TLR2 Signaling Decreases Transmission of Streptococcus pneumoniae by Limiting Bacterial Shedding in an Infant Mouse Influenza A Co-infection Model

ABSTRACT The dynamics underlying respiratory contagion (the transmission of infectious agents from the airways) are poorly understood. We investigated host factors involved in the transmission of the leading respiratory pathogen Streptococcus pneumoniae. Using an infant mouse model, we examined whether S. pneumoniae triggers inflammatory pathways shared by influenza A virus (IAV) to promote nasal secretions and shedding from the upper respiratory tract to facilitate transit to new hosts. Here, we show that amplification of the type I interferon (IFN-I) response is a critical host factor in this process, as shedding and transmission by both IAV and S. pneumoniae were decreased in pups lacking the common IFN-I receptor (Ifnar1−/− mice). Additionally, providing exogenous recombinant IFN-I to S. pneumoniae-infected pups was sufficient to increase bacterial shedding. The expression of IFN-stimulated genes (ISGs) was upregulated in S. pneumoniae-infected wild-type (WT) but not Ifnar1−/− mice, including genes involved in mucin type O-glycan biosynthesis; this correlated with an increase in secretions in S. pneumoniae- and IAV-infected WT compared to Ifnar1−/− pups. S. pneumoniae stimulation of ISGs was largely dependent on its pore-forming toxin, pneumolysin, and coinfection with IAV and S. pneumoniae resulted in synergistic increases in ISG expression. We conclude that the induction of IFN-I signaling appears to be a common factor driving viral and bacterial respiratory contagion. IMPORTANCE Respiratory tract infections are a leading cause of childhood mortality and, globally, Streptococcus pneumoniae is the leading cause of mortality due to pneumonia. Transmission of S. pneumoniae primarily occurs through direct contact with respiratory secretions, although the host and bacterial factors underlying transmission are poorly understood. We examined transmission dynamics of S. pneumoniae in an infant mouse model and here show that S. pneumoniae colonization of the upper respiratory tract stimulates host inflammatory pathways commonly associated with viral infections. Amplification of this response was shown to be a critical host factor driving shedding and transmission of both S. pneumoniae and influenza A virus, with infection stimulating expression of a wide variety of genes, including those involved in the biosynthesis of mucin, a major component of respiratory secretions. Our findings suggest a mechanism facilitating S. pneumoniae contagion that is shared by viral infection.

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A novel pneumococcal surface protein K of nonencapsulated Streptococcus pneumoniae promotes transmission among littermates in an infant mouse model with influenza A virus co-infection

Infection and Immunity ◽

10.1128/iai.00622-21 ◽

2022 ◽

Author(s):

Hideki Sakatani ◽

Masamitsu Kono ◽

Denisa Nanushaj ◽

Daichi Murakami ◽

Saori Takeda ◽

...

Keyword(s):

Streptococcus Pneumoniae ◽

Mouse Model ◽

Influenza A ◽

Capsular Polysaccharide ◽

Surface Protein ◽

Nasal Colonization ◽

Infant Mouse ◽

Key Factor ◽

Protective Strategy ◽

New Hosts

We established an infant mouse model for colonization and transmission by nonencapsulated Streptococcus pneumoniae (NESp) strains to gain important information about its virulence among children. Invasive pneumococcal diseases have decreased dramatically since the worldwide introduction of pneumococcal capsular polysaccharide vaccines. Increasing prevalence of non-vaccine serotypes including NESp has been highlighted as a challenge in treatment strategy, but the virulence of NESp is not well understood. Protective strategy against NESp colonization and transmission between children require particularly urgent evaluation. NESp lacks capsules, a major virulent factor of pneumococci, but can cause a variety of infections in children and older people. PspK, a specific surface protein of NESp, is a key factor in establishing nasal colonization. In our infant mouse model for colonization and transmission by NESp strains, NESp could establish stable nasal colonization at the same level as encapsulated serotype 6A in infant mice, and could be transmitted between littermates. Transmission was promoted by NESp surface virulence factor PspK and influenza virus co-infection. However, PspK-deletion mutants lost the ability to colonize and transmit to new hosts. Promotion of NESp transmission by influenza was due to increased susceptibility of the new hosts. PspK was a key factor not only in establishment of nasal colonization, but also in transmission to new hosts. PspK may be targeted as a new candidate vaccine for NESp infection in children.

