Neuraminidase A exposed galactose promotes Streptococcus pneumoniae biofilm formation during colonization.

Streptococcus pneumoniae is an opportunistic pathogen that colonizes the nasopharynx. Herein we show that carbon availability is distinct between the nasopharynx and bloodstream of adult humans: glucose being absent in the nasopharynx whereas galactose being abundant. We demonstrate that pneumococcal neuraminidase A (NanA), which cleaves terminal sialic acid residues from host glycoproteins, exposed galactose on the surface of septal epithelial cells thereby increasing its availability during colonization. We observed that mutants of S. pneumoniae deficient in NanA and β-galactosidase A (BgaA) failed to form biofilms in vivo despite normal biofilm-forming abilities in vitro Subsequently, we observed that glucose, sucrose, and fructose were inhibitory for biofilm formation, whereas galactose, lactose and low concentrations of sialic acid were permissive. Together these findings suggested that the genes involved in biofilm formation were under some form of carbon catabolite repression (CCR), a regulatory network during which genes involved in the uptake and metabolism of less-preferred sugars are silenced during growth with preferred sugars. Supporting this notion, we observed that a mutant deficient in pyruvate oxidase, which converts pyruvate to acetyl-phosphate during non-CCR inducing growth conditions, was unable to form biofilms. Subsequent comparative RNA-seq analyses of planktonic- and biofilm-grown pneumococci showed that metabolic pathways involving the conversion of pyruvate to acetyl-phosphate and subsequently leading to fatty acid biosynthesis were consistently up-regulated during diverse biofilm growth conditions. We conclude carbon availability in the nasopharynx impacts pneumococcal biofilm formation in vivo Additionally, biofilm formation involves metabolic pathways not previously appreciated to play an important role

Killing of Serratia marcescens biofilms with chloramphenicol

Abstract Serratia marcescens is a Gram-negative bacterium with proven resistance to multiple antibiotics and causative of catheter-associated infections. Bacterial colonization of catheters mainly involves the formation of biofilm. The objectives of this study were to explore the susceptibility of S. marcescens biofilms to high doses of common antibiotics and non-antimicrobial agents. Biofilms formed by a clinical isolate of S. marcescens were treated with ceftriaxone, kanamycin, gentamicin, and chloramphenicol at doses corresponding to 10, 100 and 1000 times their planktonic minimum inhibitory concentration. In addition, biofilms were also treated with chemical compounds such as polysorbate-80 and ursolic acid. S. marcescens demonstrated susceptibility to ceftriaxone, kanamycin, gentamicin, and chloramphenicol in its planktonic form, however, only chloramphenicol reduced both biofilm biomass and biofilm viability. Polysorbate-80 and ursolic acid had minimal to no effect on either planktonic and biofilm grown S. marcescens. Our results suggest that supratherapeutic doses of chloramphenicol can be used effectively against established S. marcescens biofilms

Severity and properties of cardiac damage caused by Streptococcus pneumoniae are strain dependent.

Streptococcus pneumoniae is an opportunistic Gram-positive pathogen that can cause invasive disease. Recent studies have shown that S. pneumoniae is able to invade the myocardium and kill cardiomyocytes, with one-in-five adults hospitalized for pneumococcal pneumonia having a pneumonia-associated adverse cardiac event. Furthermore, clinical reports have shown up to a 10-year increased risk of adverse cardiac events in patients formerly hospitalized for pneumococcal bacteremia. In this study, we investigated the ability of nine S. pneumoniae clinical isolates, representing eight unique serotypes, to cause cardiac damage in a mouse model of invasive disease. Following intraperitoneal challenge of C57BL/6 mice, four of these strains (D39, WU2, TIGR4, and 6A-10) caused high-grade bacteremia, while CDC7F:2617-97 and AMQ16 caused mid- and low-grade bacteremia, respectively. Three strains did not cause any discernible disease. Of note, only the strains capable of high-grade bacteremia caused cardiac damage, as inferred by serum levels of cardiac troponin-I. This link between bacteremia and heart damage was further corroborated by Hematoxylin & Eosin and Trichrome staining which showed cardiac cytotoxicity only in D39, WU2, TIGR4, and 6A-10 infected mice. Finally, hearts infected with these strains showed varying histopathological characteristics, such as differential lesion formation and myocytolysis, suggesting that the mechanism of heart damage varied between strains

