Microbial interactions in the respiratory tract

Associations between nasopharyngeal carriage of Group B Streptococcus and other respiratory pathogens during early infancy

BACKGROUND

In West Africa, the carriage of Group B Streptococcus (GBS), among infants is poorly characterised. We investigated co-carriage of GBS with other respiratory pathogens in the infants' nasopharynx in The Gambia.

METHODS

We assessed the carriage, serotypes and antibiotic susceptibility of Beta-haemolytic Streptococci (BHS) groups A-G; along with the carriage of Streptococcus pneumoniae; Haemophilus influenzae; Staphylococcus aureus and Moraxella catarrhalis in 1200 two-month old infants.

RESULTS

The BHS prevalence was 20.0 % and GBS dominated (13.8 %), particularly serotypes V and II; serotype V being negatively associated with H. Influenzae carriage (OR 0.41 [95 % CI: 0.18-0.93], p = 0.033). Although co-colonization of GBS and other BHS was not seen, colonization with GBS was positively associated with S. aureus (OR 1.89 [95 % CI: 1.33-2.69], P < 0.001) and negatively associated with S. pneumoniae (OR 0.47 [95 % CI: 0.33-0.67], p < 0.001) and M. catarrhalis (OR 0.61 [95 % CI: 0.40-0.92], p = 0.017). ≥ 89 % of GBS isolates were susceptible to most antibiotics tested, except for tetracycline resistance, which was 89 %.

CONCLUSION

This study provides baseline data on the carriage of GBS in two month old infants from West Africa. The dominant serotypes of GBS in this setting are serotypes V and II. This may be important for future GBS vaccine development for the West African sub-region.

Haemophilus haemolyticus Interaction with Host Cells Is Different to Nontypeable Haemophilus influenzae and Prevents NTHi Association with Epithelial Cells

Nontypeable Haemophilus influenzae (NTHi) is an opportunistic pathogen that resides in the upper respiratory tract and contributes to a significant burden of respiratory related diseases in children and adults. Haemophilus haemolyticus is a respiratory tract commensal that can be misidentified as NTHi due to high levels of genetic relatedness. There are reports of invasive disease from H. haemolyticus, which further blurs the species boundary with NTHi. To investigate differences in pathogenicity between these species, we optimized an in vitro epithelial cell model to compare the interaction of 10 H. haemolyticus strains with 4 NTHi and 4 H. influenzae-like haemophili. There was inter- and intra-species variability but overall, H. haemolyticus had reduced capacity to attach to and invade nasopharyngeal and bronchoalveolar epithelial cell lines (D562 and A549) within 3 h when compared with NTHi. H. haemolyticus was cytotoxic to both cell lines at 24 h, whereas NTHi was not. Nasopharyngeal epithelium challenged with some H. haemolyticus strains released high levels of inflammatory mediators IL-6 and IL-8, whereas NTHi did not elicit an inflammatory response despite higher levels of cell association and invasion. Furthermore, peripheral blood mononuclear cells stimulated with H. haemolyticus or NTHi released similar and high levels of IL-6, IL-8, IL-10, IL-1β, and TNFα when compared with unstimulated cells but only NTHi elicited an IFNγ response. Due to the relatedness of H. haemolyticus and NTHi, we hypothesized that H. haemolyticus may compete with NTHi for colonization of the respiratory tract. We observed that in vitro pre-treatment of epithelial cells with H. haemolyticus significantly reduced NTHi attachment, suggesting interference or competition between the two species is possible and warrants further investigation. In conclusion, H. haemolyticus interacts differently with host cells compared to NTHi, with different immunostimulatory and cytotoxic properties. This study provides an in vitro model for further investigation into the pathogenesis of Haemophilus species and the foundation for exploring whether H. haemolyticus can be used to prevent NTHi disease.

Simultaneous Antibiofilm and Antiviral Activities of an Engineered Antimicrobial Peptide during Virus-Bacterium Coinfection

Antimicrobial-resistant infections are an urgent public health threat, making development of novel antimicrobials able to effectively treat these infections extremely important. Chronic and polymicrobial infections further complicate antimicrobial therapy, often through the development of microbial biofilms. Here, we describe the ability of an engineered antimicrobial peptide to disrupt biofilms formed by the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogen Pseudomonas aeruginosa during coinfection with respiratory syncytial virus. We also observed antiviral activity, indicating the ability of engineered antimicrobial peptides to act as cross-kingdom single-molecule combination therapies.

Antimicrobial-resistant infections are an urgent public health threat, and development of novel antimicrobial therapies has been painstakingly slow. Polymicrobial infections are increasingly recognized as a significant source of severe disease and also contribute to reduced susceptibility to antimicrobials. Chronic infections also are characterized by their ability to resist clearance, which is commonly linked to the development of biofilms that are notorious for antimicrobial resistance. The use of engineered cationic antimicrobial peptides (eCAPs) is attractive due to the slow development of resistance to these fast-acting antimicrobials and their ability to kill multidrug-resistant clinical isolates, key elements for the success of novel antimicrobial agents. Here, we tested the ability of an eCAP, WLBU2, to disrupt recalcitrant Pseudomonas aeruginosa biofilms. WLBU2 was capable of significantly reducing biomass and viability of P. aeruginosa biofilms formed on airway epithelium and maintained activity during viral coinfection, a condition that confers extraordinary levels of antibiotic resistance. Biofilm disruption was achieved in short treatment times by permeabilization of bacterial membranes. Additionally, we observed simultaneous reduction of infectivity of the viral pathogen respiratory syncytial virus (RSV). WLBU2 is notable for its ability to maintain activity across a broad range of physiological conditions and showed negligible toxicity toward the airway epithelium, expanding its potential applications as an antimicrobial therapeutic.

IMPORTANCE Antimicrobial-resistant infections are an urgent public health threat, making development of novel antimicrobials able to effectively treat these infections extremely important. Chronic and polymicrobial infections further complicate antimicrobial therapy, often through the development of microbial biofilms. Here, we describe the ability of an engineered antimicrobial peptide to disrupt biofilms formed by the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogen Pseudomonas aeruginosa during coinfection with respiratory syncytial virus. We also observed antiviral activity, indicating the ability of engineered antimicrobial peptides to act as cross-kingdom single-molecule combination therapies.

Intercellular adhesion molecule 1 serves as a primary cognate receptor for the Type IV pilus of nontypeable Haemophilus influenzae

Nontypeable Haemophilus influenzae (NTHI) utilizes the Type IV pilus (Tfp) to adhere to respiratory tract epithelial cells thus colonizing its human host; however, the host cell receptor to which this adhesive protein binds is unknown. From a panel of receptors engaged by Tfp expressed by other bacterial species, we showed that the majority subunit of NTHI Tfp, PilA, bound to intercellular adhesion molecule 1 (ICAM1) and that this interaction was both specific and of high affinity. Further, Tfp-expressing NTHI inoculated on to polarized respiratory tract epithelial cells that expressed ICAM1 were significantly more adherent compared to Tfp-deficient NTHI or NTHI inoculated on to epithelial cells to which ICAM1 gene expression was silenced. Moreover, pre-incubation of epithelial cells with recombinant soluble PilA (rsPilA) blocked adherence of NTHI, an outcome that was abrogated by admixing rsPilA with ICAM1 prior to application on to the target cells. Epithelial cells infected with adenovirus or respiratory syncytial virus showed increased expression of ICAM1; this outcome supported augmented adherence of Tfp-expressing NTHI. Collectively, these data revealed the cognate receptor for NTHI Tfp as ICAM1 and promote continued development of a Tfp-targeted vaccine for NTHI-induced diseases of the airway wherein upper respiratory tract viruses play a key predisposing role.

Histophilus somni Stimulates Expression of Antiviral Proteins and Inhibits BRSV Replication in Bovine Respiratory Epithelial Cells

Our previous studies showed that bovine respiratory syncytial virus (BRSV) followed by Histophilus somni causes more severe bovine respiratory disease and a more permeable alveolar barrier in vitro than either agent alone. However, microarray analysis revealed the treatment of bovine alveolar type 2 (BAT2) epithelial cells with H. somni concentrated culture supernatant (CCS) stimulated up-regulation of four antiviral protein genes as compared with BRSV infection or dual treatment. This suggested that inhibition of viral infection, rather than synergy, may occur if the bacterial infection occurred before the viral infection. Viperin (or radical S-adenosyl methionine domain containing 2—RSAD2) and ISG15 (IFN-stimulated gene 15—ubiquitin-like modifier) were most up-regulated. CCS dose and time course for up-regulation of viperin protein levels were determined in treated bovine turbinate (BT) upper respiratory cells and BAT2 lower respiratory cells by Western blotting. Treatment of BAT2 cells with H. somni culture supernatant before BRSV infection dramatically reduced viral replication as determined by qRT PCR, supporting the hypothesis that the bacterial infection may inhibit viral infection. Studies of the role of the two known H. somni cytotoxins showed that viperin protein expression was induced by endotoxin (lipooligosaccharide) but not by IbpA, which mediates alveolar permeability and H. somni invasion. A naturally occurring IbpA negative asymptomatic carrier strain of H. somni (129Pt) does not cause BAT2 cell retraction or permeability of alveolar cell monolayers, so lacks virulence in vitro. To investigate initial steps of pathogenesis, we showed that strain 129Pt attached to BT cells and induced a strong viperin response in vitro. Thus colonization of the bovine upper respiratory tract with an asymptomatic carrier strain lacking virulence may decrease viral infection and the subsequent enhancement of bacterial respiratory infection in vivo.

