Increasing importance of multidrug-resistant serotype 6A Streptococcus pneumoniae clones in acute otitis media in southern Israel

A novel immuno-molecular strategy for the detection of Streptococcus pneumoniae serotypes in human cerebrospinal and middle ear fluids

Streptococcus pneumoniae is one of the most common microorganisms causing acute otitis media (AOM) in children. While bacterial culture of middle ear fluid (MEF) is the gold standard to detect the etiological organisms, several host and pathogen factors impact the survival of the organisms resulting in false negatives. To overcome this limitation, we have developed and validated an innovative multiplex immuno-molecular assay to screen and detect the S. pneumoniae 15-valent pneumococcal conjugate vaccine (PCV15; STs 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, 22F, 23F, and 33F) vaccine serotypes in MEF. This novel in vitro approach involves two-step testing. First, the MEF specimens were tested for highly conserved pneumococcal genes, autolysin, lytA, and pneumolysin, ply using direct PCR to identify pneumococcus positive specimens. The pneumococcus positive specimens were screened for the presence of vaccine serotype specific pneumococcal polysaccharides using a 15-plex Pneumococcal Antigen Detection (PAD) assay, with specific capture and detection monoclonal antibodies. Due to the lack of availability of MEF samples, cerebrospinal fluid (CSF) was used as the surrogate matrix for the development and validation of the PCR-PAD assays. The PCR and PAD assays were separately evaluated for sensitivity and specificity. Subsequently, the PCR-PAD assays were cross-validated with human MEF samples (n = 39) which were culture confirmed to contain relevant bacterial strains. The combined PCR-PAD assays demonstrated high rate of agreement 94.9% (95% CI; 82.7, 99.4%) with historical Quellung serotype data of these MEF samples. This novel PCR-PAD assay demonstrates the feasibility of combining molecular and immunological assays to screen and identify PCV15 pneumococcal vaccine serotypes in AOM clinical samples.

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.

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.

Pneumococcal nasopharyngeal carriage in children <5 years of age visiting the pediatric emergency room in relation to PCV7 and PCV13 introduction in southern Israel

The 7-valent and the 13-valent pneumococcal conjugate vaccines (PCV7 and PCV13, respectively) were introduced to the Israeli National Immunization plan in July 2009 and November 2010, respectively. Our aim was to assess pneumococcal conjugate vaccines (PCVs) uptake and dynamics in serotype-specific pneumococcal nasopharyngeal (NP) carriage in children <5  years old in southern Israel, during the immediate 5 y following PCV introduction. This was an ongoing, prospective, population-based, active surveillance, from July 2009 through December 2014. PCVs uptake and NP cultures were obtained daily from children seen at the Pediatric Emergency Room for any reason. Overall, 10,702 vaccine status and 7,610 NP swabs were obtained. Both PCV7 and PCV13 uptake were high, reaching ˜90% by July 2012 and December 2013, respectively. All-pneumococcal carriage rates significantly declined by 10%, from 54.3% in the early-PCV7 period, to 49.1% in the PCV13 impact period. The respective declines for PCV7, 6A and additional PCV13 serotypes carriage rates were 76%, 90% and 66%. In contrast, non-PCV13 serotypes carriage rates increased significantly throughout the study by 71%. All-pneumococcal carriage rates in children <12  months old decreased significantly by 15%, with similar trends observed in other age groups. Initially, all-pneumococcal carriage rates were 45.7%, and 61.9% in Jewish and Bedouin children, respectively (P < 0.001), with a significant 17% reduction throughout the study observed only in Bedouins. While early carriage rates were higher in unvaccinated children compared to vaccinated children, PCV impact on carriage were similar in both groups. In conclusion, a relatively moderate decline in pneumococcal carriage rates, facilitated by a substantial decrease of vaccine-serotypes and increase of non-vaccine serotypes was observed in the immediate period following PCVs introduction in southern Israel.

Predominant Bacteria Detected from the Middle Ear Fluid of Children Experiencing Otitis Media: A Systematic Review

BACKGROUND

Otitis media (OM) is amongst the most common childhood diseases and is associated with multiple microbial pathogens within the middle ear. Global and temporal monitoring of predominant bacterial pathogens is important to inform new treatment strategies, vaccine development and to monitor the impact of vaccine implementation to improve progress toward global OM prevention.

METHODS

A systematic review of published reports of microbiology of acute otitis media (AOM) and otitis media with effusion (OME) from January, 1970 to August 2014, was performed using PubMed databases.