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Infant Mouse Model for the Study of Shedding and Transmission during Streptococcus pneumoniae Monoinfection

Infection and Immunity ◽

10.1128/iai.00416-16 ◽

2016 ◽

Vol 84 (9) ◽

pp. 2714-2722 ◽

Cited By ~ 29

Author(s):

M. Ammar Zafar ◽

Masamitsu Kono ◽

Yang Wang ◽

Tonia Zangari ◽

Jeffrey N. Weiser

Keyword(s):

Streptococcus Pneumoniae ◽

Mouse Model ◽

Influenza A ◽

Carrier State ◽

High Ratio ◽

New Host ◽

Content Type ◽

Infant Mouse ◽

Colonization Density ◽

Pneumococcal Colonization

One of the least understood aspects of the bacteriumStreptococcus pneumoniae(pneumococcus) is its transmission from host to host, the critical first step in both the carrier state and the disease state. To date, transmission models have depended on influenza A virus coinfection, which greatly enhances pneumococcal shedding to levels that allow acquisition by a new host. Here, we describe an infant mouse model that can be utilized to study pneumococcal colonization, shedding, and transmission during bacterial monoinfection. Using this model, we demonstrated that the level of bacterial shedding is highest in pups infected intranasally at age 4 days and peaks over the first 4 days postchallenge. Shedding results differed among isolates of five different pneumococcal types. Colonization density was found to be a major factor in the level of pneumococcal shedding and required expression of capsule. Transmission within a litter occurred when there was a high ratio of colonized “index” pups to uncolonized “contact” pups. Transmission was observed for each of the well-colonizing pneumococcal isolates, with the rate of transmission proportional to the level of shedding. This model can be used to examine bacterial and host factors that contribute to pneumococcal transmission without the effects of viral coinfection.

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Increased Nasopharyngeal Bacterial Titers and Local Inflammation Facilitate Transmission of Streptococcus pneumoniae

mBio ◽

10.1128/mbio.00255-12 ◽

2012 ◽

Vol 3 (5) ◽

Cited By ~ 48

Author(s):

Kirsty R. Short ◽

Patrick C. Reading ◽

Nancy Wang ◽

Dimitri A. Diavatopoulos ◽

Odilia L. Wijburg

Keyword(s):

Streptococcus Pneumoniae ◽

Mouse Model ◽

Influenza A ◽

Pneumococcal Disease ◽

Present Report ◽

Bacterial Load ◽

Disease Development ◽

Proinflammatory Response ◽

Content Type ◽

Infant Mouse

ABSTRACTThe transmission of the bacteriumStreptococcus pneumoniae(the pneumococcus) marks the first step toward disease development. To date, our ability to prevent pneumococcal transmission has been limited by our lack of understanding regarding the factors which influence the spread of this pathogen. We have previously developed an infant mouse model of pneumococcal transmission which was strictly dependent on influenza A virus (IAV) coinfection of both the experimentally colonized “index mice” and the naive cohoused “contact mice.” Here, we sought to use this model to further elucidate the factors which facilitateS. pneumoniaetransmission. In the present report, we demonstrate that increasing the nasopharyngeal load ofS. pneumoniaein the colonized index mice (via the depletion of neutrophils) and inducing a proinflammatory response in the naive cohoused contact mice (as demonstrated by cytokine production) facilitatesS. pneumoniaetransmission. Thus, these data provide the first insights into the factors that help mediate the spread ofS. pneumoniaethroughout the community.IMPORTANCEStreptococcus pneumoniae(the pneumococcus) is a major cause of worldwide morbidity and mortality and is a leading cause of death among children under the age of five years. Transmission ofS. pneumoniaemarks the first step toward disease development. Therefore, understanding the factors that influence the spread of pneumococci throughout the community plays an essential role in preventing pneumococcal disease. We previously developed the first reproducible infant mouse model for pneumococcal transmission and showed that coinfection with influenza virus facilitates the spread ofS. pneumoniae. Here, we show that increasing the bacterial load in the nasal cavity of colonized individuals as well as inducing an inflammatory response in naive “contact cases” facilitates the spread of pneumococci. Therefore, this study helps to identify the factors which must be inhibited in order to successfully prevent pneumococcal disease.

