Hospital-acquired infections due to gram-negative bacteria

Anti-Pseudomonas aeruginosa Vaccines and Therapies: An Assessment of Clinical Trials

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that causes high morbidity and mortality in cystic fibrosis (CF) and immunocompromised patients, including patients with ventilator-associated pneumonia (VAP), severely burned patients, and patients with surgical wounds. Due to the intrinsic and extrinsic antibiotic resistance mechanisms, the ability to produce several cell-associated and extracellular virulence factors, and the capacity to adapt to several environmental conditions, eradicating P. aeruginosa within infected patients is difficult. Pseudomonas aeruginosa is one of the six multi-drug-resistant pathogens (ESKAPE) considered by the World Health Organization (WHO) as an entire group for which the development of novel antibiotics is urgently needed. In the United States (US) and within the last several years, P. aeruginosa caused 27% of deaths and approximately USD 767 million annually in health-care costs. Several P. aeruginosa therapies, including new antimicrobial agents, derivatives of existing antibiotics, novel antimicrobial agents such as bacteriophages and their chelators, potential vaccines targeting specific virulence factors, and immunotherapies have been developed. Within the last 2-3 decades, the efficacy of these different treatments was tested in clinical and preclinical trials. Despite these trials, no P. aeruginosa treatment is currently approved or available. In this review, we examined several of these clinicals, specifically those designed to combat P. aeruginosa infections in CF patients, patients with P. aeruginosa VAP, and P. aeruginosa-infected burn patients.

Worldwide Dissemination of blaKPC Gene by Novel Mobilization Platforms in Pseudomonas aeruginosa: A Systematic Review

The dissemination of blaKPC-harboring Pseudomonas aeruginosa (KPC-Pa) is considered a serious public health problem. This study provides an overview of the epidemiology of these isolates to try to elucidate novel mobilization platforms that could contribute to their worldwide spread. A systematic review in PubMed and EMBASE was performed to find articles published up to June 2022. In addition, a search algorithm using NCBI databases was developed to identify sequences that contain possible mobilization platforms. After that, the sequences were filtered and pair-aligned to describe the blaKPC genetic environment. We found 691 KPC-Pa isolates belonging to 41 different sequence types and recovered from 14 countries. Although the blaKPC gene is still mobilized by the transposon Tn4401, the non-Tn4401 elements (NTEKPC) were the most frequent. Our analysis allowed us to identify 25 different NTEKPC, mainly belonging to the NTEKPC-I, and a new type (proposed as IVa) was also observed. This is the first systematic review that consolidates information about the behavior of the blaKPC acquisition in P. aeruginosa and the genetic platforms implied in its successful worldwide spread. Our results show high NTEKPC prevalence in P. aeruginosa and an accelerated dynamic of unrelated clones. All information collected in this review was used to build an interactive online map.

Extended-spectrum beta-lactamase-producing Enterobacteriaceae related urinary tract infection in adult cancer patients: a multicenter retrospective study, 2015-2019

BACKGROUND

The aim of this study was to investigate the prevalence and risk factors of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae related urinary tract infections (UTI) in adult cancer patients.

METHODS

We conducted a retrospective study of three cancer hospitals centered on Cancer Hospital of Chinese Academy of Medical Sciences from 2015 to 2019. The clinical characters, risk factors and antimicrobial susceptibility of ESBL-producing Enterobacteriaceae UTI in adult cancer patients were described and analyzed.

RESULTS

A total of 4967 specimens of UTI were evaluated, of which 909 were positive. After excluding multiple infection bacteria, non-conforming strains, inconsistent pathological information, no drug sensitivity test or medical records, 358 episodes remained. Among them, 160 episodes belonged to ESBL-producing Enterobacteriaceae, while 198 were classified into non-ESBL group. The prevalence of ESBL UTI circled around 39.73 to 53.03% for 5 years. Subgroup analysis by tumor type revealed that 62.5% of isolates from patients with urological tumors were ESBL positive. Multivariate analysis showed that tumor metastasis (OR 3.41, 95%CI 1.84-6.30), urological cancer (OR 2.96, 95%CI 1.34-6.53), indwelling catheter (OR 2.08, 95%CI 1.22-3.55) and surgery or invasive manipulation (OR 1.98, 95%CI 1.13-3.50) were the independent risk factors. According to antimicrobial sensitivity, meropenem, imipenem and piperacillin/tazobactam were the most commonly used antibiotics for ESBL-producing Enterobacteriaceae UTI.

CONCLUSIONS

In view of the high prevalence, clinicians should be alert to the occurrence of ESBL UTI, especially for patients with urological cancer or metastatic tumors. Regular replacement of urinary catheters, reduction of unnecessary invasive operations and selection of appropriate antibiotics are the necessary conditions to deal with the occurrence of ESBL UTI in adult cancer patients.

Puerarin@Chitosan composite for infected bone repair through mimicking the bio-functions of antimicrobial peptides

It is important to eliminate lipopolysaccharide (LPS) along with killing bacteria in periprosthetic joint infection (PJI) therapy for promoting bone repair due to its effect to regulate macrophages response. Although natural antimicrobial peptides (AMPs) offer a good solution, the unknown toxicity, high cost and exogenetic immune response hamper their applications in clinic. In this work, we fabricated a nanowire-like composite material, named P@C, by combining chitosan and puerarin via solid-phase reaction, which can finely mimic the bio-functions of AMPs. Chitosan, serving as the bacteria membrane puncture agent, and puerarin, serving as the LPS target agent, synergistically destroy the bacterial membrane structure and inhibit its recovery, thus endowing P@C with good antibacterial property. In addition, P@C possesses good osteoimmunomodulation due to its ability of LPS elimination and macrophage differentiation modulation. The in vivo results show that P@C can inhibit the LPS induced bone destruction in the Escherichia coli infected rat. P@C exhibits superior bone regeneration in Escherichia coli infected rat due to the comprehensive functions of its superior antibacterial property, and its ability of LPS elimination and immunomodulation. P@C can well mimic the functions of AMPs, which provides a novel and effective method for treating the PJI in clinic.

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P@C was fabricated through solid reaction with chitosan and puerarin.

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P@C punctures bacteria membrane and eliminates LPS, thus sterilizes bacteria.

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P@C improves bone formation of PEEK under infection via polarizing macrophage to M2.

Genomic Comparative Analysis of Two Multi-Drug Resistance (MDR) Acinetobacter baumannii Clinical Strains Assigned to International Clonal Lineage II Recovered Pre- and Post-COVID-19 Pandemic

BACKGROUND

After the emergence of COVID-19, numerous cases of A. baumannii/SARS-CoV-2 co-infection were reported. Whether the co-infecting A. baumannii strains have distinctive characteristics remains unknown.

METHODS AND RESULTS

A. baumannii AMA_NO was isolated in 2021 from a patient with COVID-19. AMA166 was isolated from a mini-BAL used on a patient with pneumonia in 2016. Both genomes were similar, but they possessed 337 (AMA_NO) and 93 (AMA166) unique genes that were associated with biofilm formation, flagellar assembly, antibiotic resistance, secretion systems, and other functions. The antibiotic resistance genes were found within mobile genetic elements. While both strains harbored the carbapenemase-coding gene blaOXA-23, only the strain AMA_NO carried blaNDM-1. Representative functions coded for by virulence genes are the synthesis of the outer core of lipooligosaccharide (OCL5), biosynthesis and export of the capsular polysaccharide (KL2 cluster), high-efficiency iron uptake systems (acinetobactin and baumannoferrin), adherence, and quorum sensing. A comparative phylogenetic analysis including 239 additional sequence type (ST) 2 representative genomes showed high similarity to A. baumannii ABBL141. Since the degree of similarity that was observed between A. baumannii AMA_NO and AMA166 is higher than that found among other ST2 strains, we propose that they derive from a unique background based on core-genome phylogeny and comparative genome analysis.

CONCLUSIONS

Acquisition or shedding of specific genes could increase the ability of A. baumannii to infect patients with COVID-19.

Bacterial Outer Membrane Vesicles Promote Lung Inflammatory Responses and Macrophage Activation via Multi-Signaling Pathways

Emerging evidence suggests that Gram-negative bacteria release bacterial outer membrane vesicles (OMVs) and that these play an important role in the pathogenesis of bacterial infection-mediated inflammatory responses and organ damage. Despite the fact that scattered reports have shown that OMVs released from Gram-negative bacteria may function via the TLR2/4-signaling pathway or induce pyroptosis in macrophages, our study reveals a more complex role of OMVs in the development of inflammatory lung responses and macrophage pro-inflammatory activation. We first confirmed that various types of Gram-negative bacteria release similar OMVs which prompt pro-inflammatory activation in both bone marrow-derived macrophages and lung alveolar macrophages. We further demonstrated that mice treated with OMVs via intratracheal instillation developed significant inflammatory lung responses. Using mouse inflammation and autoimmune arrays, we identified multiple altered cytokine/chemokines in both bone marrow-derived macrophages and alveolar macrophages, suggesting that OMVs have a broader spectrum of function compared to LPS. Using TLR4 knock-out cells, we found that OMVs exert more robust effects on activating macrophages compared to LPS. We next examined multiple signaling pathways, including not only cell surface antigens, but also intracellular receptors. Our results confirmed that bacterial OMVs trigger both surface protein-mediated signaling and intracellular signaling pathways, such as the S100-A8 protein-mediated pathway. In summary, our studies confirm that bacterial OMVs strongly induced macrophage pro-inflammatory activation and inflammatory lung responses via multi-signaling pathways. Bacterial OMVs should be viewed as a repertoire of pathogen-associated molecular patterns (PAMPs), exerting more robust effects than Gram-negative bacteria-derived LPS.