Streptococcus pneumoniae proteomics: determinants of pathogenesis and vaccine development

Streptococcus pneumoniae is a major pathogen that is responsible for a variety of invasive diseases. The bacteria gain entry initially by establishing a carriage state in the nasopharynx from where they migrate to other sites in the body. The worldwide distribution of the bacteria and the severity of the diseases have led to a significant level of interest in the development of vaccines against the bacteria. Current vaccines, based on the bacterial polysaccharide, have a number of limitations including poor immunogenicity and limited effectiveness against all pneumococcal serotypes. There are many challenges in developing vaccines that will be effective against the diverse range of isolates and serotypes for this highly variable bacterial pathogen. This review considers how proteomic technologies have extended our understanding of the pathogenic mechanisms of nasopharyngeal colonization and disease development as well as the critical areas in developing protein-based vaccines.

Moraxella catarrhalis-produced nitric oxide has dual roles in pathogenicity and clearance of infection in bacterial-host cell co-cultures

In humans, the free radical nitric oxide (NO) is a concentration-dependent multifunctional signaling or toxic molecule that modulates various physiological and pathological processes, and innate immunity against bacterial infections. Because the expression of bacterial genes encoding nitrite reductase (AniA) and NO reductase (NorB) is highly upregulated in biofilms in vitro, it is important to investigate whether bacterial NO-metabolism might subvert host NO signaling and play pathogenic roles during infection. The Moraxella catarrhalis AniA and NorB directly function in production and reduction of NO. Using M. catarrhalis-human bronchial epithelial cell (HBEC) co-cultures, we recently reported AniA/nitrite-dependent cytotoxic effects on HBECs, including altered protein profiles of HBECs and induced HBEC apoptosis, suggesting bacterial nitrite reduction likely dysregulates host cell gene expression. To further clarify whether nitrite reduction-derived NO or nitrite-dependent stimulation of bacterial growth was responsible for adverse effects on HBECs, we monitored bacterial nitrite reduction, levels of NO in co-cultures and resulted dynamic effects on HBEC proliferation and bacterial viability. This study demonstrated that M. catarrhalis nitrite reduction-derived NO was responsible for observed adverse effects on HBECs at mid-to-late stages of infection. More importantly, our data showed that while nitrite promoted bacterial growth and biofilm formation at early hours of infection, nitrite reduction-derived NO was toxic towards M. catarrhalis in maturing biofilms, suggesting nitrite reduction-derived NO might be a possible dualistic mechanism by which M. catarrhalis promotes diseases and spontaneous resolutions.

The Gene Polymorphism of IL-17 G-152A is Associated with Increased Colonization of Streptococcus pneumoniae in Young Finnish Children

BACKGROUND

Streptococcus pneumoniae is a common respiratory pathogen, and up to 50% of children acquire S. pneumoniae in their nasopharynx during the first 12 months of life. The cytokine interleukin-17A (IL-17A) plays an important role in host defense against extracellular bacterial pathogens. We investigated the effect of IL-17 G-152A polymorphism on pneumococcal colonization in children.

METHODS

Nasopharyngeal swabs and blood samples were collected from healthy Finnish children at 2.6 (N = 405), 13 (N = 198) and 24 (N = 176) months of age. Of them, 160 had both nasopharyngeal swabs and blood samples at each time point. The semiquantitative culture method was used for bacterial culture, Sequenom iPlex Gold System for IL-17A genotyping and Luminex 200 for serum IL-17A determination.

RESULTS

The frequency of IL-17 G-152A genotypes G/G, G/A and A/A was 36%, 45% and 19% in 405 studied subjects, respectively. The colonization rates of S. pneumoniae increased from 10% at 2.6 months to 33% at 24 months of age. Significantly higher pneumococcal colonization was found in subjects with A/A genotype at 13 and 24 months of age compared with those of G/G (RR, 2.30; P = 0.02; RR, 1.91, P = 0.03). This genotype was associated with lower levels of serum IL-17A, and only 6% of subjects with A/A had detectable serum IL-17A compared with 75% and 33% of subjects with G/G and G/A (P < 0.001 and P < 0.01), respectively.

CONCLUSIONS

Our results indicate that IL-17 G-152A is associated with increased colonization rate of S. pneumoniae in young children, suggesting that IL-17A plays an important role in protection against pneumococcal colonization.

Nasopharyngeal bacterial burden and antibiotics: Influence on inflammatory markers and disease severity in infants with respiratory syncytial virus bronchiolitis

OBJECTIVES

Animal studies suggest that RSV increases nasopharyngeal (NP) bacterial colonization facilitating bacterial infections. We investigated the influence of antibiotic treatment and colonization with potentially pathogenic bacteria on inflammatory markers and disease severity in RSV-infected in infants.

METHODS

Healthy young infants hospitalized with RSV bronchiolitis (n = 136) and age-matched healthy controls (n = 23) were enrolled and NP samples cultured for potentially pathogenic bacteria including: Gram-positive bacteria (GPB): Staphylococcus aureus, Streptococcus pneumoniae, β-hemolytic Streptococcus; and Gram-negative bacteria (GNB): Moraxella catarrhalis and Haemophilus influenzae. Clinical parameters and plasma IL-8, IL-6 and TNF-α concentrations were compared according to the bacterial class and antibiotic treatment.

RESULTS

Antibiotic treatment decreased by 10-fold NP bacterial recovery. Eighty-one percent of RSV infants who did not receive antibiotics before sample collection were colonized with pathogenic bacteria. Overall, GNB were identified in 21% of patients versus 4% of controls who were mostly colonized with GPB. Additionally, in RSV patients NP white blood cell counts (p = 0.026), and blood neutrophils (p = 0.02) were higher in those colonized with potentially pathogenic bacteria versus respiratory flora. RSV patients colonized with GNB had higher plasma IL-8 (p = 0.01) and IL-6 (p < 0.01) concentrations than controls, and required longer duration of oxygen (p = 0.049).

CONCLUSIONS

Infants with RSV bronchiolitis colonized with potentially pathogenic bacteria had increased numbers of mucosal and systemic inflammatory cells. Specifically, colonization with GNB was associated with higher concentrations of proinflammatory cytokines and a trend towards increased disease severity.

Nasopharyngeal and Adenoid Colonization by Haemophilus influenzae and Haemophilus parainfluenzae in Children Undergoing Adenoidectomy and the Ability of Bacterial Isolates to Biofilm Production

Haemophili are pathogenic or opportunistic bacteria often colonizing the upper respiratory tract mucosa. The prevalence of Haemophilus influenzae (with serotypes distribution), and H. parainfluenzae in the nasopharynx and/or the adenoid core in children with recurrent pharyngotonsillitis undergoing adenoidectomy was assessed. Haemophili isolates were investigated for their ability to biofilm production.Nasopharyngeal swabs and the adenoid core were collected from 164 children who underwent adenoidectomy (2-5 years old). Bacteria were identified by the standard methods. Serotyping of H. influenzae was performed using polyclonal and monoclonal antisera. Biofilm formation was detected spectrophotometrically using 96-well microplates and 0.1% crystal violet.Ninety seven percent (159/164) children who underwent adenoidectomy were colonized by Haemophilus spp. The adenoid core was colonized in 99.4% (158/159) children, whereas the nasopharynx in 47.2% (75/159) children (P < 0.0001). In 32% (51/159) children only encapsulated (typeable) isolates of H. influenzae were identified, in 22.6% (36/159) children only (nonencapsulated) H. influenzae NTHi (nonencapsulated) isolates were present, whereas 7.5% (12/159) children were colonized by both types. 14.5% (23/159) children were colonized by untypeable (rough) H. influenzae. In 22% (35/159) children H. influenzae serotype d was isolated. Totally, 192 isolates of H. influenzae, 96 isolates of H. parainfluenzae and 14 isolates of other Haemophilus spp. were selected. In 20.1% (32/159) children 2 or 3 phenotypically different isolates of the same species (H. influenzae or H. parainfluenzae) or serotypes (H. influenzae) were identified in 1 child. 67.2% (129/192) isolates of H. influenzae, 56.3% (54/96) isolates of H. parainfluenzae and 85.7% (12/14) isolates of other Haemophilus spp. were positive for biofilm production. Statistically significant differences (P = 0.0029) among H. parainfluenzae biofilm producers and nonproducers in the adenoid core and the nasopharynx were detected.H. influenzae and H. parainfluenzae carriage rate was comparatively higher in the adenoid core than that in the nasopharynx in children undergoing adenoidectomy, suggesting that their involvement in chronic adenoiditis. The growth in the biofilm seems to be an important feature of haemophili colonizing the upper respiratory tract responsible for their persistence.

