Global mortality associated with 33 bacterial pathogens in 2019: a systematic analysis for the Global Burden of Disease Study 2019

[Empirical antibiotic therapy in life-threatening infections-current concepts and controversies]

Along with early administration and the selection of the right drug, it is important to consider pharmacokinetic and pharmacodynamic principles, especially in life-threatening infections. Therefore, successful antibiotic therapy requires a clear understanding of the relationship between microbiology, pharmacology, and intensive care medicine. Open and transparent communication among professionals is essential for improving the quality of care. This article discusses current concepts and controversies by presenting a relevant case study of community-acquired pneumonia. It aims to help clinicians select the right drug for each patient, including the correct dose, the appropriate administration, and the right duration of treatment.

Pneumococcal serotypes and their association with death risk in invasive pneumococcal disease: a systematic review and meta-analysis

Background

Streptococcus pneumoniae and its infections are a global public health concern. Invasive pneumococcal disease accounts for significant mortality in the aged and immunocompromised. Over 100 unique capsular serotypes have been identified, with 80-90% of invasive disease attributable to about 23 serotypes. Pneumococcal serotype influences invasiveness, virulence, carriage, and IPD outcome. Case fatality rates among different pneumococcal serotypes in IPD have been inconsistently reported, prompting the need for a comprehensive meta-analysis. We hypothesized that specific pneumococcal serotypes would be associated with higher case fatality rates and that non-vaccine serotypes may exhibit increased mortality risks over time.

Methods

We conducted a systematic review and meta-analysis of serotype-specific risk of death due to invasive pneumococcal disease (IPD) in the last decade. We calculated the risk ratio (RR) and 95% confidence interval (CI) for each serotype compared with serotype 14 in each study. Pooled risk ratios were computed using random effects size model analysis. We also conducted heterogeneity testing and meta-regression sub-analysis.

Results

In total, 45 eligible studies were included, and 16 were selected for meta-analysis. Study distribution showed a global disparity, with Europe as the major data source. Serotype 31 had the highest case fatality rate (31.4%), indicating a concerning mortality risk associated with this serotype, particularly in immunocompromised patients. Overall, IPD patients with serotypes 3, 6A, 11A, 15A, 19F, and 31 were more likely to die. In contrast, serotypes 1, 5, 7F, and 8 IPD isolates recorded a reduced risk ratio compared to serotype 14. Subgroup analysis showed that vaccine serotypes were associated with a greater risk of death than non-vaccine serotypes, but there were no significant differences in risk estimates between population groups.

Conclusion

The study confirms the stable role of pneumococcal serotype in determining the clinical outcomes of invasive pneumococcal disease. Our findings underscore the importance of serotype-specific surveillance in IPD and call for the reconsideration of current pneumococcal vaccine formulations to address high-risk non-vaccine serotypes. Efforts to build research capacity, especially in low-resource regions such as Africa and South America, are highly recommended.

Cardiac Device-Related Infective Endocarditis Caused by Salmonella Infantis-Case Report and Review of Clinical and Epidemiologic Implications

BACKGROUND

Salmonella enterica serovar Infantis (S. Infantis) is a widespread pathogen in agriculture, causing epidemics in chicken flocks. Despite being primarily an animal pathogen, it may pose significant health risks to immunocompromised individuals.

METHODS

This report describes the first known case of cardiac device-related infective endocarditis (CDRIE) attributed to S. Infantis, highlighting its emerging pathogenic potential. It also reviews the literature for microbiologic and epidemiologic perspectives.

RESULTS

A 61-year-old male with a history of high-grade multiple myeloma presented with nonspecific symptoms, including low-grade fever and exertional dyspnoea. Blood cultures identified a pure culture of S. Infantis, and transoesophageal echocardiography revealed vegetations on pacing leads. Following pacemaker extraction and appropriate antimicrobial therapy, the patient's condition temporary improved, but later deteriorated due to the progression of underlying malignancy.

CONCLUSIONS

This case underscores the importance of considering S. Infantis in the differential diagnosis of endocarditis in immunocompromised patients, along with the critical need for stringent food safety measures to mitigate infection risks from contaminated poultry products.

Pseudomonas aeruginosa population dynamics in a vancomycin-induced murine model of gastrointestinal carriage

Pseudomonas aeruginosa is a common nosocomial pathogen and a major cause of morbidity and mortality in hospitalized patients. Multiple reports highlight that P. aeruginosa gastrointestinal colonization may precede systemic infections by this pathogen. Gaining a deeper insight into the dynamics of P. aeruginosa gastrointestinal carriage is an essential step in managing gastrointestinal colonization and could contribute to preventing bacterial transmission and progression to systemic infection. Here, we present a clinically relevant mouse model relying on parenteral vancomycin pretreatment and a single orogastric gavage of a controlled dose of P. aeruginosa. Robust carriage was observed with multiple clinical isolates, and carriage persisted for up to 60 days. Histological and microbiological examination of mice indicated that this model indeed represented carriage and not infection. We then used a barcoded P. aeruginosa library along with the sequence tag-based analysis of microbial populations (STAMPR) analytic pipeline to quantify bacterial population dynamics and bottlenecks during the establishment of the gastrointestinal carriage. Analysis indicated that most of the P. aeruginosa population was rapidly eliminated in the stomach, but the few bacteria that moved to the small intestine and the cecum expanded rapidly. Hence, the stomach constitutes a significant barrier against gastrointestinal carriage of P. aeruginosa, which may have clinical implications for hospitalized patients.

IMPORTANCE

While Pseudomonas aeruginosa is rarely part of the normal human microbiome, carriage of the bacterium is quite frequent in hospitalized patients and residents of long-term care facilities. P. aeruginosa carriage is a precursor to infection. Options for treating infections caused by difficult-to-treat P. aeruginosa strains are dwindling, underscoring the urgency to better understand and impede pre-infection stages, such as colonization. Here, we use vancomycin-treated mice to model antibiotic-treated patients who become colonized with P. aeruginosa in their gastrointestinal tracts. We identify the stomach as a major barrier to the establishment of gastrointestinal carriage. These findings suggest that efforts to prevent gastrointestinal colonization should focus not only on judicious use of antibiotics but also on investigation into how the stomach eliminates orally ingested P. aeruginosa.

Colistin sulfate versus polymyxin B for the treatment of infections caused by carbapenem-resistant Acinetobacter baumannii: a multicenter retrospective cohort study

Background

Polymyxins are the last line of defense against carbapenem-resistant Gram-negative bacilli infections. However, the efficacy of polymyxins against the independent risk factor of bacterial species is unknown. We aimed to compare the efficacy and safety of colistin sulfate (CS) and polymyxin B (PMB) for carbapenem-resistant Acinetobacter baumannii (CRAB) infections.

Methods

We carried out a retrospective multicenter study that included patients with CRAB infections at three tertiary hospitals in Guizhou province, China, from 1 Jan 2020 to 30 Jun 2024. Patients were grouped into the CS group and PMB group. The main outcomes were all-cause 28-day mortality and clinical failure rate. The secondary outcomes included the microbiological cure rate, duration of CS or PMB treatment, and length of hospital stay. Safety was evaluated based on the rates of adverse drug reactions.

Results

A total of 140 patients were included, with 58 patients in the CS group and 82 patients in the PMB group. All-cause 28-day mortality was 32.8% in the CS group and 37.8% in the PMB group (adjusted HR = 0.73, 95% CI 0.38-1.37, p = 0.316), and the clinical failure rate was 48.3% and 56.1% (adjusted OR = 0.64, 95% CI 0.29-1.39, p = 0.262) in the CS group and PMB group, respectively. There were no significant differences in any of the secondary outcomes. The incidence of acute kidney injury (AKI) in the CS group was lower than that in the PMB group (5.2% vs. 19.5%). Compared to the PMB group, the adjusted odds ratio of AKI was 0.24 (95% Cl 0.06-0.96, p = 0.044) for the CS group.

Conclusion

Our results suggest that CS is similarly effective to PMB for CRAB infections but it is associated with fewer safety concerns than PMB. This clinical research provides significant information on the efficacy and safety of CS and PMB for CRAB infections.

