is a Gram-negative bacterium found ubiquitously in the environment that has historically been regarded as nonpathogenic.
is increasingly observed in patient sputa in cystic fibrosis (CF), and while ...existing epidemiology indicates that patients with
have poorer diagnoses, its clinical significance remains unclear. Moreover, as multidrug resistance is common among
isolates, treatment options for these infections may be limited. Here, we investigated the pathogenicity of
alone and during polymicrobial infection with
Colonization, persistence, and virulence of
were assessed in experimental respiratory infections of mice. The results of this study indicate that
transiently colonizes the lung accompanied by significant weight loss and immune cell infiltration and the expression of early inflammatory markers, including interleukin 6 (IL-6), IL-1α, and tumor necrosis factor alpha (TNF-α). Importantly, polymicrobial infection with
elicited significantly higher
counts in bronchoalveolar lavages and lung tissue homogenates. This increase in bacterial load was directly correlated with the density of the
population and required viable
bacteria. Microscopic analysis of biofilms formed
revealed that
formed well-integrated biofilms with
, and these organisms colocalize in the lung during dual-species infection. Based on these results, we conclude that active cellular processes by
afford a significant benefit to
during polymicrobial infections. Furthermore, these results indicate that
may have clinical significance in respiratory infections.
Bacterial vaginosis (BV) is the most common cause of vaginal discharge. It is associated with an increased risk of preterm delivery, pelvic inflammatory disease, and an increased risk of acquisition ...of sexually transmitted infections including human immunodeficiency virus (HIV). The epidemiology of BV supports sexual transmission. However, its etiology remains unknown. At the center of the debate is whether BV is caused by a primary pathogen or a polymicrobial consortium of microorganisms that are sexually transmitted. We previously published a conceptual model hypothesizing that BV is initiated by sexual transmission of Gardnerella vaginalis. Critics of this model have iterated that G. vaginalis is found in virginal women and in sexually active women with a normal vaginal microbiota. In addition, colonization does not always lead to BV. However, recent advances in BV pathogenesis research have determined the existence of 13 different species within the genus Gardnerella. It may be that healthy women are colonized by nonpathogenic Gardnerella species, whereas virulent strains are involved in BV development. Based on our results from a recent prospective study, in addition to an extensive literature review, we present an updated conceptual model for the pathogenesis of BV that centers on the roles of virulent strains of G. vaginalis, as well as Prevotella bivia and Atopobium vaginae.
B-1 cells produce natural Abs which provide an integral first line of defense against pathogens while also performing important homeostatic housekeeping functions. In this study, we demonstrate that ...programmed cell death 1 ligand 2 (PD-L2) regulates the production of natural Abs against phosphorylcholine (PC). Naive PD-L2-deficient (PD-L2
) mice produced significantly more PC-reactive IgM and IgA. This afforded PD-L2
mice with selectively enhanced protection against PC-expressing nontypeable
, but not PC-negative nontypeable
, relative to wild-type mice. PD-L2
mice had significantly increased PC-specific CD138
splenic plasmablasts bearing a B-1a phenotype, and produced PC-reactive Abs largely of the T15 Id. Importantly, PC-reactive B-1 cells expressed PD-L2 and irradiated chimeras demonstrated that B cell-intrinsic PD-L2 expression regulated PC-specific Ab production. In addition to increased PC-specific IgM, naive PD-L2
mice and irradiated chimeras reconstituted with PD-L2
B cells had significantly higher levels of IL-5, a potent stimulator of B-1 cell Ab production. PD-L2 mAb blockade of wild-type B-1 cells in culture significantly increased CD138 and Blimp1 expression and PC-specific IgM, but did not affect proliferation. PD-L2 mAb blockade significantly increased IL-5
T cells in culture. Both IL-5 neutralization and STAT5 inhibition blunted the effects of PD-L2 mAb blockade on B-1 cells. Thus, B-1 cell-intrinsic PD-L2 expression inhibits IL-5 production by T cells and thereby limits natural Ab production by B-1 cells. These findings have broad implications for the development of therapeutic strategies aimed at altering natural Ab levels critical for protection against infectious disease, autoimmunity, allergy, cancer, and atherosclerosis.
is a Gram-negative emerging opportunistic pathogen often present in people with respiratory diseases such as cystic fibrosis (CF). People with CF (pwCF) experience lifelong polymicrobial infections ...of the respiratory mucosa. Our prior work showed that
promotes persistence of
in mouse respiratory infections. As is typical for environmental opportunistic pathogens,
has a large genome and a high degree of genetic diversity. In this study, we evaluated the genomic content of
combining short and long read sequencing to construct nearly complete genomes of 10 clinical isolates. The genomes of these isolates were then compared with all publicly available
genome assemblies, and each isolate was then evaluated for colonization/persistence
, both alone and in coinfection with
. We found that while the overall genome size and GC content were fairly consistent between strains, there was considerable variability in both genome structure and gene content. Similarly, there was significant variability in
colonization and persistence in experimental mouse respiratory infections in the presence or absence of
. Ultimately, this study gives us a greater understanding of the genomic diversity of clinical
isolates, and how this genomic diversity relates to both interactions with other pulmonary pathogens and to host disease progression. Identifying the molecular determinants of infection with
can facilitate development of novel antimicrobial strategies for a highly drug-resistant pathogen.