A role for CCL28-CCR3 in T-cell homing to the human upper airway mucosa

Lymphocyte recruitment to peripheral tissues is fundamental for immune surveillance and homeostasis, but the chemokines and chemokine receptors responsible for tissue-specific homing of T cells to the upper airway mucosa have not been determined. To address this, we analyzed the chemokines expressed in the normal human nasal mucosa and found that CCL28 is preferentially expressed at a high level on the lumenal face of vascular endothelial cells in the mucosa. Analysis of the cognate chemokine receptors revealed that close to 50% of the CD4(+) T cells in the human nasal mucosa expressed the CCL28 receptor CCR3, whereas CCR3 was hardly detectable on T cells in the small intestine and skin. In the circulation, CCR3(+) T cells comprised a small subset that did not express homing receptors to the intestine or skin. Moreover, depletion of CCR3(+)CD4(+) T cells abrogated the proliferative response of human blood CD4(+) T cells against the opportunistic nasopharyngeal pathogen Haemophilus influenzae, indicating that the CCR3(+)CD4(+) T-cell subset in the circulation contains antigen specificities relevant for the upper airways. Together, these findings indicate that CCL28-CCR3 interactions are involved in the homeostatic trafficking of CD4(+) T cells to the upper airways.

Divergent mucosal and systemic responses in children in response to acute otitis media

Acute otitis media (AOM), induced by respiratory bacteria, is a significant cause of children seeking medical attention worldwide. Some children are highly prone to AOMs, suffering three to four recurrent infections per year (prone). We previously determined that this population of children could have diminished anti-bacterial immune responses in peripheral blood that could fail to limit bacterial colonization in the nasopharynx (NP). Here, we examined local NP and middle ear (ME) responses and compared them to peripheral blood to examine whether the mucosa responses were similar to the peripheral blood responses. Moreover, we examined differences in effector cytokine responses between these two populations in the NP, ME and blood compartments at the onset of an AOM caused by either Streptococcus pneumoniae or non-typeable Haemophilus influenzae. We found that plasma effector cytokines patterned antigen-recall responses of CD4 T cells, with lower responses detected in prone children. ME cytokine levels did not mirror blood, but were more similar to the NP. Interferon (IFN)-γ and interleukin (IL)-17 in the NP were similar in prone and non-prone children, while IL-2 production was higher in prone children. The immune responses diverged in the mucosal and blood compartments at the onset of a bacterial ME infection, thus highlighting differences between local and systemic immune responses that could co-ordinate anti-bacterial immune responses in young children.

Secondary bacterial infections in influenza virus infection pathogenesis

Influenza is often complicated by bacterial pathogens that colonize the nasopharynx and invade the middle ear and/or lung epithelium. Incidence and pathogenicity of influenza-bacterial coinfections are multifactorial processes that involve various pathogenic virulence factors and host responses with distinct site- and strain-specific differences. Animal models and kinetic models have improved our understanding of how influenza viruses interact with their bacterial co-pathogens and the accompanying immune responses. Data from these models indicate that considerable alterations in epithelial surfaces and aberrant immune responses lead to severe inflammation, a key driver of bacterial acquisition and infection severity following influenza. However, further experimental and analytical studies are essential to determining the full mechanistic spectrum of different viral and bacterial strains and species and to finding new ways to prevent and treat influenza-associated bacterial coinfections. Here, we review recent advances regarding transmission and disease potential of influenza-associated bacterial infections and discuss the current gaps in knowledge.

Effects of bovine colostrum supplementation on upper respiratory illness in active males

Bovine colostrum (COL) has been advocated as a nutritional countermeasure to exercise-induced immune dysfunction and increased risk of upper respiratory illness (URI) in athletic populations, however, the mechanisms remain unclear. During winter months, under double-blind procedures, 53 males (mean training load±SD, 50.5±28.9 MET-hweek(-1)) were randomized to daily supplementation of 20g of COL (N=25) or an isoenergetic/isomacronutrient placebo (PLA) (N=28) for 12weeks. Venous blood was collected at baseline and at 12weeks and unstimulated saliva samples at 4 weeks intervals. There was a significantly lower proportion of URI days and number of URI episodes with COL compared to PLA over the 12weeks (p<0.05). There was no effect of COL on in vitro neutrophil oxidative burst, salivary secretory IgA or salivary antimicrobial peptides (p>0.05), which does not support previously suggested mechanisms. In a subset of participants (COL=14, PLA=17), real-time quantitative PCR, targeting the 16S rRNA gene showed there was an increase in salivary bacterial load over the 12 weeks period with PLA (p<0.05) which was not as evident with COL. Discriminant function analysis of outputs received from serum metabolomics showed changes across time but not between groups. This is the first study to demonstrate that COL limits the increased salivary bacterial load in physically active males during the winter months which may provide a novel mechanism of immune-modulation with COL and a relevant marker of in vivo (innate) immunity and risk of URI.

Nasopharyngeal vs. adenoid cultures in children undergoing adenoidectomy: prevalence of bacterial pathogens, their interactions and risk factors

Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus colonization of the adenoids and nasopharynx in 103 preschool children who underwent adenoidectomy for recurrent upper respiratory tract infections was examined. Bacterial interactions and risk factors for bacterial colonization of the nasopharynx and adenoids, separately, were analysed statistically. The prevalence of simultaneous isolation from both anatomical sites was 45·6% for S. pneumoniae, 29·1% for H. influenzae, 15·5% for M. catarrhalis and 18·4% for S. aureus. Three pathogens were significantly more frequent together from adenoid samples; nasopharyngeal swabs more often yielded a single organism, but without statistical significance. M. catarrhalis and S. aureus significantly more frequently co-existed with S. pneumoniae and H. influenzae than with each other and a positive association of S. pneumoniae and H. influenzae in adenoid samples was evident. Several differences between risk factors for nasopharyngeal and adenoid colonization by the individual pathogens were observed. We conclude that the adenoids and nasopharynx appear to differ substantially in colonization by pathogenic microbes but occurrence of H. influenzae and S. pneumoniae in the nasopharynx could be predictive of upper respiratory tract infections.

Haemophilus influenzae stores and distributes hemin by using protein E

The human pathogen Haemophilus influenzae causes mainly respiratory tract infections such as acute otitis media in children and exacerbations in patients with chronic obstructive pulmonary disease. We recently revealed the crystal structure of H. influenzeae protein E (PE), a multifunctional adhesin that is involved in direct interactions with lung epithelial cells and host proteins. Based upon the PE structure we here suggest a hypothetical binding pocket that is compatible in size with a hemin molecule. An H. influenzae mutant devoid of PE bound significantly less hemin in comparison to the PE-expressing wild type counterpart. In addition, E. coli expressing PE at the surface resulted in a hemin-binding phenotype. An interaction between hemin and recombinant soluble PE was also demonstrated by native-PAGE and UV-visible spectrophotometry. Surface plasmon resonance revealed an affinity (Kd) of 1.6 × 10(-6)M for the hemin-PE interaction. Importantly, hemin that was bound to PE at the H. influenzae surface, was donated to co-cultured luciferase-expressing H. influenzae that were starved of hemin. When hemin is bound to PE it thus may serve as a storage pool for H. influenzae. To our knowledge this is the first report showing that H. influenzae can share hemin via a surface-located outer membrane protein.

Zinc oxide nanoparticles impair bacterial clearance by macrophages

AIM

The extensive development of nanoparticles (NPs) and their widespread employment in daily life have led to an increase in environmental concentrations of substances that may pose a biohazard to humans. The aim of this work was to examine the effects of zinc oxide nanoparticles (ZnO-NPs) on the host's pulmonary immune system response to nontypeable Haemophilus influenzae (NTHi) infection.

MATERIALS & METHODS

A murine infection model was employed to assess pulmonary inflammation and bacterial clearance in response to exposure to ZnO-NPs. The molecular mechanisms underlying ZnO-NP-impaired macrophage activation were investigated.