Infection characteristics among Serratia marcescens capsule lineages

Serratia marcescens is a healthcare-associated pathogen that can cause severe infections, including bacteremia and pneumonia. The capsule polysaccharide of S. marcescens is a bacteremia fitness determinant, and previous work defined capsule locus (KL) diversity within the species. Strains belonging to KL1 and KL2 capsule clades produce sialylated polysaccharides and represent the largest subpopulation of isolates from clinical origin. In this study, the contribution of these and other S. marcescens capsules to infection was determined in animal and cellular models. Using a murine model of primary bacteremia, clinical isolates of multiple KL types demonstrated capsule-dependent colonization of the spleen, liver, and kidney following tail vein inoculation. Similar results were observed using a bacteremic pneumonia model, in that all tested strains of clinical origin demonstrated a requirement for capsule in both the primary lung infection site and for bloodstream dissemination to secondary organs. Finally, the capsule from each KL clade was examined for the ability to resist internalization by bone marrow-derived macrophages. Only the sialylated KL1 and KL2 clade strains exhibited capsule-dependent inhibition of internalization, including KL2 capsule produced in a heterologous background. Together, these findings indicate that lineage-specific resistance to macrophage phagocytosis may enhance survival and antibacterial defenses of clinically adapted S. marcescens.

IMPORTANCE

Bacteremia occurs when the host immune system fails to contain bacterial bloodstream replication following an initial inoculation event from either an internal or external source. Capsule polysaccharides play a protective role for Serratia marcescens during bacteremia, but there is abundant genetic diversity at the capsule-encoding locus within the species. This study compares the infection characteristics of S. marcescens isolates belonging to five capsule types and defines the contributions to infection fitness for each. By characterizing the differences in capsule dependence and infection potential between S. marcescens strains, efforts to combat these life-threatening infections can be focused toward identifying strategies that target the most critical genetic lineages of this important opportunistic pathogen.

Acinetobacter Baumannii Secreted Protease CpaA Inhibits Factor XII-Mediated Bradykinin Generation and Neutrophil Activation

BACKGROUND

FXII (coagulation factor XII) is best known for its roles in the contact and kallikrein-kinin pathways. FXII is converted to its active enzyme (FXIIa [activated factor XII]) by PKa (plasma kallikrein) or its unique ability to autoactivate on bacterial or other biologic surfaces. In vivo, FXIIa initiates the intrinsic coagulation pathway and promotes inflammation by reciprocal activation of prekallikrein, which cleaves HK (high-molecular-weight kininogen) to liberate bradykinin. CpaA (coagulation targeting metallo-endopeptidase of A baumannii) is a secreted metalloprotease identified in a human clinical isolate of Acinetobacter baumannii that cleaves FXII at O-linked glycosylated sites, inhibiting contact activation. While CpaA facilitates a modest in vivo fitness advantage in mice, the role of CpaA in human infection remains unclear. As such, the objectives of this study were to characterize the structural details of the interaction between CpaA, FXII, and the KKSs (kallikrein-kinin systems) and to determine the downstream consequences on thromboinflammatory responses.

METHODS

The effect of purified CpaA on the coagulant activity of FXII and the generation of bradykinin was characterized. Neutrophil signaling, flow cytometry, and functional assays were performed to define how CpaA-mediated cleavage of FXII affects innate immune functions. Bacterial killing by human neutrophils was performed with wild-type and mutant A baumannii strains lacking CpaA.

RESULTS

We found that CpaA cleaves both FXII zymogen and FXIIa but not beta Factor XII. However, cleavage of FXIIa by CpaA does not significantly inhibit its clotting activity, demonstrating that CpaA does not inactivate FXIIa, but rather prevents activation of zymogen FXII. CpaA also cleaves HK, resulting in reduced kallikrein activation and bradykinin generation. We previously identified that zymogen FXII interacts with the urokinase receptor on neutrophils and upregulates neutrophil activation. Here, we demonstrate that CpaA cleaves neutrophil FXII, resulting in reduced Akt2 phosphorylation, chemotaxis, oxidative burst, and neutrophil extracellular trap formation. Importantly, CpaA decreases the human neutrophil killing efficiency of A baumannii in culture.

CONCLUSIONS

These data identify a role for FXII in responding to bacterial infection and suggest that by inhibiting the contact and KKSs and impairing neutrophil activation, CpaA may blunt the innate immune response and help prevent the elimination of A baumannii from the human host.

Identification and Quantification of Multiple Pathogenic Escherichia coli Strains Based on a Plasmonic Sensor Array

Pathogenic Escherichia coli (E. coli) is a widespread and clinically significant foodborne pathogen. Due to its high mutation rates and phenotypic diversity, rapid identification of its subtypes remains challenging and prone to false positives when detecting single strains. In this study, we developed a plasmonic sensor array with high-dimensional signal readouts (ζ-potential, dynamic light-scattering (DLS), surface-enhanced Raman scattering (SERS), and ultraviolet-visible (UV-vis) absorption spectra) for the selective discrimination of pathogenic E. coli, integrated with bacterial culture methods. The plasmonic sensor units demonstrated strong encoding capabilities, facilitating the differentiation of subtle variations among various E. coli strains and showing excellent anti-interference performance. The array realized different pathogenic E. coli strains, bacterial mixture identification, and even quantitative detection. Remarkably, the working concentration for the sensor array was notably low, at 104 CFU/mL. Finally, by incorporating bacterial isolation culture, the designed sensor array obtained 100% accuracy in detecting E. coli in real food samples. These findings highlight the sensor array's potential for applications in food safety monitoring and clinical diagnostics, offering a sensitive, rapid, and reliable tool for pathogen detection in complex samples.

Improved humanized mouse model of Staphylococcus aureus infection

Staphylococcus aureus is a significant cause of pulmonary infections, but existing mouse models fail to recapitulate human-specific responses. In this study, we developed a novel mouse model of S. aureus infection using humanized mice implanted with autologous fetal lung tissue. We show that these human lung implants support S. aureus survival and dissemination. Immunological profiling revealed extensive immune cell death after infection and an absence of chemokine induction. Transcriptomic profiling of the human lung implants revealed significant changes in gene expression, including NF-κB and JAK/STAT signaling. We identified upregulation of Cyp24a1, suggesting a role for vitamin D metabolism in host defense, but it had a mild effect on dissemination. Examination of the bacterial response to the host environment, found downregulation of virulence factors and metabolic genes, and upregulation of stress response pathways. The importance of the heat shock response in bacterial survival was shown as hrcA-deficient S. aureus exhibited reduced tissue colonization. These findings underscore the utility of this humanized lung model for studying S. aureus pathogenesis and bacterial adaptation to the human pulmonary environment.

Real-Time in Vivo Bacterial Imaging by Computed Tomography and Fluorescence Using Phage-Gold Nanorod Bioconjugates as Contrast Agents

Real-time in vivo imaging of bacterial infections is an important goal to aid the study and treatment of bacterial infections. Phages can be genetically engineered to ensure a particular biomolecular target specificity, and gold nanomaterials can be conjugated to phages for a variety of applications including biosensing. In this paper, we describe methods to use phage-gold nanorod conjugates for in vivo detection and imaging of the bacterial species Pseudomonas aeruginosa in mice. The imaging modalities are computed tomography (CT), using gold as a contrast agent, and fluorescence, which can be applied when the FDA-approved near-infrared (NIR) dye indocyanine green (ICG) is also chemically cross-linked to the bioconjugates. In addition, rapid protocols for validating bioconjugate synthesis and the initial assessment of toxicity are given. In this example, the phage-gold nanorod probe is shown to specifically highlight P. aeruginosa without cross-reactivity to another Gram-negative organism (V. cholerae) in vivo and appears to be biocompatible. Phage-directed imaging probes may thus be useful for the characterization and diagnosis of bacterial infections.

Linker and Head-Group Exploration of Anti-MRSA Triaromatic Pleuromutilins

Based on hit 6, a triaromatic pleuromutilin (TAP) and potent bacterial protein synthesis inhibitor, we explored the chemical space surrounding its pharmacophore by synthesizing 45 new conjugates. Herein, the adenine head was exchanged for new heterocycles, and the benzyl linker exchanged for aniline-, ether-, amide-, and hydroxybenzyl linkages, with all of them successfully engaging the pharmacophore, a result which was mirrored in a strict 3D pharmacophore model. The aniline- and amide-linked conjugates moreover demonstrated greater stability in liver microsomes, while especially conjugate 21, but also 31, 43, 45, and 55 displayed excellent potency, with MRSA activities on par with 6 or better. Docking to the ribosome suggested a shifted engagement with C2469 for 21 over 6, resulting in greater multivalency, while 43/45 likely coordinates Mg2+. Lastly, conjugate 21 displayed efficacy equal to commercial Fucidin LEO (5) in a mouse Staphylococcus aureus skin infection model, highlighting its potential as a topical antibiotic lead.

