Dynamic pattern and genotypic diversity of Staphylococcus aureus nasopharyngeal carriage in healthy pre-school children.

OBJECTIVES: It is common wisdom that persistent carriage of Staphylococcus aureus is more frequent in young children than in adults. The objectives of this study were to assess the S. aureus temporal carriage pattern among a healthy community of pre-school children, with concomitant description of genotype diversity, toxin-encoding genes and antibiotic resistance. METHODS: Among 333 children 3-6 years of age, S. aureus nasopharyngeal carriage was assessed over one school year by culture of three sequential nasopharyngeal aspirates. Identification, methicillin resistance and toxin production profile were determined by PCR. Genotyping was performed by spa sequencing and multilocus sequence typing (MLST). RESULTS: Out of 830 samples collected, 286 (34%) yielded S. aureus from 185 carriers (55%). Based on consecutive genotype analysis, only 40/268 (15%) children could be classified as persistent carriers, and the remaining 118 (44%) showed intermittent carriage. spa typing revealed 82 types clustered into 13 spa clonal complexes (CCs). Fourteen strains isolated from 11 (3%) children were methicillin-resistant S. aureus (MRSA), half of these strains belonged to the commonly hospital-associated spa t008-ST8-SCCmec IV. Methicillin-susceptible S. aureus (MSSA) were genotypically more diverse. Toxic shock syndrome toxin and egc1/2 complexes were highly prevalent (24%). Contrastingly, Panton-Valentine leucocidin (PVL) was carried only by three MSSA strains (0.6% of children). Exfoliative toxins were detected in 10 (3.5%) MSSA strains, of which 5 were related to the impetigo clone CC121. CONCLUSIONS: Although S. aureus nasopharyngeal carriage was high among healthy pre-school children, persistent carriage seems to be less frequent than previously reported. The prevalence of MRSA carriage was 3%, but was not associated with PVL.

Multisystem inflammatory syndrome in children during the first two years of the COVID-19 pandemic in Luxembourg.

Objective: Estimate the incidence of multisystem inflammatory syndrome (MIS-C) in children (0-15 years), the role of SARS-CoV-2 variants during the first two years of COVID-19 pandemic in Luxembourg; and describe the demographic, biological and clinical characteristics of the patients. Method: Observational retrospective cohort study. Cases between March 2020 and February 2022 were ascertained from the national registry of MIS-C cases by a retrospective review of medical records. Reported SARS-CoV-2 infections were obtained from the national COVID-19 surveillance system. We calculated monthly MIS-C incidence, the ratio between MIS-C and SARS-CoV-2 infections and associated rate ratios by the periods corresponding to the circulation of different variants. Results: 18 children were diagnosed with MIS-C among 35,200 reported infections. The incidence rate of MIS-C was 7.2 [95% confidence interval (CI) 4.5-11.4] per 1,000,000 person-months. A higher incidence of MIS-C was observed between September and December 2021, corresponding to the circulation of the Delta variant than during the first year of the pandemic (RR 3.6, 95% CI, 1.1-12.3). The lowest rate of MIS-C per infection was observed during the Omicron (RR 0.17, 95% CI, 0.03-0.82). Median age at diagnosis was 6.5 years. Previously healthy children made up 88% of MIS-C cases, none were vaccinated against SARS-CoV-2. 33% required intensive care. All patients recovered fully. Conclusions: MIS-C incidence and MIS-C risk per infection changed significantly over time during the first two years of COVID-19 pandemic. Monitoring of MIS-C incidence in future SARS-CoV-2 waves will be essential to guide public health interventions and vaccination policies for children.

Risk of hospitalization and death for healthcare workers with COVID-19 in nine European countries, January 2020-January 2021.

This article presents and compares coronavirus disease 2019 attack rates for infection, hospitalization, intensive care unit (ICU) admission and death in healthcare workers (HCWs) and non-HCWs in nine European countries from 31st January 2020 to 13th January 2021. Adjusted attack rate ratios in HCWs (compared with non-HCWs) were 3.0 [95% confidence interval (CI) 2.2-4.0] for infection, 1.8 (95% CI 1.2-2.7) for hospitalization, 1.9 (95% CI 1.1-3.2) for ICU admission and 0.9 (95% CI 0.4-2.0) for death. Among hospitalized cases, the case-fatality ratio was 1.8% in HCWs and 8.2% in non-HCWs. Differences may be due to better/earlier access to treatment, differential underascertainment and the healthy worker effect.