RESULTS

Treatment with ZnO-NPs impaired macrophage activation, leading to a delay in NTHi clearance in the bronchial alveolar lavage fluids and lungs. Exposure to ZnO-NPs followed by NTHi challenge decreased levels of nitric oxide compared with NTHi infection alone. The effects of ZnO-NPs involved downregulation of NTHi-activated expression of inducible nitric oxide synthase and the translocation of active NF-kB into the nucleus.

CONCLUSION

These results demonstrate that exposure to ZnO-NPs can impair innate immune responses and attenuate macrophage responses to bacterial infection.

Diversity of nontypeable Haemophilus influenzae strains colonizing Australian Aboriginal and non-Aboriginal children

Nontypeable Haemophilus influenzae (NTHI) strains are responsible for respiratory-related infections which cause a significant burden of disease in Australian children. We previously identified a disparity in NTHI culture-defined carriage rates between Aboriginal and non-Aboriginal children (42% versus 11%). The aim of this study was to use molecular techniques to accurately determine the true NTHI carriage rates (excluding other culture-identical Haemophilus spp.) and assess whether the NTHI strain diversity correlates with the disparity in NTHI carriage rates. NTHI isolates were cultured from 595 nasopharyngeal aspirates collected longitudinally from asymptomatic Aboriginal (n=81) and non-Aboriginal (n=76) children aged 0 to 2 years living in the Kalgoorlie-Boulder region, Western Australia. NTHI-specific 16S rRNA gene PCR and PCR ribotyping were conducted on these isolates. Confirmation of NTHI by 16S rRNA gene PCR corrected the NTHI carriage rates from 42% to 36% in Aboriginal children and from 11% to 9% in non-Aboriginal children. A total of 75 different NTHI ribotypes were identified, with 51% unique to Aboriginal children and 13% unique to non-Aboriginal children (P<0.0001). The strain richness (proportion of different NTHI ribotypes) was similar for Aboriginal (19%, 65/346) and non-Aboriginal children (19%, 37/192) (P=0.909). Persistent carriage of the same ribotype was rare in the two groups, but colonization with multiple NTHI strains was more common in Aboriginal children than in non-Aboriginal children. True NTHI carriage was less than that estimated by culture. The Aboriginal children were more likely to carry unique and multiple NTHI strains, which may contribute to the chronicity of NTHI colonization and subsequent disease.

Comparative analyses of a cystic fibrosis isolate of Bordetella bronchiseptica reveal differences in important pathogenic phenotypes

Bordetella bronchiseptica is a Gram-negative bacterium that infects and causes disease in a wide variety of animals. B. bronchiseptica also infects humans, thereby demonstrating zoonotic transmission. An extensive characterization of human B. bronchiseptica isolates is needed to better understand the distinct genetic and phenotypic traits associated with these zoonotic transmission events. Using whole-genome transcriptome and CGH analysis, we report that a B. bronchiseptica cystic fibrosis isolate, T44625, contains a distinct genomic content of virulence-associated genes and differentially expresses these genes compared to the sequenced model laboratory strain RB50, a rabbit isolate. The differential gene expression pattern correlated with unique phenotypes exhibited by T44625, which included lower motility, increased aggregation, hyperbiofilm formation, and an increased in vitro capacity to adhere to respiratory epithelial cells. Using a mouse intranasal infection model, we found that although defective in establishing high bacterial burdens early during the infection process, T44625 persisted efficiently in the mouse nose. By documenting the unique genomic and phenotypic attributes of T44625, this report provides a blueprint for understanding the successful zoonotic potential of B. bronchiseptica and other zoonotic bacteria.

Characterization of the nasopharyngeal microbiota in health and during rhinovirus challenge

BACKGROUND

The bacterial communities of the nasopharynx play an important role in upper respiratory tract infections (URTIs). Our study represents the first survey of the nasopharynx during a known, controlled viral challenge. We aimed to gain a better understanding of the composition and dynamics of the nasopharyngeal microbiome during viral infection.

METHODS

Rhinovirus illnesses were induced by self-inoculation using the finger to nose or eye natural transmission route in ten otherwise healthy young adults. Nasal lavage fluid samples (NLF) samples were collected at specific time points before, during, and following experimental rhinovirus inoculation. Bacterial DNA from each sample (N = 97 from 10 subjects) was subjected to 16S rRNA sequencing by amplifying the V1-V2 hypervariable region followed by sequencing using the 454-FLX platform.

RESULTS

This survey of the nasopharyngeal microbiota revealed a highly complex microbial ecosystem. Taxonomic composition varied widely between subjects and between time points of the same subject. We also observed significantly higher diversity in not infected individuals compared to infected individuals. Two genera - Neisseria and Propionibacterium - differed significantly between infected and not infected individuals. Certain phyla, including Firmicutes, Actinobacteria, and Proteobacteria, were detected in all samples.

CONCLUSIONS

Our results reveal the complex and diverse nature of the nasopharyngeal microbiota in both healthy and viral-challenged adults. Although some phyla were common to all samples, differences in levels of diversity and selected phyla were detected between infected and uninfected participants. Deeper, species-level metagenomic sequencing in a larger sample is warranted.

Co-colonization by Haemophilus influenzae with Streptococcus pneumoniae enhances pneumococcal-specific antibody response in young children

BACKGROUND

Streptococcus pneumoniae (Spn), Haemophilus influenzae (Hi) and Moraxella catarrhalis (Mcat) are common bacterial pathogens of respiratory infections and common commensal microbes in the human nasopharynx (NP). The effect of interactions among theses bacteria during co-colonization of the NP on the host immune response has not been evaluated. The objective of this study was to assess the impact of co-colonization by Hi or Mcat on the systemic antibody response to vaccine protein candidate antigens of Spn and similarly the impact of co-colonization by Spn and Mcat on antibody responses to Hi vaccine protein candidate antigens.

METHODS

Serum samples were collected from healthy children at 6, 9, 15, 18, and 24 months of age when they were colonized with Spn, Hi, Mcat or their combinations. Quantitative ELISA was used to determine serum IgA and IgG against three Spn antigens and three Hi antigens, and as well as whole cells of non-typeable (NT) Spn and Hi.

RESULTS

NP colonization by Spn increased serum IgA and IgG titers against Spn antigens PhtD, PcpA and PlyD and whole cells of NTSpn, and co-colonization of Hi or Mcat with Spn resulted in further increases of serum pneumococcal-specific antibody levels. NP colonization by Hi increased serum IgA and IgG titers against Hi antigens P6, Protein D and OMP26 and whole cells of NTHi, but co-colonization of Spn or Mcat with Hi did not result in further increase of serum NTHi-specific antibody levels.

CONCLUSION

Co-colonization of Hi or Mcat with Spn enhances serum antibody response to NTSpn whole cells and Spn vaccine candidate antigens PhtD, PcPA and PlyD1. Co-colonization appears to variably modulate pathogen species-specific host adaptive immune response.

Risk of repeated Moraxella catarrhalis colonization is increased in children with Toll-like receptor 4 Asp299Gly polymorphism

BACKGROUND

Moraxella catarrhalis is a common causative agent of acute otitis media and other respiratory infections in children. Toll-like receptor (TLR) 4 is an important protein of human innate immunity. One polymorphic site Asp299Gly of TLR4 is proven to result in an impaired response to lipopolysaccharide from Gram-negative bacteria. We investigated whether Finnish children who carry Asp299Gly had increased risk of M. catarrhalis colonization during their first 2 years of life.

METHODS

This was a prospective cohort study carried out in Turku, Finland. We studied M. catarrhalis colonization in 161 Finnish children, whose nasopharyngeal specimens were taken at 2, 12 and 24 months of age. The semiquantitative culture method was used for identification of different bacterial species and the pyrosequencing-based method for detection of TLR4 Asp299Gly.

RESULTS

Of 161 subjects, 126 (78%) were TLR4 A/A wild type and 35 (22%) were A/G heterozygote variants. The prevalence of M. catarrhalis increased from 24% at 2 months to 48% at 12 months and to 58% at 24 months of age. Of the 35 subjects with TLR4 variant, 15 (43%) were M. catarrhalis positive at all 3 time points, whereas only 11 (9%) subjects with TLR4 wild type were positive at these time points (relative risk 4.91, 95% confidence interval: 2.482-9.711, P=0.0001). Moreover, subjects with TLR4 variant had significantly higher bacterial load of M. catarrhalis in their nasopharynx than those with TLR4 wild type (P=0.0032).

CONCLUSIONS

Our results indicate that children with TLR4 Asp299Gly polymorphism have an increased risk of repeated M. catarrhalis colonization.

