Pneumococcal disease manifestation in children before and after vaccination: what's new?

A multicenter study on the epidemiology of complicated parapneumonic effusion in the era of currently available pneumococcal conjugate vaccines

BACKGROUND

Parapneumonic effusion (PPE) is a common complication of pneumonia. Streptococcus pneumoniae is the most common cause of bacterial pneumonia. A reduction in pneumonia hospitalizations has been observed since the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7). Despite this apparent benefit, an increase in the incidence of PPE was recorded in some countries following PCV7 implementation. As the 13-valent pneumococcal conjugate vaccine (PCV13) was expected to provide a wider protection against PPE, the aim of the present study was to evaluate the impact of PCV13 introduction on the epidemiology of complicated parapneumonic effusion (c-PPE) among children in the Athens greater area.

METHODS

All cases of community-acquired pneumonia (CAP) with PPE requiring chest tube insertion (complicated PPE, c-PPE) hospitalized in the 3 public Children's hospitals in Athens between 01/01/2004 and 31/12/2019 were included in the study.

RESULTS

A total of 426 cases of c-PPE associated with pneumonia were recorded of which 198 were admitted during 2004-2010 (period A, prePCV13/PCV -7 introduction period) and 228 during 2011-2018 (period B, post - PCV13 period). A definite bacterial etiology was established in 44.4 % of all cases and of those 25.4 % were caused by S. pneumoniae. An increasing trend in c-PPE incidence was observed during period A; although, a significant decrease on c-PPE annual rates was observed during the period B (p = 0.011), a remarkable increase in serotype 3 cases was recorded.

CONCLUSION

A decreasing time trend in c-PPE cases among children was shown after the introduction of PCV13 in our area. However, serotype 3 is nowadays a common cause of PPE. Hence, continuous surveillance is imperative in order to follow c-PPE epidemiology over time.

[Primary pneumococcal peritonitis in a pediatric hospital from Argentina]

Pneumococcal peritonitis represents a small subset of patients suffering from invasive pneumococcal disease (IPD). We describe 5 cases of primary peritonitis documented in the pediatric hospital over 15 years (2005-2020) of IPD surveillance. The patients, 3girls and 2boys with a mean age of 5 years, experienced peritoneal signs and symptoms; 3of them suffered from nephrotic syndrome. Based on the local resistance profiles, all isolates were sensitive to beta-lactams, one strain showed resistance to cotrimoxazole and tetracycline while another strain, to cotrimoxazole only. Serotypes found in 4/5 strains (one was non-viable) were: 1, 19F, 15C and 23A. Children were treated with third-generation cephalosporins or ampicillin, gentamicin and metronidazole and all of them evolved favorably. Pneumococcal etiology should be included in the differential diagnosis of acute abdominal pain in children. Our study aims to contribute to the knowledge of this condition and to the local epidemiology of IPD.

[Pneumococcal osteoarticular infections in children admitted to a Pediatric Reference Hospital from Misiones, Argentina. Thirteen years of surveillance]

Streptococcus pneumoniae is a rare cause of osteoarticular infections. We describe 5documented cases that occurred in 2005, 2009, 2011, 2015 and 2017 in patients admitted to the Pediatric Provincial Reference Hospital of Misiones. These cases corresponded to a 4-year-old boy and 4 girls aged 11, 10, 6 years and 4 months with a diagnosis of osteomyelitis of the scapula and humerus, arthritis of the hip, ankle and osteomyelitis of the distal fibula. All of them were in good general condition on admission and one of them was seropositive for human immunodeficiency virus. All the recovered isolates were susceptible to β-lactams and only one isolate showed joint resistance to macrolides and tetracycline. Three isolates were serotyped, 2of which carried vaccine serotypes (19F and 7F). Despite its low frequency, the etiology of S.pneumoniae should be considered among the osteoarticular infections. Our findings enhance the role of the Bacteriology laboratory in the diagnosis by microbiological culture and contribute to documenting the epidemiological behavior of this pathogen.

