Pneumococcal carriage in children and their household contacts six years after introduction of the 13-valent pneumococcal conjugate vaccine in England.

BACKGROUND: In April 2010, 13-valent pneumococcal conjugate vaccine (PCV13) replaced PCV7 in the infant immunisation schedule in England and Wales. Despite limited serotype replacement in invasive pneumococcal disease (IPD) during the first four post-PCV13 years, non-vaccine type (NVT) IPD increased substantially in 2014/15. We undertook a carriage study in 2015/16 to help understand the reasons for this increase. METHODS AND FINDINGS: Families with a child aged <5 years attending a participating general practice in Gloucestershire or Hertfordshire were invited to provide nasopharyngeal swabs from all consenting members. Swabs from 650 individuals (293 under five, 73 five to twenty and 284 >twenty years) were cultured and serotyped for Streptococcus pneumoniae. Results were compared with those from three previous household studies conducted in the same populations between 2001 to 2013, and with the serotypes causing IPD to estimate case-carrier ratios (CCRs). Overall carriage prevalence did not differ between the four carriage studies with reductions in vaccine-type carriage offset by increases in NVT carriage. While no individual NVT serotype showed an increase in CCR from 2012/13, the composition of the serotypes comprising the NVT group differed such that the overall CCR of the NVT group had significantly increased since 2012/13. Carriage of two PCV13 serotypes, 3 and 19A, was found in 2015/16 (3/650 = 0.5% and 2/650 = 0.3% respectively) with no overall reduction in carriage prevalence of PCV13-7 serotypes since 2012/13, though 6C prevalence, a vaccine-related serotype, had reduced from 1.8% in 2012/13 to 2/648 (0.3%) in 2015/16, p = 0.013. CONCLUSIONS: There was continuing evolution in carried NVTs six years after PCV13 introduction which, in addition to being vaccine-driven, could also reflect natural secular changes in certain NVTs. This poses challenges in predicting future trends in IPD. Elimination of carriage and disease due to serotypes 3 and 19A may not be achieved by PCV13.

The Enterohemorrhagic Escherichia coli Effector EspW Triggers Actin Remodeling in a Rac1-Dependent Manner.

Enterohemorrhagic Escherichia coli (EHEC) is a diarrheagenic pathogen that colonizes the gut mucosa and induces attaching-and-effacing lesions. EHEC employs a type III secretion system (T3SS) to translocate 50 effector proteins that hijack and manipulate host cell signaling pathways, which allow bacterial colonization and subversion of immune responses and disease progression. The aim of this study was to characterize the T3SS effector EspW. We found espW in the sequenced O157:H7 and non-O157 EHEC strains as well as in Shigella boydii Furthermore, a truncated version of EspW, containing the first 206 residues, is present in EPEC strains belonging to serotype O55:H7. Screening a collection of clinical EPEC isolates revealed that espW is present in 52% of the tested strains. We report that EspW modulates actin dynamics in a Rac1-dependent manner. Ectopic expression of EspW results in formation of unique membrane protrusions. Infection of Swiss cells with an EHEC espW deletion mutant induces a cell shrinkage phenotype that could be rescued by Rac1 activation via expression of the bacterial guanine nucleotide exchange factor, EspT. Furthermore, using a yeast two-hybrid screen, we identified the motor protein Kif15 as a potential interacting partner of EspW. Kif15 and EspW colocalized in cotransfected cells, while ectopically expressed Kif15 localized to the actin pedestals following EHEC infection. The data suggest that Kif15 recruits EspW to the site of bacterial attachment, which in turn activates Rac1, resulting in modifications of the actin cytoskeleton that are essential to maintain cell shape during infection.

Campylobacter jejuni outer membrane vesicles play an important role in bacterial interactions with human intestinal epithelial cells.

Campylobacter jejuni is the most prevalent cause of food-borne gastroenteritis in the developed world; however, the molecular basis of pathogenesis is unclear. Secretion of virulence factors is a key mechanism by which enteric bacterial pathogens interact with host cells to enhance survival and/or damage the host. However, C. jejuni lacks the virulence-associated secretion systems possessed by other enteric pathogens. Many bacterial pathogens utilize outer membrane vesicles (OMVs) for delivery of virulence factors into host cells. In the absence of prototypical virulence-associated secretion systems, OMVs could be an important alternative for the coordinated delivery of C. jejuni proteins into host cells. Proteomic analysis of C. jejuni 11168H OMVs identified 151 proteins, including periplasmic and outer membrane-associated proteins, but also many determinants known to be important in survival and pathogenesis, including the cytolethal distending toxin (CDT). C. jejuni OMVs contained 16 N-linked glycoproteins, indicating a delivery mechanism by which these periplasm-located yet immunogenic glycoproteins can interact with host cells. C. jejuni OMVs possess cytotoxic activity and induce a host immune response from T84 intestinal epithelial cells (IECs), which was not reduced by OMV pretreatment with proteinase K or polymyxin B prior to coincubation with IECs. Pretreatment of IECs with methyl-beta-cyclodextrin partially blocks OMV-induced host immune responses, indicating a role for lipid rafts in host cell plasma membranes during interactions with C. jejuni OMVs. OMVs isolated from a C. jejuni 11168H cdtA mutant induced interleukin-8 (IL-8) to the same extent as did wild-type OMVs, suggesting OMV induction of IL-8 is independent of CDT.