Prevalent Multidrug-resistant Nonvaccine Serotypes in Pneumococcal Carriage of Healthy Korean Children Associated with the Low Coverage of the Seven-valent Pneumococcal Conjugate Vaccine

Objectives

Our previous longitudinal multicenter-based carriage study showed that the average carriage rate of Streptococcus pneumoniae was 16.8% in 582 healthy children attending kindergarten or elementary school in Seoul, Korea. We assessed serotype-specific prevalence and antimicrobial resistance among colonizing pneumococcal isolates from young children in the era of low use of the seven-valent pneumococcal conjugate vaccine (PCV7).

Methods

Serotypes were determined by an agglutination test with specific antisera or by a multiplex polymerase chain reaction (PCR) assay. An antimicrobial susceptibility test was performed with broth microdilution in Korean 96-well panels from Dade-MicroScan (Sacramento, CA, USA).

Results

Pneumococcal colonization patterns were dynamic and longterm persistent carriage was rare, which indicated a sequential turnover of pneumococcal strains. Of the 369 pneumococci (except for 23 killed isolates), 129 (34.9%) isolates were PCV7 vaccine serotypes (VTs); 213 (57.8%) isolates were nonvaccine serotypes (NVTs); and the remaining 27 (7.2%) isolates were nontypable (NT). The highest rates of multidrug resistance (MDR) were observed in VTs (86.0%; 111/129 isolates) and NVTs (70.0%; 149/213 isolates).

Conclusion

This study overall showed the frequent carriage of VTs and NVTs with MDR in healthy children attending kindergarten or elementary school. Efforts should be directed toward reducing the extensive prescription of antibiotics and using new broader vaccines to reduce the expansion of MDR strains of NVTs in our community.

Dominance of Haemophilus influenzae in ear discharge from Indigenous Australian children with acute otitis media with tympanic membrane perforation

Background

Indigenous Australian children living in remote communities experience high rates of acute otitis media with tympanic membrane perforation (AOMwiP). Otitis media in this population is associated with dense nasopharyngeal colonization of three primary otopathogens; Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis. Little is known about the relative abundance of these pathogens during infection. The objective of this study was to estimate the abundance and concordance of otopathogens in ear discharge and paired nasopharyngeal swabs from children with AOMwiP (discharge of not more than 6 weeks’ duration and perforation size <2%).

Methods

Culture and quantitative PCR (qPCR) estimation of H. influenzae, S. pneumoniae, M. catarrhalis and total bacterial load were performed on paired nasopharyngeal and ear discharge swabs from 55 Indigenous children with AOMwiP aged 3.5 – 45.6 months and resident in remote communities.

Results

By culture, H. influenzae, S. pneumoniae, and M. catarrhalis were detected in 80%, 84% and 91% of nasopharyngeal swabs, and 49%, 33% and 4% of ear discharge swabs, respectively. Using qPCR, H. influenzae, S. pneumoniae, and M. catarrhalis were detected in 82%, 82%, and 93% of nasopharyngeal swabs, and 89%, 41% and 18% of ear discharge swabs, respectively. Relative abundance of H. influenzae in ear discharge swabs was 0-68% of the total bacterial load (median 2.8%); whereas S. pneumoniae and M. catarrhalis relative abundances were consistently <2% of the total bacterial load. S. pneumoniae and M. catarrhalis abundances were significantly lower in ear discharge compared with nasopharyngeal swabs (p = 0.001, p < 0.001); no significant difference was observed in H. influenzae mean abundance at the two sites.

Conclusions

H. influenzae was the dominant otopathogen detected in ear discharge swabs collected from children with AOMwiP. High prevalence and abundance of S. pneumoniae and M. catarrhalis in the nasopharynx did not predict ear discharge prevalence and abundances of these pathogens. PCR was substantially more sensitive than culture for ear discharge, and a necessary adjunct to standard microbiology. Quantitative methods are required to understand species abundance in polymicrobial infections and may be needed to measure accurately the microbiological impact of interventions and to provide a better understanding of clinical failure in these children.

Chronic cough in preschool children

Cough may be the first overt sign of disease of the airways or lungs when it represents more than a defense mechanism, and may by its persistence become a helpful pointer of potential disease for both patient and physician. On the other hand, impairment or absence of the coughing mechanism can be harmful and even fatal; this is why cough suppression is rarely indicated in childhood. Pediatricians are concerned more with the etiology of the cough and making the right diagnosis. Whereas chronic cough in adults has been universally defined as a cough that lasts more than 8 weeks, in childhood, different timing has been reported. Many reasons support defining a cough that lasts more than 4 weeks in preschool children as chronic, however; and this is particularly true when the cough is wet. During childhood, the respiratory tract and nervous system undergo a series of anatomical and physiological maturation processes that influence the cough reflex. In addition, immunological response undergoes developmental and memorial processes that make infection and congenital abnormalities the overwhelming causes of cough in preschool children. Cough in children should be treated on the basis of etiology, and there is no evidence in support of the use of medication for symptomatic cough relief or adopting empirical approaches. Most cases of chronic cough in preschool age are caused by protracted bacterial bronchitis, tracheobronchomalacia, foreign body aspiration, post-infectious cough or some combination of these. Other causes of chronic cough, such as bronchiectasis, asthma, gastroesophageal reflux, and upper respiratory syndrome appear to be less frequent in this age group. The prevalence of each depends on the population in consideration, the epidemiology of infectious diseases, socioeconomic aspects, and the local health system.

Otitis media and ear tubes

The placement of myringotomy tubes remains an effective treatment of recurrent acute otitis media and chronic otitis media with effusion. Infants and young children are prone to these entities because of their immature anatomy and immunology. Several host, pathogenic, and environmental factors contribute to the development of these conditions. The identification and modification of some these factors can preclude the need for intervention. The procedure continues to be one of the most common outpatient pediatric procedures. Close vigilance and identification of potential complications is of utmost importance in the ongoing management of the child with middle ear disease.

Nasopharyngeal bacterial interactions in children

TOC summary: Pathogen prevalence differs during periods of health and at onset of acute otitis media.

Bacterial bronchitis caused by Streptococcus pneumoniae and nontypable Haemophilus influenzae in children: the impact of vaccination

BACKGROUND

Protracted bacterial bronchitis is a major cause of persistent cough in childhood. The organisms most commonly isolated are nontypable Haemophilus influenzae and Streptococcus pneumoniae . There are no studies addressing typing of these organisms when recovered from the lower airways.

METHODS

Isolates of these two organisms (identified in BAL samples from children undergoing routine investigation of a chronic cough thought to be attributable to a protracted bacterial bronchitis) were subject to typing. Samples were collected in Sheffield, England, and Athens, Greece. The majority of the children from Sheffield had received pneumococcal-conjugate vaccines 7 or 13 (PCV-7 or PCV-13) conjugate vaccine but only a minority of Greek children had received PCV-7.

RESULTS

All 18 S pneumoniae isolates from Greek BAL samples are serotypes contained in PCV-13 while 10 are contained in PCV-7. In contrast, 28 of the 39 samples from Sheffield contained serotypes that are not included in PCV-13. All 26 of the nontypable H influenzae samples obtained in Sheffield produced distinct multilocus variable-number tandem repeat analysis profiles. There was a significant difference between children from Athens and Sheffield in the distribution of serotypes contained or not contained in the pneumococcal vaccine ( P = .04). More specifically, immunization with pneumococcal vaccine was related with isolation of S pneumoniae serotypes not included in the vaccine (OR, 0.021; CI, 0.003-0.115; P < .001).

CONCLUSIONS

The data suggest that both vaccine and nonvaccine S pneumoniae serotypes may play a role in protracted bacterial bronchitis and provide some hints that serotype replacement may occur in response to the introduction of conjugate vaccines.

Nasopharyngeal microbial interactions in the era of pneumococcal conjugate vaccination

The nasopharynx of children is often colonised by microorganisms such as Streptococcus pneumoniae (the pneumococcus) that can cause infections including pneumonia and otitis media. In this complex environment, bacteria and viruses may impact each other through antagonistic as well as synergistic interactions. Vaccination may alter colonisation dynamics, evidenced by the rise in non-vaccine serotypes following pneumococcal conjugate vaccination. Discovery of an inverse relationship between S. pneumoniae and Staphylococcus aureus carriage generated concern that pneumococcal vaccination could increase S. aureus carriage and disease. Here we review data on co-colonisation of pathogens in the nasopharynx, focusing on S. pneumoniae and the impact of pneumococcal vaccination. Thus far, pneumococcal vaccination has not had a sustained impact on S. aureus carriage but it is associated with an increase in non-typeable Haemophilus influenzae in acute otitis media aetiology. Advances in bacterial and viral detection methodologies have facilitated research in nasopharyngeal microbiology and will aid investigation of potential vaccine-induced changes, particularly when baseline studies can be conducted prior to pneumococcal vaccine introduction.

