MRSA in persons not living or working on a farm in a livestock-dense area: prevalence and risk factors

Objectives

MRSA emerged in livestock and persons in contact with livestock is referred to as livestock-associated MRSA (LA-MRSA). We assessed the prevalence and risk factors for MRSA carriage in persons not living or working on a farm.

Methods

A cross-sectional study was performed among 2492 adults living in close proximity of livestock farms. Persons working and/or living on farms were excluded. Nasal swabs were cultured using selective media. Participants completed questionnaires and the distance from the residential address to the nearest farm was calculated. The Mann-Whitney U -test was used to compare median distances. Risk factors were explored with logistic regression.

Results

Fourteen persons carried MRSA (0.56%; 95% CI 0.32%-0.92%), 10 of which carried LA-MRSA of multiple-locus variable-number tandem repeat analysis complex (MC) 398 (0.40%; 95% CI 0.20%-0.71%). MRSA MC 398 carriers lived significantly closer to the nearest farm than non-carriers (median: 184 versus 402 m; P  <   0.01). In bivariate analyses correcting for contact with livestock, this difference remained significant.

Conclusions

Although the prevalence was low, living near farms increased the risk of MRSA MC 398 carriage for persons not living or working on a farm. Further research is necessary to identify the transmission routes.

Adhering to a national surgical care bundle reduces the risk of surgical site infections

Background

In 2008, a bundle of care to prevent Surgical Site Infections (SSIs) was introduced in the Netherlands. The bundle consisted of four elements: antibiotic prophylaxis according to local guidelines, no hair removal, normothermia and ‘hygiene discipline’ in the operating room (i.e. number of door movements). Dutch hospitals were advised to implement the bundle and to measure the outcome. This study’s goal was to assess how effective the bundle was in reducing SSI risk.

Methods

Hospitals assessed whether their staff complied with each of the bundle elements and voluntary reported compliance data to the national SSI surveillance network (PREZIES). From PREZIES data, we selected data from 2009 to 2014 relating to 13 types of surgical procedures. We excluded surgeries with missing (non)compliance data, and calculated for each remaining surgery with reported (non)compliance data the level of compliance with the bundle (that is, being compliant with 0, 1, 2, 3, or 4 of the elements). Subsequently, we used this level of compliance to assess the effect of bundle compliance on the SSI risk, using multilevel logistic regression techniques.

Results

217 489 surgeries were included, of which 62 486 surgeries (29%) had complete bundle reporting. Within this group, the SSI risk was significantly lower for surgeries with complete bundle compliance compared to surgeries with lower compliance levels. Odds ratios ranged from 0.63 to 0.86 (risk reduction of 14% to 37%), while a 13% risk reduction was demonstrated for each point increase in compliance-level. Sensitivity analysis indicated that due to analysing reported bundles only, we probably underestimated the total effect of implementing the bundle.

Conclusions

This study demonstrated that adhering to a surgical care bundle significantly reduced the risk of SSIs. Reporting of and compliance with the bundle compliance can, however, still be improved. Therefore an even greater effect might be achieved.

Clinical and Microbiological Characteristics of Clostridium difficile Infection Among Hospitalized Children in the Netherlands

BACKGROUND

Little is known about pediatric Clostridium difficile infection (CDI) epidemiology. We describe the clinical and microbiological characteristics of CDI among hospitalized children in the Netherlands.

METHODS

Between May 2009 and May 2015, 26 hospitals registered characteristics of pediatric (aged 2-18 years) and adult (aged 18 years) CDI in a national sentinel surveillance study. Routine polymerase chain reaction (PCR) ribotyping and multiple-locus variable-number tandem-repeat analysis (MLVA) of selected strains was performed. Pediatric and adult results were compared using proportion and 95% confidence interval (CI). Time trend of pediatric CDI was evaluated using a mixed-effect Poisson model.