Patients with cystic fibrosis (CF) experience lifelong respiratory infections, which are a significant cause of morbidity and death. These infections are polymicrobial in nature, and the predominant ...bacterial species undergo a predictable series of changes as patients age. Young patients have populations dominated by opportunists that are typically found within the microbiome of the human nasopharynx, such as nontypeable Haemophilus influenzae (NTHi); these are eventually supplanted, and the population within the CF lung is later dominated by pathogens such as Pseudomonas aeruginosa. In this study, we investigated how initial colonization with NTHi impacts colonization and persistence of P. aeruginosa in the respiratory tract. Analysis of polymicrobial biofilms
by confocal microscopy revealed that NTHi promoted greater P. aeruginosa biofilm volume and diffusion. However, sequential respiratory infection of mice with NTHi followed by P. aeruginosa resulted in significantly lower levels of P. aeruginosa, compared to infection with P. aeruginosa alone. Coinfected mice also had reduced airway tissue damage and lower levels of inflammatory cytokines, compared with P. aeruginosa-infected mice. Similar results were observed after instillation of heat-inactivated NTHi bacteria or purified NTHi lipooligosaccharide endotoxin prior to P. aeruginosa introduction. Based on these results, we conclude that NTHi significantly reduces susceptibility to subsequent P. aeruginosa infection, most likely due to priming of host innate immunity rather than a direct competitive interaction between species. These findings have potential significance with regard to therapeutic management of early-life infections in patients with CF.
is a nutritionally fastidious, Gram-negative bacterium with an oropharyngeal/nasopharyngeal carriage niche that is associated with a range of opportunistic infections, including infectious ...endocarditis and otitis media (OM). These infections are often chronic/recurrent in nature and typically involve bacterial persistence within biofilm communities that are highly resistant to host clearance. This study addresses the primary hypothesis that
forms biofilm communities that are important determinants of persistence
The results from
biofilm studies confirmed that
formed biofilm communities within which the polymeric matrix was mainly composed of extracellular DNA and proteins. Using a chinchilla OM infection model, we demonstrated that
formed surface-associated biofilm communities containing bacterial and host components that included neutrophil extracellular trap (NET) structures and that the bacteria mainly persisted in these biofilm communities. We also used this model to examine the possible interaction between
and its close relative
, which is also commonly carried within the same host environments and can cause OM. The results showed that coinfection with
promoted clearance of
from biofilm communities during OM infection. The underlying mechanisms for bacterial persistence and biofilm formation by
and knowledge about the survival defects of
during coinfection with
are topics for future work.
Like many pathogens inhabiting mucosal surfaces, nontypeable Haemophilus influenzae (NTHi) forms multicellular biofilm communities both in vitro and in various infection models. In the past 15 years ...much has been learned about determinants of biofilm formation by this organism and potential roles in bacterial virulence, especially in the context of chronic and recurrent infections. However, this concept has not been without some degree of controversy, and in the past some have expressed doubts about the relevance of NTHi biofilms to disease. In this review, I will summarize the present information on the composition and potential role(s) of NTHi biofilms in different clinical contexts, as well as highlight potential areas for future work.
Cystic fibrosis (CF) is a genetic disorder affecting epithelial ion transport, which among other impacts results in defective mucociliary clearance and innate defenses in the respiratory tract. ...Consequently, people with CF experience lifelong infections of the respiratory mucosa that are chronic and polymicrobial in nature. Young children with CF are initially colonized by opportunists like nontypeable
(NTHi), which normally resides within the microbiome of the nasopharynx and upper airways and can also cause infections of the respiratory mucosa that include bronchitis and otitis media. NTHi is typically supplanted by other microbes as patients age; for example, people with CF are often chronically infected with mucoid strains of
, which prior work in our laboratory has shown to promote colonization and persistence by other opportunists that include
. Our previous work has shown that polymicrobial infection impacts host colonization and persistence of incoming microbes via diverse mechanisms that include priming of host immunity that can promote microbial clearance, and cooperativity within polymicrobial biofilms, which can promote persistence. In infection studies with BALB/c Cftr
mice, results showed, as previously observed for WT BALB/c mice, preceding infection with NTHi decreased colonization and persistence by
. Likewise, polymicrobial infection of BALB/c Cftr
and C57BL/6 Cftr
(FABPhCFTR)1Jaw/J mice showed correlation between
and
, with increased bacterial colonization and lung pathology. Based on these results, we conclude that our previous observations regarding polymicrobial infections with CF opportunists in WT mice are also validated using CF mice.
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.
Cystic fibrosis (CF) is a genetic disease affecting epithelial ion transport, resulting in thickened mucus and impaired mucociliary clearance. Persons with CF (pwCF) experience life-long infections ...of the respiratory mucosa caused by a diverse array of opportunists, which are leading causes of morbidity and mortality. In recent years, there has been increased appreciation for the range and diversity of microbes causing CF-related respiratory infections. The introduction of new therapeutics and improved detection methodology has revealed CF-related opportunists such as
(
).
is a Gram-negative bacterial species which is widely distributed in environmental sources and has been increasingly observed in sputa and other samples from pwCF, typically in patients in later stages of CF disease. In this study, we characterized CF clinical isolates of
and tested colonization and persistence of
in respiratory infection using immortalized human CF respiratory epithelial cells and BALB/c mice. Genomic analyses of clinical
isolates showed homologs for factors including flagellar synthesis, antibiotic resistance, and toxin secretion systems.
isolates adhered to polarized cultures of CFBE41o- human immortalized CF bronchial epithelial cells and caused significant cytotoxicity and depolarization of cell layers.
colonized and persisted in mouse lungs for up to 72 h post infection, with inflammatory consequences that include increased neutrophil influx in the lung, lung damage, cytokine production, and mortality. We also identified genes that are differentially expressed in synthetic CF sputum media. Based on these results, we conclude that
is an opportunistic pathogen of significance in CF.
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