RESULTS

This review confirmed that Streptococcus pneumoniae and Haemophilus influenzae, remain the predominant bacterial pathogens, with S. pneumoniae the predominant bacterium in the majority reports from AOM patients. In contrast, H. influenzae was the predominant bacterium for patients experiencing chronic OME, recurrent AOM and AOM with treatment failure. This result was consistent, even where improved detection sensitivity from the use of polymerase chain reaction (PCR) rather than bacterial culture was conducted. On average, PCR analyses increased the frequency of detection of S. pneumoniae and H. influenzae 3.2 fold compared to culture, whilst Moraxella catarrhalis was 4.5 times more frequently identified by PCR. Molecular methods can also improve monitoring of regional changes in the serotypes and identification frequency of S. pneumoniae and H. influenzae over time or after vaccine implementation, such as after introduction of the 7-valent pneumococcal conjugate vaccine.

CONCLUSIONS

Globally, S. pneumoniae and H. influenzae remain the predominant otopathogens associated with OM as identified through bacterial culture; however, molecular methods continue to improve the frequency and accuracy of detection of individual serotypes. Ongoing monitoring with appropriate detection methods for OM pathogens can support development of improved vaccines to provide protection from the complex combination of otopathogens within the middle ear, ultimately aiming to reduce the risk of chronic and recurrent OM in vulnerable populations.

Streptococcus pneumoniae serogroup 6 clones over two decades

The major evolutionary stresses on Streptococcus pneumoniae are thought to be the widespread use of antibiotics and the deployment of effective vaccines against the capsular polysaccharides. Our current knowledge of genetic lineages among pneumococcal isolates comes largely from investigations just before and after the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) introduced in 2000. We examined 66 serogroup 6 isolates from the 1970s, long before the introduction of PCV7 and before widespread penicillin resistance was common in Birmingham, Alabama, to look for ancestors of the clones that came into play around the introduction of the PCV7 vaccine. The hypothesis was that some clonal complexes, if not individual clones, would be stable enough to persist over this period of time. We compared the 1970s isolates with 122 isolates from the 1990s in US and worldwide collections. Genotyping with pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) revealed that while some clones were probably localized to our area, others have persisted within groups that have expanded or diminished over the years.

Comparative immunogenicity and efficacy of 13-valent and 7-valent pneumococcal conjugate vaccines in reducing nasopharyngeal colonization: a randomized double-blind trial

BACKGROUND

The 13-valent pneumococcal conjugate vaccine (PCV13) was licensed to replace the 7-valent pneumococcal conjugate vaccine (PCV7) based on serological noninferiority criteria. To date no randomized PCV13 pediatric trial has included clinical endpoints.

METHODS

This randomized double-blind trial compared the impact of PCV13 versus PCV7 on nasopharyngeal (NP) colonization and immunogenicity. Healthy infants were randomized (1:1) to receive PCV7 or PCV13 at ages 2, 4, 6, and 12 months; NP swabs were collected at 2, 4, 6, 7, 12, 13, 18, and 24 months, and blood was drawn at 7 and 13 months. Rates of NP acquisition and prevalence, and serotype-specific immunoglobulin G (IgG) concentrations were assessed.

RESULTS

The per protocol analysis population included 881 PCV13 and 873 PCV7 recipients. PCV13 significantly reduced NP acquisition of the additional PCV13 serotypes 1, 6A, 7F, and 19A; the cross-reacting serotype 6C; and the common PCV7 serotype 19F. For serotype 3, and the other PCV7 serotypes, there were no significant differences between the vaccine groups. There were too few serotype 5 events to draw inference. The impact on prevalence at predefined time points was similar to that observed with NP acquisition. PCV13 elicited significantly higher IgG responses for PCV13 additional serotypes and serotype 19F, and similar or lower responses for 6/7 PCV7 serotypes.

CONCLUSIONS

PCV13 resulted in lower acquisition and prevalence of NP colonization than PCV7 did for 4 additional PCV13 serotypes, and serotypes 6C and 19F. It was comparable with PCV7 for all other common serotypes. These findings predict vaccine effectiveness through both direct and indirect protection.

CLINICAL TRIALS REGISTRATION

NCT00508742.

Pneumococcal serotypes causing acute otitis media among children in Barcelona (1992-2011): emergence of the multiresistant clone ST320 of serotype 19A

BACKGROUND

There is scarce information about changes in serotypes and clonal types of Streptococcus pneumoniae causing acute otitis media (AOM) in recent years, particularly in European countries.