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Faculty Opinions recommendation of In vitro infection model characterizing the effect of efflux pump inhibition on prevention of resistance to levofloxacin and ciprofloxacin in Streptococcus pneumoniae.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1098459.553373 ◽

2008 ◽

Author(s):

David Stephens ◽

Scott Chancey

Keyword(s):

Streptococcus Pneumoniae ◽

Efflux Pump ◽

Infection Model ◽

Efflux Pump Inhibition

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Influenza A virus facilitates Streptococcus pneumoniae transmission and disease

The FASEB Journal ◽

10.1096/fj.09-146779 ◽

2010 ◽

Vol 24 (6) ◽

pp. 1789-1798 ◽

Cited By ~ 117

Author(s):

Dimitri A. Diavatopoulos ◽

Kirsty R. Short ◽

John T. Price ◽

Jonathan J. Wilksch ◽

Lorena E. Brown ◽

...

Keyword(s):

Streptococcus Pneumoniae ◽

Influenza A Virus ◽

Influenza A

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Protection against Streptococcus pneumoniae Invasive Pathogenesis by a Protein-Based Vaccine Is Achieved by Suppression of Nasopharyngeal Bacterial Density during Influenza A Virus Coinfection

Infection and Immunity ◽

10.1128/iai.00530-16 ◽

2016 ◽

Vol 85 (2) ◽

Cited By ~ 12

Author(s):

M. Nadeem Khan ◽

Qingfu Xu ◽

Michael E. Pichichero

Keyword(s):

T Cells ◽

Streptococcus Pneumoniae ◽

Influenza A Virus ◽

Influenza A ◽

Passive Transfer ◽

Bacterial Density ◽

Content Type ◽

Adult Mice ◽

Significant Difference ◽

Colonization Density

ABSTRACTAn increase inStreptococcus pneumoniaenasopharynx (NP) colonization density during a viral coinfection initiates pathogenesis. To mimic naturalS. pneumoniaepathogenesis, we commensally colonized the NPs of adult C57BL/6 mice withS. pneumoniaeserotype (ST) 6A or 8 and then coinfected them with mouse-adapted H1N1 influenza A virus (PR/8/34).S. pneumoniaeestablished effective commensal colonization, and influenza virus coinfection causedS. pneumoniaeNP density to increase, resulting in bacteremia and mortality. We then studied histidine triad protein D (PhtD), anS. pneumoniaeadhesin vaccine candidate, for its ability to prevent invasiveS. pneumoniaedisease in adult and infant mice. In adult mice, the efficacy of PhtD vaccination was compared with that of PCV13. Vaccination with PCV13 led to a greater reduction ofS. pneumoniaeNP density (>2.5 log units) than PhtD vaccination (∼1-log-unit reduction). However, no significant difference was observed with regard to the prevention ofS. pneumoniaebacteremia, and there was no difference in mortality. Depletion of CD4+T cells in PhtD-vaccinated adult mice, but not PCV13-vaccinated mice, caused a loss of vaccine-induced protection. In infant mice, passive transfer of antisera or CD4+T cells from PhtD-vaccinated adult mice led to a nonsignificant reduction in NP colonization density, whereas passive transfer of antisera and CD4+T cells was needed to cause a significant reduction in NP colonization density. For the first time, these data show an outcome with regard to prevention of invasiveS. pneumoniaepathogenesis with a protein vaccine similar to that which occurs with a glycoconjugate vaccine despite a less robust reduction in NP bacterial density.

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Influenza-Induced Inflammation Drives Pneumococcal Otitis Media

Infection and Immunity ◽

10.1128/iai.01278-12 ◽

2013 ◽

Vol 81 (3) ◽

pp. 645-652 ◽

Cited By ~ 43

Author(s):

Kirsty R. Short ◽

Patrick C. Reading ◽

Lorena E. Brown ◽

John Pedersen ◽

Brad Gilbertson ◽

...

