Polymicrobial–Host Interactions during Infection

DJK-5, an anti-biofilm peptide, increases Staphylococcus aureus sensitivity to colistin killing in co-biofilms with Pseudomonas aeruginosa

Chronic infections represent a significant global health and economic challenge. Biofilms, which are bacterial communities encased in an extracellular polysaccharide matrix, contribute to approximately 80% of these infections. In particular, pathogens such as Pseudomonas aeruginosa and Staphylococcus aureus are frequently co-isolated from the sputum of patients with cystic fibrosis and are commonly found in chronic wound infections. Within biofilms, bacteria demonstrate a remarkable increase in resistance and tolerance to antimicrobial treatment. We investigated the efficacy of combining the last-line antibiotic colistin with a membrane- and stringent stress response-targeting anti-biofilm peptide DJK-5 against co-biofilms comprised of multidrug-resistant P. aeruginosa and methicillin-resistant S. aureus (MRSA). Colistin lacks canonical activity against S. aureus. However, our study revealed that under co-biofilm conditions, the antibiofilm peptide DJK-5 synergized with colistin against S. aureus. Similar enhancement was observed when daptomycin, a cyclic lipopeptide against Gram-positive bacteria, was combined with DJK-5, resulting in increased activity against P. aeruginosa. The combinatorial treatment induced morphological changes in both P. aeruginosa and S. aureus cell shape and size within co-biofilms. Importantly, our findings also demonstrate synergistic activity against both P. aeruginosa and S. aureus in a murine subcutaneous biofilm-like abscess model. In conclusion, combinatorial treatments with colistin or daptomycin and the anti-biofilm peptide DJK-5 show significant potential for targeting co-biofilm infections. These findings offer promising avenues for developing new therapeutic approaches to combat complex chronic infections.

Exploring the Potential of Nitrofurantoin for Infection Control in Regenerative Endodontics: In Vitro Study

INTRODUCTION

This study assessed a new antimicrobial paste formulation containing nitrofurantoin for regenerative endodontics against multispecies biofilms.

METHODS

Four groups of 11 single-root teeth each were tested: Negative control group (brain-heart infusion broth + micro-organisms); Hoshino 1 conventional tri-antibiotic paste group (1:1:1 ratio); Hoshino 5 group (5:5:5 ratio); Experimental group with nitrofurantoin, ciprofloxacin, and metronidazole. Minimum inhibitory concentrations of each antimicrobial were determined. A polymicrobial biofilm (Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans) was created in root canals, and pastes were inserted for 3 minutes with lentulo. After 7 days, samples were sonicated and spectrophotometrically analyzed. Microbiological assays, plasma membrane permeabilization, confocal laser scanning microscopy, and scanning electron microscopy evaluated biofilm eradication. Statistical significance was set at P < .05.

RESULTS

Spectrophotometry indicated Experimental group outperformed Hoshino 1 group and Negative control group (P < .05), with results similar to Hoshino 5 group (P > .05). Experimental group showed increased membrane damage compared to Hoshino 1 group and Hoshino 5 group. Confocal laser scanning microscopy and scanning electron microscopy revealed fewer microorganisms and no residual biofilm in Experimental group.

CONCLUSIONS

Substituting minocycline with nitrofurantoin in the paste effectively reduced microorganism counts in root canals system.

Increased Involvement of Staphylococcus epidermidis in the Rise of Polymicrobial Periprosthetic Joint Infections

BACKGROUND

In this study, we aimed to analyze the temporal distribution of polymicrobial periprosthetic joint infections (PJIs), while also evaluating the patient risk factors associated with these infections following total joint arthroplasty at our institution across 2 distinct periods.

METHOD

This retrospective cross-sectional study evaluated 259 patients who had knee or hip PJI from 2001 to 2006 and 2018 to 2022. A PJI was diagnosed using the 2018 International Consensus Meeting criteria. We utilized the Polymicrobial Pathogens' Co-occurrence Network Analysis, a novel approach that leverages network theory to map and quantify the complex interplay of organisms in PJIs.

RESULTS

Of the 259 patients who had polymicrobial PJI, 58.7% were men, with mean age 67 years (range, 24 to 90). Of the 579 identified pathogens, Staphylococcus epidermidis was the most common (22.1%), followed by Staphylococcus aureus (9.0%) and Cutibacterium acnes (7.8%). The co-occurrence analysis indicated that Staphylococcus epidermidis frequently coexisted with Cutibacterium acnes (26 cultures) and Staphylococcus capitis (22 cultures). A notable increase in body mass index from 27.7 ± 4.4 in 2001 to 2006 to 29.7 ± 6.2 in 2018 to 2022 was observed (P = .001). Moreover, infections from Staphylococcus epidermidis, Cutibacterium acnes, and Staphylococcus capitis saw a significant uptick (P < .001).

CONCLUSIONS

The study shows that from 2001 to 2022, there was a significant change in the pathogens responsible for polymicrobial PJIs, particularly an increase in Staphylococcus epidermidis, Cutibacterium acnes, and Staphylococcus capitis. Alongside these microbial changes, there was a rise in body mass index and shifts in comorbid conditions, such as more renal disease and fewer cases of congestive heart failure. These changes highlight the dynamic interplay between host and microbial factors in the pathogenesis of polymicrobial PJIs, necessitating adaptive strategies in both surgical and postoperative care to mitigate the rising tide of these complex infections.

Interplay of virulence factors shapes ecology and treatment outcomes in polymicrobial infections

Polymicrobial infections, caused by a community of multiple micro-organisms, are often associated with increased infection severity and poorer patient outcomes. The design of improved antimicrobial treatment strategies for PMIs can be supported by an understanding of their ecological and evolutionary dynamics. Bacterial species present in polymicrobial infections can produce virulence factors to inhibit host immune responses, such as neutrophil recruitment and phagocytosis. The presence of virulence factors can indirectly affect other bacterial species acting as a type of host-mediated interspecies interaction. The aim of this study was to assess how bacterial virulence factors targeting neutrophil function influence ecology and treatment outcomes of PMIs. An agent-based model was constructed which describes a dual-species bacterial population in the presence of neutrophils and a bacteriostatic drug. Our analysis has revealed unforeseen dynamics of the interplay of multiple virulence factors acting as interspecies interaction. We found that the distribution of two phagocytosis-inhibiting virulence factors amongst species can impact whether they have a mutually protective effect for both species. The addition of a virulence factor inhibiting neutrophil recruitment was found to reduce the protective effect of phagocytosis-inhibiting virulence factors. Furthermore we demonstrate the importance of virulence strength of a species relative to other virulent species to determine the fate of a species. We conclude that virulence factors are an important driver of population dynamics in polymicrobial infections, and may be a relevant therapeutic target for treatment of polymicrobial infections.

RNA-Seq reveals that Pseudomonas aeruginosa mounts growth medium-dependent competitive responses when sensing diffusible cues from Burkholderia cenocepacia

Most habitats host diverse bacterial communities, offering opportunities for inter-species interactions. While competition might often dominate such interactions, little is known about whether bacteria can sense competitors and mount adequate responses. The competition sensing hypothesis proposes that bacteria can use cues such as nutrient stress and cell damage to prepare for battle. Here, we tested this hypothesis by measuring transcriptome changes in Pseudomonas aeruginosa exposed to the supernatant of its competitor Burkholderia cenocepacia. We found that P. aeruginosa exhibited significant growth-medium-dependent transcriptome changes in response to competition. In an iron-rich medium, P. aeruginosa upregulated genes encoding the type-VI secretion system and the siderophore pyoverdine, whereas genes encoding phenazine toxins and hydrogen cyanide were upregulated under iron-limited conditions. Moreover, general stress response and quorum sensing regulators were upregulated upon supernatant exposure. Altogether, our results reveal nuanced competitive responses of P. aeruginosa when confronted with B. cenocepacia supernatant, integrating both environmental and social cues.

Co-infection of Helicobacter pylori and intestinal parasites in children of selected low-income communities in Lagos State, Nigeria

Helicobacter pylori and intestinal parasites cause gastrointestinal diseases with a high prevalence in children in resource limited developing countries. There is paucity of information in Nigeria on co-infection of H. pylori and intestinal parasites. The study was conducted to determine the prevalence of H. pylori and parasite co-infection in children from selected low-income communities in Lagos, Nigeria. Fecal samples were collected from 151 healthy children aged ≤11 years across six low-income communities in Lagos. H. pylori was detected using stool antigen test and conventional PCR assay, intestinal parasites were detected using formol-ether concentration and nested PCR assay. Structured questionnaires were administered to parents and legal guardians of the children by an interviewer to collect relevant data on demographic and lifestyle factors. The prevalence of H. pylori was 31.79% (48), with a higher prevalence in children aged 2-3 years. The prevalence of intestinal parasites was 21.19% (32) with the lowest frequency found in children aged 8-9 years. The parasites detected include: A. lumbricoides (10.6%), G. intestinalis (7.3%), hookworm (1.99%), E. histolytica (0.66%), S. mansoni (0.66%). There was co-infection prevalence of 10.6% (16) which was associated with the parasites: G. intestinalis (7.3%) and A. lumbricoides (3.97%). Polyparasitism with G. intestinalis and A. lumbricoides was reported in 2 children infected with H. pylori. This study which is the first reported in Lagos established a low prevalence of H. pylori and intestinal parasite co-infection in children and provides better understanding of the epidemiology of H. pylori infection associated with intestinal parasites in Nigeria.

