Antimicrobial susceptibility of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis clinical isolates from children with acute otitis media in Japan from 2014 to 2017

Comparative efficacy and optimal duration of first-line antibiotic regimens for acute otitis media in children and adolescents: a systematic review and network meta-analysis of 89 randomized clinical trials

INTRODUCTION

Antibiotic use for acute otitis media (AOM) is one of the major sources of antimicrobial resistance. However, the effective minimal antibiotic duration for AOM remains unclear. Moreover, guidelines often recommend broad ranges (5-10 days) of antibiotic use, yet the clinical impact of such a wide window has not been assessed.

METHODS

We systematically searched PubMed/MEDLINE, Embase, Scopus, Web of Science, and Cochrane Library from database inception to 6 October 2021. Network meta-analysis was conducted on randomized controlled trials that assessed antibiotic treatment for AOM in children (PROSPERO CRD42020196107).

RESULTS

For amoxicillin and amoxicillin-clavulanate, 7-day regimens were noninferior to 10-day regimens in clinical responses [amoxicillin: risk ratio (RR) 0.919 (95% CI 0.820-1.031), amoxicillin-clavulanate: RR 1.108 (0.957-1.282)], except for ≤ 2 years. For the third-generation cephalosporins, 7-day and 10-day regimens had similar clinical responses compared to placebo [7-day: RR 1.420 (1.190-1.694), 10-day: RR 1.238 (1.125-1.362) compared to placebo]. However, 5-day regimens of amoxicillin-clavulanate and third-generation cephalosporins were inferior to 10-day regimens. Compared to amoxicillin, a shorter treatment duration was tolerable with amoxicillin-clavulanate.

CONCLUSIONS

Our findings indicated that 10 days of antibiotic use may be unnecessarily long, while the treatment duration should be longer than 5 days. Otherwise, 5-day regimens would be sufficient for a modest treatment goal. Our findings revealed that the current wide range of recommended antibiotic durations may have influenced the clinical outcome of AOM, and a narrower antibiotic duration window should be re-established.

Investigation of oral macrolide prescriptions in Japan using a retrospective claims database, 2013-2018

Macrolide usage in Japan exceeds that in Europe and the United States. Investigating the actual conditions in which macrolides are used is important for identifying further interventions for appropriate antimicrobial use; however, this situation has not been evaluated in Japan. Therefore, we aimed to clarify the number of macrolide prescriptions and their changes before and after implementation of the Antimicrobial Resistance (AMR) Action Plan. In addition, we also investigated the names of diseases for which macrolides have been prescribed and the number of days of prescription. A retrospective observational study was conducted using JMDC claims data from January 2013 to December 2018. The proportion of all oral antimicrobials and macrolides used during this period and the diseases for which macrolides were used in the 3 years before and after the AMR Action Plan were determined separately for acute (< 14 prescription days) and chronic (> 14 prescription days) diseases. The number of prescriptions for macrolides constituted approximately 30% of those for all oral antimicrobials; of these, clarithromycin accounted for approximately 60%. Most prescriptions for acute diseases were for common cold, whereas allergic and dermatological diseases were included among chronic diseases. The names of these illnesses did not change before and after the AMR Action Plan. Overall, these results indicate that appropriate macrolide use involves a review of their use for common cold along with appropriate evaluation of their long-term use for skin and allergic diseases. They also indicate the need for further fact-finding studies and ongoing AMR measures.

Macrolides Decrease the Proinflammatory Activity of Macrolide-Resistant Streptococcus pneumoniae