Multicentre surveillance of epidemiologically important pathogens causing nosocomial bloodstream infections and pneumonia trials in Brazilian adult intensive care units

Introduction. Healthcare-associated infections (HAIs) are the most recurrent adverse event in hospitals worldwide and represent an important public health problem.Gap statement. There are a paucity of multicentric data describing severe HAIs such as bloodstream infection (BSI) and pneumonia in Brazil.Aim. To provide an up-to-date picture of the extent and patterns of HAIs in adult intensive care units (ICUs), as well as to identify variables associated with the risk of development of severe infections.Methodology. Point prevalence surveys were conducted using standardized protocols in 35 ICUs from Minas Gerais state, Brazil. Medical records of eligible inpatients at or before 8 am on the survey day were reviewed to identify HAIs present at the time of the survey. A matched-pairs case-control study was performed on a total of 66 pairs for BSI and 115 pairs for pneumonia according to the selection criteria developed.Results. Overall, 171 patients (45.7%) had at least one HAI, with most (78.4%) acquired in the ICU. These patients presented a total of 240 infections; including 123 pneumonia (51.3%) and 66 BSI (27.5%), and 78.9 and 80.3 %, respectively, were acquired in the ICU. Their aetiology showed a predominance of Gram-negative bacteria versus Gram-positive bacteria (48.9 versus 43.3 %), with Acinetobacter baumannii (13.7%) and Pseudomonas aeruginosa (12.8%) being prominent. One striking observation from our data was the higher prevalence of Staphylococcus aureus (14.5%) and coagulase-negative staphylococci (10.2%) observed in the overall HAIs.Conclusion. A high severe ICU-acquired HAI burden was found when compared with findings from other low- and middle-income countries. These data can be utilized for better planning of nosocomial infection surveillance programmes in our hospitals.

Analysis of Whole-Genome Sequences of Pathogenic Gram-Positive and Gram-Negative Isolates from the Same Hospital Environment to Investigate Common Evolutionary Trends Associated with Horizontal Gene Exchange, Mutations and DNA Methylation Patterning

Hospital-acquired infections are a generally recognized problem for healthcare professionals. Clinical variants of Gram-negative and Gram-positive pathogens are characterized with enhanced antibiotic resistance and virulence due to mutations and the horizontal acquisition of respective genetic determinants. In this study, two Escherichia coli, two Klebsiella pneumoniae, three Pseudomonas aeruginosa, two Staphylococcus aureus, one Staphylococcus epidermidis and one Streptococcus pneumoniae showing broad spectra of antibiotic resistance were isolated from patients suffering from nosocomial infections in a local hospital in Almaty, Kazakhstan. The aim of the study was to compare general and species-specific pathways of the development of virulence and antibiotic resistance through opportunistic pathogens causing hospital-acquired infections. The whole-genome PacBio sequencing of the isolates allowed for the genotyping and identification of antibiotic resistance and virulence genetic determinants located in the chromosomes, plasmids and genomic islands. It was concluded that long-read sequencing is a useful tool for monitoring the epidemiological situation in hospitals. Marker antibiotic resistance mutations common for different microorganisms were identified, which were acquired due to antibiotic-selective pressure in the same clinical environment. The genotyping and identification of strain-specific DNA methylation motifs were found to be promising in estimating the risks associated with hospital infection outbreaks and monitoring the distribution and evolution of nosocomial pathogens.

Characterisation of genes encoding for extended spectrum β-lactamase in Gram-negative bacteria causing healthcare-associated infections in Mwanza, Tanzania

Healthcare-associated infections (HCAIs) caused by extended spectrum β-lactamase-producing Gram-negative bacteria (ESBL-GNB) increase morbidity and mortality. This cross-sectional study characterised ESBL genes (bla _CTX-M, bla _TEM and bla _SHV) among 30 ceftriaxone-resistant GNB causing HCAIs between January 2022 and July 2022 by multiplex polymerase chain reaction assay at the zonal referral hospital in Mwanza, Tanzania. Twenty-five (83.3%) had at least one ESBL gene, of which 23/25 (92.0%) carried the bla _CTX-M gene. Seventy-two percent (18/25) of the GNB-ESBL isolates carried more than one ESBL gene, of which the majority (88.8%; n = 16/25) carried the bla _CTX-M and bla _TEM genes. Extended spectrum β-lactamase genes, particularly bla _CTX-M, are common among ceftriaxone-resistant GNB causing HCAIs.

What this study adds

This study revealed the distribution of genes (bla _CTX-M, bla _TEM and bla _SHV) coding for ESBL production among ceftriaxone resistant GNB causing HCAIs However, all ESBL producing GNB were susceptible towards ceftriaxone-sulbactam indicating that ceftriaxone-sulbactam may be empirically prescribed for treating patients with HCAIs.

Advances in image-guided drug delivery for antibacterial therapy

The emergence of antibiotic-resistant bacterial strains is seriously endangering the global healthcare system. There is an urgent need for combining imaging with therapies to realize the real-time monitoring of pathological condition and treatment progress. It also provides guidance on exploring new medicines and enhance treatment strategies to overcome the antibiotic resistance of existing conventional antibiotics. In this review, we provide a thorough overview of the most advanced image-guided approaches for bacterial diagnosis (e.g., computed tomography imaging, magnetic resonance imaging, photoacoustic imaging, ultrasound imaging, fluorescence imaging, positron emission tomography, single photon emission computed tomography imaging, and multiple imaging), and therapies (e.g., photothermal therapy, photodynamic therapy, chemodynamic therapy, sonodynamic therapy, immunotherapy, and multiple therapies). This review focuses on how to design and fabricate photo-responsive materials for improved image-guided bacterial theranostics applications. We present a potential application of different image-guided modalities for both bacterial diagnosis and therapies with representative examples. Finally, we highlighted the current challenges and future perspectives image-guided approaches for future clinical translation of nano-theranostics in bacterial infections therapies. We envision that this review will provide for future development in image-guided systems for bacterial theranostics applications.

Differentiating methicillin resistant and susceptible Staphylococcus aureus from ocular infections using photoacoustic labeling

Introduction

Antibiotic resistance in bacterial species constitutes a growing problem in the clinical management of infections. Not only does it limit therapeutic options, but application of ineffective antibiotics allows resistant species to progress prior to prescribing more effective treatment to patients. Methicillin resistance in Staphylococcus aureus is a major problem in clinical infections as it is the most common hospital acquired infection.

Methods

We developed a photoacoustic flow cytometer using engineered bacteriophage as probes for rapid determination of methicillin resistance in Staphylococcus aureus with thirteen clinical samples obtained from keratitis patients. This method irradiates cells under flow with 532 nm laser light and selectively generates acoustic waves in labeled bacterial cells, thus enabling detection and enumeration of them. Staphylococcus aureus isolates were classified from culture isolation as either methicillin resistant or susceptible using cefoxitin disk diffusion testing. The photoacoustic method enumerates bacterial cells before and after treatment with antibiotics. Decreasing counts of bacteria after treatment indicate susceptible strains. We quantified the bacterial cells in the treated and untreated samples.

Results

Using k-means clustering on the data, we achieved 100% concordance with the classification of Staphylococcus aureus resistance using culture.

Discussion

Photoacoustics can be used to differentiate methicillin resistant and susceptible strains of bacteria from ocular infections. This method may be generalized to other bacterial species using appropriate bacteriophages and testing for resistance using other antibiotics.

Probing human proteins for short encrypted antimicrobial peptides reveals Hs10, a peptide with selective activity for gram-negative bacteria

BACKGROUND

Some cationic and amphiphilic α-helical segments of proteins adsorb to prokaryotic membranes when synthesized as individual polypeptide sequences, resulting in broad and potent antimicrobial activity. However, amphiphilicity, a determinant physicochemical property for peptide-membrane interactions, can also be observed in some β-sheets.

METHODS

The software Kamal was used to scan the human reference proteome for short (7-11 amino acid residues) cationic and amphiphilic protein segments with the characteristic periodicity of β-sheets. Some of the uncovered peptides were chemically synthesized, and antimicrobial assays were conducted. Biophysical techniques were used to probe the molecular interaction of one peptide with phospholipid vesicles, lipopolysaccharides (LPS) and the bacterium Escherichia coli.