RESULTS

Pediatric CDIs were reported in 17 of the 26 participating hospitals (n = 135; 3% of all CDIs); the monthly number was constant over time. The median age of pediatric cases was 10 years (interquartile range, 4.7-14.5 years). Fifty-five percent of the children had community onset and 31% had severe CDI. Compared with adults (n = 4,556), complication and mortality rates were lower. Clostridium difficile PCR ribotype 265 (toxin A negative, B positive) was most prevalent in children (15%; 95% CI, 8.8%-24.0%) but rarely found in adults (1%; 95% CI, 0.9%-1.6%). This strain was rarely found in other countries, except for Belgium. MLVA showed genetic relatedness between three-fourths of pediatric and adult ribotype 265 strains, without a clear epidemiological link.

CONCLUSIONS

Pediatric CDI in hospitals has remained stable over the last 6 years and resulted in fewer complications than for adult CDI. Further studies are needed to elucidate the source and epidemiology of PCR ribotype 265, primarily found in children.

Diagnosis and management of aspergillosis in the Netherlands: a national survey

A survey of diagnosis and treatment of invasive aspergillosis was conducted in eight University Medical Centers (UMCs) and eight non-academic teaching hospitals in the Netherlands. Against a background of emerging azole resistance in Aspergillus fumigatus routine resistance screening of clinical isolates was performed primarily in the UMCs. Azole resistance rates at the hospital level varied between 5% and 10%, although rates up to 30% were reported in high-risk wards. Voriconazole remained first choice for invasive aspergillosis in 13 out of 16 hospitals. In documented azole resistance 14 out of 16 centres treated patients with liposomal amphotericin B.

Molecular characteristics of extended-spectrum cephalosporin-resistant Enterobacteriaceae from humans in the community

OBJECTIVE

To investigate the molecular characteristics of extended-spectrum cephalosporin (ESC)-resistant Enterobacteriaceae collected during a cross-sectional study examining the prevalence and risk factors for faecal carriage of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in humans living in areas with high or low broiler density.

METHODS

ESC-resistant Enterobacteriaceae were identified by combination disc-diffusion test. ESBL/AmpC/carbapenemase genes were analysed using PCR and sequencing. For E. coli, phylogenetic groups and MLST were determined. Plasmids were characterized by transformation and PCR-based replicon typing. Subtyping of plasmids was done by plasmid multilocus sequence typing.

RESULTS

175 ESC-resistant Enterobacteriaceae were cultured from 165/1,033 individuals. The isolates were Escherichia coli(n=65), Citrobacter freundii (n=52), Enterobacter cloacae (n=38), Morganella morganii (n=5), Enterobacter aerogenes (n=4), Klebsiella pneumoniae (n=3), Hafnia alvei (n=2), Shigella spp. (n=2), Citrobacter amalonaticus (n=1), Escherichia hermannii (n=1), Kluyvera cryocrescens (n=1), and Pantoea agglomerans (n=1). The following ESBL genes were recovered in 55 isolates originating from 49 of 1,033 (4.7 %) persons: blaCTX-M-1 (n=17), blaCTX-M-15 (n=16), blaCTX-M-14 (n=9), blaCTX-M-2 (n=3), blaCTX-M-3 (n=2), blaCTX-M-24 (n=2), blaCTX-M-27 (n=1), blaCTX-M-32 (n=1), blaSHV-12 (n=2), blaSHV-65 (n=1) and blaTEM-52 (n=1). Plasmidic AmpC (pAmpC) genes were discovered in 6 out of 1,033 (0.6 %) persons. One person carried two different E. coli isolates, one with blaCTX-M-1 and the other with blaCMY-2 and therefore the prevalence of persons carrying Enterobacteriaceae harboring ESBL and/or pAmpC genes was 5.2 %. In eight E. coli isolates the AmpC phenotype was caused by mutations in the AmpC promoter region. No carbapenemase genes were identified. A large variety of E. coli genotypes was found, ST131 and ST10 being most common.

