcus faecalis: an overlooked cell invader

SUMMARYEnterococcus faecalis and Enterococcus faecium are human pathobionts that exhibit a dual lifestyle as commensal and pathogenic bacteria. The pathogenic lifestyle is associated with specific conditions involving host susceptibility and intestinal overgrowth or the use of a medical device. Although the virulence of E. faecium appears to benefit from its antimicrobial resistance, E. faecalis is recognized for its higher pathogenic potential. E. faecalis has long been considered a predominantly extracellular pathogen; it adheres to and is taken up by a wide range of mammalian cells, albeit with less efficiency than classical intracellular enteropathogens. Carbohydrate structures, rather than proteinaceous moieties, are likely to be primarily involved in the adhesion of E. faecalis to epithelial cells. Consistently, few adhesins have been implicated in the adhesion of E. faecalis to epithelial cells. On the host side, very little is known about cognate receptors, except for the role of glycosaminoglycans during macrophage infection. Several lines of evidence indicate that E. faecalis internalization may involve a zipper-like mechanism as well as a macropinocytosis pathway. Conversely, E. faecalis can use several strategies to prevent engulfment in phagocytes. However, the bacterial and host mechanisms underlying cell infection by E. faecalis are still in their infancy. The most recent striking finding is the existence of an intracellular lifestyle where E. faecalis can replicate within a variety of host cells. In this review, we summarize and discuss the current knowledge of E. faecalis-host cell interactions and argue on the need for further mechanistic studies to prevent or reduce infections.

Non-HACEK gram-negative bacilli infective endocarditis: data from a retrospective German cohort study

PURPOSE

Infective endocarditis caused by non-HACEK gram-negative bacilli (GNB-IE) is rare but associated with significant morbidity and case fatality. Evidence on optimal treatment and management is limited. We aimed to describe the characteristics and management of GNB-IE patients, investigating factors associated with disease acquisition and unfavorable outcomes.

METHODS

We conducted a retrospective descriptive single-center study (tertiary care and referral hospital) between 2015 and 2021, including adult patients with definite GNB-IE. We reviewed demographic, clinical and microbiological data, focusing on predisposing factors, clinical outcomes and 1-year mortality.

RESULTS

Of 1093 patients with probable or definite IE, 19 patients (median age 69 years) had definite GNB-IE, with an increasing incidence throughout the study period. Median age-adjusted Charlson Comorbidity Index score was 4 points. Prosthetic valve IE (PVIE) was present in 7/19 (37%) patients. Nosocomial acquisition occurred in 8/19 (42%) patients. Escherichia coli and Klebsiella pneumoniae were the most common pathogens. Beta-lactam (BL) based combination therapy was applied in 12/19 (63%) patients (58% BL + fluoroquinolone, 42% BL + aminoglycoside). Cardiac surgery was required in 8/19 (42%) patients (PVIE 71%, native valve IE 25%), primarily for embolism prevention and heart failure. Complications occurred in 14/19 (74%) patients. The in-hospital mortality rate was 21% (4/19); the one-year mortality rate was 44% (7/16). One-year mortality did not significantly differ between patients who underwent cardiac surgery and patients managed with anti-infective treatment alone (p = 0.633).

CONCLUSIONS

GNB-IE affects elderly patients with high comorbidity levels and recent health-care exposure. GNB-IE was associated with high complication rates and high mortality.