RESULTS

Thousands of compatible segments were found in human proteins, five were synthesized, and three presented antimicrobial activity in the micromolar range. Hs10, a nonapeptide fragment of the Complement C3 protein, could inhibit only the growth of tested Gram-negative microorganisms, presenting also little cytotoxicity to human fibroblasts. Hs10 interacted with LPS while transitioning from an unstructured segment to a β-sheet and increased the hydrodynamic radius of LPS particles. This peptide also promoted morphological alterations in E. coli cells.

CONCLUSIONS

Data presented herein introduce yet another molecular template to probe proteins in search for encrypted membrane-active segments and demonstrates that, using this approach, short peptides with low cytotoxicity and high selectivity to prokaryotic cells might be obtained.

GENERAL SIGNIFICANCE

This work widens the biotechnological potential of the human proteome as a source of antimicrobial peptides with application in human health.

Effect of restricting piperacillin/tazobactam prescription on rates of antimicrobial resistance in gram-negative bacteria and antibiotic consumption

The increasing resistance of gram-negative bacteria is a serious global public health concern. One way to prevent increasing antibiotic resistance is by implementing the antibiotic stewardship program. This study aimed to assess the changes in the consumption of antimicrobials and antimicrobial resistance rates after implementing piperacillin/tazobactam restriction. This study was conducted at Kandong Sacred Heart Hospital. We retrospectively collected and analysed data between October 2018 and May 2021 to evaluate antibiotic consumption and resistance patterns after restricting piperacillin/tazobactam. This study included two periods, a 16-month pre-restriction period and a 16-month post-restriction period. During the study period, there was a significant decrease in the consumption of piperacillin/tazobactam after implementing the restriction policy (127.82 ± 9.39 to 104.82 ± 15.66 defined daily doses/1000 patient days, p < 0.001). A significant decrease in the resistance rate of Acinetobacter spp. was observed for cefepime (p = 0.001), ceftazidime (p = 0.004), levofloxacin (p = 0.021), meropenem (p = 0.002) and piperacillin (p = 0.028). The introduction of piperacillin/tazobactam restriction reduced their use and positively impacted the resistance rates of Acinetobacter spp., carbapenem-resistant Pseudomonas spp. and carbapenem-resistant Enterobacteriaceae which are major threats to nosocomial infections.

Overcoming Barriers to Preventing and Treating P. aeruginosa Infections Using AAV Vectored Immunoprophylaxis

Pseudomonas aeruginosa is a bacterial pathogen of global concern and is responsible for 10-15% of nosocomial infections worldwide. This opportunistic bacterial pathogen is known to cause serious complications in immunocompromised patients and is notably the leading cause of morbidity and mortality in patients suffering from cystic fibrosis. Currently, the only line of defense against P. aeruginosa infections is antibiotic treatment. Due to the acquired and adaptive resistance mechanisms of this pathogen, the prevalence of multidrug resistant P. aeruginosa strains has increased, presenting a major problem in healthcare settings. To date, there are no approved licensed vaccines to protect against P. aeruginosa infections, prompting the urgent need alternative treatment options. An alternative to traditional vaccines is vectored immunoprophylaxis (VIP), which utilizes a safe and effective adeno-associated virus (AAV) gene therapy vector to produce sustained levels of therapeutic monoclonal antibodies (mAbs) in vivo from a single intramuscular injection. In this review, we will provide an overview of P. aeruginosa biology and key mechanisms of pathogenesis, discuss current and emerging treatment strategies for P. aeruginosa infections and highlight AAV-VIP as a promising novel therapeutic platform.

Antimicrobial treatment of monomicrobial phenotypic carbapenem-resistant Klebsiella pneumoniae bacteremia: Two are better than one

BACKGROUNDS

Infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) are emerging worldwide. The optimal treatment for CRKP infections is challenging for clinicians because therapeutic agents are greatly limited.

MATERIAL AND METHODS

A retrospective study of CRKP monomicrobial bacteremia was conducted at a medical center between 2010 and 2016. The use of at least one or more drugs with in vitro activity against the blood isolates was defined as appropriate combination therapy. The logistic regression model and propensity score analysis was used to assess clinical effects of therapeutic strategies. The 30-day crude mortality was the primary end point.

RESULTS

Two hundred and three patients were eligible and the 30-day mortality rate was 37.9% (77 patients). As compared with monotherapy, empirical (11.6 vs. 57.3%, p < .001) or definitive (26.5% vs. 48.6%, p = .001) combination antibiotic therapy showed a lower 30-day mortality rate independently. The propensity score analysis showed that those receiving combination therapy had less clinical (p ≤ .001) or microbiological failure (p = .003) and a lower 30-day mortality rate (p < .001). Among various regimens of definitive therapy, the 30-day mortality rate was the lowest among patients with appropriate combination therapy 23.6%, (p < .001; by log rank test). The primary outcome was similar in those with definitive carbapenem-containing and carbapenem-sparing combination regimens (p = .81). The presence or absence of carbapenemase production did not affect the mortality rate (p = .26).

CONCLUSION

Combination therapy, regardless of carbapenem-containing or carbapenem-sparing regimens, was associated with a favorable outcome.

Outcomes in participants with failure of initial antibacterial therapy for hospital-acquired/ventilator-associated bacterial pneumonia prior to enrollment in the randomized, controlled phase 3 ASPECT-NP trial of ceftolozane/tazobactam versus meropenem

BACKGROUND

Ceftolozane/tazobactam, a combination antibacterial agent comprising an anti-pseudomonal cephalosporin and β-lactamase inhibitor, is approved for the treatment of hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP) in adults. Participants in the ASPECT-NP trial received ceftolozane/tazobactam (3 g [2 g ceftolozane/1 g tazobactam] every 8 h) or meropenem (1 g every 8 h). Participants failing prior antibacterial therapy for the current HABP/VABP episode at study entry had lower 28-day all-cause mortality (ACM) rates with ceftolozane/tazobactam versus meropenem treatment. Here, we report a post hoc analysis examining this result.

METHODS

The phase 3, randomized, controlled, double-blind, multicenter, noninferiority trial compared ceftolozane/tazobactam versus meropenem for treatment of adults with ventilated HABP/VABP; eligibility included those failing prior antibacterial therapy for the current HABP/VABP episode at study entry. The primary and key secondary endpoints were 28-day ACM and clinical response at test of cure (TOC), respectively. Participants who were failing prior therapy were a prospectively defined subgroup; however, subgroup analyses were not designed for noninferiority testing. The 95% CIs for treatment differences were calculated as unstratified Newcombe CIs. Post hoc analyses were performed using multivariable logistic regression analysis to determine the impact of baseline characteristics and treatment on clinical outcomes in the subgroup who were failing prior antibacterial therapy.

RESULTS

In the ASPECT-NP trial, 12.8% of participants (93/726; ceftolozane/tazobactam, n = 53; meropenem, n = 40) were failing prior antibacterial therapy at study entry. In this subgroup, 28-day ACM was higher in participants who received meropenem versus ceftolozane/tazobactam (18/40 [45.0%] vs 12/53 [22.6%]; percentage difference [95% CI]: 22.4% [3.1 to 40.1]). Rates of clinical response at TOC were 26/53 [49.1%] for ceftolozane/tazobactam versus 15/40 [37.5%] for meropenem (percentage difference [95% CI]: 11.6% [- 8.6 to 30.2]). Multivariable regression analysis determined concomitant vasopressor use and treatment with meropenem were significant factors associated with risk of 28-day ACM. Adjusting for vasopressor use, the risk of dying after treatment with ceftolozane/tazobactam was approximately one-fourth the risk of dying after treatment with meropenem.

CONCLUSIONS

This post hoc analysis further supports the previously demonstrated lower ACM rate for ceftolozane/tazobactam versus meropenem among participants who were failing prior therapy, despite the lack of significant differences in clinical cure rates.

CLINICALTRIALS

gov registration NCT02070757 . Registered February 25, 2014, clinicaltrials.gov/ct2/show/NCT02070757 .

Silver Carboxylate as an Antibiotic-Independent Antimicrobial: A Review of Current Formulations, in vitro Efficacy, and Clinical Relevance

The increasing prevalence of multi-drug resistant pathogens has led to a renewed focus on the use of silver as an antibiotic-independent antimicrobial. Unfortunately, the use of many silver formulations may be limited by an uncontrolled release of silver with the potential for significant cytotoxic effects. Silver carboxylate (AgCar) has emerged as an alternative formulation of silver with the potential to mitigate these concerns while still displaying significant bactericidal activity. This article reviews the efficacy of silver carboxylate formulations as a promising novel antibiotic-independent antimicrobial. This study was conducted through a search of five electronic databases (PubMed, Embase, MEDLINE, Cochrane Library, and Web of Science) for relevant studies up to September 2022. Searches were conducted for types of "silver carboxylate" formulations. Sources were compiled based on title and abstract and screened for inclusion based on relevance and study design. A review of the antimicrobial activity and cytotoxicity of silver carboxylate was compiled based on this search. Current body of data suggests that silver carboxylate shows promise as an emerging antibiotic-independent antimicrobial, with significant bactericidal effects while minimizing cytotoxicity. Silver carboxylate addresses several of the limitations of more primitive formulations, including controlled dosing and fewer negative effects on eukaryotic cell lines. These factors are concentration-dependent and largely rely on the vehicle system used to deliver it. Although several silver carboxylate-based formulations like titanium dioxide/polydimethylsiloxane (TiO₂/PDMS) matrix-eluting AgCar have shown promising results in vitro, and could potentially be utilized independently or in conjunction with current and future antimicrobial therapies, there is a need for further in vivo studies to validate their overall safety and efficacy profile.