A Choline-Recognizing Monomeric Lysin, ClyJ-3m, Shows Elevated Activity against Streptococcus pneumoniae

Streptococcus pneumoniae is a leading pathogen for bacterial pneumonia, which can be treated with bacteriophage lysins harboring a conserved choline binding module (CBM). Such lysins regularly function as choline-recognizing dimers. Previously, we reported a pneumococcus-specific lysin ClyJ comprising the binding domain from the putative endolysin gp20 from the Streptococcus phage SPSL1 and the CHAP (cysteine, histidine-dependent amidohydrolase/peptidase) catalytic domain from the PlyC lysin. A variant of ClyJ with a shortened linker, i.e., ClyJ-3, shows improved activity and reduced cytotoxicity. Resembling typical CBM-containing lysins, ClyJ-3 dimerized upon binding with choline. Herein, we further report a choline-recognizing variant of ClyJ-3, i.e., ClyJ-3m, constructed by deleting its C-terminal tail. Biochemical characterization showed that ClyJ-3m remains a monomer after it binds to choline yet exhibits improved bactericidal activity against multiple pneumococcal strains with different serotypes. In an S. pneumoniae-infected bacteremia model, a single intraperitoneal administration of 2.32 μg/mouse of ClyJ-3m showed 70% protection, while only 20% of mice survived in the group receiving an equal dose of ClyJ-3 (P < 0.05). A pharmacokinetic analysis following single intravenously doses of 0.29 and 1.16 mg/kg of ClyJ-3 or ClyJ-3m in BALB/c mice revealed that ClyJ-3m shows a similar half-life but less clearance and a greater area under curve than ClyJ-3. Taken together, the choline-recognizing monomer ClyJ-3m exhibited enhanced bactericidal activity and improved pharmacokinetic proprieties compared to those of its parental ClyJ-3 lysin. Our study also provides a new way for rational design and programmed engineering of lysins targeting S. pneumoniae.

Characterization of MSlys, the endolysin of Streptococcus pneumoniae phage MS1

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MSlys is a choline binding protein from pneumococcal MS1 phage.

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Planktonic and biofilm S. pneumoniae cells are affected by MSlys treatment.

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MSlys is active against isolates from otitis media infections and works in the conditions commonly found in this environment.

Despite the use of pneumococcal conjugate vaccines, the number of infections related to Streptococcus pneumoniae continues to be alarming.

Herein, we identified, characterized the MSlys endolysin encoded in the phage MS1. We further tested its antimicrobial efficacy against planktonic and biofilm cells, assessing the culturability of cells and biofilm structure by scanning electron microscopy, and confocal laser scanning microscopy.

The modular MSlys endolysin consists of an amidase catalytic domain and a choline-binding domain. MSlys is active against isolates of children with otitis media, and conditions close to those found in the middle ear. Treatment with MSlys (2 h, 4 μM) reduced planktonic cultures by 3.5 log10 CFU/mL, and 24- and 48-h-old biofilms by 1.5 and 1.8 log10 CFU/mL, respectively. Imaging of the biofilms showed thinner and damaged structures compared to control samples.

The recombinantly expressed MSlys may be a suitable candidate for treating pneumococcal infections, including otitis media.

Linker Editing of Pneumococcal Lysin ClyJ Conveys Improved Bactericidal Activity

Streptococcus pneumoniae is a leading human pathogen uniquely characterized by choline moieties on the bacterial surface. Our previous work reported a pneumococcus-specific chimeric lysin, ClyJ, which combines the CHAP (cysteine, histidine-dependent amidohydrolase/peptidase) enzymatically active domain (EAD) from the PlyC lysin and the cell wall binding domain (CBD) from the phage SPSL1 lysin, which imparts choline binding specificity. Here, we demonstrate that the lytic activity of ClyJ can be further improved by editing the linker sequence adjoining the EAD and CBD. Keeping the net charge of the linker constant, we constructed three ClyJ variants containing different lengths of linker sequence. Circular dichroism showed that linker editing has only minor effects on the folding of the EAD and CBD. However, thermodynamic examination combined with biochemical analysis demonstrated that one variant, ClyJ-3, with the shortest linker, displayed improved thermal stability and bactericidal activity, as well as reduced cytotoxicity. In a pneumococcal mouse infection model, ClyJ-3 showed significant protective efficacy compared to that of the ClyJ parental lysin or the Cpl-1 lysin, with 100% survival at a single ClyJ-3 intraperitoneal dose of 100 μg/mouse. Moreover, a ClyJ-3 dose of 2 μg/mouse had the same efficacy as a ClyJ dose of 40 μg/mouse, suggesting a 20-fold improvement in vivo Taking these results together, the present study not only describes a promising pneumococcal lysin with improved potency, i.e., ClyJ-3, but also implies for the first time that the linker sequence plays an important role in determining the activity of a chimeric lysin, providing insight for future lysin engineering studies.

