Editorial: Rising stars in biofilms 2022

[Excerpt] The emergence of antibiotic-resistant bacteria, including globally-disseminated multidrug-resistant strains, has become one of the most alarming threats for human health. Fundamentally originated by an inadequate use of antibiotics in clinical and nonclinical settings, infections caused by multidrug-resistant bacteria are currently responsible for around two million deaths each year and are estimated to be the cause of death of as many as 10 million people yearly by 2050 (O'Neill, 2016).info:eu-repo/semantics/publishedVersio

Indirect Pathogenicity of Haemophilus influenzae and Moraxella catarrhalis in Polymicrobial Otitis Media Occurs via Interspecies Quorum Signaling

Otitis media (OM) is among the leading diseases of childhood and is caused by opportunists that reside within the nasopharynx, such as Haemophilus influenzae and Moraxella catarrhalis. As with most airway infections, it is now clear that OM infections involve multiple organisms. This study addresses the hypothesis that polymicrobial infection alters the course, severity, and/or treatability of OM disease. The results clearly show that coinfection with H. influenzae and M. catarrhalis promotes the increased resistance of biofilms to antibiotics and host clearance. Using H. influenzae mutants with known biofilm defects, these phenotypes were shown to relate to biofilm maturation and autoinducer-2 (AI-2) quorum signaling. In support of the latter mechanism, chemically synthesized AI-2 (dihydroxypentanedione [DPD]) promoted increased M. catarrhalis biofilm formation and resistance to antibiotics. In the chinchilla infection model of OM, polymicrobial infection promoted M. catarrhalis persistence beyond the levels seen in animals infected with M. catarrhalis alone. Notably, no such enhancement of M. catarrhalis persistence was observed in animals infected with M. catarrhalis and a quorum signaling-deficient H. influenzae luxS mutant strain. We thus conclude that H. influenzae promotes M. catarrhalis persistence within polymicrobial biofilms via interspecies quorum signaling. AI-2 may therefore represent an ideal target for disruption of chronic polymicrobial infections. Moreover, these results strongly imply that successful vaccination against the unencapsulated H. influenzae strains that cause airway infections may also significantly impact chronic M. catarrhalis disease by removing a reservoir of the AI-2 signal that promotes M. catarrhalis persistence within biofilm

How Often Do Clinically Diagnosed Catheter‐Associated Urinary Tract Infections in Nursing Homes Meet Standardized Criteria?

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136339/1/jgs14533_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136339/2/jgs14533.pd

Arginine promotes Proteus mirabilis motility and fitness by contributing to conservation of the proton gradient and proton motive force

Swarming contributes to Proteus mirabilis pathogenicity by facilitating access to the catheterized urinary tract. We previously demonstrated that 0.1–20 mmol/L arginine promotes swarming on normally nonpermissive media and that putrescine biosynthesis is required for arginine‐induced swarming. We also previously determined that arginine‐induced swarming is pH dependent, indicating that the external proton concentration is critical for arginine‐dependent effects on swarming. In this study, we utilized survival at pH 5 and motility as surrogates for measuring changes in the proton gradient (ΔpH) and proton motive force ( μ H + ) in response to arginine. We determined that arginine primarily contributes to ΔpH (and therefore μ H + ) through the action of arginine decarboxylase ( speA ), independent of the role of this enzyme in putrescine biosynthesis. In addition to being required for motility, speA also contributed to fitness during infection. In conclusion, consumption of intracellular protons via arginine decarboxylase is one mechanism used by P. mirabilis to conserve ΔpH and μ H + for motility. We previously determined that Proteus mirabilis swarming can be initiated under normally nonpermissive conditions in response to cues, such as L‐arginine, and this process requires putrescine biosynthesis or exogenously supplied putrescine. In this study, we describe a mechanism by which P. mirabilis utilizes L‐arginine and arginine decarboxylase (SpeA) for conservation of proton motive force, affecting both motility and fitness independent of the role of this enzyme in putrescine biosynthesis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109334/1/mbo3194.pd

Nontypeable Haemophilus influenzae Initiates Formation of Neutrophil Extracellular Traps▿ †

Nontypeable Haemophilus influenzae (NTHI) is a leading cause of otitis media infections, which are often chronic and/or recurrent in nature. NTHI and other bacterial species persist in vivo within biofilms during otitis media and other persistent infections. These biofilms have a significant host component that includes neutrophil extracellular traps (NETs). These NETs do not mediate clearance of NTHI, which survives within NET structures by means of specific subpopulations of lipooligosaccharides on the bacterial surface that are determinants of biofilm formation in vitro. In this study, the ability of NTHI and NTHI components to initiate NET formation was examined using an in vitro model system. Both viable and nonviable NTHI strains were shown to promote NET formation, as did preparations of bacterial DNA, outer membrane proteins, and lipooligosaccharide (endotoxin). However, only endotoxin from a parental strain of NTHI exhibited equivalent potency in NET formation to that of NTHI. Additional studies showed that NTHI entrapped within NET structures is resistant to both extracellular killing within NETs and phagocytic killing by incoming neutrophils, due to oligosaccharide moieties within the lipooligosaccharides. Thus, we concluded that NTHI elicits NET formation by means of multiple pathogen-associated molecular patterns (most notably endotoxin) and is highly resistant to killing within NET structures. These data support the conclusion that, for NTHI, formation of NET structures may be a persistence determinant by providing a niche within the middle-ear chamber

