Clonal distribution of common pneumococcal serotypes not included in the 7-valent conjugate vaccine (PCV7): marked differences between two ethnic populations in southern Israel

CIRCULATING CLONAL COMPLEXES AND SEQUENCE TYPES OF STREPTOCOCCUS PNEUMONIAE SEROTYPE 19A WORLDWIDE: THE IMPORTANCE OF MULTIDRUG RESISTANCE: A SYSTEMATIC LITERATURE REVIEW

INTRODUCTION

Streptococcus pneumoniae is a major cause of morbidity and mortality, especially amongst young children and the elderly. Childhood implementation of pneumococcal conjugate vaccines (PCVs) significantly reduced the incidence of invasive pneumococcal disease (IPD), while several nonvaccine serotypes remained substantial. Although there is evidence of the impact of higher-valent PCVs on serotype 19A, 19A IPD burden and antibiotic resistance remain a major concern post-vaccination.

AREAS COVERED

We performed a systematic literature review to analyze the frequency and clonal distribution of serotype 19A isolates in the pre- and post-PCV era worldwide providing a scientific background on the factors that influence multidrug resistance in pneumococcal isolates.

EXPERT COMMENTARY

Serotype 19A IPD incidence increased in all regions following the introduction of the 7-valent PCV. The higher-valent PCVs have reduced the rates of 19A IPD isolates, but several circulating strains with diverse antibiotic resistance prevailed. Heterogeneous clonal distribution in serotype 19A was observed within countries and regions, irrespective of higher-valent PCV used. An increase of 19A isolates from pre- to post-vaccination periods were associated with frequently occurring serotype switching events and with the prevalence of multidrug resistant strains. Rational antibiotic policies must be implemented to control the emergence of resistance.Plain Language SummaryWhat is the context?Streptococcus pneumoniae is a major cause of pneumococcal diseases especially amongst young children and the elderly. Vaccination with pneumococcal conjugate vaccines has significantly reduced the incidence of invasive pneumococcal disease worldwide. However, the invasive pneumococcal disease remains an important health problem due to the increase of nonvaccine serotypes. Serotype 19A is predominant in many countries worldwide. Factors contributing to its prevalence include serotype replacement, the emergence of clones with multidrug resistance due to antibiotic overuse, and potential bacteria adaptation in response to the vaccine.What is new?We performed a systematic literature review to 1) analyze the incidence and clonal distribution of serotype 19A isolates pre- and post-vaccination worldwide, and to collect data evaluating antimicrobial resistance patterns displayed by the clones of serotype 19A. We found that 1) clonal distribution in serotype 19A was heterogeneous within countries and regions, irrespective of the vaccine used; 2) the diversity of 19A isolates increased after vaccination. It was associated with frequent serotype switching events and with the prevalence of multidrug resistant strains.What is the impact?Implementation of policies to educate on sustainable antibiotic use and infectious prevention measures may help control the emergence of antibiotic resistance. High-quality active surveillance and future molecular epidemiology studies are needed to understand rapid genetic changes.

Understanding the Evolution of Antibiotic-nonsusceptible Pneumococcal Nasopharyngeal Colonization Following Pneumococcal Conjugate Vaccine Implementation in Young Children

BACKGROUND

Four main processes determine pneumococcal conjugate vaccine (PCV) antibiotic-nonsusceptible Streptococcus pneumoniae (ANSP) carriage: reduction of PCV serotypes, increase of non-PCV serotypes, potential overall reduction in carriage, and within-serotype nonsusceptibility resulting from continuous antibiotic pressure. The post-PCV implementation dynamics of these components were examined in young children from 2 distinct ethnic populations: Jewish and Bedouin.

METHODS

We performed ongoing, prospective, population-based, active surveillance initiated at the time of 7- and 13-valent PCVs (PCV7; PCV13) implementation. Nasopharyngeal cultures for S. pneumoniae were obtained daily from children aged <5 years who visited the only pediatric emergency room in the district during a 6-year period (2009 to 2015).