CONCLUSIONS

ESBL/pAmpC genes resembled those from patients in Dutch hospitals, indicating that healthy humans form a reservoir for transmission of these determinants to vulnerable people. The role of poultry in the transmission to humans in the community remains to be elucidated.

Impact of livestock-associated MRSA in a hospital setting

OBJECTIVES

The Netherlands is known for a stringent search and destroy policy to prevent spread of MRSA. In the hospital setting, livestock-associated MRSA (LA-MRSA) is frequently found in patients coming from the high density farming area in the south of the Netherlands. The aim of the study was to determine the contribution of LA-MRSA in the epidemiology of MRSA in cases found following the Dutch search and destroy policy.

PATIENTS AND METHODS

From two hospitals serving a population of 550,000 persons all data on MRSA cultures and subsequent control measures from 2008 and 2009 were retrospectively collected and analyzed.

RESULTS

A total of 3856 potential index patients were screened for MRSA, 373 (9.7%) were found to be positive, 292 ( 78%) LA-MRSA and 81 (22%) non-LA-MRSA respectively. No secondary cases were found among contact research in persons exposed to LA-MRSA (0/416), whereas similar contact research for non-LA-MRSA resulted in 83 (2.5%) secondary cases. LA-MRSA were rarely found to cause infections.

CONCLUSIONS

LA-MRSA is more prevalent than non-LA-MRSA in Dutch Hospitals in the South of the Netherlands. However, retrospectively studied cases show that the transmission rate for LA-MRSA was much lower than for non-LA-MRSA. This suggest that infection control practices for LA-MRSA may possibly be less stringent than for non-LA-MRSA.

Effect of tailored antibiotic stewardship programmes on the appropriateness of antibiotic prescribing in nursing homes

OBJECTIVES

To evaluate the effect of tailored interventions on the appropriateness of decisions to prescribe or withhold antibiotics, antibiotic use and guideline-adherent antibiotic selection in nursing homes (NHs).

METHODS

We conducted a quasi-experimental study in 10 NHs in the Netherlands. A participatory action research (PAR) approach was applied, with local stakeholders in charge of selecting tailored interventions based on opportunities for improved antibiotic prescribing that they derived from provided baseline data. An algorithm was used to evaluate the appropriateness of prescribing decisions, based on infections recorded by physicians. Effects of the interventions on the appropriateness of prescribing decisions were analysed with a multilevel logistic regression model. Pharmacy data were used to calculate differences in antibiotic use and recorded infections were used to calculate differences in guideline-adherent antibiotic selection.

RESULTS

The appropriateness of 1059 prescribing decisions was assessed. Adjusting for pre-test differences in the proportion of appropriate prescribing decisions (intervention, 82%; control, 70%), post-test appropriateness did not differ between groups (crude: P = 0.26; adjusted for covariates: P = 0.35). We observed more appropriate prescribing decisions at the start of data collection and before receiving feedback on prescribing behaviour. No changes in antibiotic use or guideline-adherent antibiotic selection were observed in intervention NHs.

CONCLUSIONS

The PAR approach, or the way PAR was applied in the study, was not effective in improving antibiotic prescribing behaviour. The study findings suggest that drawing prescribers' attention to prescribing behaviour and monitoring activities, and increasing use of diagnostic resources may be promising interventions to improve antibiotic prescribing in NHs.

[Healthcare-associated infections on readmission: 1 in 3 is linked to previous hospital admission]

OBJECTIVE

To gain insight into the prevalence of healthcare-associated (HAI) infections in hospital patients in the Netherlands, and their link with previous hospital admission.

DESIGN

Cross-sectional study.

METHOD

This prevalence study was carried out in 36 hospitals at 42 locations in the Netherlands in March 2014. All inpatients at the time of the study were evaluated for the presence of an HAI, according to the standard protocol and in accordance with internationally determined definitions. It was subsequently determined whether the HAI had been acquired during the current admission or was linked to a previous recent admission. Readmission had to have taken place within a predetermined time period.