Over the past 2 decades, the prevalence of macrolide-resistant Streptococcus pneumoniae (MRSP) has increased considerably, due to widespread macrolide use. Although macrolide usage has been proposed to be associated with treatment failure in patients with pneumococcal diseases, macrolides may be clinically effective for treating these diseases, regardless of the susceptibility of the causative pneumococci to macrolides. As we previously demonstrated that macrolides downregulate the transcription of various genes in MRSP, including the gene encoding the pore-forming toxin pneumolysin, we hypothesized that macrolides affect the proinflammatory activity of MRSP. Using HEK-Blue cell lines, we found that the supernatants from macrolide-treated MRSP cultures induced decreased NF-κB activation in cells expressing Toll-like receptor 2 and nucleotide-binding oligomerization domain 2 compared to the supernatants from untreated MRSP cells, suggesting that macrolides inhibit the release of these ligands from MRSP. Real-time PCR analysis revealed that macrolides significantly downregulated the transcription of various genes encoding peptidoglycan synthesis-, lipoteichoic acid synthesis-, and lipoprotein synthesis-related molecules in MRSP cells. The silkworm larva plasma assay demonstrated that the peptidoglycan concentrations in the supernatants from macrolide-treated MRSP cultures were significantly lower than those from untreated MRSP cultures. Triton X-114 phase separation revealed that lipoprotein expression decreased in macrolide-treated MRSP cells compared to the lipoprotein expression in untreated MRSP cells. Consequently, macrolides may decrease the expression of bacterial ligands of innate immune receptors, resulting in the decreased proinflammatory activity of MRSP. IMPORTANCE To date, the clinical efficacy of macrolides in pneumococcal disease is assumed to be linked to their ability to inhibit the release of pneumolysin. However, our previous study demonstrated that oral administration of macrolides to mice intratracheally infected with macrolide-resistant Streptococcus pneumoniae resulted in decreased levels of pneumolysin and proinflammatory cytokines in bronchoalveolar lavage fluid samples compared to the levels in samples from untreated infected control mice, without affecting the bacterial load in the fluid. This finding suggests that additional mechanisms by which macrolides negatively regulate proinflammatory cytokine production may be involved in their efficacy in vivo. Furthermore, in this study, we demonstrated that macrolides downregulated the transcription of various proinflammatory-component-related genes in S. pneumoniae, which provides an additional explanation for the clinical benefits of macrolides.

Erythromycin Restores Osteoblast Differentiation and Osteogenesis Suppressed by Porphyromonas gingivalis Lipopolysaccharide

The macrolide erythromycin (ERM) inhibits excessive neutrophil accumulation and bone resorption in inflammatory tissues. We previously reported that the expression of developmental endothelial locus-1 (DEL-1), an endogenous anti-inflammatory factor induced by ERM, is involved in ERM action. Furthermore, DEL-1 is involved in the induction of bone regeneration. Therefore, in this study, we investigated whether ERM exerts an osteoblastogenic effect by upregulating DEL-1 under inflammatory conditions. We performed in vitro cell-based mechanistic analyses and used a model of Porphyromonas gingivalis lipopolysaccharide (LPS)-induced periodontitis to evaluate how ERM restores osteoblast activity. In vitro, P. gingivalis LPS stimulation suppressed osteoblast differentiation and bone formation. However, ERM treatment combined with P. gingivalis LPS stimulation upregulated osteoblast differentiation-related factors and Del1, indicating that osteoblast differentiation was restored. Alveolar bone resorption and gene expression were evaluated in a periodontitis model, and the results confirmed that ERM treatment increased DEL-1 expression and suppressed bone loss by increasing the expression of osteoblast-associated factors. In conclusion, ERM restores bone metabolism homeostasis in inflammatory environments possibly via the induction of DEL-1.

Mutation of TonB-Dependent Receptor Encoding Gene MCR_0492 Potentially Associates with Macrolides Resistance in Moraxella catarrhalis Isolates

Introduction

Moraxella catarrhalis, which is an opportunistic pathogen and is one of the three major pathogens of community-acquired pneumonia, causes a variety of infections in clinic. In recent years, the isolation rate of Moraxella catarrhalis has gradually increased. In China, due to the clinical empirical use of antibiotics, the resistance rate of Moraxella catarrhalis isolated from children to β-lactam antibiotics has reached 99%. The non-susceptible rate of Moraxella catarrhalis to macrolide antibiotics has also increased significantly.

Methods

Two isolates of Moraxella catarrhalis (R17123922_R and R18013231_R) were isolated from in-patients and were confirmed to be resistant to macrolide antibiotics using the standard disk diffusion and broth microdilution method recommended by CLSI. Whole-genome sequencing (WGS) analysis was performed in these two resistant strains.

Results

A total of 696 SNVs (single nucleotide variations), and 79 indels (Insertion and Deletion) were found in R17123922_R and R18013231_R. These SNVs and indels were distributed evenly in the genome, and no centralized distribution occurred. Moreover, two isolates did not harbor any previously reported mutations in the 23S rRNA and ribosomal proteins.