Role of Bacterial Surface Components in the Pathogenicity of <i>Proteus mirabilis</i> in a Murine Model of Catheter-Associated Urinary Tract Infection

Proteus mirabilis (PM) is a Gram-negative, rod-shaped bacterium that causes catheter-associated urinary tract infections (CAUTIs). The specific roles of bacterial surface components (BSCs) in PM pathogenicity and CAUTIs remain unknown. To address this knowledge gap, we utilized relevant in vitro adhesion/invasion models and a well-established murine model of CAUTI to assess the ability of wildtype (WT) and seven mutant strains (MSs) of PM with deficiencies in various genes encoding BSCs to undergo the infectious process (including adhesion to catheters) in both model systems. Overall, MSs adhesion to catheters and the different cell types tested was significantly reduced compared to WT, while no invasion of cells was evident at 24 h. In vivo, WT showed a greater number of planktonic (urine) bacteria, bacteria adherent to catheters, and bacteria adherent to/invading bladder tissue when compared to the MSs. Bacterial counts in urine for PMI3191 and waaE mutants were lower than that for WT and other MSs. The complementation of mutated BSC genes resulting in the biggest defects restored the invasion phenotype both in vitro and in vivo. BSCs play a critical role at various steps in the pathogenicity of PM including adhesion to indwelling medical devices and adhesion/invasion of urinary tissue in vivo

Arginine promotes Proteus mirabilis

Swarming contributes to Proteus mirabilis pathogenicity by facilitating access to the catheterized urinary tract. We previously demonstrated that 0.1–20 mmol/L arginine promotes swarming on normally nonpermissive media and that putrescine biosynthesis is required for arginine‐induced swarming. We also previously determined that arginine‐induced swarming is pH dependent, indicating that the external proton concentration is critical for arginine‐dependent effects on swarming. In this study, we utilized survival at pH 5 and motility as surrogates for measuring changes in the proton gradient (ΔpH) and proton motive force ( μ H + ) in response to arginine. We determined that arginine primarily contributes to ΔpH (and therefore μ H + ) through the action of arginine decarboxylase ( speA ), independent of the role of this enzyme in putrescine biosynthesis. In addition to being required for motility, speA also contributed to fitness during infection. In conclusion, consumption of intracellular protons via arginine decarboxylase is one mechanism used by P. mirabilis to conserve ΔpH and μ H + for motility. We previously determined that Proteus mirabilis swarming can be initiated under normally nonpermissive conditions in response to cues, such as L‐arginine, and this process requires putrescine biosynthesis or exogenously supplied putrescine. In this study, we describe a mechanism by which P. mirabilis utilizes L‐arginine and arginine decarboxylase (SpeA) for conservation of proton motive force, affecting both motility and fitness independent of the role of this enzyme in putrescine biosynthesis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109334/1/mbo3194.pd

LuxS Promotes Biofilm Maturation and Persistence of Nontypeable Haemophilus influenzae In Vivo via Modulation of Lipooligosaccharides on the Bacterial Surface▿ †

Nontypeable Haemophilus influenzae (NTHI) is an extremely common airway commensal which can cause opportunistic infections that are usually localized to airway mucosal surfaces. During many of these infections, NTHI forms biofilm communities that promote persistence in vivo. For many bacterial species, density-dependent quorum-signaling networks can affect biofilm formation and/or maturation. Mutation of luxS, a determinant of the autoinducer 2 (AI-2) quorum signal pathway, increases NTHI virulence in the chinchilla model for otitis media infections. For example, bacterial counts in middle-ear fluids and the severity of the host inflammatory response were increased in luxS mutants compared with parental strains. As these phenotypes are consistent with those that we have observed for biofilm-defective NTHI mutants, we hypothesized that luxS may affect NTHI biofilms. A luxS mutant was generated using the well-characterized NTHI 86-028NP strain and tested to determine the effects of the mutation on biofilm phenotypes in vitro and bacterial persistence and disease severity during experimental otitis media. Quantitation of the biofilm structure by confocal microscopy and COMSTAT analysis revealed significantly reduced biomass for NTHI 86-028NP luxS biofilms, which was restored by a soluble mediator in NTHI 86-028NP supernatants. Analysis of lipooligosaccharide moieties using an enzyme-linked immunosorbent assay and immunoblotting showed decreased levels of biofilm-associated glycoforms in the NTHI 86-028NP luxS strain. Infection studies showed that NTHI 86-028NP luxS had a significant persistence defect in vivo during chronic otitis media infection. Based on these data, we concluded that a luxS-dependent soluble mediator modulates the composition of the NTHI lipooligosaccharides, resulting in effects on biofilm maturation and bacterial persistence in vivo