Nanoformulations for dismantling fungal biofilms: The latest arsenals of antifungal therapy

Globally, fungal infections have evolved as a strenuous challenge for clinicians, particularly in patients with compromised immunity in intensive care units. Fungal co-infection in Covid-19 patients has made the situation more formidable for healthcare practitioners. Surface adhered fungal population known as biofilm often develop at the diseased site to elicit antifungal tolerance and recalcitrant traits. Thus, an innovative strategy is required to impede/eradicate developed biofilm and avoid the formation of new colonies. The development of nanocomposite-based antibiofilm solutions is the most appropriate way to withstand and dismantle biofilm structures. Nanocomposites can be utilized as a drug delivery medium and for fabrication of anti-biofilm surfaces capable to resist fungal colonization. In this context, the present review comprehensively described different forms of nanocomposites and mode of their action against fungal biofilms. Amongst various nanocomposites, efficacy of metal/organic nanoparticles and nanofibers are particularly emphasized to highlight their role in the pursuit of antibiofilm strategies. Further, the inevitable concern of nanotoxicology has also been introduced and discussed with the exigent need of addressing it while developing nano-based therapies. Further, a list of FDA-approved nano-based antifungal formulations for therapeutic usage available to date has been described. Collectively, the review highlights the potential, scope, and future of nanocomposite-based antibiofilm therapeutics to address the fungal biofilm management issue.

Analysis of In-Patient Evolution of Escherichia coli Reveals Potential Links to Relapse of Bone and Joint Infections

Bone and joint infections (BJIs) are difficult to treat and affect a growing number of patients, in which relapses are observed in 10-20% of case. These relapses, which call for prolonged antibiotic treatment and increase resistance emergence risk, may originate from ill-understood adaptation of the pathogen to the host. Here, we investigated 3 pairs of Escherichia coli strains from BJI cases and their relapses to unravel adaptations within patients. Whole-genome comparison presented evidence for positive selection and phenotypic characterization showed that biofilm formation remained unchanged, contrary to what is usually described in such cases. Although virulence was not modified, we identified the loss of 2 virulence factors contributing to immune system evasion in one of the studied strains. Other strategies, including global growth optimization and colicin production, likely allowed the strains to outcompete competitors. This work highlights the variety of strategies allowing in-patient adaptation in BJIs.

The role of single and mixed biofilms in Clostridioides difficile infection and strategies for prevention and inhibition

Clostridioides difficile infection (CDI) is a serious disease with a high recurrence rate. The single and mixed biofilms formed by C. difficile in the gut contribute to the formation of recurrent CDI (rCDI). In parallel, other gut microbes influence the formation and development of C. difficile biofilms, also known as symbiotic biofilms. Interactions between members within the symbiotic biofilm are associated with the worsening or alleviation of CDI. These interactions include effects on C. difficile adhesion and chemotaxis, modulation of LuxS/AI-2 quorum sensing (QS) system activity, promotion of cross-feeding by microbial metabolites, and regulation of intestinal bile acid and pyruvate levels. In the process of C. difficile biofilms control, inhibition of C. difficile initial biofilm formation and killing of C. difficile vegetative cells and spores are the main targets of action. The role of symbiotic biofilms in CDI suggested that targeting interventions of C. difficile-promoting gut microbes could indirectly inhibit the formation of C. difficile mixed biofilms and improved the ultimate therapeutic effect. In summary, this review outlines the mechanisms of C. difficile biofilm formation and summarises the treatment strategies for such single and mixed biofilms, aiming to provide new ideas for the prevention and treatment of CDI.

Development of a risk prediction model for subsequent infection after colonization with carbapenem-resistant Enterobacterales: a retrospective cohort study

BACKGROUND

Colonization of carbapenem-resistant Enterobacterale (CRE) is considered as one of vital preconditions for infection, with corresponding high morbidity and mortality. It is important to construct a reliable prediction model for those CRE carriers with high risk of infection.

METHODS

A retrospective cohort study was conducted in two Chinese tertiary hospitals for patients with CRE colonization from 2011 to 2021. Univariable analysis and the Fine-Gray sub-distribution hazard model were utilized to identify potential predictors for CRE-colonized infection, while death was the competing event. A nomogram was established to predict 30-day and 60-day risk of CRE-colonized infection.

RESULTS

879 eligible patients were enrolled in our study and divided into training (n = 761) and validation (n = 118) group, respectively. There were 196 (25.8%) patients suffered from subsequent CRE infection. The median duration of subsequent infection after identification of CRE colonization was 20 (interquartile range [IQR], 14-32) days. Multisite colonization, polymicrobial colonization, catheterization and receiving albumin after colonization, concomitant respiratory diseases, receiving carbapenems and antimicrobial combination therapy before CRE colonization within 90 days were included in final model. Model discrimination and calibration were acceptable for predicting the probability of 60-day CRE-colonized infection in both training (area under the curve [AUC], 74.7) and validation dataset (AUC, 81.1). Decision-curve analysis revealed a significantly better net benefit in current model. Our prediction model is freely available online at https://ken-zheng.shinyapps.io/PredictingModelofCREcolonizedInfection/ .

CONCLUSIONS

Our nomogram has a good predictive performance and could contribute to early identification of CRE carriers with a high-risk of subsequent infection, although external validation would be required.

Polymicrobial bloodstream infections a risk factor for mortality in neonates at the national hospital, Tanzania: A case-control study

BACKGROUND

Polymicrobial bloodstream infections (BSI) are difficult to treat since empiric antibiotics treatment are frequently less effective against multiple pathogens. The study aimed to compare outcomes in patients with polymicrobial and monomicrobial BSIs.

METHODS

The study was a retrospective case-control design conducted at Muhimbili National Hospital for data processed between July 2021 and June 2022. Cases were patients with polymicrobial BSI, and controls had monomicrobial BSI. Each case was matched to three controls by age, admitting ward, and duration of admission. Logistic regression was performed to determine independent risk factors for in-hospital and 30-day mortality.

RESULTS

Fifty patients with polymicrobial BSI and 150 with monomicrobial BSI were compared: the two arms had no significant differences in sex and comorbidities. The most frequent bacteria in polymicrobial BSI were Klebsiella pneumoniae 17% (17/100) and Enterobacter species 15% (15/100). In monomicrobial BSI, S. aureus 17.33% (26/150), Klebsiella pneumoniae 16.67% (25/150), and Acinetobacter species 15% (15/150) were more prevalent. Overall, isolates were frequently resistant to multiple antibiotics tested, and 52% (130/250) were multidrug resistance. The 30-day and in-hospital mortality were 33.5% (67/200) and 36% (72/200), respectively. On multivariable analysis, polymicrobial BSIs were independent risk factors for both in-hospital mortality (aOR 2.37, 95%CI 1.20-4.69, p = 0.01) and 30-day mortality (aOR 2.05, 95%CI 1.03-4.08), p = 0.04). In sub-analyses involving only neonates, polymicrobial BSI was an independent risk factor for both 30-day mortality (aOR 3.13, 95%CI 1.07-9.10, p = 0.04) and in-hospital mortality (aOR 5.08, 95%CI 1.60-16.14, p = 0.006). Overall, the median length of hospital stay post-BSIs was numerically longer in patients with polymicrobial BSIs.

CONCLUSION

Overall, polymicrobial BSI was a significant risk for mortality. Patients with polymicrobial BSI stay longer at the hospital than those with monomicrobial BSI. These findings call for clinicians to be more aggressive in managing polymicrobial BSI.

Improving bacteria identification from digital melt assay via oligonucleotide-based temperature calibration

BACKGROUND

Bacterial infections, especially polymicrobial infections, remain a threat to global health and require advances in diagnostic technologies for timely and accurate identification of all causative species. Digital melt - microfluidic chip-based digital PCR combined with high resolution melt (HRM) - is an emerging method for identification and quantification of polymicrobial bacterial infections. Despite advances in recent years, existing digital melt instrumentation often delivers nonuniform temperatures across digital chips, resulting in nonuniform digital melt curves for individual bacterial species. This nonuniformity can lead to inaccurate species identification and reduce the capacity for differentiating bacterial species with similar digital melt curves.