Potential use of Atlantic cod trypsin in biomedicine

Surface proteins of viruses and bacteria used for cell attachment and invasion are candidates for degradation by proteases. Trypsin from Atlantic cod (Gadus morhua) was previously demonstrated to have efficacy against influenza viruses in vitro and on skin. In this paper, cod trypsin is shown to be 3–12 times more effective in degrading large native proteins than its mesophilic analogue, bovine trypsin. This is in agreement with previous findings where cod trypsin was found to be the most active among twelve different proteases in cleaving various cytokines and pathological proteins. Furthermore, our results show that cod trypsin has high efficacy against herpes simplex virus type 1 (HSV-1) and the respiratory syncytial virus (RSV) in vitro. The results on the antipathogenic properties of cod trypsin are important because rhinovirus, RSV, and influenza are the most predominant pathogenic viruses in upper respiratory tract infections. Results from a clinical study presented in this paper show that a specific formulation containing cod trypsin was preferred for wound healing over other methods used in the study. Apparently, the high digestive ability of the cold-adapted cod trypsin towards large native proteins plays a role in its efficacy against pathogens and its positive effects on wounds.

Pneumococcal 13-valent conjugate vaccine for the prevention of invasive pneumococcal disease in children and adults

Pneumococcal disease remains a global problem despite the availability of effective conjugate vaccines. The 13-valent pneumococcal conjugate vaccine (PCV13) extends the valency of PCV7 by including six additional serotypes highly associated with invasive pneumococcal disease (IPD). Comparisons between PCV13 and PCV7 or the pneumococcal polysaccharide vaccine have established noninferiority of PCV13 for both safety and immunogenicity profiles for use in children and adults, respectively. At the end of 2011, PCV13 had been approved and launched in 104 countries worldwide, with 54 including the vaccine in their pediatric national immunization program. Surveillance data from early adopters of PCV13 has indicated reductions are occurring in both overall IPD and IPD caused by the six non-PCV7 serotypes; early reports of serotype replacement in carriage are also emerging. While serotype replacement for PCV7 was observed to varying degrees for both carriage and disease, the extent to which this will occur for PCV13 is yet to be determined.

Moraxella catarrhalis: from interactions with the host immune system to vaccine development

Moraxella catarrhalis is a human-restricted commensal that over the last two decades has developed into an emerging respiratory tract pathogen. The bacterial species is equipped with various adhesins to facilitate its colonization. Successful evasion of the human immune system is a prerequisite for Moraxella infection. This strategy involves induction of an excessive proinflammatory response, intervention of granulocyte recruitment to the infection site, activation of selected pattern recognition receptors and cellular adhesion molecules to counteract the host bacteriolytic attack, as well as, finally, reprogramming of antigen presenting cells. Host immunomodulator molecules are also exploited by Moraxella to aid in resistance against complement killing and host bactericidal molecules. Thus, breaking the basis of Moraxella immune evasion mechanisms is fundamental for future invention of effective therapy in controlling Moraxella infection.

Viral and bacterial interactions in the upper respiratory tract

Respiratory infectious diseases are mainly caused by viruses or bacteria that often interact with one another. Although their presence is a prerequisite for subsequent infections, viruses and bacteria may be present in the nasopharynx without causing any respiratory symptoms. The upper respiratory tract hosts a vast range of commensals and potential pathogenic bacteria, which form a complex microbial community. This community is assumed to be constantly subject to synergistic and competitive interspecies interactions. Disturbances in the equilibrium, for instance due to the acquisition of new bacteria or viruses, may lead to overgrowth and invasion. A better understanding of the dynamics between commensals and pathogens in the upper respiratory tract may provide better insight into the pathogenesis of respiratory diseases. Here we review the current knowledge regarding specific bacterial–bacterial and viral–bacterial interactions that occur in the upper respiratory niche, and discuss mechanisms by which these interactions might be mediated. Finally, we propose a theoretical model to summarize and illustrate these mechanisms.

Density interactions among Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus in the nasopharynx of young Peruvian children

Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus are commonly carried in the nasopharynx of young children, and have been speculated to interact with each other. Although earlier studies used cultures alone to assess these interactions, the addition of real-time quantitative polymerase chain reaction (qPCR) provides further insight into these interactions. We compared results of culture and qPCR for the detection of these 3 bacteria in 446 nasopharynx samples collected from 360 healthy young children in a prospective cohort study in the Peruvian Andes. Patterns of concurrent bacterial colonization were studied using repeated measures logistic regression models with generalized estimating equations. Spearman correlation coefficients were used to assess correlations among bacterial densities. At a bacterial density <10 colony forming units/mL measured by qPCR, culture detected significantly less carriers (P < 0.0001) for all 3 pathogens, than at a bacterial density >10 colony forming units/mL. In addition, there was a positive association between S. pneumoniae and H. influenzae colonization measured by both culture (odds ratio [OR] 3.11-3.17, P < 0.001) and qPCR (OR 1.95-1.97, P < 0.01). The densities of S. pneumoniae and H. influenzae, measured by qPCR, were positively correlated (correlation coefficient 0.32, P < 0.001). A negative association was found between the presence of S. pneumoniae and Staphylococcus aureus in carriage with both culture (OR 0.45, P = 0.024) and qPCR (OR 0.61, P < 0.05). The impact of density on detection by culture and the observed density-related interactions support use of qPCR in additional studies to examine vaccine effects on diverse bacterial species.

Influence of bacterial interactions on pneumococcal colonization of the nasopharynx

Streptococcus pneumoniae (the pneumococcus) is a common commensal inhabitant of the nasopharynx and a frequent etiologic agent in serious diseases such as pneumonia, otitis media, bacteremia, and meningitis. Multiple pneumococcal strains can colonize the nasopharynx, which is also home to many other bacterial species. Intraspecies and interspecies interactions influence pneumococcal carriage in important ways. Co-colonization by two or more pneumococcal strains has implications for vaccine serotype replacement, carriage detection, and pneumonia diagnostics. Interactions between the pneumococcus and other bacterial species alter carriage prevalence, modulate virulence, and affect biofilm formation. By examining these interactions, this review highlights how the bacterial ecosystem of the nasopharynx changes the nature and course of pneumococcal carriage.

Haemophilus influenzae protein F mediates binding to laminin and human pulmonary epithelial cells

The mucosal pathogen nontypeable Haemophilus influenzae (NTHi) adheres to the respiratory epithelium or, in the case of epithelial damage, to the underlying basement membrane and extracellular matrix that, among other proteins, consists of laminin. We have recently identified protein F, an ABC transporter involved in NTHi immune evasion. Homology modeling of the protein F tertiary structure revealed a strong resemblance to the streptococcal laminin-binding proteins Lbp and Lmb. Here, we show that protein F promotes binding of NTHi to laminin and primary bronchial epithelial cells. Analyses with recombinant proteins and synthetic peptides revealed that the N-terminal part of protein F contains the host-interacting region. Moreover, protein F exists in all clinical isolates, and isogenic NTHi Δhpf mutants display significantly reduced binding to laminin and epithelial cells. We thus suggest protein F to be an important and ubiquitous NTHi adhesin.

Associations between potential bacterial pathogens in the nasopharynx of HIV infected children

OBJECTIVE

To investigate bacterial associations of S. pneumoniae, S. aureus, and H. influenzae in the nasopharynx of ambulatory children with HIV infection.

METHODS

A cross-sectional nasopharyngeal swab survey of 148 children with HIV infection from West Bengal presenting for routine outpatient care was conducted.

RESULTS

Forty-one (28 %) children carried S. pneumoniae, 35 (24 %) carried S. aureus and 39 (26 %) carried H. influenzae. Seventeen (11 %) had dual colonization with S. pneumoniae and H. influenzae, 13(8.8 %) had dual colonization with S. pneumoniae and S. aureus, and 6(4 %) had dual colonization with S. aureus and H. influenzae. Three (2 %) had triple carriage with H. influenzae, S. aureus, and S. pneumoniae. Neither Cotrimoxazole prophylaxis nor ART (antiretroviral therapy) affected colonization with any organism. There was no association between HIV immune status, recent antibiotic use, exposure to other children, household tuberculosis exposure and colonization with any organism. There was a strong negative association between malnutrition and colonization with H. influenzae.

CONCLUSIONS

The negative association between S. pneumoniae and S. aureus colonization in the nasopharynx described in healthy populations was not present. The authors found a strong positive association between carriage with H. influenzae and S. pneumoniae. These findings provide insight into the increased risk of invasive disease from these organisms in HIV infected children.