Keyword(s):

Otitis Media ◽

Middle Ear ◽

Influenza A ◽

Pneumococcal Disease ◽

Influenza Viruses ◽

Dependent Manner ◽

Proinflammatory Response ◽

Content Type ◽

Infant Mouse ◽

Human Middle Ear

ABSTRACTInfluenza A virus (IAV) predisposes individuals to secondary infections with the bacteriumStreptococcus pneumoniae(the pneumococcus). Infections may manifest as pneumonia, sepsis, meningitis, or otitis media (OM). It remains controversial as to whether secondary pneumococcal disease is due to the induction of an aberrant immune response or IAV-induced immunosuppression. Moreover, as the majority of studies have been performed in the context of pneumococcal pneumonia, it remains unclear how far these findings can be extrapolated to other pneumococcal disease phenotypes such as OM. Here, we used an infant mouse model, human middle ear epithelial cells, and a series of reverse-engineered influenza viruses to investigate how IAV promotes bacterial OM. Our data suggest that the influenza virus HA facilitates disease by inducing a proinflammatory response in the middle ear cavity in a replication-dependent manner. Importantly, our findings suggest that it is the inflammatory response to IAV infection that mediates pneumococcal replication. This study thus provides the first evidence that inflammation drives pneumococcal replication in the middle ear cavity, which may have important implications for the treatment of pneumococcal OM.

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Streptococcus pneumoniae Transmission Is Blocked by Type-Specific Immunity in an Infant Mouse Model

mBio ◽

10.1128/mbio.00188-17 ◽

2017 ◽

Vol 8 (2) ◽

Cited By ~ 13

Author(s):

Tonia Zangari ◽

Yang Wang ◽

Jeffrey N. Weiser

Keyword(s):

Streptococcus Pneumoniae ◽

Mouse Model ◽

Pneumococcal Conjugate Vaccine ◽

Herd Immunity ◽

Mechanistic Explanation ◽

Epidemiological Studies ◽

Contributing Factors ◽

Infant Mouse ◽

Major Benefit

ABSTRACT Epidemiological studies on Streptococcus pneumoniae show that rates of carriage are highest in early childhood and that the major benefit of the pneumococcal conjugate vaccine (PCV) is a reduction in the incidence of nasopharyngeal colonization through decreased transmission within a population. In this study, we sought to understand how anti- S. pneumoniae immunity affects nasal shedding of bacteria, the limiting step in experimental pneumococcal transmission. Using an infant mouse model, we examined the role of immunity (passed from mother to pup) on shedding and within-litter transmission of S. pneumoniae by pups infected at 4 days of life. Pups from both previously colonized immune and PCV-vaccinated mothers had higher levels of anti- S. pneumoniae IgG than pups from non-immune or non-vaccinated mothers and shed significantly fewer S. pneumoniae over the first 5 days of infection. By setting up cross-foster experiments, we demonstrated that maternal passage of antibody to pups either in utero or post-natally decreases S. pneumoniae shedding. Passive immunization experiments showed that type-specific antibody to capsular polysaccharide is sufficient to decrease shedding and that the agglutinating function of immunoglobulin is required for this effect. Finally, we established that anti-pneumococcal immunity and anti-PCV vaccination block host-to-host transmission of S. pneumoniae . Moreover, immunity in either the donor or recipient pups alone was sufficient to reduce rates of transmission, indicating that decreased shedding and protection from acquisition of colonization are both contributing factors. Our findings provide a mechanistic explanation for the reduced levels of S. pneumoniae transmission between hosts immune from prior exposure and among vaccinated children. IMPORTANCE Rates of carriage of the bacterial pathogen Streptococcus pneumoniae are highest among young children, and this is the target group for the pneumococcal conjugate vaccine (PCV). Epidemiological studies have suggested that a major benefit of the PCV is a reduction in host-to-host transmission, which also protects the non-vaccinated population (“herd immunity”). In this study, we examined the role of anti-pneumococcal immunity on nasal shedding and transmission of the pathogen using an infant mouse model. We found that shedding is decreased and transmission is blocked by anti-pneumococcal immunity and PCV vaccination. Additionally, transmission rates decreased if either the infected or contact pups were immune, indicating that reduced shedding and protection from the establishment of colonization are both contributing factors. Our study provides a mechanistic explanation for the herd immunity effect seen after the introduction of PCV and identifies potential points of intervention, which may have implications for future vaccine development.