A small regulatory RNA controls antibiotic adaptation in Staphylococcus aureus by modulating efflux pump expression

Staphylococcus aureus is an opportunistic pathogen that poses a considerable burden to healthcare settings worldwide, aided by its ability to thrive in different environmental growth conditions and survive exposure to antibiotics. Small regulatory RNAs (sRNAs) are decisive in enhancing bacterial fitness by modulating gene expression in response to changing environmental conditions. We investigated the role of sRNAs in the adaptation of S. aureus to antibiotics. By assessing the fitness of a library of sRNA mutants, we identified that RsaA sRNA is required for optimal bacterial growth when exposed to low concentrations of fluoroquinolone, a class of antibiotics targeting DNA replication. We also found that in the absence of RsaA, S. aureus is less susceptible to β-lactam antibiotics, which act on the cell wall. RsaA has been reported to prevent the expression of MgrA, a master regulatory protein controlling the expression of efflux pumps. Here, we show that RsaA affects the sensitivity of S. aureus to fluoroquinolone and β-lactam antibiotics through MgrA. RsaA has two forms, a short one commonly referred to in RsaA studies, and a long form about twice the length, of which less is known. Interestingly, our phenotype was only restored when complemented with the long form of the gene or when it was supplied in two parts, the short form and the missing part to obtain the long form. This work demonstrates the role of regulatory RNAs in the adaptation of S. aureus to antibiotic resistance and highlights their value as potential therapeutic targets for manipulating individual sRNA responses to promote the efficacy of existing antibiotics.

Nano-Infrared Detection and Identification of Bacteria at the Single-Cell Level

Every year, bacterial infections are responsible for over 7 million deaths globally. Timely detection and identification of these pathogens enable timely administration of antimicrobial agents, which can save thousands of lives. Most of the currently known approaches that can address these needs are time- and labor consuming. In this study, we examine the potential of innovative nano-infrared spectroscopy, also known as atomic force microscopy infrared (AFM-IR) spectroscopy, and machine learning in the identification of different bacteria. We demonstrate that a single bacteria cell is sufficient to identify Borreliella burgdorferi, Escherichia coli, Mycobacterium smegmatis, and two strains of Acinetobacter baumannii with 100% accuracy. The identification is based on the vibrational bands that originate from the components of the cell wall as well as the interior biomolecules of the bacterial cell. These results indicate that nano-IR spectroscopy can be used for the nondestructive, confirmatory, and label-free identification of pathogenic microorganisms at the single-cell level.

Agent-based model of the human colon to investigate mechanisms of pathogen colonization resistance

Recent global burden of disease studies have shown that bacterial infections are responsible for over 13 million deaths worldwide, or 1 in every 8 deaths, each year. Enteric diarrheal infections, in particular, pose a significant challenge and strain on healthcare systems as many are difficult to address pharmaceutically, and thus rely primarily on the patient's own immune system and gut microbiome to fight the infection. Nonetheless, the specific mechanisms behind gut microbiome colonization resistance of enteric pathogens are not well defined and microbiome diversity is difficult to represent and study experimentally. To address this gap, we have constructed an agent-based computational model of the colonic epithelium cross section to investigate the colonic invasion of enteric pathogens. The model focuses on three main regions: epithelial layer, mucosal bilayer, and adjacent lumen, and utilizes four main cell types as agents: anaerobic bacteria, facultative anaerobic bacteria, human goblet cells, and pathogens. Utilizing this model, we are able to describe the healthy microbiome cell localization and dynamics from our mucosal bilayer. In addition, we are also able to investigate the impact of host dietary fiber consumption and simulate pathogen invasion. The model exemplifies the possibility and potential to explore key gut microbiome colonization resistance mechanisms and environmental impacts on the gut microbiome using computational methods.

Clinical manifestations, serotype distribution, and incidence of pediatric invasive pneumococcal disease in Catalonia (Spain), 2018-2022

The global incidence of invasive pneumococcal disease (IPD) decreased after the switch from PCV7 to PCV13 in 2010. However, serotype 3 remains the leading cause of IPD in Catalonia (Spain), due to the low effectiveness of PCV13 against it. This study aimed to analyze the clinical, epidemiological, and microbiological characteristics of IPD in children over 5 years and evaluate the potential impact of new vaccines (PCV15 and PCV20). A 5-year prospective observational study was conducted from 2018 to 2022, including children up to 18 hospitalized with IPD at three major children's hospitals in Catalonia. Data on clinical, epidemiological, and microbiological factors were collected. A total of 220 episodes were identified, with a median age of 33.0 months (range 0-209). Comparing pre-pandemic (2018-2019) to early pandemic years (2020-2021), the IPD rate in children < 18 years decreased by 60.6% (p < 0.001). However, no significant change was observed when comparing 2022 to 2018. The most common diagnoses were pneumonia (61.8%), meningitis (14.5%), and bacteremia without focus (13.2%). Serotype 3 was the leading cause (35.1%) of IPD and was associated with complicated pneumonia (84.7%) and vaccine failure (73.6%). Ninety-three IPD episodes (45.4%) were caused by PCV13 serotypes, 97 (47.3%) by PCV15 serotypes, and 132 (64.4%) by PCV20 serotypes.

CONCLUSION

The incidence of IPD has remained stable, except for a decrease during the pandemic. Serotype 3 was the most common, often associated with vaccine failures and severe pneumonia. PCV15 and PCV20 vaccines could offer better coverage against circulating serotypes and further reduce IPD incidence in Catalonia.

WHAT IS KNOWN

• Serotype 3 remains a leading cause of invasive pneumococcal disease (IPD) despite inclusion in PCV13 due to its limited vaccine effectiveness. • IPD incidence decreased globally during the COVID-19 pandemic, likely due to public health measures.

WHAT IS NEW

• In Catalonia, serotype 3 continues to dominate pediatric IPD cases and is frequently associated with complicated pneumonia and vaccine failure. • PCV15 and PCV20 offer broader serotype coverage and may significantly improve IPD prevention in children.

Secalonic acid F1 derived from an endophytic fungus Periconia verrucosa as a potential antimicrobial agent against Staphylococcus aureus

AIM

To investigate the antimicrobial potential of a secalonic acid F1 derivative produced by an endophytic Periconia verrucosa.

METHODS AND RESULTS

The endophyte RDE85 was characterized as P. verrucosa by morphological and phylogenetic analysis. We characterized a major compound from RDE85 as Secalonic acid F1 (SF1) with a 2,4'-linkage. SF1 demonstrated antimicrobial activity with an IC50 of 7.6 µg mL-1 against Staphylococcus aureus. It inhibited the biofilm formation, causing morphological changes and disruption of cell membrane integrity in the pathogen, confirmed by scanning electron microscopy (SEM). The compound depicted strong synergistic potential with ciprofloxacin and reduced DNA and RNA synthesis. The time-kill kinetics demonstrate that SF1 is an effective concentration-dependent bactericidal agent. Further, SF1 severely affected the respiratory chain dehydrogenase activity, confirmed by in-silico studies, revealing its interaction with respiratory chain succinate dehydrogenase. The treatment with this compound downregulated the staphylococcal accessory gene regulator and enterotoxin gene, two important virulence factors of the organism, and reduced the staphyloxanthin production, which is also an important virulence trait.

CONCLUSION

SF1 is a potential antimicrobial agent against S. aureus.

Pseudomonas aeruginosa Performs Chemotaxis to the Neurotransmitters Serotonin, Dopamine, Epinephrine and Norepinephrine

Bacteria use chemotaxis to move to favourable ecological niches. For many pathogenic bacteria, chemotaxis is required for full virulence, particularly for the initiation of host colonisation. There do not appear to be limits to the type of compounds that attract bacteria, and we are just beginning to understand how chemotaxis adapts them to their lifestyles. Quantitative capillary assays for chemotaxis show that P. aeruginosa is strongly attracted to serotonin, dopamine, epinephrine and norepinephrine. Chemotaxis to these compounds is greatly decreased in a mutant lacking the TlpQ chemoreceptor, and complementation of this mutant with a plasmid harbouring the tlpQ gene restores wild-type-like chemotaxis. Microcalorimetric titrations of the TlpQ sensor domain with these four compounds indicate that they bind directly to TlpQ. All four compounds are hormones and neurotransmitters that control a variety of processes and are also important signal molecules involved in the virulence of P. aeruginosa. They modulate motility, biofilm formation, the production of virulence factors and serve as siderophores that chelate iron. Additionally, this is the first report of bacterial chemotaxis to serotonin. This study provides an incentive for research to define the contribution of chemotaxis to these host signalling molecules to the virulence of P. aeruginosa.