RESULTS

We introduce herein a new temperature calibration method for digital melt by incorporating an unamplified, synthetic DNA fragment with a known melting temperature as a calibrator. When added at a tuned concentration to an established digital melt assay amplifying the commonly targeted 16S V1 - V6 region, this calibrator produced visible low temperature calibrator melt curves across-chip along with the target bacterial melt curves. This enables alignment of the bacterial melt curves and correction of heating-induced nonuniformities. Using this calibration method, we were able to improve the uniformity of digital melt curves from three causative species of bacteria. Additionally, we assessed calibration's effects on identification accuracy by performing machine learning identification of three polymicrobial mixtures comprised of two bacteria with similar digital melt curves in different ratios. Calibration greatly improved mixture composition prediction.

SIGNIFICANCE

To the best of our knowledge, this work represents the first DNA calibrator-supplemented assay and calibration method for nanoarray digital melt. Our results suggest that this calibration method can be flexibly used to improve identification accuracy and reduce melt curve variabilities across a variety of pathogens and assays. Therefore, this calibration method has the potential to elevate the diagnostic capabilities of digital melt toward polymicrobial bacterial infections and other infectious diseases.

Competition quenching strategies reduce antibiotic tolerance in polymicrobial biofilms

Bacteria typically live in dense communities where they are surrounded by other species and compete for a limited amount of resources. These competitive interactions can induce defensive responses that also protect against antimicrobials, potentially complicating the antimicrobial treatment of pathogens residing in polymicrobial consortia. Therefore, we evaluate the potential of alternative antivirulence strategies that quench this response to competition. We test three competition quenching approaches: (i) interference with the attack mechanism of surrounding competitors, (ii) inhibition of the stress response systems that detect competition, and (iii) reduction of the overall level of competition in the community by lowering the population density. We show that either strategy can prevent the induction of antimicrobial tolerance of Salmonella Typhimurium in response to competitors. Competition quenching strategies can thus reduce tolerance of pathogens residing in polymicrobial communities and could contribute to the improved eradication of these pathogens via traditional methods.

Recurrent and complicated urinary tract infections in women: Utility of advanced testing to enhance care

BACKGROUND

The United States currently faces a public health crisis with regarding to antibiotic-resistant bacteria, and new urinary tract infection (UTI) diagnostics are needed. Women with recurrent UTI (rUTI) and complicated UTI (cUTI) are at particular risk given their complexity and the paucity of adequate testing modalities. The standard urine culture (SUC) is the cornerstone for diagnosis, but it has many shortcomings. These pitfalls lead to dissatisfaction and frustration among women afflicted with rUTI and cUTI, as well as overuse of antibiotics. One innovation is PCR UTI testing, which has been shown to outperform SUC among symptomatic women.

AIMS

This article discusses UTI PCR testing, as well as a possible role in clinical practice.

MATERIALS AND METHODS

Published literature was reviewed and summarized.

RESULTS

Management of rUTI and cUTI is complex, and providers should have all diagnostics available to facilitate providing optimal care. Urine PCR testing faces reimbursement issues despite fulfilling clinical indication parameters as described by insurance companies.

DISCUSSION

The role of UTI PCR testing remains unclear. Reimbursement issues have led to underuse and limited real-world outcomes reinforcing benefit.

CONCLUSION

This study proposes an algorithm for PCR testing among women with rUTI and cUTI.

Herpesvirus reactivation in respiratory tract is associated with increased mortality of severe pneumonia patients and their respiratory microbiome dysbiosis

Severe pneumonia (SP) is a respiratory tract disease that seriously threatens human health. The herpesvirus detected in patients, especially with severe and immunodeficient diseases, is gradually attracting the attention of clinical doctors. However, little is known about the effect of herpesvirus on the prognosis of SP patients and the pulmonary microbial community. Here, we retrospectively analyzed respiratory samples from 45 SP patients detected by metagenomic next-generation sequencing (mNGS). A total of five types of herpesviruses were detected, with Human alphaherpesvirus 1 (HHV-1) in 19 patients, Human betaherpesvirus 5 (CMV) in 7 patients, Human betaherpesvirus 7 (HHV-7) in 6 patients, Human alphaherpesvirus 2 (HHV-2) in 5 patients, and Human gammaherpesvirus 4 (EBV) in 4 patients. Further analysis showed that the mortality of the herpesvirus-positive group was significantly higher than that of the negative group. The results also showed that HHV-1 was significantly associated with the prognosis of SP patients, while the other herpesviruses did not have a significant difference in patient mortality. A comparison of the microbial community characteristics of SP patients showed a significant difference in beta-diversity between herpesvirus-positive and negative groups. Species difference analysis showed that the herpesvirus-positive group was related to more conditional pathogens, such as Pneumocystis jirovecii and Burkholderia cepacia. In summary, our results suggest that the presence of herpesvirus is associated with the mortality of SP patients. Furthermore, enrichment of conditional pathogens in the respiratory tract of herpesvirus-positive SP patients may be a potential reason for the increased mortality.

In vitro biofilm inhibition efficacy of Aerva lanata flower extract against Gram negative and Gram-positive biofilm forming bacteria and toxicity analysis using Artemia salina

A biofilm consists of Gram positive and Gram-negative bacteria enclosed in a matrix. Industrial biofouling is caused by biofilms, which can exhibit antimicrobial resistance during infections. Many biofilm studies find that nearly all biofilm communities consist of Gram positive and Gram-negative bacteria. It is therefore necessary to better understand the conserved themes in biofilm formation to develop therapeutics based on biofilm formation. Plant extracts can effectively combat pathogenic bacterial biofilms. This study evaluated the antibacterial and antibiofilm activity of Aerva lanata flower extract against Staphylococcus aureus and Pseudomonas aeruginosa. Methanol extract of dried A. lanata flower was tested against S. aureus and P. aeruginosa to determine the antibacterial activity (10, 25, 50, 75, 100 μg/mL) resulted in a maximum of 0.5-1 log reduction and 2 log reduction in comparison to the control or untreated bacterial cells respectively. A. lanata showed maximum biofilm inhibition up to 1.5-fold and 1-fold against P. aeruginosa and S. aureus. Light microscopic analysis of biofilm treated with A. lanata extract showed efficient distortion of the biofilm matrix. Further, the in vivo analysis of A. lanata in the Artemia salina brine shrimp model showed >50% survival and thus proving the efficacy of A. lanata extract in rescuing the brine shrimps against P. aeruginosa and S. aureus infection.

Rapid detection of gastrointestinal pathogens using a multiplex polymerase chain reaction gastrointestinal panel and its role in antimicrobial stewardship

OBJECTIVES

The FilmArray gastrointestinal panel (FAGIP) is widely used to detect infectious diarrhoea due to its outstanding sensitivity compared to conventional methods, but there is geographic variation, such as in the distribution of pathogens, among populations.

METHODS

This was a retrospective study that analysed patients with acute diarrhoea who underwent FAGIP tests from all age groups during 2022. We compared positive rates of FAGIP between paediatric (n = 245) and adult patients (n = 242) of different origins. The targeted therapy rate and antimicrobial agent use rate were also analysed.

RESULTS

Among the 487 stool samples evaluated, the overall, community-origin (CO), and nosocomial (NC) positivity rates of paediatric patients were significantly higher than those of adults (73.9 % vs. 43.0 %, p = 0.000; 76.2 % vs. 51.7 %, p = 0.000; 50.0 % vs. 19.7 %, p = 0.000). Salmonella was the most frequently detected pathogen (35.9 %) in children, while the predominant pathogen in adult patients was toxin A/B-genic Clostridioides difficile (13.2 %). There was a significantly lower antimicrobial agent use rate after FAGIP results were available (79.1 % vs. 64.5 %, p = 0.000) and a higher rate of targeted therapy towards C. difficile infection in adults than in children (84.4 % vs. 69.0 %, p = 0.011).

CONCLUSION

Paediatric diarrhoea patients showed higher positivity rates than adult patients. Application of FAGIP for acute diarrhoea might lower unnecessary antimicrobial use.

Treatment of Staphylococcus aureus and Candida albicans polymicrobial biofilms by phloroglucinol-gold nanoparticles

The co-isolation of Staphylococcus aureus and Candida albicans from host tissues and organs and their in vitro and in vivo interaction studies suggest a synergistic relationship in forming polymicrobial biofilms. In particular, during polymicrobial biofilm formation, S. aureus becomes coated in the extracellular matrix secreted by C. albicans, leading to enhanced resistance to antibiotics. Accordingly, understanding the interactions between S. aureus and C. albicans in polymicrobial biofilms is of utmost importance in establishing treatment strategies for polymicrobial infections. As an alternate technique, nanoparticles were used in this investigation to suppress polymicrobial biofilm. The current study aims to manufacture gold nanoparticles (AuNPs) using phloroglucinol (PG), a natural chemical, and test their inhibitory capabilities against S. aureus and C. albicans biofilms in standard and host-mimicking media (like saliva and sputum). PG-AuNPs have a spherical form with an average size of 46.71 ± 6.40 nm. The minimum inhibitory concentration (MIC) values differed when PG-AuNPs were evaluated in the standard and host-mimicking artificial media. The MIC of PG-AuNPs against S. aureus and C. albicans was 2048 μg/mL in both the standard and artificial sputum media. However, the MIC in saliva was only 128 μg/mL. The initial stage polymicrobial biofilm of S. aureus and C. albicans was dramatically decreased at the sub-MIC of PG-AuNPs in both standard and host-mimicking media. S. aureus and C. albicans mature polymicrobial biofilms were more effectively eliminated by MIC and sub-MIC of PG-AuNPs. This study indicates that PG-AuNPs have the ability to limit the formation of polymicrobial biofilms caused by bacterial and fungal diseases.