Transcriptional organization of pneumococcal psrP-secY2A2 and impact of GtfA and GtfB deletion on PsrP-associated virulence properties

Pneumococcal serine-rich repeat protein (PsrP) is a glycoprotein that mediates Streptococcus pneumoniae attachment to lung cells and promotes biofilm formation. Herein, we investigated the transcriptional organization of psrP-secY2A2, the 37-kbp pathogenicity island encoding PsrP and its accessory genes. PCR amplification of cDNA and RNA-seq analysis found psrP-secY2A2 to be minimally composed of three operons: psrP-glyA, glyB, and glyC-asp5. Transcription of all three operons was greatest during biofilm growth and immunoblot analyses confirmed increased PsrP production by biofilm pneumococci. Using gas chromatography-mass spectrometry we identified monomeric N-acetylglucosamine as the primary glycoconjugate present on a recombinant intracellular version of PsrP, i.e. PsrP1-734. This finding was validated by immunoblot using lectins with known carbohydrate specificities. We subsequently deleted gtfA and gtfB, the GTFs thought to be responsible for addition of O-linked N-acetylglucosamine, and tested for PsrP and its associated virulence properties. These deletions negatively affected our ability to detect PsrP1-734 in bacterial whole cell lysates. Moreover, S. pneumoniae mutants lacking these genes pheno-copied the psrP mutant and were attenuated for: biofilm formation, adhesion to lung epithelial cells, and pneumonia in mice. Our studies identify the transcriptional organization of psrP-secY2A2 and show the indispensable role of GtfA and GtfB on PsrP-mediated pneumococcal virulence

Tuft cells are required for a rhinovirus-induced asthma phenotype in immature mice.

Infection of immature mice with rhinovirus (RV) induces an asthma-like phenotype consisting of type 2 inflammation, mucous metaplasia, eosinophilic inflammation and airways hyperresponsiveness which is dependent on IL-25 and type 2 innate lymphoid cells (ILC2s). Doublecortin-like kinase (DCLK)-1+ tuft cells are a major source of IL-25. We sought to determine the requirement of tuft cells for the RV-induced asthma phenotype in wild-type mice and mice deficient in Pou2f3, a transcription factor required for tuft cell development. C57Bl/6 mice infected with RV-A1B on day 6 of life and RV-A2 on day 13 of life showed increased DCLK1+ positive tuft cells in the large airways. Compared to wild-type mice, RV-infected Pou2f3-/- mice showed reductions in IL-25 mRNA and protein expression, ILC2 expansion, type 2 cytokine expression, mucous metaplasia, lung eosinophils and airway methacholine responsiveness. We conclude that airway tuft cells are required for the asthma phenotype observed in immature mice undergoing repeated RV infections. Furthermore, RV-induced tuft cell development provides a mechanism by which early life viral infections could potentiate type 2 inflammatory responses to future infections.http://deepblue.lib.umich.edu/bitstream/2027.42/192075/2/166136.1-20231207162808-covered-e0fd13ba177f913fd3156f593ead4cfd.pdfPublished onlineDescription of 166136.1-20231207162808-covered-e0fd13ba177f913fd3156f593ead4cfd.pdf : Accepted versio

A Non-Human Primate Model of Severe Pneumococcal Pneumonia.