METHODS

Pneumococcal serotypes and clones from S. pneumoniae strains isolated from children with AOM who were attended at Hospital Sant Joan de Déu, Barcelona (1992 to 2011), were studied. Heptavalent pneumococcal conjugate vaccine (PCV7) was introduced in June 2001. We defined 3 periods: prevaccine period 1992 to 2001, early vaccine period 2002 to 2006 and late vaccine period 2007 to 2011.

RESULTS

There were 376 pneumococcal strains causing AOM, and 373 (99.2%) of them were serotyped. AOM caused by PCV7 serotypes declined significantly: 161 of 245 (65.7%) episodes in 1992 to 2001 versus 22 of 67 (32.8%) in 2002 to 2006 versus 8 of 61 (13.1%) in 2007 to 2011 P < 0.001. In the last period (2007 to 2011), the potential serotype coverage for the PCV10 was 16.4% and for the PCV13 was 68.9% (P < 0.001). Serotype 19A increased from 5.7% in 1992 to 2001 to 42.6% in 2007 to 2011 (P < 0.001). Among strains with penicillin minimal inhibitory concentration ≥0.12 μg/mL (n = 241), serotype 19A rose from 2.3% in the first period to 57.9 % in the last period (P < 0.001). The clonal-type ST320 was initially detected in 2005, and in the period 2007 to 2011, the ST320 was found in 72.7% of nonsusceptible serotype 19A isolates.

CONCLUSIONS

Among children with AOM, a rapid expansion of the multiresistant clone ST320 expressing serotype 19A has been observed in Barcelona. The implementation of PCV13, which includes this serotype, may decrease the prevalence of AOM and reduce antimicrobial resistance.

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.

Rapid reduction in invasive pneumococcal disease after introduction of PCV7 into the National Immunization Plan in Israel

BACKGROUND

The 7-valent conjugated vaccine (PCV7) was introduced into the Israeli National Immunization Program (NIP) in July 2009 (2, 4, 12 months schedule; 2 dose catch-up in second year of life). Nationwide active prospective surveillance on invasive pneumococcal disease (IPD) has been conducted in children since 1989. In the current study, IPD epidemiology in children <5 years during the 20 years before and 18 months after PCV7 NIP initiation, is reported.

METHODS

All 27 centers performing blood/cerebrospinal fluid (CSF) cultures in children reported monthly IPD cases. Capture-recapture approach was used for completeness.

RESULTS

During 1989-2010, 6022 IPD cases were reported in children <5 years; PCV7 serotypes (7VST) caused ∼50% of all episodes. In 2009 and 2010, 7VST IPD incidences <5 years of age (per 100,000) were 15.9 and 5.4, respectively (a 43% and 81% decrease, respectively) compared to 2003-2007 (mean incidence 27.8). Serotype 6A dynamics resembled those of 7VST. The respective overall IPD incidence decreases were 23% and 42%. The incidence dynamics of serotypes 1, 3, 5, 7F and 19A IPD were characterized by considerable fluctuations over the study period without any upwards or downwards trend in any of the age groups. The overall incidence of serotypes not included in the 13-valent pneumococcal conjugate vaccine (PCV13) did not vary significantly during the study period. By the end of 2010, 72% of the remaining IPD was caused by pneumococcal serotypes included in PCV13.

CONCLUSIONS

An active prospective long-term surveillance, showed a rapid and sharp decline in IPD in children <5 years following initiation of NIP with PCV7. No serotype replacement has been observed so far. The transition from PCV7 to PCV13 initiated in October 2010 may lead to a further substantial decrease in IPD. Follow-up is needed to better determine the long-term PCV effects.

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

This study aimed to compare the clonal distribution of common pneumococcal strains not included in the 7-valent pneumococcal conjugate vaccine (PCV7) that were isolated from cases of acute otitis media (AOM) and invasive pneumococcal disease (IPD) in two distinct ethnic populations in southern Israel during the decade (1999 to 2008) preceding PCV7 implementation. Isolates recovered from Jewish and Bedouin children <5 years old were characterized by antibiotic resistance and molecular epidemiology using pulsed-field gel electrophoresis and multilocus sequence typing. Of 5,236 AOM and 425 IPD isolates, 43% and 57% were from Jewish and Bedouin children, respectively. PCV7 accounted for 54% and 45% of the AOM and IPD episodes, respectively. Eleven major non-PCV7 serotypes (1, 3, 5, 6A, 7F, 12F, 15B/C, 19A, 21, 33F, and 35B) constituted 31% and 42% of the AOM and IPD episodes, respectively. The clonal distributions of the 11 non-PCV7 serotypes and their antibiotic susceptibilities were significantly different among the two ethnic populations in both the AOM and IPD groups. About half of the AOM and IPD cases resulted from non-PCV7 pneumococci, even before PCV7 implementation. The significant differences between the two ethnic populations suggest that lifestyle and microenvironment are major determinants in the clonal distribution of disease-causing pneumococci. Post-PCV7 surveillance is important in understanding non-PCV7 clonal expansion in the two distinct populations.