Illuminating the oral microbiome and its host interactions: tools and approaches for molecular microbiology studies

Advancements in DNA sequencing technologies within the last decade have stimulated an unprecedented interest in the human microbiome, largely due the broad diversity of human diseases found to correlate with microbiome dysbiosis. As a direct consequence of these studies, a vast number of understudied and uncharacterized microbes have been identified as potential drivers of mucosal health and disease. The looming challenge in the field is to transition these observations into defined molecular mechanistic studies of symbiosis and dysbiosis. In order to meet this challenge, many of these newly identified microbes will need to be adapted for use in experimental models. Consequently, this review presents a comprehensive overview of the molecular microbiology tools and techniques that have played crucial roles in genetic studies of the bacteria found within the human oral microbiota. Here, we will use specific examples from the oral microbiome literature to illustrate the biology supporting these techniques, why they are needed in the field, and how such technologies have been implemented. It is hoped that this information can serve as a useful reference guide to help catalyze molecular microbiology studies of the many new understudied and uncharacterized species identified at different mucosal sites in the body.

Enterococcus faecalis suppresses Staphylococcus aureus-induced NETosis and promotes bacterial survival in polymicrobial infections

Enterococcus faecalis is an opportunistic pathogen that is frequently co-isolated with other microbes in wound infections. While E. faecalis can subvert the host immune response and promote the survival of other microbes via interbacterial synergy, little is known about the impact of E. faecalis-mediated immune suppression on co-infecting microbes. We hypothesized that E. faecalis can attenuate neutrophil-mediated responses in mixed-species infection to promote survival of the co-infecting species. We found that neutrophils control E. faecalis infection via phagocytosis, ROS production, and degranulation of azurophilic granules, but it does not trigger neutrophil extracellular trap formation (NETosis). However, E. faecalis attenuates Staphylococcus aureus-induced NETosis in polymicrobial infection by interfering with citrullination of histone, suggesting E. faecalis can actively suppress NETosis in neutrophils. Residual S. aureus-induced NETs that remain during co-infection do not impact E. faecalis, further suggesting that E. faecalis possess mechanisms to evade or survive NET-associated killing mechanisms. E. faecalis-driven reduction of NETosis corresponds with higher S. aureus survival, indicating that this immunomodulating effect could be a risk factor in promoting the virulence polymicrobial infection. These findings highlight the complexity of the immune response to polymicrobial infections and suggest that attenuated pathogen-specific immune responses contribute to pathogenesis in the mammalian host.

Phage Therapy in the Management of Urinary Tract Infections: A Comprehensive Systematic Review

Urinary tract infections (UTIs) are a problem worldwide, affecting almost half a billion people each year. Increasing antibiotic resistance and limited therapeutic options have led to the exploration of alternative therapies for UTIs, including bacteriophage (phage) therapy. This systematic review aims at evaluating the efficacy of phage therapy in treating UTIs. We employed a comprehensive search strategy for any language, any animal, and any publication date. A total of 55 in vivo and clinical studies were included. Of the studies, 22% were published in a non-English language, 32.7% were before the year 1996, and the rest were after 2005. The results of this review suggest that phage therapy for UTIs can be effective; more than 72% of the included articles reported microbiological and clinical improvements. On the other hand, only 5 randomized controlled trials have been completed, and case reports and case series information were frequently incomplete for analysis. Overall, this comprehensive systematic review identifies preliminary evidence supporting the potential of phage therapy as a safe and viable option for the treatment of UTIs.

Dual functional therapeutics: mitigating bacterial infection and associated inflammation

The emergence of antimicrobial resistance, coupled with the occurrence of persistent systemic infections, has already complicated clinical therapy efforts. Moreover, infections are also accompanied by strong inflammatory responses, generated by the host's innate and adaptive immune systems. The closely intertwined relationship between bacterial infection and inflammation has multiple implications on the ability of antibacterial therapeutics to tackle infection and inflammation. Particularly, uncontrolled inflammatory responses to infection can lead to sepsis, a life-threatening physiological condition. In this review, we discuss dual-functional antibacterial therapeutics that have potential to be developed for treating inflammation associated with bacterial infections. Immense research is underway that aims to develop new therapeutic agents that, when administered, regulate the excess inflammatory response, i.e. they have immunomodulatory properties along with the desired antibacterial activity. The classes of antibiotics that have immunomodulatory function in addition to antibacterial activity have been reviewed. Host defense peptides and their synthetic mimics are amongst the most sought-after solutions to develop such dual-functional therapeutics. This review also highlights the important classes of peptidomimetics that exhibit both antibacterial and immunomodulatory properties.

P. aeruginosa interactions with other microbes in biofilms during co-infection

This review addresses the topic of biofilms, including their development and the interaction between different counterparts. There is evidence that various diseases, such as cystic fibrosis, otitis media, diabetic foot wound infections, and certain cancers, are promoted and aggravated by the presence of polymicrobial biofilms. Biofilms are composed by heterogeneous communities of microorganisms protected by a matrix of polysaccharides. The different types of interactions between microorganisms gives rise to an increased resistance to antimicrobials and to the host's defense mechanisms, with the consequent worsening of disease symptoms. Therefore, infections caused by polymicrobial biofilms affecting different human organs and systems will be discussed, as well as the role of the interactions between the gram-negative bacteria Pseudomonas aeruginosa, which is at the base of major polymicrobial infections, and other bacteria, fungi, and viruses in the establishment of human infections and diseases. Considering that polymicrobial biofilms are key to bacterial pathogenicity, it is fundamental to evaluate which microbes are involved in a certain disease to convey an appropriate and efficacious antimicrobial therapy.

Clinical Features and Outcomes of VAP Due to Multidrug-Resistant Klebsiella spp.: A Retrospective Study Comparing Monobacterial and Polybacterial Episodes

VAP due to multidrug-resistant (MDR) bacteria is a frequent infection among patients in ICUs. Patient characteristics and mortality in mono- and polybacterial cases of VAP may differ. A single-centre, retrospective 3-year study was conducted in the four ICUs of a Lithuanian referral university hospital, aiming to compare both the clinical features and the 60-day ICU all-cause mortality of monobacterial and polybacterial MDR Klebsiella spp. VAP episodes. Of the 86 MDR Klebsiella spp. VAP episodes analyzed, 50 (58.1%) were polybacterial. The 60-day mortality was higher (p < 0.05) in polybacterial episodes: overall (50.0 vs. 27.8%), in the sub-group with less-severe disease (SOFA < 8) at VAP onset (45.5 vs. 15.0%), even with appropriate treatment (41.7 vs. 12.5%), and the sub-group of extended drug-resistant (XDR) Klebsiella spp. (46.4 vs. 17.6%). The ICU mortality (44.0 vs. 22.5%) was also higher in the polybacterial episodes. The monobacterial MDR Klebsiella spp. VAP was associated (p < 0.05) with prior hospitalization (61.1 vs. 40.0%), diabetes mellitus (30.6 vs. 5.8%), obesity (30.6 vs. 4.7%), prior antibiotic therapy (77.8 vs. 52.0%), prior treatment with cephalosporins (66.7 vs. 36.0%), and SOFA cardiovascular ≥ 3 (44.4 vs. 10.0%) at VAP onset. Patients with polybacterial VAP were more likely (p < 0.05) to be comatose (22.2 vs. 52.0%) and had a higher SAPS II score (median [IQR] 45.0 [35.25-51.1] vs. 50.0 [40.5-60.75]) at VAP onset. Polybacterial MDR Klebsiella spp. VAP had distinct demographic and clinical characteristics compared to monobacterial, and was associated with poorer outcomes.