Lighting up Resistance: Rapid Antimicrobial Susceptibility Testing of Gram-Negative Bacteria in Bloodstream Infections Using an Aggregation-Induced Emission Bioprobe

Rapid and accurate antimicrobial susceptibility testing (AST) is crucial for guiding treatment and combating resistance. However, conventional ASTs are time-consuming and require pure colonies, delaying the initiation of targeted antimicrobial therapy. Herein, a novel AST based on an aggregation-induced emission luminogen (AIEgen), DATVP, which can directly assess the antimicrobial susceptibility of Gram-negative bacteria in positive blood cultures, is reported. DATVP specifically lights up Gram-negative bacteria with damaged cell membranes while showing no fluorescence in intact bacteria. The antimicrobial-induced fluorescence turn-on of DATVP is found to be fast (within 6 h) and sensitive, allowing for reliable determination of antimicrobial susceptibility. Using DATVP, a wash-free AST is developed and its performance was validated on clinical isolates. The DATVP-based AST showed high categorical agreement (84-95%) with the standard method while shortening the time-to-result from days to hours. This method represents a new paradigm in phenotypic AST, offering speed, simplicity, and direct applicability to patient samples, with the potential to enable timely and targeted antimicrobial treatment.

Pneumolysin-responsive liposomal platform for selective treatment of Streptococcus pneumoniae

The bacterium Streptococcus pneumoniae has become a leading cause of meningitis, sepsis, and bacterial pneumonia worldwide, with increased prevalence of antibiotic-resistant serotypes serving to exacerbate the issue. The main factor responsible for colonization and immune response escape in pneumococcal infections is the secreted molecule pneumolysin, which is a subset within a family of related toxins that form transmembrane pores in biological membranes through cholesterol recognition and binding. The conserved activity and structure of pneumolysin between all observed S. pneumoniae serotypes, along with its requirement for pathogenicity, has made this molecule an attractive target for vaccination, diagnostic, and sequestration platforms, but not yet as a facilitative agent for therapeutic treatment. Consequently, the present work aimed to examine the impact of liposomal cholesterol content for pneumolysin-induced release of the encapsulated antimicrobial peptide nisin. It was determined that a cholesterol content above 45 mol% was necessary to facilitate interactions with both purified pneumolysin toxin and S. pneumoniae culture, demonstrated through enhanced nisin release and a reduction in hemolytic rates upon exposure of the toxin with cholesterol-rich vesicles. Antibacterial testing highlighted the ability of the developed platform to elicit a potent and specific bactericidal response in vitro against cultured S. pneumoniae when compared to a control strain, Staphylococcus epidermidis. It further improved viability of a fibroblast cell line upon S. pneumoniae challenge, outperforming free nisin via the synergistic impact of simultaneous bacterial clearance and pneumolysin neutralization. These findings collectively indicate that cholesterol-rich liposomes hold promise as a selective treatment platform against pneumococcal infections.

Bloodstream infections in a rural hospital in Sierra Leone: a retrospective database study

Background. The health system in Sierra Leone has limited infrastructure to provide data on the epidemiology of infectious diseases and to inform clinical decision-making. The diagnostic and research laboratory capacity at Masanga Teaching Hospital was systematically expanded with microbiology infrastructure-building as one of the centrepieces.Objective. This study aims to report the spectrum of bacterial pathogens from bloodstream infections (BSIs) in a rural hospital in Sierra Leone during the first year after the implementation of a blood culture infrastructure and characterize the detected antimicrobial resistances.Patients and methods. Patients treated at Masanga Hospital (Sierra Leone, March 2023-March 2024) were included in this database analysis if they were tested for BSI (BD BACTEC). Demographic and medical data were recorded for each patient. Antimicrobial susceptibility testing was done following EUCAST clinical guidelines.Results. Of the 340 blood cultures, 34 (10%) were positive for obligate pathogens. The three most frequent pathogens were Escherichia coli (n=8), followed by Burkholderia cepacia complex (n=7) and Salmonella enterica (n=5). Almost all Klebsiella pneumoniae (n=3/3) and E. coli (n=7/8) were resistant to third-generation cephalosporins. All four Staphylococcus aureus isolates were methicillin susceptible (mecA negative). Carbapenem resistance was detected in Acinetobacter baumannii complex (bla NDM)Conclusion. The proportion of positive blood cultures with obligate pathogens (10%) was within the suggested benchmark (5-15%). Gram-negative bacteria dominated the pathogen spectrum of BSI with high resistance rates to third-generation cephalosporins.

Ceftaroline for bloodstream infections caused by methicillin-resistant Staphylococcus aureus: a multicentre retrospective cohort study

OBJECTIVES

To evaluate the effectiveness of ceftaroline vs. vancomycin or daptomycin in the treatment of methicillin-resistant Staphylococcus aureus bloodstream infections (BSIs) (MRSA-BSIs).

METHODS

This multicentre retrospective study conducted in 15 Spanish hospitals included data from the first MRSA-BSIs of adult patients between January 2019 and December 2022. The ceftaroline group included patients who received ceftaroline for ≥72 hours within the first week of BSI onset; the standard-of-care (SOC) group included patients who received vancomycin or daptomycin ≥72 hours after BSI onset. Primary outcome was 30-day all-cause mortality; secondary outcomes included 90-day mortality and incidence of adverse events (AEs). Propensity-score matching and Cox proportional hazards analyses were performed.

RESULTS

A total of 429 MRSA-BSIs were included: 133 in the ceftaroline group and 296 in the SOC group. More patients in the ceftaroline group had a Sequential Organ Failure Assessment score >2 (51.1% vs. 36.5%; p < 0.01), complicated BSI (66.2% vs. 42.2%; p < 0.01), infective endocarditis (18.8% vs. 6.4%; p < 0.01) and prescribed in combination treatment (65.4% vs. 11.5%; p < 0.01), with no statistically significant differences in 30-day mortality: 23.3% ceftaroline (95% CI, 16.1-30.5%) vs. 16.2% SOC (95% CI, 12.0-20.4%), p 0.08. There were no statistically significant differences in 90-day mortality (33.1% ceftaroline vs. 26.7% SOC; p 0.17). After propensity-score matching, 105 patients treated with ceftaroline were matched with 105 controls: the 30-day mortality rates were 21.9% and 16.2% (p 0.38). Cox regression analysis of the entire cohort (n = 429) revealed that age (hazard ratio [HR], 1.05; 95% CI, 1.03-1.07) and Sequential Organ Failure Assessment score >2 (HR, 2.34; 95% CI, 1.50-3.65) were associated with 90-day mortality risk, although ceftaroline treatment did not demonstrate a significant effect (HR, 1.00; 95% CI, 0.97-1.02). Incidence of AEs was 12.0% in ceftaroline vs. 4.4% in the SOC group (p < 0.01). Most AEs occurred when ceftaroline was used in combination vs. monotherapy (17.2% vs. 2.2%; p 0.01).

DISCUSSION

Ceftaroline was an effective treatment for MRSA-BSIs but was commonly prescribed in combination showing a higher incidence of AEs.

Prevalence and Risk Factors of Staphylococcus aureus Nasal Colonization in Horses Admitted to a Veterinary Teaching Hospital

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of nosocomial infections, including in veterinary settings.

HYPOTHESIS/OBJECTIVES

To investigate the prevalence, risk factors for Staphylococcus aureus (SA) and MRSA colonization, and the duration of MRSA colonization.

ANIMALS

Elective cases admitted to the Veterinary Teaching Hospital were recruited (228 horses).

METHODS

A cross-sectional study was conducted over 3 years. Nasal swabs were collected at admission and cultured for SA. Methicillin-resistant isolates were identified using matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) technology, oxacillin minimal inhibitory concentration (MIC), and PCR testing. Horses colonized with MRSA were resampled until two negative cultures were obtained. Stabling management, activity, and medical history were obtained from owners and medical files. Multivariable logistic regressions were used to model associations between risk factors and colonization.

RESULTS

The prevalence of SA and of MRSA nasal carriage was 17.5% (95% CI: 12.4-22.7) and 6.2% (95% CI: 2.9-9.4), respectively. Of the 10 horses colonized by MRSA and monitored over time, only one tested positive after 3 months. More than 10 horses on the premises (OR 6.0 - 95% CI 1.1-64.2), previous hospitalization (OR 6.0 - 95% CI 1.0-35.2), and year of admission (2022 vs. 2020-2021; OR 9.0 - 95% CI 1.7-92.2) were associated with MRSA nasal carriage.

CONCLUSIONS AND CLINICAL IMPORTANCE

The prevalence of MRSA nasal colonization is of concern; however, the carriage seems transitory. Apart from the medical risk factors, the importance of social interactions in MRSA transmission needs to be elucidated in horses.