Kinetic analysis and evaluation of the mechanisms involved in the resolution of experimental nontypeable Haemophilus influenzae-induced otitis media after transcutaneous immunization

Transcutaneous immunization (TCI) is a simple and needle-free method with which to induce protective immune responses. Using a chinchilla model of nontypeable Haemophilus influenzae (NTHI)-induced otitis media (OM), we examined the efficacy afforded by TCI with a novel chimeric immunogen called 'chimV4' which targets two critical adhesins expressed by NTHI, outer membrane protein P5 and the majority subunit of NTHI Type IV pilus, PilA. Experimental OM was first established in cohorts of animals, and then TCI performed via a therapeutic immunization regime by rubbing vaccine formulations on hydrated pinnae. The kinetics of resolution of established experimental disease was evaluated by clinically-relevant assessments of OM, bacterial culture of planktonic and adherent NTHI within the middle ear and gross examination of the relative amount of NTHI mucosal biofilms within the middle ear space. Within seven days after primary TCI, a significant reduction in the signs of OM, significantly fewer NTHI adherent to the middle ear mucosa and significant resolution of mucosal biofilms was detected in animals that received chimV4+ the adjuvant LT(R192G-L211A), compared to animals administered LT(R192G-L211A) alone or saline by TCI (p<0.05) with eradication of NTHI within an additional seven days. The mechanism for rapid disease resolution involved efflux of activated dermal dendritic cells from the pinnae after TCI, secretion of factors chemotactic for CD4(+) T-cells, induction of polyfunctional IFNγ- and IL-17-producing CD4(+) T-cells and secretion of host defense peptide within the middle ear. These data support TCI as a therapeutic intervention against experimental NTHI-induced OM and begin to elucidate the host response to immunization by this noninvasive regimen.

Prevention of pneumococcal diseases in the post-seven valent vaccine era: a European perspective

BACKGROUND

The burden of invasive pneumococcal disease in young children decreased dramatically following introduction of the 7-valent pneumococcal conjugate vaccine (PCV7). The epidemiology of S. pneumoniae now reflects infections caused by serotypes not included in PCV7. Recently introduced higher valency pneumococcal vaccines target the residual burden of invasive and non-invasive infections, including those caused by serotypes not included in PCV7. This review is based on presentations made at the European Society of Pediatric Infectious Diseases in June 2011.

DISCUSSION

Surveillance data show increased circulation of the non-PCV7 vaccine serotypes 1, 3, 6A, 6C, 7 F and 19A in countries with routine vaccination. Preliminary evidence suggests that broadened serotype coverage offered by higher valency vaccines may be having an effect on invasive disease caused by some of those serotypes, including 19A, 7 F and 6C. Aetiology of community acquired pneumonia remains a difficult clinical diagnosis. However, recent reports indicate that pneumococcal vaccination has reduced hospitalisations of children for vaccine serotype pneumonia. Variations in serotype circulation and occurrence of complicated and non-complicated pneumonia caused by non-PCV7 serotypes highlight the potential of higher valency vaccines to decrease the remaining burden. PCVs reduce nasopharyngeal carriage and acute otitis media (AOM) caused by vaccine serotypes. Recent investigations of the interaction between S. pneumoniae and non-typeable H. influenzae suggest that considerable reduction in severe, complicated AOM infections may be achieved by prevention of early pneumococcal carriage and AOM infections. Extension of the vaccine serotype spectrum beyond PCV7 may provide additional benefit in preventing the evolution of AOM. The direct and indirect costs associated with pneumococcal disease are high, thus herd protection and infections caused by non-vaccine serotypes both have strong effects on the cost effectiveness of pneumococcal vaccination. Recent evaluations highlight the public health significance of indirect benefits, prevention of pneumonia and AOM and coverage of non-PCV7 serotypes by higher valency vaccines.

SUMMARY

Routine vaccination has greatly reduced the burden of pneumococcal diseases in children. The pneumococcal serotypes present in the 7-valent vaccine have greatly diminished among disease isolates. The prevalence of some non-vaccine serotypes (e.g. 1, 7 F and 19A) has increased. Pneumococcal vaccines with broadened serotype coverage are likely to continue decreasing the burden of invasive disease, and community acquired pneumonia in children. Further reductions in pneumococcal carriage and increased prevention of early AOM infections may prevent the evolution of severe, complicated AOM. Evaluation of the public health benefits of pneumococcal conjugate vaccines should include consideration of non-invasive pneumococcal infections, indirect effects of vaccination and broadened serotype coverage.

'Recurrent lower respiratory tract infections' - going around in circles, respiratory medicine style

Recurrent lower respiratory tract infections are very common in childhood, particularly the pre-school years. The term lower respiratory tract infection [LTRI] is, as with many terms used in respiratory medicine, used very loosely and carries little more information than the often decried term 'chest infections'. LRTIs should more accurately be characterised by the type of infection [viral or bacterial], the site of infection [conducting airways, or respiratory compartment or both - bronchitis/pneumonia/bronchopneumonia], the nature of the episode [acute or acute on chronic (exacerbation)], the interaction with co-morbidities such as asthma. The limited nature of the responses of the lower airways to any insult whether it is infective or irritation due to inhaled or aspirated chemicals means that almost any aetiology can lead to cough, shortness of breath and noisy breathing. We lack good non-invasive techniques to study the nature of the inflammation in the lower airways and hence the cause of chronic and recurrent symptoms in patients is frequently mis-diagnosed.

Cigarette smoke increases Staphylococcus aureus biofilm formation via oxidative stress

The strong epidemiological association between cigarette smoke (CS) exposure and respiratory tract infections is conventionally attributed to immunosuppressive and irritant effects of CS on human cells. Since pathogenic bacteria such as Staphylococcus aureus are members of the normal microbiota and reside in close proximity to human nasopharyngeal cells, we hypothesized that bioactive components of CS might affect these organisms and potentiate their virulence. Using Staphylococcus aureus as a model organism, we observed that the presence of CS increased both biofilm formation and host cell adherence. Analysis of putative molecular pathways revealed that CS exposure decreased expression of the quorum-sensing agr system, which is involved in biofilm dispersal, and increased transcription of biofilm inducers such as sarA and rbf. CS contains bioactive compounds, including free radicals and reactive oxygen species, and we observed transcriptional induction of bacterial oxidoreductases, including superoxide dismutase, following exposure. Moreover, pretreatment of CS with an antioxidant abrogated CS-mediated enhancement of biofilms. Exposure of bacteria to hydrogen peroxide alone increased biofilm formation. These observations are consistent with the hypothesis that CS induces staphylococcal biofilm formation in an oxidant-dependent manner. CS treatment induced transcription of fnbA (encoding fibronectin binding protein A), leading to increased binding of CS-treated staphylococci to immobilized fibronectin and increased adherence to human cells. These observations indicate that the bioactive effects of CS may extend to the resident microbiota of the nasopharynx, with implications for the pathogenesis of respiratory infection in CS-exposed humans.

Epidemiology of acute otitis media among young children: a multiple database study in Taiwan

BACKGROUND/PURPOSE

Acute otitis media (AOM) is a common complication of upper respiratory tract infection (URTI) among children. The purpose of this study was to evaluate the epidemiology of AOM among young children in Taiwan, including the age incidence and seasonality by combining multiple databases.

METHODS

Two country-based questionnaire survey studies had been conducted to evaluate the experience of otitis media (OM) among young children: one in 2007 and the other between 2005 and 2010. The number of OM cases (5% of population younger than 7 years) in 2005 and annual visiting rates for URTI from 2005 to 2010 obtained from the National Health Insurance Research Database of Taiwan were collected and comprised the third database. The fourth database comprised ambulatory visits of children with OM to a medical center in central Taiwan between 2005 and 2010.

RESULTS

Data from a total of 1099 questionnaires were entered into Database I in 2007, and data from 9705 questionnaires between 2005 and 2010 comprised Database II. There were 86,702 children (younger than 7 years, representing 5% of the whole population for this age group) retrieved from Database III in 2007, and 5,904 cases of OM in children between 2005 and 2010 in a hospital. In Database I, 7.46% children experienced at least one episode of AOM compared with 9.21% in Database II for children aged 5 years and younger. In Database III, 13.2% children younger than 7 years had AOM in 2005. The peak season of AOM among children was from March to May (Databases III and IV).

CONCLUSION

AOM was thought to be a very common disease among children; however, this comparative analysis showed that the overall prevalence of AOM among children younger than 5 years was only 20%, much lower than in other countries. AOM was more prevalent during the spring season, and still was similarly common after age 2 years.

Otitis media

Otitis media represents a broad spectrum of disease, which include acute otitis media and otitis media with effusion. As immunization with the pneumococcal conjugate vaccine has become more widespread, the microbiological landscape of otitis media has changed, which affects the treatment options facing clinicians worldwide. This review discusses the diagnosis and medical management of acute and chronic suppurative otitis media, the changes noted over the past decade, and briefly expounds on the surgical management of their severe complications.