Silver Nanoparticles Phytofabricated through Azadirachta indica: Anticancer, Apoptotic, and Wound-Healing Properties

Silver nanoparticles (AgNPs) have unlocked numerous novel disciplines in nanobiotechnological protocols due to their larger surface area-to-volume ratios, which are attributed to the marked reactivity of nanosilver, and due to their extremely small size, which enables AgNPs to enter cells, interact with organelles, and yield distinct biological effects. AgNPs are capable of bypassing immune cells, staying in the system for longer periods and with a higher distribution, reaching target tissues at higher concentrations, avoiding diffusion to adjacent tissues, releasing therapeutic agents or drugs for specific stimuli to achieve a longer duration at a specific rate, and yielding desired effects. The phytofabrication of AgNPs is a cost-effective, one-step, environmentally friendly, and easy method that harnesses sustainable resources and naturally available components of plant extracts (PEs). In addition, it processes various catalytic activities for the degradation of various organic pollutants. For the phytofabrication of AgNPs, plant products can be used in a multifunctional manner as a reducing agent, a stabilizing agent, and a functionalizing agent. In addition, they can be used to curtail the requirements for any additional stabilizing agents and to help the reaction stages subside. Azadirachta indica, a very common and prominent medicinal plant grown throughout the Indian subcontinent, possesses free radical scavenging and other pharmaceutical properties via the regulation of proinflammatory enzymes, such as COX and TOX. It also demonstrates anticancer activities through cell-signaling pathways, modulating tumor-suppressing genes such as p53 and pTEN, transcriptional factors, angiogenesis, and apoptosis via bcl2 and bax. In addition, it possesses antibacterial activities. Phytofabricated AgNPs have been applied in the areas of drug delivery, bioimaging, biosensing, cancer treatment, cosmetics, and cell biology. Such pharmaceutical and biological activities of phytofabricated AgNPs are attributed to more than 300 phytochemicals found in Azadirachta indica, and are especially abundant in flavonoids, polyphenols, diterpenoids, triterpenoids, limonoids, tannins, coumarin, nimbolide, azadirachtin, azadirone, azadiradione, and gedunin. Parts of Azadirachta indica, including the leaves in various forms, have been used for wound healing or as a repellent. This study was aimed at examining previously biosynthesized (from Azadirachta indica) AgNPs for anticancer, wound-healing, and antimicrobial actions (through MTT reduction assay, scratch assay, and microbroth dilution methods, respectively). Additionally, apoptosis in cancer cells and the antibiofilm capabilities of AgNPs were examined through caspase-3 expression, dentine block, and crystal violet methods. We found that biogenic silver nanoparticles are capable of inducing cytotoxicity in HCT-116 colon carcinoma cells (IC50 of 744.23 µg/mL, R2: 0.94), but are ineffective against MCF-7 breast cancer cells (IC50 >> 1000 µg/mL, R2: 0.86). AgNPs (IC50 value) induced a significant increase in caspase-3 expression (a 1.5-fold increase) in HCT-116, as compared with control cells. FITC-MFI was 1936 in HCT-116-treated cells, as compared to being 4551 in cisplatin and 1297 in untreated cells. AgNPs (6.26 µg/mL and 62.5 µg/mL) induced the cellular migration (40.2% and 33.23%, respectively) of V79 Chinese hamster lung fibroblasts; however, the improvement in wound healing was not significant as it was for the controls. AgNPs (MIC of 10 µg/mL) were very effective against MDR Enterococcus faecalis in the planktonic mode as well as in the biofilm mode. AgNPs (10 µg/mL and 320 µg/mL) reduced the E. faecalis biofilm by >50% and >80%, respectively. Natural products, such as Syzygium aromaticum (clove) oil (MIC of 312.5 µg/mL) and eugenol (MIC of 625 µg/mL), showed significant antimicrobial effects against A. indica. Our findings indicate that A. indica-functionalized AgNPs are effective against cancer cells and can induce apoptosis in HCT-116 colon carcinoma cells; however, the anticancer properties of AgNPs can also be upgraded through active targeting (functionalized with enzymes, antibiotics, photosensitizers, or antibodies) in immunotherapy, photothermal therapy, and photodynamic therapy. Our findings also suggest that functionalized AgNPs could be pivotal in the development of a novel, non-cytotoxic, biocompatible therapeutic agent for infected chronic wounds, ulcers, and skin lesions involving MDR pathogens via their incorporation into scaffolds, composites, patches, microgels, or formulations for microneedles, dressings, bandages, gels, or other drug-delivery systems.

Polymicrobial Infections and Biofilms: Clinical Significance and Eradication Strategies

Biofilms are population of cells growing in a coordinated manner and exhibiting resistance towards hostile environments. The infections associated with biofilms are difficult to control owing to the chronicity of infections and the emergence of antibiotic resistance. Most microbial infections are contributed by polymicrobial or mixed species interactions, such as those observed in chronic wound infections, otitis media, dental caries, and cystic fibrosis. This review focuses on the polymicrobial interactions among bacterial-bacterial, bacterial-fungal, and fungal-fungal aggregations based on in vitro and in vivo models and different therapeutic interventions available for polymicrobial biofilms. Deciphering the mechanisms of polymicrobial interactions and microbial diversity in chronic infections is very helpful in anti-microbial research. Together, we have discussed the role of metagenomic approaches in studying polymicrobial biofilms. The outstanding progress made in polymicrobial research, especially the model systems and application of metagenomics for detecting, preventing, and controlling infections, are reviewed.

Probing mutual interactions between Pseudomonas aeruginosa and Candida albicans in a biofabricated membrane-based microfluidic platform

Microbes are typically found in multi-species (polymicrobial) communities. Cooperative and competitive interactions between species, mediated by diffusible factors and physical contact, leads to highly dynamic communities that undergo changes in composition diversity and size. Infections can be more severe or more difficult to treat when caused by multiple species. Interactions between species can improve the ability of one or more species to tolerate anti-microbial treatments and host defenses. Pseudomonas aeruginosa (Pa), a ubiquitous bacterium, and the opportunistic pathogenic yeast, Candida albicans (Ca), are frequently found together in cystic fibrosis lung infections and wound infections. While significant progress has been made in determining interactions between Pa and Ca, there are still important questions that remain unanswered. Here, we probe the mutual interactions between Pa and Ca in a custom-made microfluidic device using biopolymer chitosan membranes that support cross-species communication. By assembling microbes in physically separated, chemically communicating populations or bringing into direct interactions in a mixed culture, in situ polymicrobial growth and biofilm morphology were qualitatively characterized and quantified. Our work reveals new dynamic details of their mutual interactions including cooperation, competition, invasion, and biofilm formation. The membrane-based microfluidic platform can be further developed to understand the polymicrobial interactions within a controlled interactive microenvironment to improve microbial infection prevention and treatment.

Potential Facilitation Between a Commensal and a Pathogenic Microbe in a Wildlife Disease

We assessed the potential for microbial interactions influencing a well-documented host-pathogen system. Mycoplasma agassizii is the known etiological agent of upper respiratory tract disease in Mojave desert tortoises (Gopherus agassizii), but disease in wild animals is extremely heterogeneous. For example, a much larger proportion of animals harbor M. agassizii than those that develop disease. With the availability of a new quantitative PCR assay for a microbe that had previously been implicated in disease, Pasteurella testudinis, we tested 389 previously collected samples of nasal microbes from tortoise populations across the Mojave desert. We showed that P. testudinis is a common commensal microbe. However, we did find that its presence was associated with higher levels of M. agassizii among the tortoises positive for this pathogen. The best predictor of P. testudinis prevalence in tortoise populations was average size of tortoises, suggesting that older populations have higher levels of P. testudinis. The prevalence of co-infection in populations was associated with the prevalence of URTD, providing additional evidence for an indirect interaction between the two microbes and inflammatory disease. We showed that URTD, like many chronic, polymicrobial diseases involving mucosal surfaces, shows patterns of a polymicrobial etiology.

Dual species biofilms are enhanced by metabolite cross-feeding

Enterococcus faecalis and Staphylococcus aureus are frequently co-isolated from biofilm-associated infections. A new study by Ch'ng et al. revealed that S. aureus-released heme feeds E. faecalis respiration, augmenting E. faecalis growth and overall biofilm biomass. Their finding further supports the theory that metabolite cross-feeding is a critical aspect shaping polymicrobial biofilm interactions.

Skeletal infections: microbial pathogenesis, immunity and clinical management

Osteomyelitis remains one of the greatest risks in orthopaedic surgery. Although many organisms are linked to skeletal infections, Staphylococcus aureus remains the most prevalent and devastating causative pathogen. Important discoveries have uncovered novel mechanisms of S. aureus pathogenesis and persistence within bone tissue, including implant-associated biofilms, abscesses and invasion of the osteocyte lacuno-canalicular network. However, little clinical progress has been made in the prevention and eradication of skeletal infection as treatment algorithms and outcomes have only incrementally changed over the past half century. In this Review, we discuss the mechanisms of persistence and immune evasion in S. aureus infection of the skeletal system as well as features of other osteomyelitis-causing pathogens in implant-associated and native bone infections. We also describe how the host fails to eradicate bacterial bone infections, and how this new information may lead to the development of novel interventions. Finally, we discuss the clinical management of skeletal infection, including osteomyelitis classification and strategies to treat skeletal infections with emerging technologies that could translate to the clinic in the future.