Increase in prevalence of Streptococcus pneumoniae serotype 6C at Eight Children's Hospitals in the United States from 1993 to 2009

Streptococcus pneumoniae serotype 6C, which was described in 2007, causes invasive disease in adults and children. We investigated the prevalence of 6C among pediatric isolates obtained from eight children's hospitals in the United States. S. pneumoniae isolates were identified from a prospective multicenter study (1993 to 2009). Fifty-seven serotype 6C isolates were identified by multiplex PCR and/or Quellung reaction. Five were isolated before 2000, and the prevalence increased over time (P < 0.000001). The median patient age was 2.1 years (range, 0.2 to 22.5 years). Clinical presentations included bacteremia (n = 24), meningitis (n = 7), pneumonia (n = 4), abscess/wound (n = 3), mastoiditis (n = 2), cellulitis (n = 2), peritonitis (n = 1), septic arthritis (n = 1), otitis media (n = 10), and sinusitis (n = 3). By broth microdilution, 43/44 invasive serotype 6C isolates were susceptible to penicillin (median MIC, 0.015 μg/ml; range, 0.008 to 2 μg/ml); all were susceptible to ceftriaxone (median MIC, 0.015 μg/ml; range, 0.008 to 1 μg/ml). By disk diffusion, 16/44 invasive isolates (36%) were nonsusceptible to erythromycin, 19 isolates (43%) were nonsusceptible to trimethoprim-sulfamethoxazole (TMP-SMX), and all isolates were clindamycin susceptible. Multilocus sequence typing (MLST) revealed 24 sequence types (STs); 9 were new to the MLST database. The two main clonal clusters (CCs) were ST473 and single-locus variants (SLVs) (n = 13) and ST1292 and SLVs (n = 23). ST1292 and SLVs had decreased antibiotic susceptibility. Serotype 6C causes disease in children in the United States. Emerging CC1292 expressed TMP-SMX resistance and decreased susceptibility to penicillin and ceftriaxone. Continued surveillance is needed to monitor changes in serotype prevalence and possible emergence of antibiotic resistance in pediatric pneumococcal disease.

Multiplex PCR to determine Streptococcus pneumoniae serotypes causing otitis media in the Republic of Ireland with further characterisation of antimicrobial susceptibilities and genotypes

The purpose of this study was to determine the serotypes, genotypes and antimicrobial susceptibilities of Streptococcus pneumoniae causing otitis media (OM) in children in Dublin, Ireland. S. pneumoniae isolates (n = 28) from spontaneously discharging OM were studied. Serotyping was performed using a previously undescribed multiplex polymerase chain reaction (PCR) scheme in combination with serological methods. Multilocus sequence typing (MLST) was performed using standard procedures. Antimicrobial susceptibility testing was performed using the Etest method. Fourteen different S. pneumoniae serotypes were identified. The five most common serotypes were 3, 19F, 19A, 14 and 6A, which accounted for 68% of all infections. The 7-valent pneumococcal conjugate vaccine (PCV7), 10-valent pneumococcal conjugate vaccine (PHiD-CV) and 13-valent pneumococcal conjugate vaccine (PCV13) provided potential coverages of 43%, 46% and 86%, respectively. Reduced susceptibility to penicillin was evident for 25% of isolates and was associated with serotypes 14, 19A, 19F and 9V. A total of 21 different sequence types (STs) were identified. Pneumococcal Molecular Epidemiology Network (PMEN) clones or their variants represented 54% (15/28) of all isolates. Continued monitoring and characterisation of S. pneumoniae causing OM in Ireland is warranted in order to guide future vaccine and treatment policies.

Differential circulation of Streptococcus pneumoniae serotype 6C clones in two Israeli pediatric populations

We genotyped Streptococcus pneumoniae serotype 6C (Sp6C) isolates collected from Jewish and Bedouin children in southern Israel during the decade before vaccination. Sp6C constituted 8.2% of the presumed Sp6A isolates. All of the Sp6C clonal clusters were associated with serogroup 6, mainly Sp6A. Different clonal distributions were found in the two subpopulations.