Lipidated SNAPP-Stars Target and Kill Multidrug-Resistant Bacteria within Minutes

The fast emergence of bacteria resistance has already threatened global health, and immediate action is required before the emergence of another global pandemic. Despite substantial progress in the chemical synthesis of novel antimicrobial compounds and advancements in understanding antimicrobial resistance, there has been only a handful of new antibiotics coming to the market. Structurally Nanoengineered Antimicrobial Peptide Polymers (SNAPP-stars) are a new class of antimicrobials. Here, we show that lipidation of lysine-valine 16-armed SNAPP-star, S16 (lipo-SNAPP-star) where the N-terminal arms are conjugated with different fatty acids (caproic, C6, lauric, C12, and stearic acid, C18) enhanced the antimicrobial activity toward S. aureus and MRSA. Lipidation enhanced activity by targeting the SNAPP-stars to the bacterial surface by binding to peptidoglycan, leading to greater inner membrane disruption and depolarization. Lipo-SNAPP-stars killed bacteria in under a minute, whereas vancomycin took >16 h. Lipo-SNAPP-stars were found to preferentially target and kill MRSA rather than S. aureus in a mixed bacteria model. Lipid chain length affected activity, with C6-S16 having greater activity compared to C12-S16 > C18-S16. Lauric and stearic acid enhanced SNAPP-star binding to the bacterial surface and membrane depolarization but impeded SNAPP-stars' ability to transit through the peptidoglycan layer to disrupt the inner membrane. Microbial flow cytometry showed that lipidation aided binding to bacteria via lipoteichoic acid and specifically to peptidoglycan. Further, lipid length enhanced bacterial binding with C18-S16 > C12-S16 > C6-S16 = S16, which contrasts the activity order of C6-S16 > S16 ≫ C12-S16 ≫ C18-S16. Our data demonstrate that lipidation enhances antimicrobial activity by targeting and binding an antimicrobial to peptidoglycan, but increasing lipid length reduces activity by retaining the antimicrobial in the outer layer. Lipidation of SNAPP-stars did not increase cytotoxicity, with C6-S16 having an improved therapeutic index compared to S16. Our data show how lipidation of SNAPP-stars enhances its antimicrobial activity, resulting in a highly biocompatible antimicrobial that targets and kills the "superbug" MRSA within minutes.

Mitochondria at the Heart of Sepsis: Mechanisms, Metabolism, and Sex Differences

Sepsis is a life-threatening condition that occurs when the body is unable to effectively combat infection, leading to systemic inflammation and multi-organ failure. Interestingly, females exhibit lower sepsis incidence and improved clinical outcomes compared to males. However, the mechanisms underlying these sex-specific differences remain poorly understood. While sex hormones have been a primary focus, emerging evidence suggests that non-hormonal factors also play contributory roles. Despite sex differences in sepsis, clinical management is the same for both males and females, with treatment focused on combating infection using antibiotics and hemodynamic support through fluid therapy. However, even with these interventions, mortality remains high, highlighting the need for more effective and targeted therapeutic strategies. Sepsis-induced cardiomyopathy (SIC) is a key contributor to multi-organ failure and is characterized by left ventricular dilation and impaired cardiac contractility. In this review, we explore sex-specific differences in sepsis and SIC, with a particular focus on mitochondrial metabolism. Mitochondria generate the ATP required for cardiac function through fatty acid and glucose oxidation, and recent studies have revealed distinct metabolic profiles between males and females, which can further differ in the context of sepsis and SIC. Targeting these metabolic pathways could provide new avenues for sepsis treatment.

Prevalence, Antimicrobial Resistance, and Virulence Potential of Staphylococcus aureus in Donkeys from Nigeria

BACKGROUND

Animal-associated antimicrobial-resistant staphylococci pose a One Health concern, as they can spread into the environment and cause serious infections. Yet, donkeys in Nigeria have been largely overlooked as potential reservoirs of these pathogens.

AIM/OBJECTIVES

To isolate Staphylococcus aureus from donkeys in Obollo-Afor, southeast Nigeria, assess their antimicrobial resistance profiles, and evaluate their virulence potential.

MATERIALS AND METHODS

Staphylococci were isolated from the nasal swabs of 250 donkeys, using mannitol salt agar, confirmed biochemically, with Staphylococcus aureus identified via a latex agglutination test and mass spectrometry. The resistance profiles of the isolates, including in regard to methicillin, inducible clindamycin, and β-lactamase production, were determined using disc diffusion, while vancomycin resistance was assessed through the use of agar dilution. The virulence factors were evaluated phenotypically.

RESULTS

Of the 250 samples, 11 (4.4%) contained S. aureus and 239 (95.6%) grew other Staphylococcus species. The resistance rates of the 11 S. aureus isolates to gentamicin, penicillin, tigecycline, cefoxitin, linezolid, and chloramphenicol were 45.5%, 66.7%, 54.5%, 27.3%, 36.4%, and 18.1%, respectively. The phenotypic methicillin-resistant S. aureus prevalence was 1.2%. Additionally, 23.5% of the S. aureus isolates were multidrug resistant, with a mean antibiotic resistance index of 0.25. All the S. aureus isolates exhibited virulence factors like clumping factor expression, catalase, caseinase, lecithinase, and gelatinase activity, while the occurrence of haemagglutinin, biofilm, pellicle, and hemolysin occurred in 27.3%, 54.5%, 36.4%, 72.2%, respectively.

CONCLUSION

Although a small percentage of donkeys in Nigeria may harbor S. aureus, these animals are potentially spreading antimicrobial resistance, including multidrug and methicillin resistance, to humans and the environment.

In-vitro antimicrobial activity of new antimicrobial agents against Streptococcus pneumoniae and potential resistance mechanisms: a multicenter study

BACKGROUND

Streptococcus pneumoniae is a major cause of invasive and non-invasive diseases, particularly in children and immunocompromised individuals, with an annual mortality of approximately 800,000 children worldwide. The rise of antibiotic-resistant strains complicates treatment, especially with increasing resistance to penicillin, macrolides, and fluoroquinolones. The study on the resistance of newly developed antimicrobial agents against S. pneumoniae was rarely reported. Furthermore, understanding the relationship between serotypes, resistance mechanisms, and virulence in S. pneumoniae is essential for disease management and vaccine development.

METHODS

A total of 208 S. pneumoniae isolates were collected across nine hospitals in seven Chinese cities/provinces from January 2023 to June 2024. Molecular characteristics were analyzed using whole-genome sequencing to identify serotypes, sequence types, virulence genes, and potential resistance mechanisms. Antibiotic susceptibility test (AST) was performed against 14 agents, involving new antibiotics (eravacycline, omadacycline, nemonoxacin, and contezolid).

RESULTS

Serotypes 19 F (24.6%) and 23 F (11.1%) predominated, with vaccine coverage rates of PCV13 at 66.8%. High resistance rates in S. pneumoniae were observed for erythromycin (208/208, 100%), clindamycin (197/208, 94.7%), and tetracycline (192/208, 92.3%). 13.5% (28/208) and 2.9% (6/208) strains were intermediate and resistant to penicillin, respectively. The new antibiotics showed low resistance, namely, 1.9% (4/208), 0.5% (1/208), 1.9% (4/208), and 7.2% (15/208) resistant to eravacycline, omadacycline, contezolid, and nemonoxacin, respectively. Resistance mechanisms included mutations in 23S rRNA for oxazolidinones, tet genes for tetracyclines, and gyrA/parC for fluoroquinolones.

CONCLUSIONS

S. pneumoniae in China exhibits high genetic diversity and significant antibiotic resistance, underscoring the need for continuous surveillance and updated vaccines. New antibiotics remain effective against multidrug-resistant strains, offering potential treatment options in clinical settings.

Changing climate and socioeconomic factors contribute to global antimicrobial resistance

Climate change poses substantial challenges in containing antimicrobial resistance (AMR) from a One Health perspective. Using 4,502 AMR surveillance records involving 32 million tested isolates from 101 countries (1999-2022), we analyzed the impact of socioeconomic and environmental factors on AMR. We also established forecast models based on several scenarios, considering antimicrobial consumption reduction, sustainable development initiatives and different shared socioeconomic pathways under climate change. Our findings reveal growing AMR disparities between high-income countries and low- and middle-income countries under different shared socioeconomic pathway scenarios. By 2050, compared with the baseline, sustainable development efforts showed the most prominent effect by reducing AMR prevalence by 5.1% (95% confidence interval (CI): 0.0-26.6%), surpassing the effect of antimicrobial consumption reduction. Key contributors include reducing out-of-pocket health expenses (3.6% (95% CI: -0.5 to 21.4%)); comprehensive immunization coverage (1.2% (95% CI: -0.1% to 8.2%)); adequate health investments (0.2% (95% CI: 0.0-2.4%)) and universal access to water, sanitation and hygiene services (0.1% (95% CI: 0.0-0.4%)). These findings highlight the importance of sustainable development strategies as the most effective approach to help low- and middle-income countries address the dual challenges of climate change and AMR.