RATIONALE:Streptococcus pneumoniae is the leading cause of community-acquired pneumonia and infectious death in adults worldwide. A non-human primate model is needed to study the molecular mechanisms that underlie the development of severe pneumonia, identify diagnostic tools, explore potential therapeutic targets, and test clinical interventions during pneumococcal pneumonia. OBJECTIVE:To develop a non-human primate model of pneumococcal pneumonia. METHODS:Seven adult baboons (Papio cynocephalus) were surgically tethered to a continuous monitoring system that recorded heart rate, temperature, and electrocardiography. Animals were inoculated with 109 colony-forming units of S. pneumoniae using bronchoscopy. Three baboons were rescued with intravenous ampicillin therapy. Pneumonia was diagnosed using lung ultrasonography and ex vivo confirmation by histopathology and immunodetection of pneumococcal capsule. Organ failure, using serum biomarkers and quantification of bacteremia, was assessed daily. RESULTS:Challenged animals developed signs and symptoms of pneumonia 4 days after infection. Infection was characterized by the presence of cough, tachypnea, dyspnea, tachycardia and fever. All animals developed leukocytosis and bacteremia 24 hours after infection. A severe inflammatory reaction was detected by elevation of serum cytokines, including Interleukin (IL)1Ra, IL-6, and IL-8, after infection. Lung ultrasonography precisely detected the lobes with pneumonia that were later confirmed by pathological analysis. Lung pathology positively correlated with disease severity. Antimicrobial therapy rapidly reversed symptomology and reduced serum cytokines. CONCLUSIONS:We have developed a novel animal model for severe pneumococcal pneumonia that mimics the clinical presentation, inflammatory response, and infection kinetics seen in humans. This is a novel model to test vaccines and treatments, measure biomarkers to diagnose pneumonia, and predict outcomes

<i>Streptococcus pneumoniae</i> in the heart subvert the host response through biofilm-mediated resident macrophage killing

<div><p>For over 130 years, invasive pneumococcal disease has been associated with the presence of extracellular planktonic pneumococci, i.e. diplococci or short chains in affected tissues. Herein, we show that <i>Streptococcus pneumoniae</i> that invade the myocardium instead replicate within cellular vesicles and transition into non-purulent biofilms. Pneumococci within mature cardiac microlesions exhibited salient biofilm features including intrinsic resistance to antibiotic killing and the presence of an extracellular matrix. Dual RNA-seq and subsequent principal component analyses of heart- and blood-isolated pneumococci confirmed the biofilm phenotype <i>in vivo</i> and revealed stark anatomical site-specific differences in virulence gene expression; the latter having major implications on future vaccine antigen selection. Our RNA-seq approach also identified three genomic islands as exclusively expressed <i>in vivo</i>. Deletion of one such island, Region of Diversity 12, resulted in a biofilm-deficient and highly inflammogenic phenotype within the heart; indicating a possible link between the biofilm phenotype and a dampened host-response. We subsequently determined that biofilm pneumococci released greater amounts of the toxin pneumolysin than did planktonic or RD12 deficient pneumococci. This allowed heart-invaded wildtype pneumococci to kill resident cardiac macrophages and subsequently subvert cytokine/chemokine production and neutrophil infiltration into the myocardium. This is the first report for pneumococcal biofilm formation in an invasive disease setting. We show that biofilm pneumococci actively suppress the host response through pneumolysin-mediated immune cell killing. As such, our findings contradict the emerging notion that biofilm pneumococci are passively immunoquiescent.</p></div

Heart invaded biofilm pneumococci subvert host immune response by releasing pneumolysin and rapidly kill cardiac macrophages.