Comparative Analysis of Complicated Urinary Tract Infections Caused by Extensively Drug-Resistant Pseudomonas aeruginosa and Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae

The objective was to compare clinical characteristics, outcomes, and economic differences in complicated urinary tract infections (cUTI) caused by extensively drug-resistant Pseudomonas aeruginosa (XDR P. aeruginosa) and extended-spectrum beta-lactamase-producing Klebsiella pneumoniae (ESBL-K. pneumoniae). A retrospective study was conducted at a tertiary care hospital. Patients with XDR P. aeruginosa and ESBL-K. pneumoniae cUTIs were compared. The primary outcome was clinical failure at day 7 and at the end of treatment (EOT). Secondary outcomes: 30- and 90-day mortality, microbiological eradication, and economic cost. Two-hundred and one episodes were included, of which 24.8% were bloodstream infections. Patients with XDR P. aeruginosa cUTI more frequently received inappropriate empirical therapy (p < 0.001). Nephrotoxicity due to antibiotics was only observed in the XDR P. aeruginosa group (26.7%). ESBL-K. pneumoniae cUTI was associated with worse eradication rates, higher recurrence, and higher infection-related readmission. In multivariate analysis, XDR P. aeruginosa was independently associated with clinical failure on day 7 of treatment (OR 4.34, 95% CI 1.71−11.04) but not at EOT, or with mortality. Regarding hospital resource consumption, no significant differences were observed between groups. XDR P. aeruginosa cUTI was associated with worse early clinical cures and more antibiotic side effects than ESBL-K. pneumoniae infections. However, no differences in mortality or in hospitalization costs were observed.

Carbapenem-Resistant Klebsiella pneumoniae: Diversity, Virulence, and Antimicrobial Resistance

Background

Klebsiella pneumoniae (K. pneumoniae) is one of the most important pathogens in nosocomial infections. It has resistance to most antibiotics, even carbapenem, resulting in restricted therapeutic options.

Purpose

We tried to assess the antimicrobial resistance and virulence fitness of carbapenem-resistant K. pneumoniae (CRKP) in addition to their phenotypic and genotypic diversity.

Materials and Methods

The conventional methods, automated Vitek-32 system, and antimicrobial susceptibility pattern were used to detect CRKP isolates. Virulence and resistance genes profiles were created by using PCR technique. The correlation analysis was done by using R-program.

Results

The antimicrobial resistance profile for all our K. pneumoniae isolates was shocking as the MDR and CRKP were the most prominent phenotypes. Unfortunately, high degrees of heterogeneity among our CRKP isolates were recorded, as 97.5% of them were differentiated into different clusters. We found a negative correlation between the existence of virulence and antimicrobial resistance genes. In contrast to sputum and urine CRPK isolates, the blood isolates showed high antimicrobial resistance and low virulence fitness. Finally, K. pneumoniae creates several outbreaks and crises in Egypt owing to the highly heterogeneity and the wide spread of multidrug-resistant (MDR) and multi-virulent CRKP phenotypes.

Conclusion

Our results are significant and alarming to health organizations throughout the world for the severity and heterogeneity of K. pneumoniae infections. Therefore, the traditional method for treatment of CRKP infections must be renewed. Additionally, the treatment protocols must be well correlated with the site of infections, phenotypes, and genotypes of CRKP strains.

The Causes and Control Measures of Extended Spectrum Beta-Lactamase Producing Enterobacteriaceae in Long-Term Care Facilities: A Systematic Review and Meta-Analysis

Background

Due to extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE), infections among residents are increasing in long-term care facilities (LTCFs), resulting in a high rate of morbidity and healthcare costs. A designated infection control team is unavailable to control the disease.

Methods

A systematic review and meta-analysis were conducted to characterize the causes of ESBL-PE and evaluate the infection control strategies within LTCFs. Multiple regression analysis (MRA) was included as supplementary statistical analysis to identify relationships between LTCFs, geographical locations, infection control measures (ICMs), and ESBL-PE. A systematic search was conducted for studies from January 2008 to December 2018. Twenty-two of the 3106 studies met the inclusion criteria.

Results

The pooled prevalence for ESBL-PE among LTCFs residents was a mean difference (MD) of 15.78 (95% CI: 0.04, 31.53). Risk factors included the influence of regional areas was a standardized mean difference (SMD) of 0.61(95% CI: 0.32, 0.91) in Europe, SMD was 14.92 (95% CI: 9.17, 20.68) in Asia, and SMD was 0.51(95% CI: 0.35, 0.67) in other regions (North America and Australia). Nine of 22 studies reported ICMs were MD of 13.59 (95% CI: 5.32, 21.86).

Conclusions

Meta-analysis and MRA revealed a statistically significant association between LTCF and ESBL-PE among residents (p = .05). Strict adherence to infection control measures in LTCFs is needed to address this ESBL-PE prevalence among residents. The potential positive social change is promoting knowledge about vulnerable residents in LTCFs and the community factors responsible for ESBL infection.

Pathogen load and species monitored by droplet digital PCR in patients with bloodstream infections: A prospective case series study

Background and objectives:

Bloodstream infection (BSI) is a life-threatening condition in critically ill patients, but pathogen quantification techniques during treatment are laborious. This study aimed to explore the impact of monitoring pathogen DNA load changes and polymicrobial infection in blood by droplet digital polymerase chain reaction (ddPCR) on the prognosis of patients with BSIs.

Methods

This prospective case series study was conducted in the general intensive care unit of the Zhejiang Provincial People’s Hospital and included patients with BSIs from May 2020 to January 2021. Pathogens DNA load and presence of polymicrobial BSIs were dynamically monitored by ddPCR.

Results

Sixteen patients with BSIs proven by blood culture were recruited (87.5% men; mean age, 69.3 ± 13.7 years). All pathogens identified by blood culture were Gram-negative bacteria, among which seven were multidrug-resistant strains. The 28-day mortality rate was 62.5%. Compared to the 28-day survivors, the non-survivors were older (P = 0.04), had higher pathogen DNA load on the second (day 3–4) and third (day 6–7) ddPCR assay (P < 0.01 in both cases). In addition, the changes of pathogen DNA load in the 28-day survivors had a downward trend in the first three ddPCR assay, whereas stable load or an upward trend was observed in the 28-day non-survivors. Moreover, the number of pathogen species in patients with BSIs in the 28-day survivors decreased during the period of effective antibiotic treatment.

Conclusion

The changes of pathogen DNA load and species monitored in blood by ddPCR may be used to determine antibiotic efficacy and make a more accurate prognostic assessment in patients with BSIs.

Supplementary information

The online version contains supplementary material available at 10.1186/s12879-022-07751-2.

The Mechanism of Action of Lactoferrin - Nucleoside Diphosphate Kinase Complex in Combating Biofilm Formation

BACKGROUND

The ESKAPE group of pathogens which comprise of multidrug resistant bacteria, namely Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species are the cause of deadly nosocomial infections all over the world. While these pathogens have developed robust strategies to resist most antibiotics, their ability to form biofilms is one of their most combative properties. Hence there is an urgent need to discover new antibacterial agents which could prevent or destroy the biofilms made by these bacteria. Though it has been established that lactoferrin (LF), a potent iron binding antibacterial, antifungal, and antiviral protein displays anti-biofilm properties, its mechanisms of action, in addition to its iron chelation property, still remains unclear.

OBJECTIVE

The binding and inhibition studies of LF with the enzyme Nucleoside diphosphate Kinase (NDK) and its elastase cleaved truncated 12 kDa fragment (12-NDK).

METHODS

The characterization studies of NDK and 12-NDK using florescence spectroscopy, dynamic light scattering, size exclusion chromatography and ADP-glo Kinase Assay. Inhibition studies of LF-NDK using ADP-glo kinase assay, Surface Plasmon Resonance and Biofilm inhibition studies.

RESULTS

NDK and 12-NDK were cloned, expressed and purified from Acinetobacter baumannii and Pseudomonas aeruginosa. The characterization studies revealed NDK and 12-NDK from both species are stable and functional. The inhibition studies of LF-NDK revealed stable binding and inhibition of kinase activity by LF.

CONCLUSION

The binding and inhibition studies have shown that while LF binds with both the NDK and their truncated forms, it tends to have a higher binding affinity with the truncated 12 kDa fragments, resulting in their decreased kinase activity. This study essentially gives a new direction to the field of inhibition of biofilm formation, as it proves that LF has a novel mechanism of action in other than iron sequestration.