Antimicrobial resistance and vaccines in Enterobacteriaceae including extraintestinal pathogenic Escherichia coli and Klebsiella pneumoniae

Antimicrobial-resistant Enterobacteriaceae are increasingly a clinical challenge. In particular, extraintestinal pathogenic Escherichia coli and Klebsiella pneumoniae threaten public health. Vaccination presents a long-term strategy to reduce both drug-susceptible and resistant infections while maintaining current clinical therapies. The review aims to emphasize the need for vaccines targeting extraintestinal pathogenic E. coli and K. pneumoniae by providing an overview of disease burden, antimicrobial resistance, therapeutics, and vaccine development.

Ultrasensitive detection of clinical pathogens through a target-amplification-free collateral-cleavage-enhancing CRISPR-CasΦ tool

Clinical pathogen diagnostics detect targets by qPCR (but with low sensitivity) or blood culturing (but time-consuming). Here we leverage a dual-stem-loop DNA amplifier to enhance non-specific collateral enzymatic cleavage of an oligonucleotide linker between a fluophore and its quencher by CRISPR-CasΦ, achieving ultrasensitive target detection. Specifically, the target pathogens are lysed to release DNA, which binds its complementary gRNA in CRISPR-CasΦ to activate the collateral DNA-cleavage capability of CasΦ, enabling CasΦ to cleave the stem-loops in the amplifier. The cleavage product binds its complementary gRNA in another CRISPR-CasΦ to activate more CasΦ. The activated CasΦ collaterally cleaves the linker, releasing the fluophore to recover its fluorescent signal. The cycle of stem-loop-cleavage/CasΦ-activation/fluorescence-recovery amplifies the detection signal. Our target amplification-free collateral-cleavage-enhancing CRISPR-CasΦ method (TCC), with a detection limit of 0.11 copies/μL, demonstrates enhanced sensitivity compared to qPCR. It can detect pathogenic bacteria as low as 1.2 CFU/mL in serum within 40 min.

Red Blood Cell-Induced Bacterial Margination Improves Microbial Hemoadsorption on Engineered Cell-Depleted Thrombi, Restoring Severe Bacteremia in Rats

Extracorporeal hemoadsorption for treating bacteremia has exhibited limited success due to the lack of a clear strategy for effectively bringing bacterial cells into contact with the surface and universal bacteria-capturing substances. Here, a novel extracorporeal device is reported that can eliminate various intact bacteria from whole blood, employing microfluidic bacterial margination and engineered cell-depleted thrombus (CDT) presenting bacterial adhesin receptors. The critical strain rate of red blood cells (RBCs) (0.83 × 10-2) and the flow path height within about 300 µm required for RBC axial migration in the flows are found. The subsequent RBC-bacteria collisions induced bacterial margination, facilitating their effective capture on the CDT surface on the channel wall. Fibrinogen and fibronectin in CDT are found to primarily contribute to capturing various bacteria. The extracorporeal CDT filters (eCDTF), which integrate all these principles, demonstrate significant depletion of major antibiotic-resistant and human fecal bacteria from the whole blood in vitro. Remarkable reductions in bacterial load and inflammatory markers in the rats lethally infected with methicillin-resistant Staphylococcus aureus are further confirmed, resulting in the restoration from bacteremia following extracorporeal treatment. The demonstration may propose a new design principle for hemoadsorption devices and elucidate the limited success of conventional treatments.

Lipopolysaccharide Detection with Glycan-Specific Lectins-a Nonspecific Binding Approach Applied to Surface Plasmon Resonance

The detection and classification of lipopolysaccharides (LPS), pivotal constituents of Gram-negative bacteria, are fundamental to the progression of biosensing technologies in fields such as healthcare, environmental monitoring, and food safety. This study presents an innovative approach utilizing a panel of glycan-selective lectins in conjunction with surface plasmon resonance (SPR) providing a novel perspective on the evolution of biosensors within the context of the ongoing tension between the highly selective, one-probe-one-target methodology and the broader, resource-intensive approach that integrates complex and costly technological tools into the biosensing discipline. Guided by the principles of lean development, we employed a panel of lectins to construct multiprobe detection profiles, thereby facilitating the precise classification of LPS variants while minimizing both variability and resource expenditure. Advanced machine learning techniques were applied to optimize feature selection and enhance classification accuracy, demonstrating that a minimal set of four lectins sustains exceptional predictive performance. This synergy between traditional affinity techniques and data science enhances assay engineering efficiency, scalability, and integration into routine workflows, supporting frontline pathogen monitoring. This innovative approach holds promise for addressing global health challenges, providing more profound insights into biosensing methodologies, and expanding pathogen screening networks closer to the public and health safety management bodies.

A SpA+LukAB vaccine targeting Staphylococcus aureus evasion factors restricts infection in two minipig infection models

Staphylococcus aureus is a major cause of bacterial infection-related deaths. Increasing antimicrobial resistance highlights the urgent need for effective preventative strategies. Antibody-mediated opsonophagocytosis, the key mechanism for protection against S. aureus, is disabled by critical virulence factors such as Staphylococcal protein A (SpA) and leukocidin AB (LukAB). In our study, we combined genetically detoxified vaccine candidates SpA* and LukAB RARPR-33 with a TH1 adjuvant aiming to restore host antibody functionality. To evaluate these vaccine candidates, we developed both surgical site infection (SSI) and superficial wound infection (SWI) models in minipigs. Our results showed a significant reduction in bacterial load and systemic dissemination in the SSI model, while skin infection severity was markedly decreased after intradermal immunization in the SWI model. This study introduces a novel S. aureus vaccine strategy by targeting immune evasion factors SpA and LukAB, utilizing potent TH1 adjuvants, and employing minipig challenge models.

The lack of a biorepository during vaccine trials: A lost opportunity to understand staphylococcal immunity

Development of a vaccine against Staphylococcus aureus has proven to be difficult, in no small measure due to our lack of understanding of the human immune response to this pathogen. Because the human immune response is distinct from other species often used for pre-clinical animal models, including non-human primates, it will be necessary to perform studies in humans to guide vaccine development. One can view the staphylococcal vaccine clinical trials as an opportunity to study human immune response to S. aureus infections, which of course provide outcome data. In order to gain maximal information from these clinical trials, biological materials should be taken during the trial. In this commentary article, we explore a mechanism for such collection.

METTL3-mediated m6A modification in sepsis: current evidence and future perspectives

Sepsis, a severe systemic inflammatory condition triggered by infection, is associated with high morbidity and mortality worldwide. While medical diagnosis and treatment have advanced in recent years, a specific therapy remains unavailable. Recently, significant progress has been made in studying the epigenetic RNA modification N6-methyladenosine (m6A) and its core methyltransferase METTL3. The role of m6A in sepsis has also been increasingly elucidated. This review aims to explore the pathological mechanisms of sepsis and its relationship with m6A, focusing on the role of the key m6A writer, METTL3, in sepsis.

Targeting mTOR in myeloid cells prevents infection-associated inflammation

Infections, cancer, and trauma can cause life-threatening hyperinflammation. In the present study, using single-cell RNA sequencing of circulating immune cells, we found that the mammalian target of rapamycin (mTOR) pathway plays a critical role in myeloid cell regulation in COVID-19 patients. Previously, we developed an mTOR-inhibiting nanobiologic (mTORi-nanobiologic) that efficiently targets myeloid cells and their progenitors in the bone marrow. In vitro, we demonstrated that mTORi-nanobiologics potently inhibit infection-associated inflammation in human primary immune cells. Next, we investigated the in vivo effect of mTORi-nanobiologics in mouse models of hyperinflammation and acute respiratory distress syndrome. Using 18F-FDG uptake and flow cytometry readouts, we found mTORi-nanobiologic therapy to efficiently reduce hematopoietic organ metabolic activity and inflammation to levels comparable to those of healthy control animals. Together, we show that regulating myelopoiesis with mTORi-nanobiologics is a compelling therapeutic strategy to prevent deleterious organ inflammation in infection-related complications.

Prevalence of genes encoding carbapenem-resistance in Klebsiella pneumoniae recovered from clinical samples in Africa: systematic review and meta-analysis

BACKGROUND

The potential of Klebsiella pneumoniae (K. pneumoniae) to acquire and spread carbapenem-resistant genes is the most concerning characteristic of the bacteria. In hospitals and other healthcare settings, multidrug-resistant K. pneumoniae can be prevalent and cause severe infections, posing significant challenges to patient management. Studying genetic variants and drug-resistant mutations in pathogenic bacteria of public health importance is essential. Therefore, this study aimed to assess the overall prevalence of carbapenemase-encoding genes in K. pneumoniae across Africa.