RESULTS

Of 8446 nasopharyngeal samples, 48.3% were positive (42.0% and 52.8% for Jewish and Bedouin children, respectively; P < .001). Nonsusceptibility was significantly more frequent among PCV serotypes than among non-PCV serotypes and among Bedouin children than among Jewish children. PCV serotype carriage declined by 80%, while that of non-PCV serotypes increased by 140%. The overall (all serotypes) pneumococcal carriage significantly declined (33% and 11% in Bedouin and Jewish children, respectively). Among non-PCV isolates, the proportion of ANSP significantly increased with time in both populations. As a summation of all 4 processes, ANSP carriage significantly decreased among both Bedouin and Jewish children.

CONCLUSIONS

PCV impact on ANSP nasopharyngeal carriage is a dynamic, multicomponent process, highly dependent on antibiotic consumption in the community, which may result in a continuous increase in antibiotic resistance in the replacing serotypes.

Pneumococcal vaccines

Streptococcus pneumoniae continues to take a heavy toll on childhood mortality and morbidity across the developing world. An estimated 10.6 million invasive pneumococcal diseases (IPDs) occur every year, with nearly 1 million deaths in children under 5 years of age. Introduction of vaccines in the childhood immunisation programme in developed world has brought down the incidence of the disease considerably. However, childhood immunocompromising illnesses including HIV have increased the risk of IPD several folds. There is also a growing concern on the increasing antibiotic resistance among these invasive strains to penicillin, other beta-lactams and macrolides, making treatment difficult and expensive. It is estimated that about 62% of IPD worldwide is caused by the 10 most common serotypes. Although the ranking of individual pneumococcal serotypes causing serious disease varies among nations, the 7-13 serotypes included in pneumococcal conjugate vaccines (PCVs) may prevent 50%-80% of all paediatric pneumococcal diseases globally. The World Health Organization has recommended the use of PCV-10/13 in the national immunisation programmes (NIPs) of developing countries. Four doses of PCV-13 have been recommended by the US Association of Pediatrics and Centers for Disease Control and Prevention, at intervals of each 2 months for the first 6 months and by the 12^th to 15^th months after birth. This is expected to reduce the morbidity and mortality associated with IPD and simultaneously decrease colonisation with circulating antibiotic-resistant strains in immunized communities. Nevertheless, continued surveillance of antimicrobial resistance in non-vaccine serotypes is necessary to prevent the resurgence of resistance. Other virulence factors which are not serotype specific also need to be studied to overcome the drawbacks of serotype-specific pneumococcal vaccines. PCV-13 was launched during May 2017 under the NIP of five Indian states with the highest pneumococcal diseases in the country and is expected to be rolled out in the other parts of the country in the coming days.

Emergence of Streptococcus pneumoniae Serotype 12F after Sequential Introduction of 7- and 13-Valent Vaccines, Israel

Israel implemented use of 7- and 13-valent pneumococcal vaccine in 2009 and 2010, respectively. We describe results of prospective, population-based, nationwide active surveillance of Streptococcus pneumoniae serotype 12F (Sp12F) invasive pneumococcal disease (IPD) dynamics in the 7 years after vaccine introduction. Of 4,573 IPD episodes during July 2009-June 2016, a total of 434 (9.5%) were caused by Sp12F. Sp12F IPD rates (cases/100,000 population) increased in children <5 years of age, from 1.44 in 2009-2010 to >3.9 since 2011-2012, followed by an increase in all ages. During 2011-2016, Sp12F was the most prevalent IPD serotype. Sp12F isolates were mostly penicillin nonsusceptible (MIC >0.06 µg/mL; MIC₅₀ = 0.12) and predominantly of sequence type 3774), a clone exclusively found in Israel (constituting ≈90% of isolates in 2000-2009). The sharp increase, long duration, and predominance of Sp12F IPD after vaccine implementation reflect a single clone expansion and may represent more than a transient outbreak.

What is Known About Health and Morbidity in the Pediatric Population of Muslim Bedouins in Southern Israel: A Descriptive Review of the Literature from the Past Two Decades

The Bedouins comprise one of the ethnic groups in Israeli society. They are Muslims, most of who live in the Negev desert region of southern Israel and live by their unique traditions and customs. At the present they are going through a period of "society in transition", a unique condition that has ramifications for health and morbidity. In recent years the number of publications on the health of Bedouins in the Negev has increased. Recognition of unique socio-economic features, characteristics of health and diseases can help the medical team treat various health problems in this population as well as other populations with similar characteristics. In the present paper we survey and discuss publications on the health of Bedouin children over the past 20 years.