Bioinformatics and systems-biology analysis to determine the effects of Coronavirus disease 2019 on patients with allergic asthma

Background

The coronavirus disease (COVID-19) pandemic has posed a significant challenge for global health systems. Increasing evidence shows that asthma phenotypes and comorbidities are major risk factors for COVID-19 symptom severity. However, the molecular mechanisms underlying the association between COVID-19 and asthma are poorly understood. Therefore, we conducted bioinformatics and systems biology analysis to identify common pathways and molecular biomarkers in patients with COVID-19 and asthma, as well as potential molecular mechanisms and candidate drugs for treating patients with both COVID-19 and asthma.

Methods

Two sets of differentially expressed genes (DEGs) from the GSE171110 and GSE143192 datasets were intersected to identify common hub genes, shared pathways, and candidate drugs. In addition, murine models were utilized to explore the expression levels and associations of the hub genes in asthma and lung inflammation/injury.

Results

We discovered 157 common DEGs between the asthma and COVID-19 datasets. A protein–protein-interaction network was built using various combinatorial statistical approaches and bioinformatics tools, which revealed several hub genes and critical modules. Six of the hub genes were markedly elevated in murine asthmatic lungs and were positively associated with IL-5, IL-13 and MUC5AC, which are the key mediators of allergic asthma. Gene Ontology and pathway analysis revealed common associations between asthma and COVID-19 progression. Finally, we identified transcription factor–gene interactions, DEG–microRNA coregulatory networks, and potential drug and chemical-compound interactions using the hub genes.

Conclusion

We identified the top 15 hub genes that can be used as novel biomarkers of COVID-19 and asthma and discovered several promising candidate drugs that might be helpful for treating patients with COVID-19 and asthma.

A Superhydrophilic, Light/Microwave-Absorbing Coating with Remarkable Antibacterial Efficacy

Driven by the overuse of antibiotics, pathogenic infections, dominated by the rapid emergence of antibiotic resistant bacteria, have become one of the greatest current global health challenges. Thus, there is an urgent need to explore novel strategies that integrate multiple antibacterial modes to deal with bacterial infections. In this work, a Co(Ni,Ag)/Fe(Al,Cr)₂O₄ composite duplex coating was fabricated using template-free sputtering deposition technology. The phase constitution of the coating was estimated to be 79 wt % Fe(Al,Cr)₂O₄ phase and 21 wt % of an Ag-containing metallic phase. The composite coating consisted of a ∼10 μm-thick porous outer-layer and a ∼6 μm-thick compact inner-layer, in which the outer-layer is composed of a densely stacked array of microscale cones. After exposure to ambient air for 14 days, the composite coating showed a wettability transition from a superhydrophilic nature to exhibit adhesive superhydrophobic behavior with a water contact angle of 142° ± 2.8°, but it reverted to its initial superhydrophilic state after annealing in air at 200 °C for 5 h. The absorption rate of the as-received composite coating exceeds 99% in a broad band spanning both the visible and NIR regions and showed a high photothermal efficiency to convert photon energy into heat. Similarly, the composite coating showed microwave absorption behavior with a minimum reflection loss value of 38 dB at 4.4 GHz. In vitro antibacterial tests were used to determine the antibacterial behavior of the composite coating against Escherichia coli and Staphylococcus aureus after 60 min of visible light irradiation. After this exposure, the as-prepared composite coating exhibited nearly 100% bactericidal efficiency against these bacteria. The antibacterial behavior of the coating was attributed to the synergistic effects of the superhydrophilic surface, the release of Ag⁺ ions, and the photothermal effect. Therefore, this composite coating may be a promising candidate to efficiently combat medical device-associated infections.

Cooperative action of SP-A and its trimeric recombinant fragment with polymyxins against Gram-negative respiratory bacteria

The exploration of therapies combining antimicrobial lung proteins and conventional antibiotics is important due to the growing problem of multidrug-resistant bacteria. The aim of this study was to investigate whether human SP-A and a recombinant trimeric fragment (rfhSP-A) have cooperative antimicrobial activity with antibiotics against pathogenic Gram-negative bacteria. We found that SP-A bound the cationic peptide polymyxin B (PMB) with an apparent dissociation constant (K D) of 0.32 ± 0.04 µM. SP-A showed synergistic microbicidal activity with polymyxin B and E, but not with other antibiotics, against three SP-A-resistant pathogenic bacteria: Klebsiella pneumoniae, non-typable Haemophilus influenzae (NTHi), and Pseudomonas aeruginosa. SP-A was not able to bind to K. pneumoniae, NTHi, or to mutant strains thereof expressing long-chain lipopolysaccharides (or lipooligosaccharides) and/or polysaccharide capsules. In the presence of PMB, SP-A induced the formation of SP-A/PMB aggregates that enhance PMB-induced bacterial membrane permeabilization. Furthermore, SP-A bound to a molecular derivative of PMB lacking the acyl chain (PMBN) with a K D of 0.26 ± 0.02 μM, forming SP-A/PMBN aggregates. PMBN has no bactericidal activity but can bind to the outer membrane of Gram-negative bacteria. Surprisingly, SP-A and PMBN showed synergistic bactericidal activity against Gram-negative bacteria. Unlike native supratrimeric SP-A, the trimeric rfhSP-A fragment had small but significant direct bactericidal activity against K. pneumoniae, NTHi, and P. aeruginosa. rfhSP-A did not bind to PMB under physiological conditions but acted additively with PMB and other antibiotics against these pathogenic bacteria. In summary, our results significantly improve our understanding of the antimicrobial actions of SP-A and its synergistic action with PMB. A peptide based on SP-A may aid the therapeutic use of PMB, a relatively cytotoxic antibiotic that is currently being reintroduced into clinics due to the global problem of antibiotic resistance.

Fecal Carriage of Extended-Spectrum β-Lactamases and pAmpC Producing Enterobacterales in an Iranian Community: Prevalence, Risk Factors, Molecular Epidemiology, and Antibiotic Resistance

This study aimed to determine the prevalence and risk factors associated with intestinal carriage of extended-spectrum β-lactamases producing Enterobacterales (ESBL-PE) and plasmid-mediated AmpC β-lactamase producing Enterobacterales (AmpC-PE) in healthy children in Ardabil, Iran. A total of 305 fecal samples were collected. Isolates underwent antimicrobial susceptibility testing, phenotypic and genotypic identification of β-lactamase production, and epidemiologic molecular typing. In total, 21.5%, 1.5%, and 1.2% of volunteers were extended-spectrum β-lactamase (ESBL)-, AmpC-, and simultaneous ESBL/AmpC-PE carriers, respectively. Escherichia coli was the predominant ESBL producing bacterium (70.2%) found in ESBL-PE colonized subjects. Beyond ESBL positive isolates, bla _CTX-M group genes were the most common type (75.6%) and bla _TEM (non-bla _TEM-1 and non- bla _TEM-2) were in the second place (25.6%). Among bla _CTX-M genes, bla _CTX-M-1 (55.3%) and bla _CTX-M-15 (55.3%) were the most predominant types with equal prevalence. Some isolates were multi-enzyme producers. bla _CIT and bla _DHA genes were common AmpC type enzyme encoding genes found in AmpC-PE isolates. Most isolates produced both enzymes at the same time. The number of students in the classes was statistically associated with ESBL-PE intestinal carriage (p < 0.05). Moreover, 46 (65.7%), 3 (60%), 4 (100%), and 98 (39.8%) ESBL-, AmpC-, ESBL/AmpC, and non-ESBL/AmpC-PE isolates were multidrug-resistant, respectively. Overall, regardless of β-lactam antibiotics, 62% and 59.5% of isolates were resistant to co-trimoxazole and tetracycline, respectively. The majority of ESBL producing E. coli isolates (69.2%) belonged to phylogroup A. According to Enterobacterial repetitive intergenic consensus polymerase chain reaction, there was no clonal relatedness between isolates. This study showed a high rate of multi-resistant ESBL-PE intestinal carriage among healthy individuals in Iran.

ZnO-based antimicrobial coatings for biomedical applications

Rapid transmission of infectious microorganisms such as viruses and bacteria through person-to-person contact has contributed significantly to global health issues. The high survivability of these microorganisms on the material surface enumerates their transmissibility to the susceptible patient. The antimicrobial coating has emerged as one of the most interesting technologies to prevent growth and subsequently kill disease-causing microorganisms. It offers an effective solution a non-invasive, low-cost, easy-in-use, side-effect-free, and environmentally friendly method to prevent nosocomial infection. Among antimicrobial coating, zinc oxide (ZnO) stands as one of the excellent materials owing to zero toxicity, high biocompatibility to human organs, good stability, high abundancy, affordability, and high photocatalytic performance to kill various infectious pathogens. Therefore, this review provides the latest research progress on advanced applications of ZnO nanostructure-based antibacterial coatings for medical devices, biomedical applications, and health care facilities. Finally, future challenges and clinical practices of ZnO-based antibacterial coating are addressed.