METHODS

All studies published between January 2010, and December 2023, were retrieved from the electronic databases PubMed, Science Direct, and Scopus, as well as through the Google Scholar search engine. This systematic review and meta-analysis adhered strictly to the PRISMA guidelines. Data analysis was performed using STATA version 17. The quality of the included studies was critically evaluated using the "Joanna Briggs Institute" criteria. To evaluate heterogeneity among the studies, inverse variance (I2) tests were utilized. Subgroup analysis was conducted when heterogeneity exists among studies. To assess publication bias, we used a funnel plot and Egger's regression test. A random effects model was used to calculate the weighted pooled prevalence of genetic variants associated with carbapenem resistance in K. pneumoniae.

RESULTS

A total of 49 potential studies were included in this systematic review and meta-analysis, encompassing 8,021 K. pneumoniae isolates. Among these isolates, 2,254 (28.1%) carbapenems-resistance-conferring genes were identified. The overall pooled prevalence of carbapenemase-encoding genes in K. pneumoniae isolated from clinical specimens across Africa was found to be 34.0% (95% CI: 26.01-41.98%). Furthermore, the pooled prevalence of the carbapenemase genes blaOXA-48 and blaNDM-1 was 16.96% (95% CI: 12.17-21.76%) and 15.08% (95% CI: 9.79-20.37%), respectively. The pooled prevalence of carbapenemase genes in K. pneumoniae isolates from clinical samples across Africa increased over time, reported as 20.4%(-0.7-41.4%) for 2010-2015, 34.5% (20.2-48.8%) for 2016-2020, and 35.2% (24.8-45.5%) for 2021-2023, with heterogeneity (I2) values of 36.5%, 96.7%, and 99.3%, respectively.

CONCLUSIONS

The emergence and spread of carbapenemase-encoding genes in K. pneumoniae pose a major threat to public health. Knowledge on the genetic mechanisms of carbapenem resistance is crucial for developing effective strategies to combat these multidrug-resistant infections and reduce their impact on healthcare systems. The carbapenemase genes blaOXA-48 and blaNDM-1 were the most prevalent and showed an increasing trend over time.

Maternal transfer of anti-GAPDH IgG prevents neonatal infections caused by Staphylococcus aureus and group B Streptococcus

Group B Streptococcus (GBS) and Staphylococcus aureus cause 200.000 neonatal deaths every year and no vaccine has been developed yet. Here, we described that extracellular glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from S. aureus is an immunomodulatory protein. Antibody mediated neutralization of S. aureus extracellular GAPDH promotes a protective inflammatory response by inhibiting an early and abnormal production of IL-10 in infected neonatal mice. As an immunomodulatory role for extracellular GAPDH was already described for GBS, we selected peptides exposed on bacterial GAPDH from both bacteria but completely absent from human GAPDH. These peptides were chemically synthesized and conjugated to a carrier protein. Maternal vaccination with these conjugated peptides induced an increased survival of mouse pups from infection with GBS or S. aureus, when compared to controls. The addition of anti-bacterial GAPDH IgG into infected human cord-blood cells caused a significant reduction in bacterial replication, suggesting a putative efficacy for humans.

Inhibiting Staphylococcus aureus Virulence Factors: Advances in Traditional Chinese Medicines and Active Compounds

Staphylococcus aureus is one of the most prevalent antibiotic-resistant bacteria, characterized by high morbidity and mortality. The pathogenicity of S. aureus relies on the production of multiple virulence factors. In recent years, antivirulence strategies have shown promise in developing antiinfective drugs by targeting the inhibition of bacterial virulence factors rather than directly killing pathogens. In Asia, some traditional Chinese medicines have a long history of antiinfective application and have demonstrated therapeutic efficacy. However, their antiinfective mechanism has not been fully elucidated. Recent studies have revealed that numerous extracts of TCM, as well as pure compounds from TCM, significantly inhibited the expression of virulence factors of S. aureus, which might be one of their antiinfective mechanisms with potential for the development of novel antiinfective agents. In this review, we summarized the major virulence factors of S. aureus and recent advances in TCM-derived antivirulence agents, including TCM formulae, single herbs, and isolated bioactive compounds, which showed antivirulence capability against S. aureus. Investigating the antivirulence mechanism of TCM not only enhances our understanding of TCM's antiinfective mechanisms but also facilitates the isolation of active compounds with therapeutic potential against S. aureus infection.

Biological sex influences severity and outcomes in Acinetobacter baumannii pneumonia

Biological sex is known to affect the incidence and outcomes of infection, varying significantly by pathogen. The bacterial pathogen Acinetobacter baumannii is recognized as a serious global healthcare threat worldwide, yet understanding of how biological sex impacts its infection course is limited. We previously documented in a murine model of acute pneumonia that female mice were more susceptible to infection, but there are no published studies looking at outcomes in humans according to biological sex. We conducted a retrospective cohort study of 220 adult patients with a positive A. baumannii culture and clinical evidence of pneumonia. Contrary to the animal data, we observed male patients to have a longer overall (32 vs 24 days, P < 0.05) and intensive care unit (ICU) length of stay (LOS) (23 vs 17 days, P < 0.001) compared to females. The primary diagnosis at admission was only a factor when it was respiratory in nature. Younger male patients had higher Pneumonia Severity Index score on admission compared to younger females. Older males required more interventions than younger males. We also observed that mortality rates were increased for patients with chronic obstructive pulmonary disease (P = 0.024) and renal disease (P < 0.001), while alcohol use or smoking within 30 days prior to admission or recent surgery all negatively impacted LOS. This study highlights the importance of sex-and-gender-based studies, identifying worse outcomes in men, the elderly, and patients with certain underlying conditions and guiding efforts to improve management of patients with A. baumannii pneumonia.

IMPORTANCE

Biological sex has been shown to influence the incidence and outcomes of infection. We had previously documented that in a mouse model of infection, the pathogen Acinetobacter baumannii caused more serious pulmonary disease in female animals. In this study, we aimed to determine if this was evident in human pneumonia data. We found that, opposite to the mice data, human males had extended hospital stays due to A. baumannii pneumonia. We also identified a number of risk factors that can impact mortality and duration of hospital stay. This information could be used to guide efforts to improve management of patients with A. baumannii pneumonia.

Description of Pseudomonas imrae sp. nov., carrying a novel class C β-lactamase gene variant, isolated from gut samples of Atlantic mackerel (Scomber scombrus)

Three β-lactam resistant bacterial strains isolated from gut samples of wild Atlantic mackerel (Scomber scombrus) collected from the northern North Sea were characterized by polyphasic analyses. The strains were determined to belong to the genus Pseudomonas but could not be assigned to a known species. The nearly-complete 16S rRNA gene sequence showed the highest similarity (99.9%) to four different species, although partial rpoD sequence exhibited relatively low similarities to Pseudomonas proteolytica (93.4%) and other Pseudomonas spp. Genome sequencing and subsequent digital DNA-DNA hybridization (dDDH), average nucleotide identity (ANI) analysis and core genome analysis confirmed that these strains represent a novel species within the genus Pseudomonas. The three strains demonstrated ANIb values >99.5% with each other, confirming that all three strains (CCUG 74779T = CECT 30571T, CCUG 74780 and CCUG 74781) belong to the same genomospecies. Phylogenomic analysis confirmed that the strains form a distinct genomic clade, representing a novel taxonomic species, for which the name Pseudomonas imrae sp. nov., is proposed, with strain CCUG 74779T (=CECT 30571T) designated as the type strain. We report the complete genome sequence of the type strain of P. imrae sp. nov. and show that it carries a gene encoding a novel variant of a chromosomally-encoded class C β-lactamase, which has been designated as PFL-7.

Genomic epidemiology and phylodynamics of Acinetobacter baumannii bloodstream isolates in China

In recent decades, Acinetobacter baumannii has become a major global nosocomial pathogen, with bloodstream infections (BSIs) exhibiting mortality rates exceeding 60% and imposing substantial economic burdens. However, limited large-scale genomic epidemiology has hindered understanding of its population dynamics. Here, we analyzed 1506 non-repetitive BSI-causing A. baumannii isolates from 76 Chinese hospitals over a decade (2011-2021). We identified 149 sequence types (STs) and 101 K-locus types (KLs), revealing increased population diversity. International clone (IC) 2 accounted for 81.74% of isolates, with a notable shift in prevalent STs: ST208 increased while ST191 and ST195 declined, aligning with global trends. ST208 exhibited higher virulence, greater antibiotic resistance, enhanced desiccation tolerance, and more complex transmission patterns compared to ST191 and ST195. Its genomic plasticity drives its adaptation and spread. Using the high-resolution Oxford MLST scheme, this study uncovered greater diversity and genetic factors behind ST208's rise. A. baumannii is evolving from a low-virulence, multidrug-resistant pathogen to a more virulent one, highlighting the urgent need to address its growing threat. These findings have critical implications for infection control and public health policies.