RESULTS

A total of 9,420 patients were evaluated for the presence of an HAI; 470 (5.0%) HAI were reported, of which almost 36% was linked to a previous admission. Two-thirds of the HAI were post-operative surgical-site infections. Almost 88% of the patients with HAI were treated with antibiotics, versus 32% of the patients without HAI.

CONCLUSION

Registration of HAI on admission to hospital provides insight into the frequency of HAI that become apparent after discharge. There is no insight into the treatment frequency of HAI by general practitioners. An inventory of the treatment frequency of HAI in primary care is advised, to evaluate infection-prevention policy in hospitals and to optimise primary care.

Estimation of the serial interval of pertussis in Dutch households

Increasing incidence has led to the re-appearance of pertussis as a public health problem in developed countries. Pertussis infection is usually mild in vaccinated children and adults, but it can be fatal in infants who are too young for effective vaccination (≤3 months). Tailoring of control strategies to prevent infection of the infant hinges on the availability of estimates of key epidemiological quantities. Here we estimate the serial interval of pertussis, i.e., the time between symptoms onset in a case and its infector, using data from a household-based study carried out in the Netherlands in 2007-2009. We use statistical methodology to tie infected persons to probable infector persons, and obtain statistically supported stratifications of the data by person-type (infant, mother, father, sibling). The analyses show that the mean serial interval is 20 days (95% CI: 16-23 days) when the mother is the infector of the infant, and 28 days (95% CI: 23-33 days) when the infector is the father or a sibling. These time frames offer opportunities for early mitigation of the consequences of infection of an infant once a case has been detected in a household. If preventive measures such as social distancing or antimicrobial treatment are taken promptly they could decrease the probability of infection of the infant.

Recommendations for the empirical treatment of complicated urinary tract infections using surveillance data on antimicrobial resistance in the Netherlands

BACKGROUND

Complicated urinary tract infections (c-UTIs) are among the most common nosocomial infections and a substantial part of the antimicrobial agents used in hospitals is for the treatment of c-UTIs. Data from surveillance can be used to guide the empirical treatment choices of clinicians when treating c-UTIs. We therefore used nation-wide surveillance data to evaluate antimicrobial coverage of agents for the treatment of c-UTI in the Netherlands.

METHODS

We included the first isolate per patient of urine samples of hospitalised patients collected by the Infectious Disease Surveillance Information System for Antibiotic Resistance (ISIS-AR) in 2012, and determined the probability of inadequate coverage for antimicrobial agents based on species distribution and susceptibility. Analyses were repeated for various patient groups and hospital settings.

RESULTS

The most prevalent bacteria in 27,922 isolates of 23,357 patients were Escherichia coli (47%), Enterococcus spp. (14%), Proteus mirabilis (8%), and Klebsiella pneumoniae (7%). For all species combined, the probability of inadequate coverage was <5% for amoxicillin or amoxicillin-clavulanic acid combined with gentamicin and the carbapenems. When including gram-negative bacteria only, the probability of inadequate coverage was 4.0%, 2.7%, 2.3% and 1.7%, respectively, for amoxicillin, amoxicillin-clavulanic acid, a second or a third generation cephalosporin in combination with gentamicin, and the carbapenems (0.4%). There were only small variations in results among different patient groups and hospital settings.

CONCLUSIONS

When excluding Enterococcus spp., considered as less virulent, and the carbapenems, considered as last-resort drugs, empirical treatment for c-UTI with the best chance of adequate coverage are one of the studied beta-lactam-gentamicin combinations. This study demonstrates the applicability of routine surveillance data for up-to-date clinical practice guidelines on empirical antimicrobial therapy, essential in patient care given the evolving bacterial susceptibility.

Pertussis in the Netherlands, is the current vaccination strategy sufficient to reduce disease burden in young infants?