Conclusion

A novel indel in the MCR_0492 gene encoding TonB-dependent receptor protein was identified, and we speculated that TonB-dependent protein receptor may play an important role in macrolide resistance of Moraxella catarrhalis.

Matcha Green Tea Exhibits Bactericidal Activity against Streptococcus pneumoniae and Inhibits Functional Pneumolysin

Streptococcus pneumoniae is a causative pathogen of several human infectious diseases including community-acquired pneumonia. Pneumolysin (PLY), a pore-forming toxin, plays an important role in the pathogenesis of pneumococcal pneumonia. In recent years, the use of traditional natural substances for prevention has drawn attention because of the increasing antibacterial drug resistance of S. pneumoniae. According to some studies, green tea exhibits antibacterial and antitoxin activities. The polyphenols, namely the catechins epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC) are largely responsible for these activities. Although matcha green tea provides more polyphenols than green tea infusions, its relationship with pneumococcal pneumonia remains unclear. In this study, we found that treatment with 20 mg/mL matcha supernatant exhibited significant antibacterial activity against S. pneumoniae regardless of antimicrobial resistance. In addition, the matcha supernatant suppressed PLY-mediated hemolysis and cytolysis by inhibiting PLY oligomerization. Moreover, the matcha supernatant and catechins inhibited PLY-mediated neutrophil death and the release of neutrophil elastase. These findings suggest that matcha green tea reduces the virulence of S. pneumoniae in vitro and may be a promising agent for the treatment of pneumococcal infections.

Clarithromycin Inhibits Pneumolysin Production via Downregulation of ply Gene Transcription despite Autolysis Activation

Streptococcus pneumoniae, the most common cause of community-acquired pneumonia, causes severe invasive infections, including meningitis and bacteremia. The widespread use of macrolides has been reported to increase the prevalence of macrolide-resistant S. pneumoniae (MRSP), thereby leading to treatment failure in patients with pneumococcal pneumonia. However, previous studies have demonstrated that several macrolides and lincosamides have beneficial effects on MRSP infection since they inhibit the production and release of pneumolysin, a pneumococcal pore-forming toxin released during autolysis. In this regard, we previously demonstrated that the mechanisms underlying the inhibition of pneumolysin release by erythromycin involved both the transcriptional downregulation of the gene encoding pneumolysin and the impairment of autolysis in MRSP. Here, using a cell supernatant of the culture, we have shown that clarithromycin inhibits pneumolysin release in MRSP. However, contrary to previous observations in erythromycin-treated MRSP, clarithromycin upregulated the transcription of the pneumococcal autolysis-related lytA gene and enhanced autolysis, leading to the leakage of pneumococcal DNA. On the other hand, compared to erythromycin, clarithromycin significantly downregulated the gene encoding pneumolysin. In a mouse model of MRSP pneumonia, the administration of both clarithromycin and erythromycin significantly decreased the pneumolysin protein level in bronchoalveolar lavage fluid and improved lung injury and arterial oxygen saturation without affecting bacterial load. Collectively, these in vitro and in vivo data reinforce the benefits of macrolides on the clinical outcomes of patients with pneumococcal pneumonia.

IMPORTANCE Pneumolysin is a potent intracellular toxin possessing multiple functions that augment pneumococcal virulence. For over 10 years, sub-MICs of macrolides, including clarithromycin, have been recognized to decrease pneumolysin production and release from pneumococcal cells. However, this study indicates that macrolides significantly slowed pneumococcal growth, which may be related to decreased pneumolysin release recorded by previous studies. In this study, we demonstrated that clarithromycin decreases pneumolysin production through downregulation of ply gene transcription, regardless of its inhibitory activity against bacterial growth. Additionally, administration of clarithromycin resulted in the amelioration of lung injury in a mouse model of pneumonia induced by macrolide-resistant pneumococci. Therefore, therapeutic targeting of pneumolysin offers a good strategy to treat pneumococcal pneumonia.

Antimicrobial resistance of Haemophilus influenzae isolates from pediatric hospitals in Mainland China: Report from the ISPED program, 2017-2019

PURPOSE

This study set out to determine the antimicrobial resistance trends of Haemophilus influenzae isolates from pediatric hospitals in Mainland China, which would provide basis for clinical treatment.