Competition between Pseudomonas aeruginosa and Staphylococcus aureus is dependent on intercellular signaling and regulated by the NtrBC two-component system

Pseudomonas aeruginosa and Staphylococcus aureus are often comorbid human pathogens, isolated from expectorated sputum of cystic fibrosis patients and chronically infected wounds. Prior studies revealed a competitive advantage of P. aeruginosa over S. aureus in vitro that was slightly muted in vivo. Here, we demonstrated that the two-component regulatory system NtrBC influences the competitive advantage of P. aeruginosa over S. aureus in skin organoid and mouse models of co-infection. Expression of ntrBC was induced during co-culture of the two species and could be recapitulated in monoculture by the addition of the metabolite N-acetylglucosamine that is released from S. aureus following lysis. P. aeruginosa LESB58 WT, but not mutant (ΔntrC and ΔntrBC) strains, induced lysis of S. aureus USA300 LAC during planktonic growth and outcompeted S. aureus USA300 LAC during biofilm formation in vitro. We confirmed these findings in a murine abscess model of high-density infection. Accordingly, the secretory profile of P. aeruginosa LESB58 mutants revealed reduced production of anti-staphylococcal virulence factors including pyoverdine, pyocyanin and elastase. These phenotypes of LESB58 ΔntrBC could be at least partly complemented by overexpression of quorum sensing molecules including homoserine lactones or alkylquinolone signaling molecules. These data implicate the NtrBC two-component system in the complex regulatory cascade triggered by interspecies signaling that gives P. aeruginosa LESB58 a competitive edge over S. aureus USA300 LAC.

Pseudomonas Synergizes with Fluconazole against Candida during Treatment of Polymicrobial Infection

Polymicrobial infections are challenging to treat because we don't fully understand how pathogens interact during infection and how these interactions affect drug efficacy. Candida albicans and Pseudomonas aeruginosa are opportunistic pathogens that can be found in similar sites of infection such as in burn wounds and most importantly in the lungs of CF and mechanically ventilated patients. C. albicans is particularly difficult to treat because of the paucity of antifungal agents, some of which lack fungicidal activity. In this study, we investigated the efficacy of anti-fungal treatment during C. albicans-P. aeruginosa coculture in vitro and co-infection in the mucosal zebrafish infection model analogous to the lung. We find that P. aeruginosa enhances the activity of fluconazole (FLC), an anti-fungal drug that is fungistatic in vitro, to promote both clearance of C. albicans during co-infection in vivo and fungal killing in vitro. This synergy between FLC treatment and bacterial antagonism is partly due to iron piracy, as it is reduced upon iron supplementation and knockout of bacterial siderophores. Our work demonstrates that FLC has enhanced activity in clinically relevant contexts and highlights the need to understand antimicrobial effectiveness in the complex environment of the host with its associated microbial communities.

Molecular Methodologies for Improved Polymicrobial Sepsis Diagnosis

Polymicrobial sepsis is associated with worse patient outcomes than monomicrobial sepsis. Routinely used culture-dependent microbiological diagnostic techniques have low sensitivity, often leading to missed identification of all causative organisms. To overcome these limitations, culture-independent methods incorporating advanced molecular technologies have recently been explored. However, contamination, assay inhibition and interference from host DNA are issues that must be addressed before these methods can be relied on for routine clinical use. While the host component of the complex sepsis host–pathogen interplay is well described, less is known about the pathogen’s role, including pathogen–pathogen interactions in polymicrobial sepsis. This review highlights the clinical significance of polymicrobial sepsis and addresses how promising alternative molecular microbiology methods can be improved to detect polymicrobial infections. It also discusses how the application of shotgun metagenomics can be used to uncover pathogen/pathogen interactions in polymicrobial sepsis cases and their potential role in the clinical course of this condition.

Rapid DNA visual detection of polymicrobial bloodstream infection using filter paper

Bloodstream infection (BSI) is a major complication in patients with cancers due to therapy-induced neutropenia and underlying conditions, which increases hospitalization time and mortality rate. Targeted and timely antimicrobial management is crucial to save the patients’ lives and reduce the social and economic burdens. Blood culture is a routine clinical diagnostic method of BSI with a long turnaround time, and generally identifies monomicrobial BSI. Thus, polymicrobial BSI often goes undetected although it occurs more frequently in these patients and results in more severe outcomes compared to monomicrobial BSI. In this work, we apply glutaric anhydride, N-hydroxysuccinimide and N,N′-dicyclohexylcarbodiimide to fabricate a functional surface on cellulose filter paper. Targeting three pathogens (Escherichia coli, Saccharomyces cerevisiae, and human cytomegalovirus) commonly occurring in BSI in neutropenic patients, we demonstrate rapid and accurate triplex pathogen DNA detection using the functionalized paper. All three pathogen DNA was identified in 1–5 min with a detection limit of 0.1–0.5 ng/µL. The developed test tool has the potential to provide rapid polymicrobial BSI diagnosis in support of timely, accurate antimicrobial treatment, and could be integrated into an automatic sample-to-result portable equipment.

A critical analysis of research methods and experimental models to study intracanal medicaments

In order to ensure predictable decontamination of the root canal system, chemo-mechanical preparation of the root canal space is sometimes supplemented with the use of intracanal medication. As microbial control of the root canal space is fundamental to the resolution of apical periodontitis, root canal disinfection strategies haven been researched intensively. The use of intracanal medication as a supplementary step to the chemo-mechanical preparation of the root canal space is one of them. Because of the costs and limitations of clinical research it is relevant and common practice to first evaluate alternative or new root canal disinfection modalities in laboratory studies. This involves the simulation of a root canal infection in a laboratory model, on which different disinfection strategies can be tested. When modelling the infected root canal, different levels of infection can be discriminated: suspended bacteria, microbial biofilms and infected dentine. This review describes the experimental models associated with these infection levels and critically appraises their value and methodological details. Suggestions for relevant research methods and experimental models are given, as well as some good practices for laboratory-based microbiological studies.

Metabolic Adaptations During Staphylococcus aureus and Candida albicans Co-Infection

Successful pathogens require metabolic flexibility to adapt to diverse host niches. The presence of co-infecting or commensal microorganisms at a given infection site can further influence the metabolic processes required for a pathogen to cause disease. The Gram-positive bacterium Staphylococcus aureus and the polymorphic fungus Candida albicans are microorganisms that asymptomatically colonize healthy individuals but can also cause superficial infections or severe invasive disease. Due to many shared host niches, S. aureus and C. albicans are frequently co-isolated from mixed fungal-bacterial infections. S. aureus and C. albicans co-infection alters microbial metabolism relative to infection with either organism alone. Metabolic changes during co-infection regulate virulence, such as enhancing toxin production in S. aureus or contributing to morphogenesis and cell wall remodeling in C. albicans. C. albicans and S. aureus also form polymicrobial biofilms, which have greater biomass and reduced susceptibility to antimicrobials relative to mono-microbial biofilms. The S. aureus and C. albicans metabolic programs induced during co-infection impact interactions with host immune cells, resulting in greater microbial survival and immune evasion. Conversely, innate immune cell sensing of S. aureus and C. albicans triggers metabolic changes in the host cells that result in an altered immune response to secondary infections. In this review article, we discuss the metabolic programs that govern host-pathogen interactions during S. aureus and C. albicans co-infection. Understanding C. albicans-S. aureus interactions may highlight more general principles of how polymicrobial interactions, particularly fungal-bacterial interactions, shape the outcome of infectious disease. We focus on how co-infection alters microbial metabolism to enhance virulence and how infection-induced changes to host cell metabolism can impact a secondary infection.

On the Offensive: the Role of Outer Membrane Vesicles in the Successful Dissemination of New Delhi Metallo-β-lactamase (NDM-1)

The emergence and worldwide dissemination of carbapenemase-producing Gram-negative bacteria are a major public health threat. Metallo-β-lactamases (MBLs) represent the largest family of carbapenemases. Regrettably, these resistance determinants are spreading worldwide. Among them, the New Delhi metallo-β-lactamase (NDM-1) is experiencing the fastest and largest geographical spread. NDM-1 β-lactamase is anchored to the bacterial outer membrane, while most MBLs are soluble, periplasmic enzymes. This unique cellular localization favors the selective secretion of active NDM-1 into outer membrane vesicles (OMVs). Here, we advance the idea that NDM-containing vesicles serve as vehicles for the local dissemination of NDM-1. We show that OMVs with NDM-1 can protect a carbapenem-susceptible strain of Escherichia coli upon treatment with meropenem in a Galleria mellonella infection model. Survival curves of G. mellonella revealed that vesicle encapsulation enhances the action of NDM-1, prolonging and favoring bacterial protection against meropenem inside the larva hemolymph. We also demonstrate that E. coli cells expressing NDM-1 protect a susceptible Pseudomonas aeruginosa strain within the larvae in the presence of meropenem. By using E. coli variants engineered to secrete variable amounts of NDM-1, we demonstrate that the protective effect correlates with the amount of NDM-1 secreted into vesicles. We conclude that secretion of NDM-1 into OMVs contributes to the survival of otherwise susceptible nearby bacteria at infection sites. These results disclose that OMVs play a role in the establishment of bacterial communities, in addition to traditional horizontal gene transfer mechanisms.