ClyJ Is a Novel Pneumococcal Chimeric Lysin with a Cysteine- and Histidine-Dependent Amidohydrolase/Peptidase Catalytic Domain

Streptococcus pneumoniae is one of the leading pathogens that cause a variety of mucosal and invasive infections. With the increased emergence of multidrug-resistant S. pneumoniae, new antimicrobials with mechanisms of action different from conventional antibiotics are urgently needed. In this study, we identified a putative lysin (gp20) encoded by the Streptococcus phage SPSL1 using the LytA autolysin as a template. Molecular dissection of gp20 revealed a binding domain (GPB) containing choline-binding repeats (CBRs) that are high specificity for S. pneumoniae By fusing GPB to the CHAP (cysteine, histidine-dependent amidohydrolase/peptidase) catalytic domain of the PlyC lysin, we constructed a novel chimeric lysin, ClyJ, with improved activity to the pneumococcal Cpl-1 lysin. No resistance was observed in S. pneumoniae strains after exposure to incrementally doubling concentrations of ClyJ for 8 continuous days in vitro In a mouse bacteremia model using penicillin G as a control, a single intraperitoneal injection of ClyJ improved the survival rate of lethal S. pneumoniae-infected mice in a dose-dependent manner. Given its high lytic activity and safety profile, ClyJ may represent a promising alternative to combat pneumococcal infections.

Hospitalization costs of severe bacterial pneumonia in children: comparative analysis considering different costing methods

Objective

To determine and compare hospitalization costs of bacterial community-acquired pneumonia cases via different costing methods under the Brazilian Public Unified Health System perspective.

Methods

Cost-of-illness study based on primary data collected from a sample of 59 children aged between 28 days and 35 months and hospitalized due to bacterial pneumonia. Direct medical and non-medical costs were considered and three costing methods employed: micro-costing based on medical record review, micro-costing based on therapeutic guidelines and gross-costing based on the Brazilian Public Unified Health System reimbursement rates. Costs estimates obtained via different methods were compared using the Friedman test.

Results

Cost estimates of inpatient cases of severe pneumonia amounted to R$ 780,70/$Int. 858.7 (medical record review), R$ 641,90/$Int. 706.90 (therapeutic guidelines) and R$ 594,80/$Int. 654.28 (Brazilian Public Unified Health System reimbursement rates). Costs estimated via micro-costing (medical record review or therapeutic guidelines) did not differ significantly (p=0.405), while estimates based on reimbursement rates were significantly lower compared to estimates based on therapeutic guidelines (p<0.001) or record review (p=0.006).

Conclusion

Brazilian Public Unified Health System costs estimated via different costing methods differ significantly, with gross-costing yielding lower cost estimates. Given costs estimated by different micro-costing methods are similar and costing methods based on therapeutic guidelines are easier to apply and less expensive, this method may be a valuable alternative for estimation of hospitalization costs of bacterial community-acquired pneumonia in children.

Changes in empyema among U.S. children in the pneumococcal conjugate vaccine era

BACKGROUND

Parapneumonic empyema, a serious complication of pneumonia, started increasing among U.S. children before the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in 2000, and continued afterwards. This increase was due in part to pneumococcal serotypes not included in PCV7 that were included in the new 13-valent (PCV13) vaccine introduced in 2010. We assessed changes in the incidence of empyema hospitalizations among U.S. children after PCV13 introduction.

METHODS

We calculated annualized empyema hospitalization rates among U.S. children <18years using Nationwide Inpatient Sample and Census data (1997-2013) for four periods based on PCV7 and PCV13 introductions. Relative rates (RR) and 95% confidence intervals (CI) were calculated by age group and sex, comparing PCV7 [early-PCV7 (2001-2005) and late-PCV7 (2006-2009)] and PCV13 (2011-2013) periods with the pre-PCV7 period (1997-1999). Secondary analyses examined changes in pneumococcal, streptococcal, staphylococcal and unspecified empyema.

RESULTS

Among children <18years of age, annualized empyema hospitalization rates peaked at 3.6 per 100,000 in the late-PCV7 period compared with 2.1 per 100,000 in the pre-PCV7 period [RR: 1.70 (95% CI: 1.11-2.60)]. However, annualized rates in the post-PCV13 period declined to 2.0 per 100,000, similar to rates in the pre-PCV7 period. Empyema rates among children <2years were lower in the post-PCV13 period compared to the pre-PCV7 period [RR: 0.77 (95% CI: 0.61-0.96)], but rates in the two periods among children 2-4 and 5-17years were similar. Most empyema were of unspecified etiology. Pneumococcal and unspecified empyema declined after PCV13 introduction.