BACKGROUND

Pertussis has resurged in the Netherlands since 1996. Several measures, i.e. acceleration of the schedule, introduction of a preschool acellular pertussis booster and change from an infant whole cell to an acellular pertussis combination vaccine were implemented in the National Immunisation Programme to decrease disease burden, in particular among very young infants who have the highest morbidity and mortality of pertussis. Nevertheless, a large outbreak occurred in 2011-2012.

METHODS

1996-2010 was divided in 3-year-periods to assess the impact of the measures taken, using notifications and hospitalisations. These results were compared with 2011-2012. Mean Incidence rates (IRs) per 100,000 were calculated.

RESULTS

Although the measures taken resulted in decreased IRs among the targeted age groups after implementation, overall mean IRs of notifications increased from 32 (1996-2004) to 37 (2005-2010) and 63 (2011-2012). Young infants, not yet vaccinated, did not benefit; during the 2011-2012 outbreak, IR in 0-2-month-olds amounted to 259.6. IR among persons over 9 years of age increased from 6.8 (1996-1999) to 59.1 (2011-2012) For hospitalisations overall mean IRs decreased from 1.95 per 100,000 (1997-2004) to 0.88 (2005-2010) and 0.76 (2011).

CONCLUSION

The measures taken reduced IRs of notifications and hospitalisations among groups eligible for vaccination, but had no effect on the increasing IRs in adolescents and adults. This trend is also observed in other countries. The high IRs in 2012 in adolescents and adults probably resulted in increased transmission to infants, who are at risk for contracting severe pertussis. Therefore, additional measures to protect this group should be considered.

Invasive pneumococcal disease and 7-valent pneumococcal conjugate vaccine, the Netherlands

Disease incidence and case fatality rates declined 4 years after introduction of the vaccine.

The use of typing methods and infection prevention measures to control a bullous impetigo outbreak on a neonatal ward

BACKGROUND

We describe an outbreak of Bullous Impetigo (BI), caused by a (methicillin susceptible, fusidic acid resistant) Staphylococcus aureus (SA) strain, spa-type t408, at the neonatal and gynaecology ward of the Jeroen Bosch hospital in the Netherlands, from March-November 2011.

METHODS

We performed an outbreak investigation with revision of the hygienic protocols, MSSA colonization surveillance and environmental sampling for MSSA including detailed typing of SA isolates. Spa typing was performed to discriminate between the SA isolates. In addition, Raman-typing was performed on all t408 isolates.

RESULTS

Nineteen cases of BI were confirmed by SA positive cultures. A cluster of nine neonates and three health care workers (HCW) with SA t408 was detected. These strains were MecA-, PVL-, Exfoliative Toxin (ET)A-, ETB+, ETAD-, fusidic acid-resistant and methicillin susceptible. Eight out of nine neonates and two out of three HCW t408 strains yielded a similar Raman type. Positive t408 HCW were treated and infection control procedures were reinforced. These measures stopped the outbreak.

CONCLUSIONS

We conclude that treatment of patients and HCW carrying a predominant SA t408, and re-implementing and emphasising hygienic measures were effective to control the outbreak of SA t408 among neonates.

Association between human papillomavirus vaccine uptake and cervical cancer screening in the Netherlands: implications for future impact on prevention

Several countries recently added human papillomavirus (HPV) vaccination to cervical cancer screening in the effort to prevent cervical cancer. They include the Netherlands, where both programs are free. To estimate their combined future impact on cancer prevention, information is needed on the association between participation in vaccination now and in screening in the future and on what groups are at risk for nonparticipation. We studied the association between participation in screening by mothers and in vaccination by their daughters. Girls' vaccination status was matched by house-address with their mothers' screening participation. We estimated the effect on cancer incidence by means of computer simulation. We investigated risk groups for nonparticipation using multivariable multilevel logistic regression and calculated population-attributable fractions. Our results, based on 89% of girls invited for vaccination in 2009 (n = 337,368), show that vaccination status was significantly associated with mothers' screening participation (odds ratio: 1.54 [95% confidence interval: 1.51-1.57]). If a mother's screening is taken as proxy of a girl's future screening, only 13% of the girls will not participate in either program compared to 23% if screening alone is available. The positive association between vaccination and screening resulted in slightly lower model estimates of the impact of vaccination on cancer incidence, compared to estimates assuming no association. Girls with nonwestern ethnicities, with young mothers, who live in urban areas with low socioeconomic status, are at risk for nonparticipation. A significant part of potential nonscreeners may be reached through HPV vaccination. Estimates made before vaccination was introduced only slightly overestimated its impact on cervical cancer incidence.