Use of Pneumococcal Disease Epidemiology to Set Policy and Prevent Disease during 20 Years of the Emerging Infections Program

This program has been a flexible platform for following trends of this disease and evaluating vaccine effectiveness.

Two decades ago, the Emerging Infections Program of the US Centers for Disease Control and Prevention implemented what seemed like a simple yet novel idea: a population- and laboratory-based surveillance system designed to identify and characterize invasive bacterial infections, including those caused by Streptococcus pneumoniae. This system, known as Active Bacterial Core surveillance, has since served as a flexible platform for following trends in invasive pneumococcal disease and studying vaccination as the most effective method for prevention. We report the contributions of Active Bacterial Core surveillance to every pneumococcal vaccine policy decision in the United States during the past 20 years.

Differences in Norovirus-Associated Hospital Visits Between Jewish and Bedouin Children in Southern Israel

Population-based surveillance during 2006-2013 showed that norovirus hospitalization rates among Bedouin (low-middle income settings) children <5 years old were 13.9/10,000 person-years compared with 7.1/10,000 among Jewish (high-income settings) children who were <5 years (rate ratio: 2.0, 95% confidence interval: 1.6-2.3). Differences were most prominent among infants (59.7 vs. 19.7/10,000, respectively; rate ratio: 3.0, 95% confidence interval: 2.5-3.8). GII.3 and GII.4 strains dominated (67%) in both populations.

The association of serotype and pulsed-field gel electrophoresis genotype in isolates of Streptococcus pneumoniae isolated in Israel

The relationship between Streptococcus pneumoniae isolates causing invasive infections in children admitted to a single center in central Israel was examined by pulsed-field gel electrophoresis (PFGE) and serotyping. Although there was a close correlation between serotype and PFGE clone, the genetic diversity varied by serotype, with some genotypes comprising multiple serotypes. Additionally, clones C and D were associated with higher penicillin minimum inhibitory concentrations. Serotyping alone may be insufficient for epidemiological mapping of pneumococcal isolates in the era of pneumococcal conjugate polysaccharide vaccines.

Serotype 5 pneumococci causing invasive pneumococcal disease outbreaks in Barcelona, Spain (1997 to 2011)

In this study, we analyzed the clinical and molecular epidemiology of invasive serotype 5 (Ser5) pneumococcal isolates in four teaching hospitals in the Barcelona, Spain, area (from 1997 to 2011). Among 5,093 invasive pneumococcal isolates collected, 134 (2.6%) Ser5 isolates were detected. Although the overall incidence of Ser5-related invasive pneumococcal disease (IPD) was low (0.25 cases/100,000 inhabitants), three incidence peaks were detected: 0.63/100,000 in 1999, 1.15/100,000 in 2005, and 0.37/100,000 in 2009. The rates of Ser5 IPD were higher among young adults (18 to 64 years old) and older adults (>64 years old) in the first two peaks, whereas they were higher among children in 2009. The majority (88.8%) of the patients presented with pneumonia. Comorbid conditions were present in young adults (47.6%) and older adults (78.7%), the most common comorbid conditions being chronic obstructive pulmonary disease (20.6% and 38.3%, respectively) and cardiovascular diseases (11.1% and 38.3%, respectively). The mortality rates were higher among older adults (8.5%). All Ser5 pneumococci tested were fully susceptible to penicillin, cefotaxime, erythromycin, and ciprofloxacin. The resistance rates were 48.5% for co-trimoxazole, 6.7% for chloramphenicol, and 6% for tetracycline. Two major related sequence types (STs), ST1223 (n = 65) and ST289 (n = 61), were detected. The Colombia(5)-ST289 clone was responsible for all the cases in the Ser5 outbreak in 1999, whereas the ST1223 clone accounted for 73.8% and 61.5% of the isolates in 2005 and 2009, respectively. Ser5 pneumococci are a frequent cause of IPD outbreaks in the community and involve children and adults with or without comorbidities. The implementation of the new pneumococcal conjugated vaccines (PCV10 and PCV13) might prevent such outbreaks.

Molecular epidemiology of serotype 19A Streptococcus pneumoniae among invasive isolates from Alaska, 1986-2010

Background

After the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in Alaska, the incidence of invasive pneumococcal disease (IPD) due to non-vaccine serotypes, particularly serotype 19A, increased. The aim of this study was to describe the molecular epidemiology of IPD due to serotype 19A in Alaska.