Prospective assessment of catheter-associated bacteriuria clinical presentation, epidemiology, and colonization dynamics in nursing home residents

BACKGROUND

Catheterization facilitates continuous bacteriuria, for which the clinical significance remains unclear. This study aimed to determine the clinical presentation, epidemiology, and dynamics of bacteriuria in a cohort of long-term catheterized nursing home residents.

METHODS

Prospective urine culture, urinalysis, chart review, and assessment of signs and symptoms of infection were performed weekly for 19 study participants over 7 months. All bacteria ≥ 1 × 10³ cfu/mL were cultured, isolated, identified, and tested for susceptibility to select antimicrobials.

RESULTS

In total, 226 of the 234 urine samples were polymicrobial (97%), with an average of 4.7 isolates per weekly specimen. A total of 228 urine samples (97%) exhibited ≥ 1 × 10⁶ CFU/mL, 220 (94%) exhibited abnormal urinalysis, 126 (54%) were associated with at least 1 possible sign or symptom of infection, and 82 (35%) would potentially meet a standardized definition of catheter-associated urinary tract infection (CAUTI), but only 3 had a caregiver diagnosis of CAUTI. Bacterial isolates (286; 30%) were resistant to a tested antimicrobial agent, and bacteriuria composition was remarkably stable despite a combined total of 54 catheter changes and 23 weeks of antimicrobial use.

CONCLUSION

Bacteriuria composition was largely polymicrobial, including persistent colonization by organisms previously considered to be urine culture contaminants. Neither antimicrobial use nor catheter changes sterilized the urine, at most resulting in transient reductions in bacterial burden followed by new acquisition of resistant isolates. Thus, this patient population exhibits a high prevalence of bacteriuria coupled with potential indicators of infection, necessitating further exploration to identify sensitive markers of true infection.

FUNDING

This work was supported by the NIH (R00 DK105205, R01 DK123158, UL1 TR001412).

Stimuli-Responsive Nanoplatform-Assisted Photodynamic Therapy Against Bacterial Infections

Bacterial infections are common diseases causing tremendous deaths in clinical settings. It has been a big challenge to human beings because of the antibiotics abuse and the newly emerging microbes. Photodynamic therapy (PDT) is a reactive oxygen species-based therapeutic technique through light-activated photosensitizer (PS). Recent studies have highlighted the potential of PDT as an alternative method of antibacterial treatment for its broad applicability and high efficiency. However, there are some shortcomings due to the low selectivity and specificity of PS. Growing evidence has shown that drug delivery nanoplatforms have unique advantages in enhancing therapeutic efficacy of drugs. Particularly, stimuli-responsive nanoplatforms, as a promising delivery system, provide great opportunities for the effective delivery of PS. In the present mini-review, we briefly introduced the unique microenvironment in bacterial infection tissues and the application of PDT on bacterial infections. Then we review the stimuli-responsive nanoplatforms (including pH-, enzymes-, redox-, magnetic-, and electric-) used in PDT against bacterial infections. Lastly, some perspectives have also been proposed to further promote the future developments of antibacterial PDT.

Metagenomic evidence for a polymicrobial signature of sepsis

Our understanding of the host component of sepsis has made significant progress. However, detailed study of the microorganisms causing sepsis, either as single pathogens or microbial assemblages, has received far less attention. Metagenomic data offer opportunities to characterize the microbial communities found in septic and healthy individuals. In this study we apply gradient-boosted tree classifiers and a novel computational decontamination technique built upon SHapley Additive exPlanations (SHAP) to identify microbial hallmarks which discriminate blood metagenomic samples of septic patients from that of healthy individuals. Classifiers had high performance when using the read assignments to microbial genera [area under the receiver operating characteristic (AUROC=0.995)], including after removal of species ‘culture-confirmed’ as the cause of sepsis through clinical testing (AUROC=0.915). Models trained on single genera were inferior to those employing a polymicrobial model and we identified multiple co-occurring bacterial genera absent from healthy controls. While prevailing diagnostic paradigms seek to identify single pathogens, our results point to the involvement of a polymicrobial community in sepsis. We demonstrate the importance of the microbial component in characterising sepsis, which may offer new biological insights into the aetiology of sepsis, and ultimately support the development of clinical diagnostic or even prognostic tools.

Mutual interaction of microbiota and host immunity during health and diseases

Microbiota-host interaction has attracted more and more attentions in recent years. The association between microbiota and host health is largely attributed to its influence on host immune system. Microbial-derived antigens and metabolites play a critical role in shaping the host immune system, including regulating its development, activation, and function. However, during various diseases the microbiota-host communication is frequently found to be disordered. In particular, gut microbiota dysbiosis associated with or led to the occurrence and progression of infectious diseases, autoimmune diseases, metabolic diseases, and neurological diseases. Pathogenic microbes and their metabolites disturb the protective function of immune system, and lead to disordered immune responses that usually correlate with disease exacerbation. In the other hand, the immune system also regulates microbiota composition to keep host homeostasis. Here, we will discuss the current advances of our knowledge about the interactions between microbiota and host immune system during health and diseases.

In Vitro Reduction of Interleukin-8 Response to Enterococcus faecalis by Escherichia coli Strains Isolated from the Same Polymicrobial Urines

Urinary tract infections are often polymicrobial and are mainly due to uropathogenic Escherichia coli (UPEC). We previously demonstrated a link among clinical fluoroquinolone susceptible E. coli reducing in vitro urothelial interleukin-8 (CXCL8) induced by E. coli K-12, polymicrobial cystitis, and pyuria absence. Here, we evaluated whether fifteen clinical fluoroquinolone susceptible UPEC were able to reduce CXCL8 induced by Enterococcus faecalis that had been isolated from the same mixed urines, other than CXCL8 induced by E. coli K-12. We also evaluated the connection between fluoroquinolone susceptibility and pathogenicity by evaluating the immune modulation of isogenic gyrA, a mutant UPEC resistant to ciprofloxacin. Using the 5637 bladder epithelial cell line, we observed that lower CXCL8 induced the most UPEC isolates than K-12 and the corresponding E. faecalis. During coinfections of UPEC/K-12 and UPEC/E. faecalis, we observed lower CXCL8 than during infections caused by K-12 and E. faecalis alone. UPEC strains showed host–pathogen and pathogen–pathogen interaction, which in part explained their persistence in the human urinary tract and coinfections, respectively. Mutant UPEC showed lower modulating activity with respect to the wildtypes, confirming the connection between acquired fluoroquinolone resistance and the decrease of innate microbial properties.

Friends or enemies? The complicated relationship between Pseudomonas aeruginosa and Staphylococcus aureus

Pseudomonas aeruginosa (Pa) and Staphylococcus aureus (Sa) are opportunistic pathogens that are most commonly co-isolated from chronic wounds and the sputum of cystic fibrosis patients. Over the last few years, there have been plenty of contrasting results from studies involving P. aeruginosa and S. aureus co-cultures. The general concept that P. aeruginosa outcompetes S. aureus has been challenged and there is more evidence now that they can co-exist. Nevertheless, it still remains difficult to mimic polymicrobial infections in vitro and in vivo. In this review, we discuss recent advances in regard to Pa-Sa molecular interactions, their physical responses, and in vitro and in vivo models. We believe it is important to optimize growth conditions in the laboratory, determine appropriate bacterial starting ratios, and consider environmental factors to study the co-existence of these two pathogens. Ideally, optimized growth media should reflect host-mimicking conditions with or without host cells that allow both bacteria to co-exist. To further identify mechanisms that could help to treat these complex infections, we propose to use relevant polymicrobial animal models. Ultimately, we briefly discuss how polymicrobial infections can increase antibiotic tolerance.

Fusobacteriumnucleatum Adheres to Clostridioides difficile via the RadD Adhesin to Enhance Biofilm Formation in Intestinal Mucus

BACKGROUND & AIMS

Although Clostridioides difficile infection (CDI) is known to involve the disruption of the gut microbiota, little is understood regarding how mucus-associated microbes interact with C difficile. We hypothesized that select mucus-associated bacteria would promote C difficile colonization and biofilm formation.

METHODS

To create a model of the human intestinal mucus layer and gut microbiota, we used bioreactors inoculated with healthy human feces, treated with clindamycin and infected with C difficile with the addition of human MUC2-coated coverslips.

