Naturally circulating pertactin-deficient strains induce distinct gene expression and inflammatory signatures in human dendritic cells.

Respiratory infections caused by are reemerging despite high pertussis vaccination coverage. Since the introduction of the acellular pertussis vaccine in the late twentieth century, circulating strains increasingly lack expression of the vaccine component pertactin (Prn). In some countries, up to 90% of the circulating strains are deficient in Prn.

Lagging Immune Response to Serotype b (Hib) Conjugate Vaccine after the Primary Vaccination with Hib of Infants in The Netherlands.

In 1993, a serotype b (Hib) conjugate vaccine was introduced in the Dutch national immunization program, resulting in a sharp decrease in invasive Hib disease. We used a population-based set of serum samples collected in the Netherlands in 2006-2007 (Pienter-II, 5696 sera) to assess the concentration of antibodies to the capsular polysaccharide of Hib, and compared the results with those obtained from a similar set collected in 1995-1996 (Pienter-I, 7837 sera). Post-primary vaccination serum samples from children aged 6-11 months from the Pienter-II study contained approximately 4-fold lower anti-Hib antibody concentrations than samples from children from the Pienter-I study.

Multiple-locus variable number tandem repeat analysis is superior to spa typing and sufficient to characterize MRSA for surveillance purposes.

Aim: Assess the best approach to type methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcal protein A (spa) typing, multiple-locus variable number tandem repeat analysis (MLVA) or both.

Materials & Methods: Discriminatory power of spa typing and MLVA was determined using 20,771 MRSA isolates.

Results: There were twice as many MLVA types (MTs) as spa types present in the collection.

Changes in the composition of the pneumococcal population and in IPD incidence in The Netherlands after the implementation of the 7-valent pneumococcal conjugate vaccine.

The implementation of nationwide pneumococcal vaccination may lead to alterations in the pneumococcal population due to selective pressure induced by the vaccine. To monitor such changes, pneumococcal isolates causing invasive pneumococcal disease (IPD) before (2004-2005, n=1154) and after (2008-2009, n=1190) the implementation of the 7-valent pneumococcal vaccine (PCV7) in 2006 in the national immunization program (NIP) of The Netherlands were characterized by molecular typing using multiple-locus variable number tandem repeat analysis (MLVA) and capsular sequence typing (CST). The IPD incidence after the implementation of PCV7 in children <5 years of age declined, mainly due to an impressive reduction of cases caused by vaccine serotypes.

Sequence diversity within the capsular genes of Streptococcus pneumoniae serogroup 6 and 19.

The main virulence factor of Streptococcus pneumoniae is the capsule. The polysaccharides comprising this capsule are encoded by approximately 15 genes and differences in these genes result in different serotypes. The aim of this study was to investigate the sequence diversity of the capsular genes of serotypes 6A, 6B, 6C, 19A and 19F and to explore a possible effect of vaccination on variation and distribution of these serotypes in the Netherlands.

Population structure of invasive Streptococcus pneumoniae in The Netherlands in the pre-vaccination era assessed by MLVA and capsular sequence typing.

The introduction of nationwide pneumococcal vaccination may lead to serotype replacement and the emergence of new variants that have expanded their genetic repertoire through recombination. To monitor alterations in the pneumococcal population structure, we have developed and utilized Capsular Sequence Typing (CST) in addition to Multiple-Locus Variable number tandem repeat Analysis (MLVA).To assess the serotype of each isolate CST was used.

Incidence of low-grade infection in aseptic loosening of total hip arthroplasty.

Purpose: We investigated the hypothesis that many total hip arthroplasty revisions that are classified as aseptic are in fact low-grade infections missed with routine diagnostics.

Methods: In 7 Dutch hospitals, 176 consecutive patients with the preoperative diagnosis of aseptic loosening of their total hip arthroplasty were enrolled. During surgery, between 14 and 20 tissue samples were obtained for culture, pathology, and broad-range 16S rRNA PCR with reverse line blot hybridization.

Two variants among Haemophilus influenzae serotype b strains with distinct bcs4, hcsA and hcsB genes display differences in expression of the polysaccharide capsule.

Background: Despite nearly complete vaccine coverage, a small number of fully vaccinated children in the Netherlands have experienced invasive disease caused by Haemophilus influenzae serotype b (Hib). This increase started in 2002, nine years after the introduction of nationwide vaccination in the Netherlands. The capsular polysaccharide of Hib is used as a conjugate vaccine to protect against Hib disease.

Identification of orthopaedic infections using broad-range polymerase chain reaction and reverse line blot hybridization.

Background: Culture remains the gold standard in the diagnosis of bacterial infection, but molecular biological techniques have yielded promising results. In this study, we validated a combined polymerase chain reaction and reverse line blot hybridization protocol for identifying musculoskeletal infections.

Methods: Samples were obtained from seventy-six patients undergoing orthopaedic surgery for various aseptic and septic indications.

Increase in genetic diversity of Haemophilus influenzae serotype b (Hib) strains after introduction of Hib vaccination in The Netherlands.

Recently, there has been an increase in The Netherlands in the number of cases of invasive disease caused by Haemophilus influenzae serotype b (Hib). To study a possible change in the Hib population that could explain the rise in incidence, a multiple-locus variable number tandem repeats analysis (MLVA) was developed to genotype H. influenzae isolates.

Horizontal transfer of segments of the 16S rRNA genes between species of the Streptococcus anginosus group.

The nature in variation of the 16S rRNA gene of members of the Streptococcus anginosus group was investigated by hybridization and DNA sequencing. A collection of 708 strains was analyzed by reverse line blot hybridization. This revealed the presence of distinct reaction patterns representing 11 different hybridization groups.

Genotyping by amplified fragment length polymorphism analysis reveals persistence and recurrence of infection with Streptococcus anginosus group organisms.

Streptococcus anginosus, Streptococcus constellatus, and Streptococcus intermedius, commonly referred to as the Streptococcus anginosus group (SAG), are commensal organisms known for their propensity to cause purulent infections which are difficult to eradicate. In this study, we determined the genetic similarities between SAG isolates consecutively recovered from single patients to assess the duration of infection or colonization. A total of 97 SAG isolates recovered from 30 patients were included; 65 (67.