METHODS

The Infectious Disease Surveillance of Pediatrics (ISPED) collaboration group conducted this study. H. influenzae strains isolated from nine pediatric hospitals in Mainland China were included. Disk diffusion method was used for antimicrobial susceptibility test. Cefinase disc was used for detection of β-lactamase.

RESULTS

In total, 13810 H. influenzae isolates were included during 2017-2019: 93.17% of which were from respiratory tract specimens, 4.63% from vaginal swabs, 1.10% from secretion, and 1.10% from others. Of all strains, 63.32% isolates produced β-lactamase; 8.22% isolates were β-lactamase-negative and ampicillin-resistant (BLNAR). The resistance to sulfamethoxazole-trimethoprim was 70.98%, followed by resistance to ampicillin (69.37%), cefuroxime (51.35%), ampicillin-sulbactam (38.82%), azithromycin (38.21%), amoxicillin-clavulanate (35.28%). More than 90% of H. influenzae isolates were susceptible to ceftriaxone, cefotaxime, meropenem, levofloxacin and chloramphenicol. The resistance rate of ampicillin and azithromycin in H. influenzae showed an increasing trend through the years. Statistically significant differences in antibiotic-resistance rates of all the antibiotics except chloramphenicol were found in different regions. The major Multi-Drug Resistance pattern was resistant to β-lactams, macrolides, and sulfonamides.

CONCLUSIONS

There is a rising trend of resistance rate of ampicillin and azithromycin in H. influenzae. Antimicrobial resistance of H. influenzae deserves our ongoing attention. Third-generation cephalosporin could be the preferred treatment option of infections caused by ampicillin-resistant H. influenzae.

Characteristics and Antibiotic Resistance of Haemophilus influenzae in Children with Lower Respiratory Tract Infection in Chengdu, China

Background: Haemophilus influenzae is an opportunistic pathogen of the human respiratory tract. Haemophilus influenzae can cause not only respiratory tract infection in children but also otitis media, epiglottitis and sinusitis. With the widespread use of antibiotics, the positive rate of β-lactamase in H. influenzae is increasing, and the rate of antimicrobial resistance is also increasing, which increases the difficulty of clinical treatment. Objectives: To study the infection characteristics of patients and the antibiotic resistance of H. influenzae in lower respiratory tract samples of children in Chengdu, so as to provide a reference for its clinical diagnosis and the rational use of antibiotics. Methods: Sputum samples of 15891 children aged 0-14 years with lower respiratory tract infection were collected. Haemophilus influenzae was cultured and identified, its drug susceptibility tested, and the results determined according to the guidelines of CLSI 2020. Results: A total of 15891 clinical isolate strains in sputum were detected for drug sensitivity from December 2018 to January 2020, of which 5488 were H. influenzae, accounting for 34.54% (5488/15891). The sex of children infected with H. influenzae was not skewed (P > 0.05). The detection rate of H. influenzae was the highest in children aged 7 - 11 months, and the lowest was in the age group ≤ 28 d. The detection rate was the highest in spring and the lowest in autumn. The positive rate of β-lactamase was 92.0%, the resistance rate to ampicillin was 92.0%, the sensitivity to amoxicillin/clavulanate was 70.2%, and the sensitivity to cefotaxime, ofloxacin, tetracycline, chloramphenicol, and rifampicin was more than 90.0%. Conclusions: Children aged 7 months to 14 years were generally susceptible to H. influenzae in spring, and the positive rate of β-lactamase was high. Doctors should refer to the infection characteristics and drug resistance of H. influenzae and choose antibiotics correctly to better control the infection.

A Prospective, Population-based Study to Determine the Incidence and Bacteriology of Bacterial Conjunctivitis in Children <2 Years of Age Following 7-Valent and 13-Valent Pneumococcal Conjugate Vaccine Sequential Implementation

BACKGROUND

Bacterial conjunctivitis is most commonly caused by nontypeable Haemophilus influenzae (NTHi), followed by Streptococcus pneumoniae. No population-based data on the impact of pneumococcal conjugate vaccines (PCVs) on the incidence of bacterial conjunctivitis have been published. We assessed rate dynamics of overall, pneumococcal, and NTHi conjunctivitis in children aged 2-23 months in southern Israel before and after PCV implementation.