Microbiome-derived antimicrobial peptides offer therapeutic solutions for the treatment of Pseudomonas aeruginosa infections

Microbiomes are rife for biotechnological exploitation, particularly the rumen microbiome, due to their complexicity and diversity. In this study, antimicrobial peptides (AMPs) from the rumen microbiome (Lynronne 1, 2, 3 and P15s) were assessed for their therapeutic potential against seven clinical strains of Pseudomonas aeruginosa. All AMPs exhibited antimicrobial activity against all strains, with minimum inhibitory concentrations (MICs) ranging from 4–512 µg/mL. Time-kill kinetics of all AMPs at 3× MIC values against strains PAO1 and LES431 showed complete kill within 10 min to 4 h, although P15s was not bactericidal against PAO1. All AMPs significantly inhibited biofilm formation by strains PAO1 and LES431, and induction of resistance assays showed no decrease in activity against these strains. AMP cytotoxicity against human lung cells was also minimal. In terms of mechanism of action, the AMPs showed affinity towards PAO1 and LES431 bacterial membrane lipids, efficiently permeabilising the P. aeruginosa membrane. Transcriptome and metabolome analysis revealed increased catalytic activity at the cell membrane and promotion of β-oxidation of fatty acids. Finally, tests performed with the Galleria mellonella infection model showed that Lynronne 1 and 2 were efficacious in vivo, with a 100% survival rate following treatment at 32 mg/kg and 128 mg/kg, respectively. This study illustrates the therapeutic potential of microbiome-derived AMPs against P. aeruginosa infections.

Lipid A Variants Activate Human TLR4 and the Noncanonical Inflammasome Differently and Require the Core Oligosaccharide for Inflammasome Activation

Detection of Gram-negative bacterial lipid A by the extracellular sensor, myeloid differentiation 2 (MD2)/Toll-like receptor 4 (TLR4), or the intracellular inflammasome sensors, CASP4 and CASP5, induces robust inflammatory responses. The chemical structure of lipid A, specifically its phosphorylation and acylation state, varies across and within bacterial species, potentially allowing pathogens to evade or suppress host immunity. Currently, it is not clear how distinct alterations in the phosphorylation or acylation state of lipid A affect both human TLR4 and CASP4/5 activation. Using a panel of engineered lipooligosaccharides (LOS) derived from Yersinia pestis with defined lipid A structures that vary in their acylation or phosphorylation state, we identified that differences in phosphorylation state did not affect TLR4 or CASP4/5 activation. However, the acylation state differentially impacted TLR4 and CASP4/5 activation. Specifically, all tetra-, penta-, and hexa-acylated LOS variants examined activated CASP4/5-dependent responses, whereas TLR4 responded to penta- and hexa-acylated LOS but did not respond to tetra-acylated LOS or penta-acylated LOS lacking the secondary acyl chain at the 3' position. As expected, lipid A alone was sufficient for TLR4 activation. In contrast, both core oligosaccharide and lipid A were required for robust CASP4/5 inflammasome activation in human macrophages, whereas core oligosaccharide was not required to activate mouse macrophages expressing CASP4. Our findings show that human TLR4 and CASP4/5 detect both shared and nonoverlapping LOS/lipid A structures, which enables the innate immune system to recognize a wider range of bacterial LOS/lipid A and would thereby be expected to constrain the ability of pathogens to evade innate immune detection.

Transcriptomic analysis reveals the regulatory role of quorum sensing in the Acinetobacter baumannii ATCC 19606 via RNA-seq

Background

Acinetobacter baumannii has emerged as the major opportunistic pathogen in healthcare-associated infections with high-level antibiotic resistance and high mortality. Quorum sensing (QS) system is a cell-to-cell bacterial communication mediated by the synthesis, secretion, and binding of auto-inducer signals. It is a global regulatory system to coordinate the behavior of individual bacteria in a population. The present study focused on the QS system, aiming to investigate the regulatory role of QS in bacterial virulence and antibiotic resistance.

Method

The auto-inducer synthase gene abaI was deleted using the A. baumannii ATCC 19606 strain to interrupt the QS process. The RNA-seq was performed to identify the differentially expressed genes (DEGs) and pathways in the mutant (△abaI) strain compared with the wild-type (WT) strain.

Results

A total of 380 DEGs [the adjusted P value < 0.05 and the absolute value of log₂(fold change) > log₂1.5] were identified, including 256 upregulated genes and 124 downregulated genes in the △abaI strain. The enrichment analysis indicated that the DEGs involved in arginine biosynthesis, purine metabolism, biofilm formation, and type VI secretion system (T6SS) were downregulated, while the DEGs involved in pathways related to fatty acid metabolism and amino acid metabolism were upregulated. Consistent with the expression change of the DEGs, a decrease in biofilm formation was observed in the △abaI strain compared with the WT strain. On the contrary, no obvious changes were found in antimicrobial resistance following the deletion of abaI.

Conclusions

The present study demonstrated the transcriptomic profile of A. baumannii after the deletion of abaI, revealing an important regulatory role of the QS system in bacterial virulence. The deletion of abaI suppressed the biofilm formation in A. baumannii ATCC 19606, leading to decreased pathogenicity. Further studies on the role of abaR, encoding the receptor of auto-inducer in the QS circuit, are required for a better understanding of the regulation of bacterial virulence and pathogenicity in the QS network.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02612-z.

Transmission of gram-negative antibiotic-resistant bacteria following differing exposure to antibiotic-resistance reservoirs in a rural community: a modelling study for bloodstream infections

Exposure to community reservoirs of gram-negative antibiotic-resistant bacteria (GN-ARB) genes poses substantial health risks to individuals, complicating potential infections. Transmission networks and population dynamics remain unclear, particularly in resource-poor communities. We use a dynamic compartment model to assess GN-ARB transmission quantitatively, including the susceptible, colonised, infected, and removed populations at the community-hospital interface. We used two side streams to distinguish between individuals at high- and low-risk exposure to community ARB reservoirs. The model was calibrated using data from a cross-sectional cohort study (N = 357) in Chile and supplemented by existing literature. Most individuals acquired ARB from the community reservoirs (98%) rather than the hospital. High exposure to GN-ARB reservoirs was associated with 17% and 16% greater prevalence for GN-ARB carriage in the hospital and community settings, respectively. The higher exposure has led to 16% more infections and attributed mortality. Our results highlight the need for early-stage identification and testing capability of bloodstream infections caused by GN-ARB through a faster response at the community level, where most GN-ARB are likely to be acquired. Increasing treatment rates for individuals colonised or infected by GN-ARB and controlling the exposure to antibiotic consumption and GN-ARB reservoirs, is crucial to curve GN-ABR transmission.

Hydrogen Sulfide and Substance P Levels in Patients with Escherichia coli and Klebsiella pneumoniae Bacteraemia

Hydrogen sulfide (H2S) and substance P (SP) are known from animal models and in vitro studies as proinflammatory mediators. In this study, peripheral blood concentrations of H2S and SP were measured in patients with Escherichia coli or Klebsiella pneumoniae bacteraemia. Fifty patients were recruited from general wards at Christchurch Hospital, during 2020–2021. Samples from age- and sex-matched healthy subjects previously recruited as controls for studies of cardiovascular disease were used as controls. The concentrations of H2S were higher than controls on day 0, day 1, and day 2, and SP was higher than controls on all 4 days. The concentrations of H2S were highest on day 0, whereas SP concentrations were higher on day 2 than other days. Interleukin-6 and C-reactive protein were significantly higher on day 0 and day 1, respectively. The concentrations of H2S and SP did not differ between 15 non-septic (SIRS 0-1) and the 35 septic subjects (SIRS ≥ 2). Substance P concentrations were higher in subjects with abdominal infection than urinary tract infections on day 0 (p = 0.0002) and day 1 (p = 0.0091). In conclusion, the peak H2S concentrations precede the SP peak in patients with Gram-negative bacteraemia, but this response varies with the site of infection.

Shielding Surfaces from Viruses and Bacteria with a Multiscale Coating

The spread of viral and bacterial pathogens mediated by contact with surfaces is a leading cause of infection worldwide. COVID-19 and the continuous rise of deaths associated with antibiotic-resistant bacteria highlight the need to impede surface-mediated transmission. A sprayable coating with an intrinsic ability to resist the uptake of bacteria and viruses from surfaces and droplets, such as those generated by sneezing or coughing, is reported. The coating also provides an effective microbicidal functionality against bacteria, providing a dual barrier against pathogen uptake and transmission. This antimicrobial functionality is fully preserved following scratching and other induced damage to its surface or 9 days of submersion in a highly concentrated suspension of bacteria. The coatings also register an 11-fold decrease in viral contamination compared to the noncoated surfaces.