<p><b>(A)</b> Western blots for pneumolysin levels in equal biomass of whole cell lysates (pellets) and supernatants of planktonic- wildtype TIGR4 (n = 3), biofilm- wildtype TIGR4 (n = 3), and planktonic T4ΩRD12 (ΩRD12) (n = 2). An isogenic pneumolysin deficient TIGR4 strain (T4 Δ<i>ply</i>) was tested as the negative control. Normalized densitometric quantification of pneumolysin levels in the supernatant is provided. Statistical analysis was performed by comparison supernatant pneumolysin levels from planktonic (PK)- wildtype TIGR4 (n = 3), and planktonic T4ΩRD12 (ΩRD12) (n = 2) to biofilm (BF)- wildtype TIGR4 (n = 3) using Welch’s <i>t</i>-test. <b>(B)</b> LDH release cytotoxicity assay of J774A.1 macrophages challenged with equal biomass of planktonic-, biofilm- TIGR4 (T4), planktonic-, biofilm- T4 Δ<i>ply</i> and planktonic-, biofilm- T4 Δ<i>ply</i> complemented with exogenous recombinant pneumolysin (rPLY, 0.3μg/mL) as determined at 0, 1, 2, 4 hours post-infection (n = 3 biological replicates, each with 3 technical replicates). Statistical analysis was performed using ordinary one-way ANOVA. <b>(C)</b> TNFα production by J774A.1 macrophages at designated time points following exposure to an equal biomass of planktonic-, biofilm- TIGR4 (T4), planktonic-, biofilm- T4 Δ<i>ply</i> and planktonic-, biofilm- T4 Δ<i>ply</i> complemented with exogenous recombinant pneumolysin (rPLY, 0.3μg/mL) as determined at 0, 1, 2, 4 hours post-infection (n = 3 biological replicates, each with 3 technical replicates). Statistical analysis was performed using ordinary one-way ANOVA. <b>(D)</b> Representative transmission electron microscopy (TEM) image of cardiac sections (magnification: 2,500X) from BALB/cJ mice infected with T4 Δ<i>ply</i> 30 hours post-infection (n = 3). <b>(E)</b> Representative high magnification immunofluorescent microscopy images of cardiac microlesions from uninfected-, passively immunized (αPly)- and naïve- mice infected with HIP or BIP 30 hours post infection, showing presence of: capsule (stained with anti-serotype 4 capsule antibody [CPS], <i>red</i>), cardiac macrophages (stained using anti-Mac-3 antibody [Mac-3], <i>green</i>), and infiltrated neutrophils (stained with anti-Ly-6G antibody [Ly-6G], <i>green</i>). A minimum of 4 stained heart sections were examined. <b>(F)</b> Absolute numbers of infiltrated neutrophils in hearts of uninfected-, passively immunized (αPly)- and naïve- mice infected with HIP or BIP 30 hours post infection. Neutrophils were identified as Gr-1⁺CD11b⁺Ly-6G⁺F4/80^- MHC-II^- cells. Statistical analysis was performed using student’s <i>t-</i>test. <b>(G)</b> Absolute numbers of cardiac macrophages in hearts of uninfected-, passively immunized (αPly)- and naïve- mice infected with HIP or BIP 30 hours post infection. Macrophages were identified as CD64⁺MerTK⁺F4/80⁺CD11b⁺ cells. Statistical analysis was performed using student’s <i>t-</i>test. <i>P</i> value: * ≤ 0.05, ** ≤ 0.01, *** ≤ 0.001; data are represented as mean ± SEM.</p

Morphogenesis of cardiac microlesions.

<p><b>(A)</b> Representative transmission electron microscopy (TEM) images of cardiac sections (magnification: 2,500X) from BALB/cJ mice infected with <i>S</i>. <i>pneumoniae</i> strain TIGR4 between 24 and 42 hours post-infection (n = 12). Panels A.1-7 depict the morphogenesis of cardiac microlesions beginning as pneumococci-containing microscopic vesicles within the myocardium. Hydropic degeneration (black bold arrows) and mitochondrial damage as evidenced by swelling (white arrows) adjacent to cardiac microlesions are evident. Images that are the most representative of what occurs during individual microlesion development are shown. The images do not necessarily depict the overall course of infection in a mouse which is mixed with different sized microlesions at late timepoints. <b>(B)</b> Representative high power (60,000X) TEM images of pneumococci within microlesions show heterogeneous capsule expression: (B.1) pneumococci within smallest vesicles surrounded by myocardium; (B.2) pneumococci at the periphery of larger microlesions; (B.3) pneumococci within the center of a larger microlesion. <b>(C)</b> Representative TEM image of TIGR4 within a 48-hour old static biofilm (n = 3) grown in a 6-well plate (3,000X). <b>Inset,</b> Representative high power (60,000X) TEM image of biofilm-pneumococci.</p