Serum IgA responses against pertussis proteins in infected and Dutch wP or aP vaccinated children: an additional role in pertussis diagnostics

Background

Whooping cough is a respiratory disease caused by Bordetella pertussis, which induces mucosal IgA antibodies that appear to be relevant in protection. Serum IgA responses are measured after pertussis infection and might provide an additional role in pertussis diagnostics. However, the possible interfering role for pertussis vaccinations in the induction of serum IgA antibodies is largely unknown.

Methods/Principal Findings

We compared serum IgA responses in healthy vaccinated children between 1 and 10 years of age with those in children who despite vaccinations recently were infected with Bordetella pertussis. All children have been vaccinated at 2, 3, 4 and 11 months of age with either the Dutch whole-cell pertussis (wP) vaccine or an acellular pertussis (aP) vaccine and additionally received an aP booster vaccination at 4 years of age. Serum IgA responses to pertussis toxin (PT), filamentous heamagglutinin (FHA) and pertactin (Prn) were measured with a fluorescent multiplex bead-based immuno-assay. An ELISPOT-assay was used for the detection of IgA-memory B-cells specific to these antigens. Serum IgA levels to all pertussis vaccine antigens were significantly higher in infected children compared with healthy children. High correlations between anti-PT, anti-FHA or anti-Prn IgA and IgG levels were found in infected children and to some degree in wP primed children, but not at all in aP primed children. Highest numbers of IgA-pertussis-specific memory B-cells were observed after infection and generally comparable numbers were found after wP and aP vaccination.

Conclusions

This study provides new insight in the diagnostic role for serum IgA responses against PT in vaccinated children. Since aP vaccines induce high serum IgG levels that interfere with pertussis diagnostics, serum IgA-PT levels will provide an additional diagnostic role. High levels of serum IgA for PT proved specific for recent pertussis infection with reasonable sensitivity, whereas the role for IgA levels against FHA and Prn in diagnosing pertussis remains controversial.

Seroprevalence of pertussis in The Netherlands: evidence for increased circulation of Bordetella pertussis

BACKGROUND

In many countries, the reported pertussis has increased despite high vaccination coverage. However, accurate determination of the burden of disease is hampered by reporting artifacts. The infection frequency is more reliably estimated on the basis of the prevalence of high IgG concentrations against pertussis toxin (IgG-Ptx). We determined whether the increase in reported pertussis in the last decade is associated with an increase in the number of infections.

METHODOLOGY/PRINCIPAL FINDINGS

In a cross-sectional population-based serosurveillance study conducted in 2006-07, from a randomly selected age-stratified sample of 7,903 persons, serum IgG-Ptx concentrations were analyzed using a fluorescent bead-based multiplex immuno assay. In 2006-07, 9.3% (95%CI 8.5-10.1) of the population above 9 years of age had an IgG-Ptx concentration above 62.5 EU/ml (suggestive for pertussis infection in the past year), which was more than double compared to 1995-96 (4.0%; 95%CI 3.3-4.7). The reported incidence showed a similar increase as the seroprevalence between both periods.

CONCLUSIONS

Although changes in the vaccination program have reduced pertussis morbidity in childhood, they have not affected the increased infection rate in adolescent and adult pertussis. Indeed, the high circulation of B. pertussis in the latter age-categories may limit the effectiveness of pediatric vaccination.