Investigating the effect of bacteriophages on bacterial FtsZ localisation

Escherichia coli is one of the most common Gram-negative pathogens and is responsible for infection leading to neonatal meningitis and sepsis. The FtsZ protein is a bacterial tubulin homolog required for cell division in most species, including E. coli. Several agents that block cell division have been shown to mislocalise FtsZ, including the bacteriophage λ-encoded Kil peptide, resulting in defective cell division and a filamentous phenotype, making FtsZ an attractive target for antimicrobials. In this study, we have used an in vitro meningitis model system for studying the effect of bacteriophages on FtsZ using fluorescent E. coli EV36/FtsZ-mCherry and K12/FtsZ-mNeon strains. We show localisation of FtsZ to the bacterial cell midbody as a single ring during normal growth conditions, and mislocalisation of FtsZ producing filamentous multi-ringed bacterial cells upon addition of the known inhibitor Kil peptide. We also show that when bacteriophages K1F-GFP and T7-mCherry were applied to their respective host strains, these phages can inhibit FtsZ and block bacterial cell division leading to a filamentous multi-ringed phenotype, potentially delaying lysis and increasing progeny number. This occurs in the exponential growth phase, as actively dividing hosts are needed. We present that ZapA protein is needed for phage inhibition by showing a phenotype recovery with a ZapA mutant strain, and we show that FtsI protein is also mislocalised upon phage infection. Finally, we show that the T7 peptide gp0.4 is responsible for the inhibition of FtsZ in K12 strains by observing a phenotype recovery with a T7Δ0.4 mutant.

Pseudomonas aeruginosa Alters Critical Lung Epithelial Cell Functions through Activation of ADAM17

Severe epithelial dysfunction is one major hallmark throughout the pathophysiological progress of bacterial pneumonia. Junctional and cellular adhesion molecules (e.g., JAMA-A, ICAM-1), cytokines (e.g., TNFα), and growth factors (e.g., TGFα), controlling proper lung barrier function and leukocyte recruitment, are proteolytically cleaved and released into the extracellular space through a disintegrin and metalloproteinase (ADAM) 17. In cell-based assays, we could show that the protein expression, maturation, and activation of ADAM17 is upregulated upon infection of lung epithelial cells with Pseudomonas aeruginosa and Exotoxin A (ExoA), without any impact of infection by Streptococcus pneumoniae. The characterization of released extracellular vesicles/exosomes and the comparison to heat-inactivated bacteria revealed that this increase occurred in a cell-associated and toxin-dependent manner. Pharmacological targeting and gene silencing of ADAM17 showed that its activation during infection with Pseudomonas aeruginosa was critical for the cleavage of junctional adhesion molecule A (JAM-A) and epithelial cell survival, both modulating barrier integrity, epithelial regeneration, leukocyte adhesion and transepithelial migration. Thus, site-specific targeting of ADAM17 or blockage of the activating toxins may constitute a novel anti-infective therapeutic option in Pseudomonas aeruginosa lung infection preventing severe epithelial and organ dysfunctions and stimulating future translational studies.

A Pseudomonas aeruginosa PQS quorum-sensing system inhibitor with anti-staphylococcal activity sensitizes polymicrobial biofilms to tobramycin

As single- and mixed-species biofilms, Staphylococcus aureus and Pseudomonas aeruginosa cause difficult-to-eradicate chronic infections. In P. aeruginosa, pseudomonas quinolone (PQS)-dependent quorum sensing regulates virulence and biofilm development that can be attenuated via antagonists targeting the transcriptional regulator PqsR (MvfR). Here, we exploited a quinazolinone (QZN) library including PqsR agonists and antagonists for their activity against S. aureus alone, when co-cultured with P. aeruginosa, and in combination with the aminoglycoside tobramycin. The PqsR inhibitor, QZN 34 killed planktonic Gram-positives but not Gram-negatives. QZN 34 prevented S. aureus biofilm formation, severely damaged established S. aureus biofilms, and perturbed P. aeruginosa biofilm development. Although P. aeruginosa protected S. aureus from tobramycin in mixed biofilms, the combination of aminoglycoside antibiotic with QZN 34 eradicated the mixed-species biofilm. The mechanism of action of QZN 34 toward Gram-positive bacteria is shown to involve membrane perturbation and dissipation of transmembrane potential.

Early detection of gram‑negative bacteria using metagenomic next‑generation sequencing in acute respiratory distress syndrome: A case report

Metagenomic next-generation sequencing (mNGS) is an effective method that can be used for the identification of early pathogens in patients with suspected severe pneumonia. However, the potential of mNGS for evaluating the prognosis of acute respiratory distress syndrome (ARDS) in patients with severe pneumonia remains unclear. In the present report, hospital-acquired gram-negative bacteria infections were detected in a case using metagenomic next-generation sequencing (mNGS) in a sample of bronchoalveolar fluid. This was obtained from a 58-year-old male patient with traumatic wet lung after a neurosurgery. According to the results, of which the profiles of the resistance genes were detected by mNGS, drugs designed to control infection were adjusted, namely to polymyxin B (500,000 U/12 h), azithromycin (0.5 g/24 h) and ganciclovir (0.25 g/12 h). Following adjusting treatment for 8 days, the symptoms of lung infection and hypoxemia were markedly improved, resulting in the patient being transferred out of the intensive care unit 15 days after treatment. To conclude, observations from the present report suggest that mNGS is a useful method for the early identification of pathogens in patients with pneumonia caused by ARDS. However, further studies are required to identify the complementary role of mNGS in supporting conventional microbiological methods in routine clinical practice.

Comparative Account of Biogenic Synthesis of Silver Nanoparticles Using Probiotics and Their Antimicrobial Activity Against Challenging Pathogens

The present work focusses on development of a safe, inexpensive, and more accessible source for biosynthesis of silver nanoparticles. Four different in-house probiotic isolates, i.e., Lactobacillus pentosus S6, Lactobacillus plantarum F22, Lactobacillus crustorum F11, and Lactobacillus paraplantarum KM1 isolated from different food sources, were used in the current study to check their ability to synthesize silver nanoparticles. All the probiotic-synthesized silver nanoparticles show maximum surface plasmon resonance (SPR) at a peak of 450 nm, which confirms the formation of silver nanoparticles. Scanning electron microscopy (SEM) analysis identified the shape and distribution of silver nanoparticles. Transmission electron microscopy (TEM) revealed the average size of synthesized nanoparticles in the range of 10–50 nm, with the smallest size of 5 nm for silver nanoparticles synthesized by L. crustorum F11. Further, Fourier-transform infrared spectroscopy (FTIR) detected the presence of different functional groups responsible for reduction of silver ion to form silver nanoparticles. The antimicrobial activity of these AgNPs was also found to be effective against different bacterial and fungal pathogens, viz., antibiotic-resistant Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Pythium aphanidermatum, Fusarium oxysporum, and Phytopthora parasitica. However, L. crustorum F11–synthesized AgNP showed maximum inhibition against all the bacterial and fungal pathogens, with highest against S. aureus (20 ± 0.61 mm) and F. oxysporum (23 ± 0.37). Findings from this study provide a durable and eco-friendly method for the biosynthesis of silver nanoparticles, having strong antimicrobial activity against different multidrug-resistant microorganisms.

Graphical abstract

Study of the persistence of selected Gram-negative bacteria pathogens of healthcare-associated infections on hospital fabrics

BACKGROUND

The ability of healthcare associate infection (HAI) pathogens to persist on fomites is crucial to their transmission within the healthcare setting, this study evaluated the persistence of 3 common HAI pathogens on fabrics materials commonly used in healthcare settings.

METHODS

Persistence of bacteria species on fabric was investigate by inoculating standardized inoculum prepared from the clinical isolates of Pseudomonas aeruginosa, Escherichia coli and Acinetobacter baumannii on sterile swatches of 100% cotton, microfiber and polyester. Viable bacteria persisting on the inoculated fabrics were evaluated immediate after inoculation and subsequently at 96-hour interval for 32 days using the drop plate technique. The effect of moisture on the persistence of the studied bacteria isolates was also evaluated.

RESULTS

Between 3 and 6 log reduction in the viability of the inoculated bacteria cells were observed after 32 days of inoculation on fabrics. Generally, lower viable cells were recovered from the microfiber fabrics compared to others, while higher viable cells were recovered from wet fabrics compared to the dry fabrics in this study.

DISCUSSION AND CONCLUSIONS

This study demonstrated that HAI bacteria pathogens can persist for more than a month on hospital fabrics, and that their persistence can be enhanced by moisture.

Assessment of disinfectant efficacy in reducing microbial growth

The incidence of hospital- and community-acquired infections has been dramatically increased worldwide. Accordingly, hands hygiene and the use of disinfectants have been increased leading to the expansion in hand sanitizers production to meet public demand. This study was conducted to assess the efficiency of common disinfectants in the market of Riyadh, Saudi Arabia in inhibiting the microbial growth during the time of Coronavirus disease 2019 (COVID-19) pandemic. Five bacterial strains of commonly hospital-acquired infections (Pseudomonas aeruginosa, Escherichia coli, Salmonella enteritidis, Staphylococcus aureus, and Enterococcus faecalis) (ATCC reference strains and clinical isolates) were examined for their susceptibility against 18 disinfectants collected from the Saudi market. The tested 18 disinfectants were broadly clustered into different groups based on their active chemical composition as following: 12 products contained alcohol, 2 products had chlorhexidine, 3 products contained mixed concentration of alcohol/chlorhexidine and 1 product had a mixture of chlorhexidine/Hexamidine/Chlorocresol. By measuring the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC), our results revealed that all the 18 disinfectants have reduced the microbial growth of all the tested strains. Generally, the MICs and the MBCs for the clinical strains are higher than those of the reference strains. Taken together, our findings showed that all tested products have high disinfectants’ killing rate against microbes of different origins, which suggest the high quality of these disinfectants and the good surveillance practice by the local authorities in Saudi Arabia.