CONCLUSIONS

Although empyema hospitalization rates among U.S. children peaked after PCV7 introduction, rates decreased substantially following the introduction of PCV13.

A novel chimeric phage lysin with high in vitro and in vivo bactericidal activity against Streptococcus pneumoniae

OBJECTIVES

Streptococcus pneumoniae is becoming increasingly antibiotic resistant worldwide and new antimicrobials are urgently needed. Our aim was new chimeric phage endolysins, or lysins, with improved bactericidal activity by swapping the structural components of two pneumococcal phage lysozymes: Cpl-1 (the best lysin tested to date) and Cpl-7S.

METHODS

The bactericidal effects of four new chimeric lysins were checked against several bacteria. The purified enzymes were added at different concentrations to resuspended bacteria and viable cells were measured after 1 h. Killing capacity of the most active lysin, Cpl-711, was tested in a mouse bacteraemia model, following mouse survival after injecting different amounts (25-500 μg) of enzyme. The capacity of Cpl-711 to reduce pneumococcal biofilm formation was also studied.

RESULTS

The chimera Cpl-711 substantially improved the killing activity of the parental phage lysozymes, Cpl-1 and Cpl-7S, against pneumococcal bacteria, including multiresistant strains. Specifically, 5 μg/mL Cpl-711 killed ≥7.5 log of pneumococcal R6 strain. Cpl-711 also reduced pneumococcal biofilm formation and killed 4 log of the bacterial population at 1 μg/mL. Mice challenged intraperitoneally with D39_IU pneumococcal strain were protected by treatment with a single intraperitoneal injection of Cpl-711 1 h later, resulting in about 50% greater protection than with Cpl-1.

CONCLUSIONS

Domain swapping among phage lysins allows the construction of new chimeric enzymes with high bactericidal activity and a different substrate range. Cpl-711, the most powerful endolysin against pneumococci, offers a promising therapeutic perspective for the treatment of multiresistant pneumococcal infections.

Clinical outcome of parapneumonic empyema in children treated according to a standardized medical treatment

Treatment of parapneumonic empyema (PE) consists of intravenous antibiotics and, in case of large effusions and persisting fever, pleural chest drain (±intrapleural fibrinolytics) or video-assisted surgical intervention. We standardized the treatment for PE in our tertiary care center choosing a first-step nonsurgical approach. The aim was to evaluate the need for surgery and to collect data on disease course, outcome, and microbiology. For all children treated for PE between 2006 and 2013, data were prospectively collected concerning treatment, length of stay, duration of fever, complications, and causative agent. Of 132 children treated for PE, 20 % needed surgical intervention. Analyzed per year, the need for surgery decreased from almost 40 % in 2007 to 0 % in 2010 again increasing to 40 % although this did not reach statistical significance (p = 0.115). Median duration of "in-hospital fever" was 5 days (IQR, 3-8). The duration of fever correlated with pleural LDH (r = 0.324; p = 0.002) and pleural glucose (r = -0.248; p = 0.021) and was inversely correlated with pleural pH (r = -0.249; p = 0.046). Based on pleural PCR data, 85 % of PE were caused by Streptococcus pneumoniae (40 % serotype 1).

CONCLUSION

After introduction of a standardized primary medical approach (chest drain ± fibrinolysis) for PE in our institution, the need for surgical rescue interventions overall remained at 20 %, which is higher than in some other reports. Difference in microbiology or disease severity could not be proven.

Necrotising pneumonia in children

Necrotising pneumonia remains an uncommon complication of pneumonia in children but its incidence is increasing. Pneumococcal infection is the predominant cause in children but Methicillin resistant Staphylococcus aureus (MRSA) and Panton-Valentine leukocidin (PVL) staphylococcal infection are also important causes of severe necrotising pneumonia. Clinical features of necrotic pneumonia are similar to those of an uncomplicated pneumonia except that the patient is clinically much more unwell and has usually failed to respond adequately to what would normally be considered as appropriate antibiotics. Pleural involvement is frequent. Initial management is similar to that for non-complicated pneumonia with careful attention to fluid balance and adequate analgesia required. Some patients will need intensive care support, particularly those with PVL-positive staphylococcal infection. Broad-spectrum antibiotics should be given intravenously, with the exact choice of agent informed by local resistance patterns. Pleural drainage is often required. Despite the severity of the illness, outcomes remain excellent with the majority of children making a full recovery.