METHODS

This is a 12-year prospective, population-based surveillance, from July 2004 through June 2017. Our medical center serves a captive population of approximately 30 000 children < 2 years of age, and its clinical microbiology laboratory processes > 80% of all community-derived cultures, enabling incidence calculation. The 7-valent and 13-valent PCVs (PCV7 and PCV13, respectively) were implemented in the national immunization program in July 2009 and November 2010, respectively. Pneumococci, NTHi, Moraxella catarrhalis, and Streptococcus pyogenes were considered pathogens. Continuous annual incidences and incidence rate ratios comparing the PCV13 period (2015-2017) to the pre-PCV period (2004-2008) were calculated.

RESULTS

Disease caused by PCV13 serotypes declined by 93%, without significant replacement with non-PCV13 serotypes. Rates of pneumococcal, NTHi, and overall culture-positive episodes declined by 59%, 41%, and 42%, respectively, while rates of culture-negative and other pathogens episodes did not change significantly. An overall reduction in all submitted culture rates of 35% was observed. This pattern was seen across all ages, including infants aged 2-5 months.

CONCLUSIONS

PCV7/PCV13 implementation resulted in a marked and significant decline in pneumococcal, NTHi, and overall conjunctivitis rates in children < 2 years of age. The impact on NTHi episodes alludes to the role of pneumococcus-NTHi interaction in conjunctivitis. The impact in infants aged < 6 months suggests herd protection.

The Role of Neutrophils and Neutrophil Elastase in Pneumococcal Pneumonia

Streptococcus pneumoniae, also known as pneumococcus, is a Gram-positive diplococcus and a major human pathogen. This bacterium is a leading cause of bacterial pneumonia, otitis media, meningitis, and septicemia, and is a major cause of morbidity and mortality worldwide. To date, studies on S. pneumoniae have mainly focused on the role of its virulence factors including toxins, cell surface proteins, and capsules. However, accumulating evidence indicates that in addition to these studies, knowledge of host factors and host-pathogen interactions is essential for understanding the pathogenesis of pneumococcal diseases. Recent studies have demonstrated that neutrophil accumulation, which is generally considered to play a critical role in host defense during bacterial infections, can significantly contribute to lung injury and immune subversion, leading to pneumococcal invasion of the bloodstream. Here, we review bacterial and host factors, focusing on the role of neutrophils and their elastase, which contribute to the progression of pneumococcal pneumonia.

Treatment of severe pneumonia by hinokitiol in a murine antimicrobial-resistant pneumococcal pneumonia model

Streptococcus pneumoniae is often isolated from patients with community-acquired pneumonia. Antibiotics are the primary line of treatment for pneumococcal pneumonia; however, rising antimicrobial resistance is becoming more prevalent. Hinokitiol, which is isolated from trees in the cypress family, has been demonstrated to exert antibacterial activity against S. pneumoniae in vitro regardless of antimicrobial resistance. In this study, the efficacy of hinokitiol was investigated in a mouse pneumonia model. Male 8-week-old BALB/c mice were intratracheally infected with S. pneumoniae strains D39 (antimicrobial susceptible) and NU4471 (macrolide resistant). After 1 h, hinokitiol was injected via the tracheal route. Hinokitiol significantly decreased the number of S. pneumoniae in the bronchoalveolar lavage fluid (BALF) and the concentration of pneumococcal DNA in the serum, regardless of whether bacteria were resistant or susceptible to macrolides. In addition, hinokitiol decreased the infiltration of neutrophils in the lungs, as well as the concentration of inflammatory cytokines in the BALF and serum. Repeated hinokitiol injection at 18 h intervals showed downward trend in the number of S. pneumoniae in the BALF and the concentration of S. pneumoniae DNA in the serum with the number of hinokitiol administrations. These findings suggest that hinokitiol reduced bacterial load and suppressed excessive host immune response in the pneumonia mouse model. Accordingly, hinokitiol warrants further exploration as a potential candidate for the treatment of pneumococcal pneumonia.

