Meningitis due to mixed infection with penicillin-resistant and penicillin-susceptible strains of Streptococcus pneumoniae

High prevalence of multiple serotypes of pneumococci in patients with pneumonia and their associated risk factors

BACKGROUND

Multiple serotypes of pneumococci have epidemiological and clinical implications, such as the emergence of non-vaccine serotypes and the acquisition of antimicrobial resistance. Prevalence of multiple serotypes of pneumococci in adults and their risk factors are not known.

METHODS

We enrolled adult patients from age ≥15 years with radiologically confirmed pneumonia in four hospitals across Japan. Pneumococcal pneumonia was defined with a pneumococcal bacterial density of ≥104/mL in sputum by lytA quantitative PCR, and serotypes were determined. Pneumonias with a single serotype were categorised as single-serotype pneumococcal pneumonia and with two or more serotypes as multiple-serotype pneumococcal pneumonia. Multivariable logistic regression was used to assess the risk factors.

RESULTS

3470 patients (median age 77 years, IQR 65-85) were enrolled. Pneumococcal pneumonia was identified in 476 (18.3%, n=2605) patients. Multiple serotypes were detected in 42% of them. Risk of having multiple serotypes was low among patients who had received 23-valent pneumococcal polysaccharide vaccine (PPSV23) vaccines (adjusted OR 0.51 (95% CI 0.27 to 0.94)). Proportion of non-PCV7 PPSV23 serotypes in overall distribution of multiple serotypes was 67.4% (n=324/481) compared with 46.4% (n=128/276) in that of single serotypes (p=0.001). Serotypes 5, 9N/9L, 10A, 12/22/46, 17F and 35F were associated with multiple-serotype pneumonia, and serotypes 6A/6B, 23F, 11 and 6C/6D were associated with single-serotype pneumonia. Proportion of more invasive serotypes (serotypes 1, 5, 7F, 8) was significantly higher in multiple-serotype pneumonia (p=0.001).

CONCLUSIONS

Multiple serotypes of pneumococci are common in sputum of adult patients with pneumonia. The risk of multiple-serotype pneumococcal pneumonia is lower than that of single-serotype pneumococcal pneumonia among PPSV23-vaccinated patients.

TRIAL REGISTRATION NUMBER

UMIN000006909.

Invasive Disease Caused Simultaneously by Dual Serotypes of Streptococcus pneumoniae

There are at least 98 known pneumococcal serotypes. Invasive pneumococcal disease (IPD) is usually caused by a single serotype, and dual-serotype IPD is rare. To assess factors associated with dual-serotype IPD, patient information obtained through laboratory-based surveillance for IPD from 2005 through 2014 in South Africa was reviewed. Genomes of isolate pairs from coinfected individuals were sequenced to determine their molecular characteristics. For 30 (91%) of 33 patients with dual serotypes, one or both isolates were a pneumococcal conjugate vaccine (PCV13) serotype. Dual-serotype IPD was associated with children <5 years of age (adjusted odds ratio [aOR], 4.7; 95% confidence interval [95% CI], 1.8 to 11.7), underlying illness (other than HIV) (aOR, 2.8; 95% CI, 1.1 to 6.6) and death (aOR, 2.5; 95% CI, 1.08 to 6.09). For each coinfecting pair, isolates were genotypically unrelated, and their genotypes were common among isolates of the same serotype in South Africa. Of 701 accessory genes identified among dual-serotype IPD isolates, four were common between isolate pairs. Coinfecting isolate pairs had different genotypic backgrounds. The association of dual serotypes with death warrants increased awareness of IPD coinfection caused by two or more serotypes.

A novel high-throughput method for molecular serotyping and serotype-specific quantification of Streptococcus pneumoniae using a nanofluidic real-time PCR system

Serotype-specific quantification data are essential for elucidating the complex epidemiology of Streptococcus pneumoniae and evaluating pneumococcal vaccine efficacy. Various PCR-based assays have been developed to circumvent the drawback of labour-intensive and time-consuming culture-based procedures for serotype determination and quantification of pneumococcus. Here, we applied a nanofluidic real-time PCR system to establish a novel assay. Twenty-nine primer pairs, 13 of which were newly designed, were selected for the assay to cover 50 serotypes including all currently available conjugate and polysaccharide vaccine serotypes. All primer pairs were evaluated for their sensitivity, specificity, efficiency, repeatability, accuracy and reproducibility on the Fluidigm Biomark HD System, a nanofluidic real-time PCR system, by drawing standard curves with a serial dilution of purified DNA. We applied the assay to 52 nasopharyngeal swab samples from patients with pneumonia confirmed by chest X-ray to validate its accuracy. Minimum detection levels of this novel assay using the nanofluidic real-time PCR system were comparable to the conventional PCR-based assays (between 30 and 300 copies per reaction). They were specific to their targets with good repeatability (sd of copy number of 0.1), accuracy (within ±0.1 fold difference in log10 copy number) and reproducibility (sd of copy number of 0.1). When artificially mixed DNA samples consisting of multiple serotypes in various ratios were tested, all the serotypes were detected proportionally, including a minor serotype of one in 1000 copies. In the nasopharyngeal samples, the PCR system detected all the culture-positive samples and 22 out of 23 serotypes identified by the conventional method were matched with PCR results. We conclude that this novel assay, which is able to differentially quantify 29 pneumococcus groups for 45 test samples in a single run, is applicable to the large-scale epidemiological study of pneumococcus. We believe that this assay will facilitate our understanding of the roles of serotype-specific bacterial loads and implications of multiple serotype detections in pneumococcal diseases.