Prevalence of pneumococcal disease, serotype distribution, and antimicrobial susceptibility in Mexican children younger than 5 years of age

BACKGROUND AND AIMS

Streptococcus pneumoniae constitutes one of the main causes of sepsis, bacteremia and meningitis (pneumococcal invasive disease - PID), and pneumonia in infants and small children. Antipneumococcal vaccination in Mexico is expected to be a useful strategy to reduce morbimortality due to this cause. We undertook this study to determine the prevalence of PID and pneumonia and the PCV vaccination status of affected children as well as serotype distribution and antimicrobial susceptibility of pneumococcal strains responsible for PID in infants and small children in Mexico.

METHODS

From March 2010-June 2011, a prospective multicenter study was carried out in four states in Mexico to determine the prevalence of bacteremia, meningitis, septic arthritis and pneumonia due to S. pneumoniae and other microorganisms in children from 28 days-59 months of age. Isolated pneumococcal strains were serotyped and their antimicrobial resistance determined.

RESULTS

During the study period, 545 children were diagnosed with bacteremia, meningitis, septic arthritis or pneumonia; 46.7% of these clinical entities occurred among children <12 months of age. Community-acquired pneumonia was the most prevalent disease. It was possible to identify a causal microorganism in 55 cases, from which 80% were S. pneumoniae. Fifteen percent of patients with PID died. The most prevalent pneumococcal serotypes were 19A, 35B, 19F and 6A. 10.2% of nonmeningeal strains were resistant to meropenem and 82% were resistant to TMP/SMX.

CONCLUSIONS

This study shows that pneumococcus was the most common bacteria isolated in the studied population, although epidemiological and laboratory-based surveillance still needs improvement.

Clinical implications of pneumococcal serotypes: invasive disease potential, clinical presentations, and antibiotic resistance

Streptococcus pneumoniae can asymptomatically colonize the nasopharynx and cause a diverse range of illnesses. This clinical spectrum from colonization to invasive pneumococcal disease (IPD) appears to depend on the pneumococcal capsular serotype rather than the genetic background. According to a literature review, serotypes 1, 4, 5, 7F, 8, 12F, 14, 18C, and 19A are more likely to cause IPD. Although serotypes 1 and 19A are the predominant causes of invasive pneumococcal pneumonia, serotype 14 remains one of the most common etiologic agents of non-bacteremic pneumonia in adults, even after 7-valent pneumococcal conjugate vaccine (PCV7) introduction. Serotypes 1, 3, and 19A pneumococci are likely to cause empyema and hemolytic uremic syndrome. Serotype 1 pneumococcal meningitis is prevalent in the African meningitis belt, with a high fatality rate. In contrast to the capsule type, genotype is more closely associated with antibiotic resistance. CC320/271 strains expressing serotype 19A are multidrug-resistant (MDR) and prevalent worldwide in the era of PCV7. Several clones of MDR serotype 6C pneumococci emerged, and a MDR 6D clone (ST282) has been identified in Korea. Since the pneumococcal epidemiology of capsule types varies geographically and temporally, a nationwide serosurveillance system is vital to establishing appropriate vaccination strategies for each country.

Pharmacotherapy for pneumococcal infections: an update

INTRODUCTION

The management of pneumococcal diseases still places a significant burden on medical and economic resources. The subjects at greatest risk of pneumococcal infections are children.

AREAS COVERED

The aim of this review is to analyse the best current therapeutic approach to pneumococcal resistance, taking into account the level of susceptibility of Streptococcus pneumoniae, and the pharmacokinetics and pharmacodynamics of different antibiotics in the various pneumococcal diseases.

EXPERT OPINION

Antibiotic treatment of a number of pneumococcal diseases remains difficult or impossible due to the presence of strains resistant to commonly used antibiotics. In children the problem is significantly more important than in adults due to the reduced number of licenced drugs for subjects in the first years of life. The new conjugate pneumococcal vaccines containing 10 (PCV10) and 13 serotypes (PCV13), which include most of the recently emerging strains, might reduce the incidence of pneumococcal infections and the circulation of resistant pathogens. However, it is likely that optimal results will only be reached after the development of effective vaccines based on conserved proteins that are capable of preventing all pneumococcal infections, regardless of the serotype of the causative organism.