Erythromycin inhibits neutrophilic inflammation and mucosal disease by upregulating DEL-1

Macrolide antibiotics exert antiinflammatory effects; however, little is known regarding their immunomodulatory mechanisms. In this study, using 2 distinct mouse models of mucosal inflammatory disease (LPS-induced acute lung injury and ligature-induced periodontitis), we demonstrated that the antiinflammatory action of erythromycin (ERM) is mediated through upregulation of the secreted homeostatic protein developmental endothelial locus-1 (DEL-1). Consistent with the anti-neutrophil recruitment action of endothelial cell-derived DEL-1, ERM inhibited neutrophil infiltration in the lungs and the periodontium in a DEL-1-dependent manner. Whereas ERM (but not other antibiotics, such as josamycin and penicillin) protected against lethal pulmonary inflammation and inflammatory periodontal bone loss, these protective effects of ERM were abolished in Del1-deficient mice. By interacting with the growth hormone secretagogue receptor and activating JAK2 in human lung microvascular endothelial cells, ERM induced DEL-1 transcription that was mediated by MAPK p38 and was CCAAT/enhancer binding protein-β dependent. Moreover, ERM reversed IL-17-induced inhibition of DEL-1 transcription, in a manner that was dependent not only on JAK2 but also on PI3K/AKT signaling. Because DEL-1 levels are severely reduced in inflammatory conditions and with aging, the ability of ERM to upregulate DEL-1 may lead to a novel approach for the treatment of inflammatory and aging-related diseases.

Oxidative killing of encapsulated and nonencapsulated Streptococcus pneumoniae by lactoperoxidase-generated hypothiocyanite

Streptococcus pneumoniae (Pneumococcus) infections affect millions of people worldwide, cause serious mortality and represent a major economic burden. Despite recent successes due to pneumococcal vaccination and antibiotic use, Pneumococcus remains a significant medical problem. Airway epithelial cells, the primary responders to pneumococcal infection, orchestrate an extracellular antimicrobial system consisting of lactoperoxidase (LPO), thiocyanate anion and hydrogen peroxide (H₂O₂). LPO oxidizes thiocyanate using H₂O₂ into the final product hypothiocyanite that has antimicrobial effects against a wide range of microorganisms. However, hypothiocyanite’s effect on Pneumococcus has never been studied. Our aim was to determine whether hypothiocyanite can kill S. pneumoniae. Bactericidal activity was measured in a cell-free in vitro system by determining the number of surviving pneumococci via colony forming units on agar plates, while bacteriostatic activity was assessed by measuring optical density of bacteria in liquid cultures. Our results indicate that hypothiocyanite generated by LPO exerted robust killing of both encapsulated and nonencapsulated pneumococcal strains. Killing of S. pneumoniae by a commercially available hypothiocyanite-generating product was even more pronounced than that achieved with laboratory reagents. Catalase, an H₂O₂ scavenger, inhibited killing of pneumococcal by hypothiocyanite under all circumstances. Furthermore, the presence of the bacterial capsule or lytA-dependent autolysis had no effect on hypothiocyanite-mediated killing of pneumococci. On the contrary, a pneumococcal mutant deficient in pyruvate oxidase (main bacterial H₂O₂ source) had enhanced susceptibility to hypothiocyanite compared to its wild-type strain. Overall, results shown here indicate that numerous pneumococcal strains are susceptible to LPO-generated hypothiocyanite.

Epidemiology of hospitalised paediatric community-acquired pneumonia and bacterial pneumonia following the introduction of 13-valent pneumococcal conjugate vaccine in the national immunisation programme in Japan

Studies on community-acquired pneumonia (CAP) and pneumococcal pneumonia (PP) related to the 13-valent pneumococcal conjugate vaccine (PCV13) introduction in Asia are scarce. This study aimed to investigate the epidemiological and microbiological determinants of hospitalised CAP and PP after PCV13 was introduced in Japan. This observational hospital-based surveillance study included children aged ⩽15 years, admitted to hospitals in and around Chiba City, Japan. Participants had bacterial pneumonia based on a positive blood or sputum culture for bacterial pathogens. Serotype and antibiotic-susceptibility testing of Streptococcus pneumoniae and Haemophilus influenzae isolates from patients with bacterial pneumonia were assessed. The CAP hospitalisation rate per 1000 child-years was 17.7, 14.3 and 9.7 in children aged <5 years and 1.18, 2.64 and 0.69 in children aged 5-15 years in 2008, 2012 and 2018, respectively. There was a 45% and 41% reduction in CAP hospitalisation rates, between the pre-PCV7 and PCV13 periods, respectively. Significant reductions occurred in the proportion of CAP due to PP and PCV13 serotypes. Conversely, no change occurred in the proportion of CAP caused by H. influenzae. The incidence of hospitalised CAP in children aged ⩽15 years was significantly reduced after the introduction of PCV13 in Japan. Continuous surveillance is necessary to detect emerging PP serotypes.