Specific labeling of outer membrane vesicles with antibiotic-conjugated probe reveals early bacterial infections in blood

Bacterial outer membrane vesicles (OMVs) are nano-sized structures derived from the outer membrane of Gram-negative bacteria, which have emerged as key players in host-pathogen interactions, yet their potential as biomarkers remains largely unexplored due to the difficulty of identification in complex biological samples. Here we show an approach for detecting and quantifying bacterial OMVs in blood using a Polymyxin B-fluorescein probe (PmBF), which targets bacterial lipopolysaccharides (LPS). The probe selectively labels OMVs, enabling their differentiation from host extracellular vesicles and quantitative analysis using nano-flow cytometry. In male mouse models of pneumonia, we observe elevated serum PmBF+ EVs as early as 6 h post-infection, preceding positive blood cultures. In clinical samples, PmBF+ EVs show superior performance for diagnosing bacterial infections and differentiate them from virus or mycoplasma infections. Our findings highlight circulating PmBF+ EVs as promising biomarkers of bacterial infections.

Optimizing nanopore adaptive sampling for pneumococcal serotype surveillance in complex samples using the graph-based GNASTy algorithm

Serotype surveillance of Streptococcus pneumoniae (the pneumococcus) is critical for understanding the effectiveness of current vaccination strategies. However, existing methods for serotyping are limited in their ability to identify co-carriage of multiple pneumococci and detect novel serotypes. To develop a scalable and portable serotyping method that overcomes these challenges, we employed nanopore adaptive sampling (NAS), an on-sequencer enrichment method that selects for target DNA in real-time, for direct detection of S. pneumoniae in complex samples. Whereas NAS targeting the whole S. pneumoniae genome was ineffective in the presence of nonpathogenic streptococci, the method was both specific and sensitive when targeting the capsular biosynthetic locus (CBL), the operon that determines S. pneumoniae serotype. NAS significantly improved coverage and yield of the CBL relative to sequencing without NAS and accurately quantified the relative prevalence of serotypes in samples representing co-carriage. To maximize the sensitivity of NAS to detect novel serotypes, we developed and benchmarked a new pangenome-graph algorithm, named GNASTy. We show that GNASTy outperforms the current NAS implementation, which is based on linear genome alignment, when a sample contains a serotype absent from the database of targeted sequences. The methods developed in this work provide an improved approach for novel serotype discovery and routine S. pneumoniae surveillance that is fast, accurate, and feasible in low-resource settings. Although NAS facilitates whole-genome enrichment under ideal circumstances, GNASTy enables targeted enrichment to optimize serotype surveillance in complex samples.

Revitalizing Antibiotics with Macromolecular Engineering: Tackling Gram-Negative Superbugs and Mixed Species Bacterial Biofilm Infections In Vivo

The escalating prevalence of multidrug-resistant Gram-negative pathogens, coupled with dwindling antibiotic development, has created a critical void in the clinical pipeline. This alarming issue is exacerbated by the formation of biofilms by these superbugs and their frequent coexistence in mixed-species biofilms, conferring extreme antibiotic tolerance. Herein, we present an amphiphilic cationic macromolecule, ACM-AHex, as an innovative antibiotic adjuvant to rejuvenate and repurpose resistant antibiotics, for instance, rifampicin, fusidic acid, erythromycin, and chloramphenicol. ACM-AHex mildly perturbs the bacterial membrane, enhancing antibiotic permeability, hampers efflux machinery, and produces reactive oxygen species, resulting in a remarkable 64-1024-fold potentiation in antibacterial activity. The macromolecule reduces bacterial virulence and macromolecule-drug cocktail significantly eradicate both mono- and multispecies bacterial biofilms, achieving >99.9% bacterial reduction in the murine biofilm infection model. Demonstrating potent biocompatibility across multiple administration routes, ACM-AHex offers a promising strategy to restore obsolete antibiotics and combat recalcitrant Gram-negative biofilm-associated infections, advocating for further clinical evaluation as a next-generation macromolecular antibiotic adjuvant.

Quorum sensing inhibition by South African medicinal plants species: an in vitro and an untargeted metabolomics study

BACKGROUND

The emergence of antimicrobial resistance (AMR) is imperiling global health, hence, the need to remedy this challenge by discovering new therapeutic strategies and agents. Quorum sensing inhibition (QSI) is opined as a potential novel strategic approach in the fight against AMR by abrogation of bacterial virulence and pathogenicity. Currently, there are no clinically approved QSI drugs. Based on this, this study evaluated the QSI properties of South African plant species.

METHODS

Twenty-nine extracts and their corresponding 203 fractions generated using solid phase extraction were screened for QSI activity in vitro against Chromobacterium violaceum ATCC 12472. Active and inactive fractions of the most potent plant species were analysed using UPLC-HRMS. The acquired mass spectral data was subjected to chemometric analysis.

RESULTS

From the QSI assays, three plant species showed remarkable QSI activity, measured by dose-dependent inhibition of violacein production (IVP), at sublethal concentrations. Terminalia phanerophlebia emerged as the most active species, with the extract and five of its fractions showing good activity in IVP (IVP IC50 ≤ 0.1 mg/mL). This was closely followed by Momordica cardiospermoides whose crude extract and two of its corresponding fractions showed good activity (IVP IC50 ≤ 0.1 mg/mL). Three fractions of Helichrysum odoratissimum also had good activity (IVP IC50 ≤ 0.1 mg/mL) marking it one of the most potent selected species. Chemometric analysis identified five compounds including olivetol and hydroxytyrosol as chemical markers positively associated with the QSI activity of T. phanerophlebia.

CONCLUSION

In conclusion, the findings of our study provided insight into the QSI properties of South African plant species. Further studies will focus on the isolation of the putative active compounds and the in vitro evaluation of their QSI activity.

Novel processes to obtain pneumococcal surface proteins for vaccines

Current pneumococcal vaccines are based on the protection offered by capsular polysaccharides from only a few from > 100 serotypes; therefore, serotype-independent vaccines composed of pneumococcal surface proteins are being developed. Despite the immense number of publications on the discovery, characterization, and evaluation of new pneumococcal vaccine candidates, there are very few that describe the bioprocess development, which is an essential step to generate material for pre-clinical and clinical tests, to obtain enough protein amount for physical-chemical, biochemical, and biological characterization, and to understand critical product and process attributes. Here, aspects of production and purification processes of pneumococcal surface proteins are reviewed, the most common bioreactor cultivation strategies are discussed, and important features of the purification process are explored to bring new insights about the correlation between protein structure and chromatography. The process development oriented to an industrial scale is an essential step for the success of novel protein-based pneumococcal vaccines and can preclude problems that could be hardly identified at flask scale production. Moreover, the early bioprocess development should favor a smooth scale-up and transfer of the process to GMP facilities for future production of new pneumococcal vaccines. KEY POINTS: • Early bioprocess development is crucial to advancing pneumococcal protein vaccines. • Bioreactor cultivation can help to identify possible process bottlenecks. • Structural features of similar proteins can orient purification process development.

Activated platelet membrane vesicles for broad-spectrum bacterial pulmonary infections management

The development of new antibiotics has lagged behind the rapid evolution of bacterial resistance, prompting the exploration of alternative antimicrobial strategies. Host-directed therapy (HDT) has emerged as a promising approach by harnessing innate immune system's natural defense mechanisms, which reduces reliance on antibiotics, and mitigates the development of resistance. Building on the important role of platelets in host immunity, activated platelet membrane vesicles (PLTv) are developed here as a host-directed therapy for broad-spectrum antibacterial infection management, leveraging several key mechanisms of action. PLTv neutralizes bacterial toxins, thereby reducing cytotoxicity. The presence of platelet receptors on PLTv enables them to act as decoys, binding bacteria through receptor interactions and facilitating their phagocytosis by neutrophils and macrophages. Additionally, PLTv bound to bacteria promote the formation of neutrophil extracellular traps (NETs), enhancing the immune system's ability to trap and kill bacteria. In mouse models of pulmonary infections caused by the Methicillin-resistant Staphylococcus aureus, P. aeruginosa, and A. baumannii, administration of PLTv significantly reduces bacterial counts in the lungs and protects against mortality. Taken together, the present work highlights PLTv as a promising host-directed therapy for combating broad-spectrum pulmonary drug-resistant bacterial infections, leveraging their ability to neutralize toxins, act as decoys, promote phagocytosis, and facilitate NETs formation.