Immunity against Neisseria meningitidis serogroup C in the Dutch population before and after introduction of the meningococcal c conjugate vaccine

Background

In 2002 a Meningococcal serogroup C (MenC) conjugate vaccine, with tetanus toxoid as carrier protein, was introduced in the Netherlands as a single-dose at 14 months of age. A catch-up campaign was performed targeting all individuals aged 14 months to 18 years. We determined the MenC-specific immunity before and after introduction of the MenC conjugate (MenCC) vaccine.

Methods and Findings

Two cross-sectional population-based serum banks, collected in 1995/1996 (n = 8539) and in 2006/2007 (n = 6386), were used for this study. The main outcome measurements were the levels of MenC polysaccharide(PS)-specific IgG and serum bactericidal antibodies (SBA) after routine immunization, 4–5 years after catch-up immunization or by natural immunity. There was an increasing persistence of PS-specific IgG and SBA with age in the catch-up immunized cohorts 4–5 years after their MenCC immunization (MenC PS-specific IgG, 0.25 µg/ml (95%CI: 0.19–0.31 µg/ml) at age 6 years, gradually increasing to 2.34 µg/ml,(95%CI: 1.70–3.32 µg/ml) at age 21–22 years). A comparable pattern was found for antibodies against the carrier protein in children immunized above 9 years of age. In case of vaccination before the age of 5 years, PS-specific IgG was rapidly lost. For all age-cohorts together, SBA seroprevalence (≥8) increased from 19.7% to 43.0% in the pre- and post-MenC introduction eras, respectively. In non-immunized adults the SBA seroprevalence was not significantly different between the pre- and post-MenC introduction periods, whereas PS-specific IgG was significantly lower in the post-MenC vaccination (GMT, age ≥25 years, 0.10 µg/ml) era compared to the pre-vaccination (GMT, age ≥25 years, 0.43 µg/ml) era.

Conclusion

MenCC vaccination administered above 5 years of age induced high IgG levels compared to natural exposure, increasing with age. In children below 14 months of age and non-immunized cohorts lower IgG levels were observed compared to the pre-vaccination era, whereas functional levels remained similar in adults. Whether the lower IgG poses individuals at increased risk for MenC disease should be carefully monitored. Large-scale introduction of a MenCC vaccine has led to improved protection in adolescents, but in infants a single-dose schedule may not provide sufficient protection on the long-term and therefore a booster-dose early in adolescence should be considered.

Effects of pneumococcal conjugate vaccine 2 years after its introduction, the Netherlands

In the Netherlands, the 7-valent pneumococcal conjugate vaccine (PCV-7) was implemented in a 3+1-dose schedule in the national immunization program for infants born after April 1, 2006. To assess the vaccine's effectiveness, we compared disease incidence before and after vaccine implementation (June 2004-June 2006 and June 2006-June 2008, respectively). We serotyped 2,552 invasive pneumococcal isolates from throughout the Netherlands, covering 25% of the country's population. Clinical characteristics were extracted from hospital records. After June 2006, vaccine-serotype invasive pneumococcal disease (IPD) decreased 90% (95% confidence interval [CI] 68%-97%) in children age eligible for PCV-7; simultaneously, however, non-vaccine-serotype IPD increased by 71% (not significant), resulting in a 44% total net IPD reduction (95% CI 7%-66%). IPD rates did not change for other age groups. In the Netherlands, PCV-7 offered high protection against vaccine-serotype IPD in vaccinated children, but increases of non-vaccine-serotype IPD reduced net vaccine benefits.

Surveillance of invasive pneumococcal disease in 30 EU countries: Towards a European system?

In this era of new pneumococcal conjugate vaccines (PCV), we described and compared surveillance of invasive pneumococcal disease (IPD) and PCV policies in 30 European countries to provide guidance for Europe-wide surveillance. We confirmed the heterogeneity of surveillance systems and case definitions across countries but identified elements common to all countries, such as the availability of serotyping and the surveillance of pneumococcal meningitis. PCV impact was monitored in 11/15 countries using it. We propose steps for the monitoring of incidence rates and serotype distribution at EU level, to assess the need to introduce PCV and monitor its impact once introduced.