Potential impact of conjugate vaccine on the incidence of invasive pneumococcal disease among children in Scotland

We sought to determine the potential impact of seven-valent pneumococcal conjugate vaccine on the incidence of invasive pneumococcal disease (IPD) among children in Scotland. Invasive pneumococci from blood and cerebrospinal fluid, isolated between 2000 and 2004 from all children aged less than 5 years in Scotland, were characterized by serotyping. Using reported efficacy data of the seven-valent pneumococcal conjugate vaccine (PCV7) along with likely coverage rates, we made an estimation of the potential impact on the incidence of IPD among children in Scotland. A total of 217 pneumococci were characterized into 22 different serogroups/types, the most common, in rank order, being 14, 19F, 6B, 18C, 23F, 9V, 4, 1, 19A, and 6A. Estimated serotype coverage for PCV7 was 76.5% in those aged less than 5 years of age but increased to 88.9% for those aged 1 year. By using serotype coverage and estimates of vaccine efficacy and uptake, the potential impact of the vaccine for those greater than 2 months of age, but less than 5 years, was estimated as 67.3%, leading to an average of 29 preventable cases per year. The introduction of PCV7 into the childhood immunization schedule would reduce the burden of pneumococcal disease in children, and the incidence would be particularly reduced in those children aged 1 year. Additional benefits may be gained in adults through herd protection. Continued surveillance of IPD is required before, during, and after the introduction of PCV7.

Control of pneumococcal disease in the United Kingdom – the start of a new era

In 2000, a multi-valent pneumococcal conjugate vaccine, known as Prevnar, was licensed for use in infants and young children in the USA. The subsequent introduction of the vaccine into the childhood immunization schedule in that country led to a significant decrease in pneumococcal disease. The vaccine is effective against invasive and non-invasive pneumococcal infection, can be used in young children as well as adults and, like all conjugate vaccines, provides long-lasting immunity. Moreover, it reduces the incidence of antibiotic resistance because a number of resistant serotypes are targeted by the vaccine. Prevnar, also known as Prevenar, has since been licensed in numerous countries, including the UK. On 8 February 2006, the Departments of Health in England, Scotland and Wales announced the inclusion of Prevenar in the childhood immunization schedule. This announcement has important implications for pneumococcal infection, disease surveillance and immunization policy in the UK.

Pneumococci causing invasive disease in children prior to the introduction of pneumococcal conjugate vaccine in Scotland

This study aimed to determine the serotypes and sequence types (STs) of pneumococci causing paediatric invasive disease in Scotland prior to the introduction of pneumococcal conjugate vaccines (PCVs). All invasive pneumococci isolated between 2000 and 2004 from children aged less than 5 years in Scotland were used. The isolates were characterized by serotyping and multi-locus sequence typing. Two hundred and seventeen pneumococci were characterized into 22 different serogroups/types, the most common, in rank order, being 14, 19F, 6B, 18C, 23F, 9V, 4, 1, 19A and 6A. They were further genotyped into 77 different STs, the three most common being 9, 162 and 176. Common serotypes possessed multiple STs, but pneumococci of a particular clone were mostly associated with a particular serotype. The seven most common serotypes are included in the 7-valent polysaccharide conjugate vaccine (PCV7). Serotype coverage for PCV7 was 76.5 % in those aged less than 5 years but increased to 88.9 % for those aged 1 year. The introduction of PCV7 into the childhood immunization schedule would reduce the burden of pneumococcal disease in children, although continued surveillance of invasive pneumococcal disease will be required before, during and after the introduction of PCVs.

Mixed bacterial meningitis due to Streptococcus pneumoniae and Neisseria meningitidis in an 18-month-old child

We report an unusual case of culture-proven pneumococcal and meningococcal mixed meningitis in an 18-month-old girl. The patient responded well to antimicrobial therapy and recovered completely without sequelae. No underlying condition could be demonstrated except a rhinitis of unknown etiology 2 days before the onset of the symptoms suggesting meningitis.

Invasive pneumococcal infection in a healthy infant caused by two different serotypes

We present a case of invasive pneumococcal infection in a healthy 10-month-old infant from whom Streptococcus pneumoniae serotype 23F was isolated from the blood and serotype 23B was isolated from the cerebrospinal fluid. Both serotypes were penicillin nonsusceptible. Pulsed-field gel electrophoresis analysis demonstrated that the two serotypes had distinct DNA patterns, indicating that infection did not occur as a result of capsular transformation but as a result of a mixed infection with two distinct pneumococcal serotypes.

rpoB gene sequence-based identification of aerobic Gram-positive cocci of the genera Streptococcus, Enterococcus, Gemella, Abiotrophia, and Granulicatella

We developed a new molecular tool based on rpoB gene (encoding the beta subunit of RNA polymerase) sequencing to identify streptococci. We first sequenced the complete rpoB gene for Streptococcus anginosus, S. equinus, and Abiotrophia defectiva. Sequences were aligned with these of S. pyogenes, S. agalactiae, and S. pneumoniae available in GenBank. Using an in-house analysis program (SVARAP), we identified a 740-bp variable region surrounded by conserved, 20-bp zones and, by using these conserved zones as PCR primer targets, we amplified and sequenced this variable region in an additional 30 Streptococcus, Enterococcus, Gemella, Granulicatella, and Abiotrophia species. This region exhibited 71.2 to 99.3% interspecies homology. We therefore applied our identification system by PCR amplification and sequencing to a collection of 102 streptococci and 60 bacterial isolates belonging to other genera. Amplicons were obtained in streptococci and Bacillus cereus, and sequencing allowed us to make a correct identification of streptococci. Molecular signatures were determined for the discrimination of closely related species within the S. pneumoniae-S. oralis-S. mitis group and the S. agalactiae-S. difficile group. These signatures allowed us to design a S. pneumoniae-specific PCR and sequencing primer pair.