RESULTS

C difficile was found to colonize and form biofilms on MUC2-coated coverslips, and 16S rRNA sequencing showed a unique biofilm profile with substantial cocolonization with Fusobacterium species. Consistent with our bioreactor data, publicly available data sets and patient stool samples showed that a subset of patients with C difficile infection harbored high levels of Fusobacterium species. We observed colocalization of C difficile and F nucleatum in an aggregation assay using adult patients and stool of pediatric patients with inflammatory bowel disease and in tissue sections of patients with CDI. C difficile strains were found to coaggregate with F nucleatum subspecies in vitro; an effect that was inhibited by blocking or mutating the adhesin RadD on Fusobacterium and removal of flagella on C difficile. Aggregation was shown to be unique between F nucleatum and C difficile, because other gut commensals did not aggregate with C difficile. Addition of F nucleatum also enhanced C difficile biofilm formation and extracellular polysaccharide production.

CONCLUSIONS

Collectively, these data show a unique interaction of between pathogenic C difficile and F nucleatum in the intestinal mucus layer.

Polymicrobial interactions in the urinary tract: is the enemy of my enemy my friend?

The vast majority of research pertaining to urinary tract infection has focused on a single pathogen in isolation, and predominantly Escherichia coli. However, polymicrobial urine colonization and infection are prevalent in several patient populations, including individuals with urinary catheters. The progression from asymptomatic colonization to symptomatic infection and severe disease is likely shaped by interactions between traditional pathogens as well as constituents of the normal urinary microbiota. Recent studies have begun to experimentally dissect the contribution of polymicrobial interactions to disease outcomes in the urinary tract, including their role in development of antimicrobial-resistant biofilm communities, modulating the innate immune response, tissue damage, and sepsis. This review aims to summarize the epidemiology of polymicrobial urine colonization, provide an overview of common urinary tract pathogens, and present key microbe-microbe and host-microbe interactions that influence infection progression, persistence, and severity.

The Immune System Fails to Mount a Protective Response to Gram-Positive or Gram-Negative Bacterial Prostatitis

Bacterial prostatitis affects 1% of men, with increased incidence in the elderly. Acute bacterial prostatitis frequently progresses to chronicity, marked by recurrent episodes interspersed with asymptomatic periods of variable duration. Antibiotic treatment is standard of care; however, dissemination of antimicrobially resistant uropathogens threatens therapy efficacy. Thus, development of nonantibiotic-based approaches to treat chronic disease is a priority. Currently, why chronic prostatitis arises is unclear, as the immune response to prostate infection is incompletely understood. As 80% of prostatitis cases are caused by Gram-negative uropathogenic Escherichia coli (UPEC) or Gram-positive Enterococcus faecalis, we used a mouse transurethral instillation model to address the hypothesis that an innate immune response fails to develop following prostate infection with these uropathogens, leading to chronic disease. Surprisingly, infection induced robust proinflammatory cytokine expression and myeloid cell infiltration. Following a second infection, cytokine responses and innate cell infiltration were largely comparable to primary infection. Characteristic of memory responses, more lymphoid cells infiltrated the prostate in a second infection compared with a first, suggesting that adaptive immunity develops to eliminate the pathogens. Unexpectedly, bacterial burden in prostates challenged with either UPEC or E. faecalis was equal or greater than primary infection despite that a protective adaptive response to UPEC infection was evident in the bladder of the same animals. Our findings support that chronic or recurrent prostatitis develops despite strong innate immune responses and may be the result of a failure to develop immune memory to infection, pointing to actionable targets for immunotherapy.

Concurrent infection of intestinal parasites and Helicobacter pylori among school-age children in Central Ethiopia

Background

Coinfection of multiple intestinal microbial pathogens plays an important role in individuals harboring these organisms. However, data on magnitude and risk factors are scarce from resource limited settings.

Objective

We examined the prevalence and associated risk factors of intestinal parasites and Helicobacter pylori co-infection among young Ethiopian school children.

Method

Data from a total of 434 Ethiopian school children from the Ziway region were analyzed in the study. Stool antigen and blood serum antibody tests were used to detect H. pylori, while the presence of any intestinal parasites was detected using direct wet mount microscopy and formol-ether concentration techniques. A structured questionnaire was delivered to mothers and legal guardians of the children by an interviewer to collect data relevant demographic and lifestyle factors. Multivariate logistic regression analysis was performed to assess the association of these sociodemographic characteristics with the coinfection of H. pylori and intestinal parasites.

Results

The prevalence of coinfection with any intestinal parasites and Helicobacter pylori was 23.0% (n = 92/400). Univariate analysis showed an increased risk for co-infection among children whose mothers had non-formal education (COR: 1.917, p < 0.01) and those who had no history of child vaccination (COR: 3.455, p = 0.084). Children aged 10–14 and those who lived in a house that had a flush or ventilated latrine were found at lower odds of coinfection between intestinal parasites and Helicobacter pylori (COR: 0.670, p = 0.382; COR: 0.189, p = 0.108). Multivariate regression analysis showed increased odds of co-infection among children whose mothers had non-formal education (AOR: 1.978, p < 0.01). Maternal education was also associated with a two-fold increase in odds for H. pylori and any protozoa co-infection (AOR: 2.047, p < 0.01).

Conclusion

Our study shows a moderate prevalence of H. pylori and intestinal parasite co-infection and identified maternal education as a significant risk factor among school children.

Characterization of baseline polybacterial versus monobacterial infections in three randomized controlled bacterial conjunctivitis trials and microbial outcomes with besifloxacin ophthalmic suspension 0.6

Background/Purpose

To date, studies examining polymicrobial infections in ocular disease have mostly been limited to keratitis or endophthalmitis. We characterized polybacterial infections compared to monobacterial infections in prior clinical studies evaluating besifloxacin ophthalmic suspension 0.6% for the treatment of bacterial conjunctivitis and report on associated microbiological outcomes.

Methods

In this post-hoc analysis, microbiological data for subjects with conjunctivitis due to one or more than one bacterial species in three previous studies (two vehicle-, one active-controlled) of besifloxacin were extracted. Bacterial species identified at baseline were deemed causative if their colony count equaled or exceeded species-specific prespecified threshold criteria. In subjects with polybacterial infections, the fold-increase over threshold was used to rank order the contribution of individual species. Baseline pathogens and their minimum inhibitory concentrations (MICs) for common ophthalmic antibiotics were compared by infection type, as were microbial eradication rates following treatment with besifloxacin.

Results

Of 1041 subjects with culture-confirmed conjunctivitis, 17% had polybacterial and 83% had monobacterial conjunctivitis at baseline. In polybacterial compared to monobacterial infections, Haemophilus influenzae and Streptococcus pneumoniae were identified less frequently as the dominant infecting species (P = 0.042 and P<0.001, respectively), whereas Streptococcus mitis/S. mitis group was identified more frequently as dominant (P<0.001). Viral coinfection was also identified more frequently in polybacterial infections (P<0.001). Staphylococcus aureus was the most common coinfecting species in polybacterial infections and the second most common dominant species in such infections. With few exceptions, MICs for individual species were comparable regardless of infection type. Clinical microbial eradication rates with besifloxacin were high regardless of infection type (P≤0.016 vs vehicle at follow-up visits).

Conclusions

Approximately one in five subjects with bacterial conjunctivitis are infected with more than one bacterial species underscoring the need for a broad-spectrum antibiotic for such infections. Besifloxacin treatment resulted in robust eradication rates of these infections comparable to monobacterial infections.

Trial registration

NCT000622908, NCT00347932, NCT00348348

Efficacy of Lytic Phage Cocktails on Staphylococcus aureus and Pseudomonas aeruginosa in Mixed-Species Planktonic Cultures and Biofilms

The efficacy of phages in multispecies infections has been poorly examined. The in vitro lytic efficacies of phage cocktails AB-SA01, AB-PA01, which target Staphylococcus aureus and Pseudomonas aeruginosa, respectively, and their combination against their hosts were evaluated in S. aureus and P. aeruginosa mixed-species planktonic and biofilm cultures. Green fluorescent protein (GFP)-labelled P. aeruginosa PAO1 and mCherry-labelled S. aureus KUB7 laboratory strains and clinical isolates were used as target bacteria. During real-time monitoring using fluorescence spectrophotometry, the density of mCherry S. aureus KUB7 and GFP P. aeruginosa PAO1 significantly decreased when treated by their respective phage cocktail, a mixture of phage cocktails, and gentamicin. The decrease in bacterial density measured by relative fluorescence strongly associated with the decline in bacterial cell counts. This microplate-based mixed-species culture treatment monitoring through spectrophotometry combine reproducibility, rapidity, and ease of management. It is amenable to high-throughput screening for phage cocktail efficacy evaluation. Each phage cocktail, the combination of the two phage cocktails, and tetracycline produced significant biofilm biomass reduction in mixed-species biofilms. This study result shows that these phage cocktails lyse their hosts in the presence of non-susceptible bacteria. These data support the use of phage cocktails therapy in infections with multiple bacterial species.