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In Vitro Infection Model Characterizing the Effect of Efflux Pump Inhibition on Prevention of Resistance to Levofloxacin and Ciprofloxacin in Streptococcus pneumoniae

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00391-07 ◽

2007 ◽

Vol 51 (11) ◽

pp. 3988-4000 ◽

Cited By ~ 16

Author(s):

Arnold Louie ◽

David L. Brown ◽

Weiguo Liu ◽

Robert W. Kulawy ◽

Mark R. Deziel ◽

...

Keyword(s):

Streptococcus Pneumoniae ◽

Efflux Pump ◽

Community Acquired Pneumonia ◽

Fluoroquinolone Resistance ◽

Infection Model ◽

Wild Type ◽

Efflux Pump Inhibition ◽

Short Term Exposure ◽

Emergence Of Resistance

ABSTRACT The prevalence of fluoroquinolone-resistant Streptococcus pneumoniae is slowly rising as a consequence of the increased use of fluoroquinolone antibiotics to treat community-acquired pneumonia. We tested the hypothesis that increased efflux pump (EP) expression by S. pneumoniae may facilitate the emergence of fluoroquinolone resistance. By using an in vitro pharmacodynamic infection system, a wild-type S. pneumoniae strain (Spn-058) and an isogenic strain with EP overexpression (Spn-RC2) were treated for 10 days with ciprofloxacin or levofloxacin in the presence or absence of the EP inhibitor reserpine to evaluate the effect of EP inhibition on the emergence of resistance. Cultures of Spn-058 and Spn-RC2 were exposed to concentration-time profiles simulating those in humans treated with a regimen of ciprofloxacin at 750 mg orally once every 12 h and with regimens of levofloxacin at 500 and 750 mg orally once daily (QD; with or without continuous infusions of 20 μg of reserpine/ml). The MICs of ciprofloxacin and levofloxacin for Spn-058 were both 1 μg/ml when susceptibility testing was conducted with each antibiotic alone and with each antibiotic in the presence of reserpine. For Spn-RC2, the MIC of levofloxacin alone and with reserpine was also 1 μg/ml; the MICs of ciprofloxacin were 2 and 1 μg/ml, respectively, when determined with ciprofloxacin alone and in combination with reserpine. Reserpine, alone, had no effect on the growth of Spn-058 and Spn-RC2. For Spn-058, simulated regimens of ciprofloxacin at 750 mg every 12 h or levofloxacin at 500 mg QD were associated with the emergence of fluoroquinolone resistance. However, the use of ciprofloxacin at 750 mg every 12 h and levofloxacin at 500 mg QD in combination with reserpine rapidly killed Spn-058 and prevented the emergence of resistance. For Spn-RC2, levofloxacin at 500 mg QD was associated with the emergence of resistance, but again, the resistance was prevented when this levofloxacin regimen was combined with reserpine. Ciprofloxacin at 750 mg every 12 h also rapidly selected for ciprofloxacin-resistant mutants of Spn-RC2. However, the addition of reserpine to ciprofloxacin therapy only delayed the emergence of resistance. Levofloxacin at 750 mg QD, with and without reserpine, effectively eradicated Spn-058 and Spn-RC2 without selecting for fluoroquinolone resistance. Ethidium bromide uptake and efflux studies demonstrated that, at the baseline, Spn-RC2 had greater EP expression than Spn-058. These studies also showed that ciprofloxacin was a better inducer of EP expression than levofloxacin in both Spn-058 and Spn-RC2. However, in these isolates, the increase in EP expression by short-term exposure to ciprofloxacin and levofloxacin was transient. Mutants of Spn-058 and Spn-RC2 that emerged under suboptimal antibiotic regimens had a stable increase in EP expression. Levofloxacin at 500 mg QD in combination with reserpine, an EP inhibitor, or at 750 mg QD alone killed wild-type S. pneumoniae and strains that overexpressed reserpine-inhibitable EPs and was highly effective in preventing the emergence of fluoroquinolone resistance in S. pneumoniae during therapy. Ciprofloxacin at 750 mg every 12 h, as monotherapy, was ineffective for the treatment of Spn-058 and Spn-RC2. Ciprofloxacin in combination with reserpine prevented the emergence of resistance in Spn-058 but not in Spn-RC2, the EP-overexpressing strain.

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