High prevalence of nasal carriage of β-lactamase-negative ampicillin-resistant Haemophilus influenzae in healthy children in Korea

This study investigated the carriage of antimicrobial resistant Haemophilus influenzae in 582 healthy children attending kindergarten or elementary school at four intervals over a 9-month period in Seoul, Korea. Diverse colonization patterns and a lower level of long-term persistent carriage by H. influenzae status were evident in this study. Colonizing H. influenzae isolates showed a high rate of resistance to β-lactams including ampicillin (51·9%), cefaclor (52·1%), and amoxicillin/clavulanate (16·3%). Based on the ampicillin resistance mechanism, H. influenzae isolates were categorized as β-lactamase-negative, ampicillin-susceptible (BLNAS) (48·1%), β-lactamase-positive, ampicillin-resistant (BLPAR) (22·6%), β-lactamase-negative, ampicillin-resistant (BLNAR) (22·8%), and β-lactamase-positive, amoxicillin/clavulanate-resistant (BLPACR) strains (6·5%). This study provides the first evidence of a high prevalence (22·8%) of BLNAR strains of H. influenzae nasal carriage in healthy children attending kindergarten or the first 2 years of elementary school in Korea. The high carriage of these resistant strains in overcrowded urban settings may create reservoirs for development of H. influenzae-resistant strains.

Innate immune properties of selected human neuropeptides against Moraxella catarrhalis and nontypeable Haemophilus influenzae

Background

Considerable evidence supports the concept of active communication between the nervous and immune systems. One class of such communicators are the neuropeptides (NPs). Recent reports have highlighted the antimicrobial activity of neuropeptides, placing them among the integral components of innate immune defense. This study examined the action of four human neuropeptides: calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), substance P (SP) and somatostatin (SOM), which are accessible in the upper respiratory tract, against two human-specific respiratory pathogens. We studied: (i) neuropeptide-mediated direct antibacterial activity exerted against Moraxella catarrhalis and nontypeable Haemophilus influenzae, and (ii) indirect immunomodulatory role of these neuropeptides in the neutrophil-mediated phagocytosis of indicated pathogens.

Results

We found that 100 micromolar concentrations of CGRP, NPY, SP, and SOM effectively permeabilized bacterial membranes and showed (except SOM) bactericidal activity against both pathogens. SOM acted only bacteriostatically. However the killing efficacy was dependent on the bactericidal assay used. The rank order of killing NP effect was: NPY ≥ CGRP > SP >> SOM and correlated with their potency to permeabilize bacterial membranes. The killing and permeabilization activity of the analyzed NPs showed significant correlation with several physicochemical properties and amino acid composition of the neuropeptides. M. catarrhalis was more sensitive to neuropeptides than nontypeable H. influenzae.

The immunomodulatory bimodal effect of physiological concentrations of CGRP, NPY, and SP on the phagocytic function of human neutrophils against M. catarrhalis and H. influenzae was observed both in the ingestion (pathogen uptake) and reactive oxygen species generation stages. This effect was also dependent on the distinct type of pathogen recognition (opsonic versus nonopsonic).

Conclusions

The present results indicate that neuropeptides such as CGRP, NPY, and SP can effectively participate in the direct and indirect elimination of human-specific respiratory pathogens. Because the studied NPs show both direct and indirect modulating antimicrobial potency, they seem to be important molecules involved in the innate host defense against M. catarrhalis and nontypeable H. influenzae.

The mucosal immune system of the respiratory tract

Most viruses use host mucosal surfaces as their initial portals of infection. The respiratory tract has the body's second-largest mucosal surface area after the digestive tract. An understanding of the unique nature of the mucosal immune system of respiratory organs is therefore extremely important for the development of new-generation vaccines and novel methods of preventing and treating respiratory infectious diseases, including viral infections.

Nasopharyngeal biofilm-producing otopathogens in children with nonsevere recurrent acute otitis media

OBJECTIVE

Bacterial biofilms have been detected in biopsies of the adenoid and middle ear mucosa of otitis-prone children and children with chronic middle otitis media. However, the invasiveness of biopsy makes it unsuitable for routine clinical practice, especially in pediatrics. This study aimed to investigate nasopharyngeal biofilm-producing otopathogens (BPOs) of nasopharyngeal swabs (NPS) in children with a history of nonsevere recurrent acute otitis media (RAOM) and healthy controls.

STUDY DESIGN

A cross-sectional study with planned data collection.

SETTING

University of Milan.

SUBJECTS AND METHODS

Transoral NPS were taken from infants and children aged 10 months to 11 years with nonsevere RAOM or healthy controls without adenoid hypertrophy. Nasopharyngeal colonization by otopathogens was assessed by means of microbiological cultures and standard bacterial identification, as well as nasopharyngeal BPOs by means of spectrophotometric analysis.

RESULTS

The study involved 113 children (56.6% males; median age 40 months; range, 10-132 months): 58 with a history of nonsevere RAOM (51.3%) and 55 controls (48.7%). Otopathogens were significantly more frequently detected in the RAOM group (24/58, 41.4%) than in controls (8/55, 14.5%; P = .003); the main pathogens were respectively Haemophilus influenzae (12/24, 50.0%) and Streptococcus pyogenes (3/8, 37.5%). Nasopharyngeal BPOs were more frequently isolated in the RAOM group (17/58, 29.3%) than in controls (6/55, 10.9%; P = .02). H influenzae (12/17, 70.6%) was confirmed as the main pathogen in the RAOM group.

CONCLUSION

The presence of nasopharyngeal BPOs is an important factor favoring RAOM; it is therefore useful investigating biofilms even in children with nonsevere recurrences of AOM without adenoid hypertrophy.

Synergistic and feedback signaling mechanisms in the regulation of inflammation in respiratory infections

Pneumonia, the most typical and frequent lower respiratory tract infection (LRTI), is a leading cause of health problems in the United States. Bacteria represent the most prevailing cause of pneumonia in both children and adults. Although pneumonia with a single bacterial infection is common, a significant portion of patients with pneumonia is polymicrobial. This infection is often complexed with other physiological factors such as cytokines and growth factors. Nontypeable Haemophilus influenzae (NTHi) is the most frequently recovered Gram-negative bacterial pathogen in the respiratory system and induces strong inflammatory responses. NTHi also synergizes with other respiratory pathogens, such as Streptococcus pneumoniae and respiratory viruses and pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α). It is noteworthy that NTHi not only synergizes with growth factors such as transforming growth factor-beta (TGF-β), but also utilizes growth factor receptors such as TGF-β receptor and epidermal growth factor receptor (EGFR), to enhance inflammatory responses. Although appropriate inflammation is a protective response against invading pathogens, an uncontrolled inflammatory response is often detrimental to the host. Thus, inflammation must be tightly regulated. The human immune system has evolved strategies for controlling overactive inflammatory response. One such important mechanism is via regulation of negative feedback regulators for inflammation. CYLD, a multifunctional deubiquitinase, was originally reported as a tumor suppressor, but was recently identified as a negative regulator for nuclear factor-kappa B (NF-κB) signaling. It is induced by NTHi and TNF-α via a NF-κB-dependent mechanism, thereby serving as an inducible negative feedback regulator for tightly controlling inflammation in NTHi infection.

Nasal colonization by four potential respiratory bacteria in healthy children attending kindergarten or elementary school in Seoul, Korea

A longitudinal analysis was carried out of the colonization by four potential respiratory pathogens - Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus - in 165 healthy children (aged 3-7 years) attending three kindergartens and 417 healthy children (aged 7-10 years) attending an elementary school in Seoul, Korea, by four consecutive examinations over 1 year. The prevalence of nasal carriers of one or more of four bacteria was found to be higher in younger children (≤7 years) (mean 68.6%) than that in older children (mean 46.8%). The mean rates of nasal carriage of Strep. pneumoniae, H. influenzae, M. catarrhalis and Staph. aureus were 16.8, 18.9, 20.2 and 18.2%, respectively. Colonization by Strep. pneumoniae, H. influenzae and M. catarrhalis was higher in pre-school children (28.6, 32.4 and 35.0%, respectively) than in school children (12.2, 13.6 and 14.3%, respectively). Carriage trends differed with age, with Strep. pneumoniae, H. influenzae and M. catarrhalis colonization decreasing with age but Staph. aureus colonization increasing. Positive associations of co-occurrence between Strep. pneumoniae, H. influenzae and M. catarrhalis were evident, with a significant negative association evident between Staph. aureus and the other three bacteria. A better understanding of the colonization and interaction of potential respiratory pathogens may be important for predicting changes in bacterial ecology and for designing control strategies that target bacterial colonization in upper respiratory tract infections.