[Pertussis in the Netherlands]

Despite high vaccination coverage, an increasing incidence of pertussis has been observed in recent years, especially among adults. Particularly in children less than three months of age, pertussis can lead to severe complications or even death. The increasing incidence of pertussis has been attributed to various factors, including increased awareness and waning vaccine-induced immunity in combination with pathogen adaptation. Changes in the vaccination schedule, the addition of a booster vaccination and an adjustment of the vaccine itself play an important part in handling this problem. A timely diagnosis of pertussis by a GP followed by antibiotic therapy can prevent potentially severe pertussis in young infants and avoid the spread of the bacteria. Targeting vaccination at adults and health care workers who are in close contact with infants may prevent transmission of pertussis to infants.

Bordetella pertussis strains with increased toxin production associated with pertussis resurgence

A more virulent strain of the disease is emerging.

Before childhood vaccination was introduced in the 1940s, pertussis was a major cause of infant death worldwide. Widespread vaccination of children succeeded in reducing illness and death. In the 1990s, a resurgence of pertussis was observed in a number of countries with highly vaccinated populations, and pertussis has become the most prevalent vaccine-preventable disease in industrialized countries. We present evidence that in the Netherlands the dramatic increase in pertussis is temporally associated with the emergence of Bordetella pertussis strains carrying a novel allele for the pertussis toxin promoter, which confers increased pertussis toxin (Ptx) production. Epidemiologic data suggest that these strains are more virulent in humans. We discuss changes in the ecology of B. pertussis that may have driven this adaptation. Our results underline the importance of Ptx in transmission, suggest that vaccination may select for increased virulence, and indicate ways to control pertussis more effectively.

An investigation into the cause of the 1983 whooping cough epidemic in the Netherlands

Despite more than 50 years of vaccination, whooping cough is still an endemic disease in the Netherlands with regular epidemic outbreaks. In the last 20 years, two periods of increased notifications were observed. The causes of the increased notifications in the first period, from 1983 to 1987, are contentious. At the time it was suggested to be a surveillance artifact, caused by changes in diagnostic procedures and increased awareness. An alternative explanation, a reduction in the vaccine dose, was downplayed at the time. The aim of this study was to reinvestigate the causes of the increased notifications by identifying changes in the Bordetella pertussis population. B. pertussis strains, isolated from 1965 to 1992, were characterized by means of fimbrial serotyping, multiple-locus sequence typing of virulence genes (MLST) and multiple-locus variable-number tandem repeat analysis (MLVA). Shifts in fimbrial serotypes and MLVA types were associated with changes in vaccine dose and increased number of notifications. One to three years after lowering of the vaccine dose, the predominant fimbrial serotype changed from Fim3 to Fim2, and the reverse trend was observed when the vaccine dose was increased. Significantly, changes in fimbrial serotypes were evident at least seven years before the increase in notifications. Our results provide evidence that the change in vaccine dose affected host immunity and, consequently, contributed to an increase in pertussis morbidity. Further, we show that MLVA and fimbrial serotyping of strains can be used as early warning for pertussis epidemics.

The case for maternal vaccination against pertussis

Despite high vaccine coverage, the incidence of pertussis is increasing in a number of countries. Particularly alarming is the increase of pertussis in infants too young to be (fully) vaccinated, because the highest morbidity and mortality is observed in this category. Maternal vaccination offers the possibility to protect infants from birth until immunity is induced by active vaccination, and has been shown to be effective and safe for tetanus over long periods of time. Maternal vaccination studies with whole-cell pertussis vaccines have not shown serious adverse effects in mother and child. In one study, protection of newborn babies was found. Additional support for the efficacy of maternal vaccination comes from studies showing that transfer of antibodies confers protection against pertussis. Maternal vaccination might be an effective way to decrease morbidity and mortality caused by pertussis in newborn babies.