Background

Widespread use of pneumococcal conjugate vaccines (PCVs) perturb the bacterial population structure, the consequences of which include changes in nasopharyngeal competition among pneumococci. Bacteriocins are antimicrobial peptides produced by bacteria, and are believed to inhibit competing bacterial strains. Twenty putative pneumococcal bacteriocins have been identified: this study aims to compare the bacteriocin distribution among pneumococci recovered pre- and post-PCV10 introduction in two countries.

Methods

Carriage and disease pneumococci collected in Iceland (n=1,916) and Kenya (n=3,257) before and after PCV10 introduction were sequenced and genomes were screened for twenty different bacteriocin sequences. Significant changes in the prevalence of genetic lineages, serotypes, and bacteriocins post-PCV10 introduction were assessed.

Results

PCV10 use led to a significant reduction in the prevalence of vaccine serotypes and associated genetic lineages in both countries. Overall, 18 of 20 bacteriocins were detected in 1% to 100% of genomes. The prevalence of six bacteriocins was significantly altered in the Kenyan dataset post-PCV10, and three of these also changed in the Icelandic dataset. These bacteriocins were associated with genetic lineages that also significantly changed in prevalence.

Conclusions

The bacteriocin distribution changed significantly following PCV10 introduction in Iceland and Kenya. The biological relevance of these changes to competition dynamics is currently under investigation.

Background

Iceland introduced PCV10 in 2011. The aim of this study was to monitor pneumococcal serotype distribution and antimicrobial resistance in invasive pneumococcal disease (IPD) eight years before (2004-2011; PreVac) and after vaccination (2012-2019; PostVac).

Methods

All IPD samples (blood, cerebrospinal fluid and joint fluid) were recorded at the reference laboratory, Landspitali University Hospital. All isolates were serotyped with Immulex Pool Antisera and/or multiplex PCR.

Results

In total, 564 IPD cases were detected, thereof 75 cases PreVac and 15 PostVac from children (<18y) and PCV10 serotypes were 82.7% and 13.3%, respectively (p<0.001). In children <2 years, 55 IPD cases were recorded PreVac and six PostVac (three of serotype 19A and one of each 14, 22F and 23A).

In adults, 270 cases were detected PreVac and 204 PostVac, thereof PCV10 serotypes 63.7% and 23.0%, respectively (p<0.001). The most common non-PCV10 serotypes in adults PostVac were 19A (12.3%), 22F (11.3%), 9N (7.4%) and 3 (6.4%).

Penicillin non-susceptible pneumococci (PNSP) Pre- and PostVac were 29/345 (8.4%) and 30/219 (13.7%), respectively (p=0.036). The most common PNSPs PostVac were 19A (23.3%), 15A (16.7%), 6C (13.3%) and 35B (10.0%).

Conclusions

PCV10 impact was greatest among children <2 years. The increasing prevalence of penicillin non-susceptible pneumococci of non-PCV10 serotypes is concerning.

Background

Healthy children frequently carry Streptococcus pneumoniae and Haemophilus influenzae. The aim was to study the association of H.influenzae carriage with S.pneumoniae serotypes.

Methods

Nasopharyngeal swabs were collected from about 500 children, 1-6 years old, in March 2009, and then annually 2012-2018. S.pneumoniae and H.influenzae were identified from the swabs using conventional culture methods and colonization density estimated by semi-quantitative grading. S.pneumoniae were serotyped with latex agglutination and/or mPCR.

Results

In total, 4,060 samples were collected. S.pneumoniae were detected in 2,501 samples (61.6%), and H.influenzae in 2,736 (67.4%). 1,882 samples were positive for both species and neither species could be detected in 705 samples. S.pneumoniae only were found in 619 samples and H.influenzae only in 854 samples. The Phi Coefficient of Association was 0.21.

Of the 147 samples with S.pneumoniae serotype 23F, 124 (84.4%) also had H.influenzae compared to 1,882 of the 2,501 (75.2%) S.pneumoniae positive samples (p=0.008). Of the 156 samples with non-encapsulated S.pneumoniae, 97 (62.2%) also had H.influenzae (p=0.002).

The proportion of positive samples for one of the species increased with increasing density of the other species.

Conclusions

A weak association was seen with co-carriage of S.pneumoniae and H.influenzae. H.influenzae was more often associated with serotype 23F than with non-encapsulated S.pneumoniae.