Streptococcus pneumoniae serotype 3 population structure in the era of conjugate vaccines, 2001-2018

Background. Despite use of highly effective conjugate vaccines, invasive pneumococcal disease (IPD) remains a leading cause of morbidity and mortality and disproportionately affects Indigenous populations. Although included in the 13-valent pneumococcal conjugate vaccine (PCV13), which was introduced in 2010, serotype 3 continues to cause disease among Indigenous communities in the Southwest USA. In the Navajo Nation, serotype 3 IPD incidence increased among adults (3.8/100 000 in 2001-2009 and 6.2/100 000 in 2011-2019); in children the disease persisted although the rates dropped from 5.8/100 000 to 2.3/100 000.Methods. We analysed the genomic epidemiology of serotype 3 isolates collected from 129 adults and 63 children with pneumococcal carriage (n=61) or IPD (n=131) from 2001 to 2018 of the Navajo Nation. Using whole-genome sequencing data, we determined clade membership and assessed changes in serotype 3 population structure over time.Results. The serotype 3 population structure was characterized by three dominant subpopulations: clade II (n=90, 46.9 %) and clade Iα (n=59, 30.7 %), which fall into Clonal Complex (CC) 180, and a non-CC180 clade (n=43, 22.4 %). The proportion of clade II-associated IPD cases increased significantly from 2001 to 2010 to 2011-2018 among adults (23.1-71.8 %; P<0.001) but not in children (27.3-33.3 %; P=0.84). Over the same period, the proportion of clade II-associated carriage increased; this was statistically significant among children (23.3-52.6 %; P=0.04) but not adults (0-50.0 %, P=0.08).Conclusions. In this setting with persistent serotype 3 IPD and carriage, clade II has increased since 2010. Genomic changes may be contributing to the observed trends in serotype 3 carriage and disease over time.

Carriage prevalence and genomic epidemiology of Staphylococcus aureus among Native American children and adults in the Southwestern USA

Native American individuals in the Southwestern USA experience a higher burden of invasive Staphylococcus aureus disease than the general population. However, little is known about S. aureus carriage in these communities. A cross-sectional study was conducted to determine the carriage prevalence, risk factors and genomic epidemiology of S. aureus among Native American children (<5 years, n=121) and adults (≥18 years, n=167) in the Southwestern USA. Short- and long-read sequencing data were generated using Illumina and Oxford Nanopore Technology platforms to produce high-quality hybrid assemblies, and antibiotic-resistance, virulence and pangenome analyses were performed. S. aureus carriage prevalence was 20.7 % among children, 30.2 % among adults 18–64 years and 16.7 % among adults ≥65 years. Risk factors among adults included recent surgery, prior S. aureus infection among household members, and recent use of gyms or locker rooms by household members. No risk factors were identified among children. The bacterial population structure was dominated by clonal complex 1 (CC1) (21.1 %), CC5 (22.2 %) and CC8 (22.2 %). Isolates from children and adults were intermixed throughout the phylogeny. While the S. aureus population was diverse, the carriage prevalence was comparable to that in the general USA population. Genomic and risk-factor data suggest household, community and healthcare transmission are important components of the local epidemiology.

Matrigel-coated stents reduce intimal thickening in a large animal vascular stent model

BACKGROUND

Restenosis within vascular stents is primarily due to intimal thickening secondary to intimal hyperplasia (IH) which occurs maximally around stent struts. Dedifferentiation of vascular smooth muscle cells (VSMC) with subsequent migration and proliferation is believed to be a key event in IH formation. Matrigel (basement membrane protein) has been shown to inhibit dedifferentiation of VSMC in vitro. Our aim was to test the in vivo effect of Matrigel on IH formation using a novel sheep vascular stent model.

METHODS

Twenty vascular stents were implanted in the renal arteries of ten sheep. The left renal artery of each sheep was used to deploy uncoated stent and the right renal artery was used to deploy Matrigel-coated stent. Five sheep were analysed at four weeks and five at eight weeks after stent implantation. The sheep were sacrificed at the end of the study periods and the stented renal artery segments were examined by histology. Luminal, intimal and medial areas were determined using computer-assisted morphometric analysis.

RESULTS

All stent sites were widely patent without thrombosis. No luminal stenosis was seen angiographically. IH was quantified from histology cross-sections and expressed as an intima to media (I/M) ratio. The ratio was significantly reduced in the matrigel-coated sites at eight weeks (uncoated 0.49+/-0.23; Matrigel-coated 0.32+/-0.12; p value <0.05).

CONCLUSIONS

The sheep renal artery vascular stent model is feasible for the study of stent biology. IH was reduced by Matrigel-coated stents.