Methods

IPD data were collected from 1986 to 2010 through population-based laboratory surveillance. Isolates were serotyped by the Quellung reaction and MICs determined by broth microdilution. Genotypes were assessed by multilocus sequence typing.

Results

Among 3,294 cases of laboratory-confirmed IPD, 2,926 (89%) isolates were available for serotyping, of which 233 (8%) were serotype 19A. Across all ages, the proportion of IPD caused by serotype 19A increased from 3.5% (63/1823) pre-PCV7 (1986–2000) to 15.4% (170/1103) post-PCV7 (2001–2010) (p<0.001); among children <5 years of age, the proportion increased from 5.0% (39/776) to 33.0% (76/230) (p<0.001). The annual incidence rate of IPD due to serotype 19A (all ages) increased from 0.73 cases pre-PCV7 to 2.56 cases/100,000 persons post-PCV7 (p<0.001); rates among children <5 years of age increased from 4.84 cases to 14.1 cases/100,000 persons (p<0.001). Among all IPD isolates with reduced susceptibility to penicillin, 17.8% (32/180) were serotype 19A pre-PCV7 and 64% (121/189) were serotype 19A post-PCV7 (p<0.001). Eighteen different sequence types (STs) were identified; ST199 or single locus variants of ST199 (n=150) and ST172 (n=59) accounted for the majority of isolates. Multidrug-resistant isolates were clustered in ST199 and ST320.

Conclusion

While PCV13 should significantly reduce the burden of disease due to 19A, these data highlight the need to continue surveillance for IPD to monitor the effects of vaccination on the expansion and emergence of non-PCV strains.

Serotypeº1 [corrected] childhood invasive pneumococcal disease has unique characteristics compared to disease caused by other streptococcus pneumoniae serotypes

BACKGROUND

We aimed to determine whether serotype 1 (SP1) invasive pneumococcal disease (IPD) can be distinguished by demographic, clinical and laboratory characteristics from IPD caused by the other most common serotypes (MCS) in our region: 5, 14, 6A, 6B, 19A, 19F, 23F.

METHODS

Data for all IPD episodes in children <18 years old treated at the Soroka University Medical Center during 2000 to 2009 were retrospectively retrieved. Episodes caused by SP1-IPD were compared with those caused by MCS-IPD (both grouped and individual serotypes). Analyses were adjusted for age and ethnicity.

RESULTS

Ninety-four SP1-IPD and 250 MCS-IPD episodes were documented. SP1-IPD cases were older (68.3 ± 52.6 months versus 30.4 ± 39.2 months; P < 0.001) and more likely to be found in Bedouin children than MCS-IPD (87.5% versus 58.6%; P < 0.001). SP1 was less frequently isolated from patients with underlying disease than MCS (14.9% versus 31.6 %; P < 0.001; relative risk 0.15 [95% confidence interval: 0.07-0.32]). SP1 was more often associated with bacteremic pneumonia and primary peritonitis than MCS (66% versus 38.4% and 7.4% versus 0.8%, respectively; P < 0.001); the proportion of bacteremia without focus was higher in MCS-IPD (32.4% versus 12.5%; P < 0.001). There were no differences in hospitalization and mortality rates (70.2% versus 68.0% [P = 0.22] and 4.3% versus 5.6% [P = 0.26], respectively).

CONCLUSIONS

SP1 was found less frequently than MCS in children with underlying diseases, but it was more frequent in older and Bedouin children with IPD. SP1 was more frequently associated with bacteremic pneumonia and primary peritonitis than MCS grouped.

Baseline epidemiology and genetic structure of Streptococcus pneumoniae serotype 6D in southern Israel prior to introduction of pneumococcal conjugate vaccines

We characterized Streptococcus pneumoniae serotype 6D from among previously identified S. pneumoniae serotype 6B strains from Jewish and Bedouin children in southern Israel during a decade before vaccination. S. pneumoniae serotype 6D isolates constituted 6.7% of the presumed S. pneumoniae serotype 6B isolates. S. pneumoniae serotype 6D strains belonged to 20 sequence types that were differentially distributed between the two ethnic groups.