Antibacterial activity of hinokitiol against both antibiotic-resistant and -susceptible pathogenic bacteria that predominate in the oral cavity and upper airways

Hinokitiol, a component of the essential oil isolated from Cupressaceae, possesses antibacterial and antifungal activities and has been used in oral care products. In this study, the antibacterial activities of hinokitiol toward various oral, nasal and nasopharyngeal pathogenic bacteria, including Streptococcus mutans, Streptococcus sobrinus, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Prevotella intermedia, Fusobacterium nucleatum, methicillin-resistant and -susceptible Staphylococcus aureus, antibiotic-resistant and -susceptible Streptococcus pneumoniae, and Streptococcus pyogenes were examined. Growth of all these bacterial strains was significantly inhibited by hinokitiol, minimal inhibitory concentrations of hinokitiol against S. mutans, S. sobrinus, P. gingivalis, P. intermedia, A. actinomycetemcomitans, F. nucleatum, methicillin-resistant S. aureus, methicillin-susceptible S. aureus, antibiotic-resistant S. pneumoniae isolates, antibiotic-susceptible S. pneumoniae, and S. pyogenes being 0.3, 1.0, 1.0, 30, 0.5, 50, 50, 30, 0.3-1.0, 0.5, and 0.3 μg/mL, respectively. Additionally, with the exception of P. gingivalis, hinokitiol exerted bactericidal effects against all bacterial strains 1 hr after exposure. Hinokitiol did not display any significant cytotoxicity toward the human gingival epithelial cell line Ca9-22, pharyngeal epithelial cell line Detroit 562, human umbilical vein endothelial cells, or human gingival fibroblasts, with the exception of treatment with 500 μg/mL hinokitiol, which decreased numbers of viable Ca9-22 cells and gingival fibroblasts by 13% and 12%, respectively. These results suggest that hinokitiol exhibits antibacterial activity against a broad spectrum of pathogenic bacteria and has low cytotoxicity towards human epithelial cells.

Immunization with pneumococcal elongation factor Tu enhances serotype-independent protection against Streptococcus pneumoniae infection

Vaccination is an effective strategy to prevent pneumococcal diseases. Currently, licensed vaccines include the pneumococcal polysaccharide vaccine (PPSV) and the pneumococcal conjugate vaccine (PCV), which target some of the most common of the 94 serotypes of S. pneumoniae based on their capsular composition. However, it has been reported that PPSV is not effective in children aged less than 2 years old and PCV induces serotype replacement, which means that the pneumococcal population has changed following widespread introduction of these vaccines, and the non-vaccine serotypes have increased in being the cause of invasive pneumococcal disease. Therefore, it is important that there is development of novel pneumococcal vaccines to either replace or complement current polysaccharide-based vaccines. Our previous study suggested that S. pneumoniae releases elongation factor Tu (EF-Tu) through autolysis followed by the induction of proinflammatory cytokines in macrophages via toll-like receptor 4, that may contribute to the development of pneumococcal diseases. In this study, we investigated the expression of EF-Tu in various S. pneumoniae strains and whether EF-Tu could be an antigen candidate for serotype-independent vaccine against pneumococcal infection. Western blotting and flow cytometry analysis revealed that EF-Tu is a common factor expressed on the surface of all pneumococcal strains tested, as well as intracellularly. In addition, we demonstrate that immunization with recombinant (r) EF-Tu induced the production of inflammatory cytokines and the IgG1 and IgG2a antibodies in mice, and increased the CD4⁺ T-cells proportion in splenocytes. We also reveal that anti-EF-Tu serum increased the phagocytic activity of mouse peritoneal macrophages against S. pneumoniae infection, independent of their serotypes. Finally, our results indicate that mice immunized with rEF-Tu were significantly and non-specifically protected against lethal challenges with S. pneumoniae serotypes (2 and 15A). Therefore, pneumococcal EF-Tu could be an antigen candidate for the serotype-independent vaccine against pneumococcal infection.