Biologically synthesized silver nanoparticles as potent antibacterial effective against multidrug-resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the most worrisome infectious bacteria due to its intrinsic and acquired resistance against several antibiotics and the recalcitrance of its infections; hence, the development of novel antimicrobials effective against multidrug‐resistant P. aeruginosa is mandatory. In this work, silver nanoparticles obtained by green synthesis using a leaf extract and fungi were tested against a battery of clinical strains from cystic fibrosis, pneumonia and burnt patients, some of them with multidrug resistance. Both nanoparticles showed a potent antibacterial effect, causing severe damage to the cell wall, membrane and DNA, and inducing the production of reactive oxygen species. Moreover, the nanoparticles derived from fungi showed synergistic antibacterial effects with the antibiotics meropenem and levofloxacin for some clinical strains and both kinds of nanoparticles were nontoxic for larvae of the moth Galleria mellonella, encouraging further research for their implementation in the treatment of P. aeruginosa infections.

Frailty and Neutrophil Lymphocyte Ratio as Predictors of Mortality in Patients with Catheter-Associated Urinary Tract Infections or Central Line-Associated Bloodstream Infections in the Neurosurgical Intensive Care Unit: Insights from a Retrospective Study in a Developing Country

OBJECTIVE

We aim to evaluate the role of frailty and inflammatory markers in predicting the short-term outcomes after catheter-associated urinary tract infections (CAUTI) and central line-associated bloodstream infections (CLABSI).

METHODS

Data regarding the patients' characteristics, isolates on CAUTI and CLABSI, antibiotic susceptibility, frailty (11-point Modified Frailty Index), and inflammatory markers were retrospectively collected. Their impact on the short-term outcomes was assessed using regression modeling response.

RESULTS

One hundred and one patients with CAUTI (n = 71) and CLABSI (n = 30) between January 2018 and December 2019 were included in this study. The pooled incidence rates for CAUTI were 5.50 and for CLABSI 3.58 episodes/1000 catheter-days. We observed 74.7% drug resistance in our CAUTI isolates and 93.3% in CLABSI. In the multivariate analysis, frailty (P = 0.006), neutrophil/lymphocyte ratio (NLR) (P = 0.007) and the presence of sepsis (P = 0.029) were found to be significant predictors of in-hospital mortality in CAUTI. In patients with CLABSI, frailty (P = 0.029) and NLR (P = 0.029) were found significant and along with sepsis (P = 0.069) resulted in a regression model with good accuracy in predicting mortality. The receiver operating characteristic curve showed that 11-point Modified Frailty Index and NLR as well as the regression model significantly predicted mortality with an area under the curve of 86.1%, 81.4%, and 95.4%, respectively, in CAUTI, and 70.9%, 77.8%, and 95.2%, respectively, in CLABSI.

Bacterial contamination of neglected hospital surfaces and equipment in an Algerian hospital: an important source of potential infection

Hospital surfaces are heavily contaminated with bacteria, which are a potential source of nosocomial infections. This study was undertaken to identify bacterial communities isolated from neglected hospital surfaces after cleaning routine in a Algerian public hospital. Screening of bacterial contamination in patient bed (PB), reception land-line phones (TF), door handles (DH) and medical equipment (ME) during five months generated 108 inocula. Isolates obtained were identified based on biochemical characteristics and confirmed by analysis of 16S rRNA sequences. Statistical analysis was performed to reveal possible relationship between bacterial diversity and swabbed surfaces. Our findings showed a high prevalence of bacteria in various hospital surfaces, reaching (65.25%), where a highest contaminated surface was the PB (47.22%) and a lowest contaminated was TF (5.55%). Gram negative bacteria were the dominant group (62.03%) mainly represented by Entrobacteriaceae (42.59%), whereas Staphylococcus aureus belonging to Gram positive was the main expanded pathogen with (15.74%).

Genomic dissection of Klebsiella pneumoniae infections in hospital patients reveals insights into an opportunistic pathogen

Klebsiella pneumoniae is a major cause of opportunistic healthcare-associated infections, which are increasingly complicated by the presence of extended-spectrum beta-lactamases (ESBLs) and carbapenem resistance. We conducted a year-long prospective surveillance study of K. pneumoniae clinical isolates in hospital patients. Whole-genome sequence (WGS) data reveals a diverse pathogen population, including other species within the K. pneumoniae species complex (18%). Several infections were caused by K. variicola/K. pneumoniae hybrids, one of which shows evidence of nosocomial transmission. A wide range of antimicrobial resistance (AMR) phenotypes are observed, and diverse genetic mechanisms identified (mainly plasmid-borne genes). ESBLs are correlated with presence of other acquired AMR genes (median n = 10). Bacterial genomic features associated with nosocomial onset are ESBLs (OR 2.34, p = 0.015) and rhamnose-positive capsules (OR 3.12, p < 0.001). Virulence plasmid-encoded features (aerobactin, hypermucoidy) are observed at low-prevalence (<3%), mostly in community-onset cases. WGS-confirmed nosocomial transmission is implicated in just 10% of cases, but strongly associated with ESBLs (OR 21, p < 1 × 10⁻¹¹). We estimate 28% risk of onward nosocomial transmission for ESBL-positive strains vs 1.7% for ESBL-negative strains. These data indicate that K. pneumoniae infections in hospitalised patients are due largely to opportunistic infections with diverse strains, with an additional burden from nosocomially-transmitted AMR strains and community-acquired hypervirulent strains.

Klebsiella pneumoniae is an opportunistic pathogen of increasing public health concern due to the prevalence of antimicrobial resistance. Here, the authors provide insight into the resistance profiles, bacterial genome features and virulence genes, in a year-long prospective study of K. pneumoniae clinical isolates.

Lipid A Structural Determination from a Single Colony

We describe an innovative use for the recently reported fast lipid analysis technique (FLAT) that allows for the generation of MALDI tandem mass spectrometry data suitable for lipid A structure analysis directly from a single Gram-negative bacterial colony. We refer to this tandem MS version of FLAT as FLATn. Neither technique requires sophisticated sample preparation beyond the selection of a single bacterial colony, which significantly reduces overall analysis time (∼1 h), as compared to conventional methods. Moreover, the tandem mass spectra generated by FLATn provides comprehensive information on fragments of lipid A, for example, ester bonded acyl chain dissociations, cross-ring cleavages, and glycosidic bond dissociations, all of which allow the facile determination of novel lipid A structures or confirmation of expected structures. In addition to generating tandem mass spectra directly from single colonies, we also show that FLATn can be used to analyze lipid A structures taken directly from a complex biological clinical sample without the need for ex vivo growth. From a urine sample from a patient with an E. coli infection, FLATn identified the organism and demonstrated that this clinical isolate carried the mobile colistin resistance-1 gene (mcr-1) that results in the addition of a phosphoethanolamine moiety and subsequently resistance to the antimicrobial, colistin (polymyxin E). Moreover, FLATn allowed for the determination of the existence of a structural isomer in E. coli lipid A that had either a 1- or 4'-phosphate group modification by phosphoethanolamine generated by a change of bacterial culture conditions.

Characterization of the First Carbapenem-Resistant Pseudocitrobacter faecalis Harboring blaOXA-181 in China

With the wide use of carbapenems, carbapenem-resistant Enterobacterales have been increasingly reported worldwide. In this study, one bla_OXA-181-positive Pseudocitrobacter faecalis strain was isolated from the blood culture of a patient with a bloodstream infection in China, which was its first clinical report outside Pakistan. Species identification of P. faecalis was initially performed using MALDI-TOF/MS and further confirmed by 16S rRNA gene and housekeeping gene sequencing. The antimicrobial susceptibility testing was determined through the broth microdilution method, and their clonal relationship was analyzed by pulsed-field gel electrophoresis. To study the transmission and genetic structure of the bla_OXA-181 gene, a transformation test and whole-genome sequencing (WGS) were performed. The results of the antimicrobial susceptibility testing indicated this P. faecalis was resistant to carbapenems, quinolones, and commonly used β-lactam/β-lactamase inhibitor combinations. Through WGS and transformation experiments, bla_OXA-181 and qnrS1 genes causing antibiotic resistance were located on a 55,148-bp length IncX3 type plasmid with a truncated ColKp3 replicon gene. As a rare species of Enterobacterales, P. faecalis was clinically reported in China for the first time, and the bla_OXA-181 gene it carried was located on a globally disseminated IncX3 plasmid. The spread of such bacteria and antibiotic resistance requires more clinical attention.