Antimicrobial therapy for intra-abdominal infections: guidelines from the Infectious Disease Advisory Board (IDAB).

Intra-abdominal infection is a common cause of severe sepsis in a hospital setting and remains associated with a significant morbidity, mortality and resource use. Early adequate surgery or drainage remain the cornerstones of intra-abdominal infection management and impact on patients outcome. Concomitant early and adequate empiric antimicrobial therapy further influences patients morbidity and mortality. Multiple empirical regimens have been proposed in this setting, but rarely supported by well designed, randomized-controlled studies. The current manuscript summarizes the recommendations of the Infection Disease Advisory Board on the management of intra-abdominal infections. Empiric antimicrobial therapy for the most common causes of abdominal infections is proposed. In addition, particular attention has been paid on antibiotic treatment duration.

Higher proportion of G2P[4] rotaviruses in vaccinated hospitalized cases compared with unvaccinated hospitalized cases, despite high vaccine effectiveness against heterotypic G2P[4] rotaviruses.

The overall vaccine effectiveness of the monovalent rotavirus vaccine in an observational, prospective, multicentre, hospital-based case-control study in Belgium (RotaBel) was 90%. However, rotavirus genotype and co-infecting pathogens are important parameters to take into account when assessing vaccine effectiveness. In this study we specifically investigated the effect of rotavirus genotypes and co-infecting pathogens on vaccine effectiveness of the monovalent vaccine. In addition, we also investigated the effect of co-infecting pathogens on disease severity. From February 2008 to June 2010 stool samples of rotavirus gastroenteritis cases of a random sample of 39 Belgian hospitals were collected and subsequently genotyped. Fisher's exact tests were performed to investigate the relationships between rotavirus genotype, co-infecting pathogens and disease severity. The vaccine effectiveness of a full series of the monovalent rotavirus vaccine against hospitalized rotavirus gastroenteritis caused by G1P[8] rotavirus strains was 95% (95% CI 77.5-98.7). Against G2P[4], the vaccine effectiveness was 85% (95% CI: 63.7-93.8). G4P[8]- and G3P[8]-specific vaccine effectiveness was 90% (95% CI 19.2-98.7) and 87% (95% CI -5.2 to 98.4), respectively. A post-hoc analysis showed that the genotype distribution was significantly related to the vaccination status (p <0.001), whereby G2P[4] strains were proportionally more prevalent in vaccinated cases than in unvaccinated cases. No statistical associations were found between co-infection status and vaccination status, Vesikari severity score or rotavirus genotype. The high vaccine effectiveness against the individual genotypes implies robust protection of the monovalent rotavirus vaccine against hospitalized rotavirus gastroenteritis caused by the major human rotavirus genotypes. The prevalence of G2P[4] requires continued monitoring.

Heterogeneity of disease and clones of community-onset methicillin-resistant Staphylococcus aureus in children attending a paediatric hospital in Belgium.

The increase in the number of methicillin-resistant Staphylococcus aureus (MRSA) infections in children has prompted paediatricians to broaden th empirical treatment of common community-onset (CO) infections in children in several countries. Most European countries have reported low rates of CO-MRSA infection, but limited data on paediatric CO-MRSA infections are available. A prospective study was conducted from January 2002 to December 2004 in Brussels. CO-MRSA was defined as MRSA first detected by culture within 48 h of admission or in outpatients. Clinical and epidemiological data were recorded. CO-MRSA strains were genotyped by pulsed-field gel electrophoresis and multilocus sequence typing. Staphylococcal chromosomal cassette mec, toxin (Panton-Valentin leukocidin (PVL), toxic shock syndrome toxin 1, and Eta/b), enterotoxin and antibiotic resistance genes were detected by PCR. The antibiotic resistance phenotype was determined by disk diffusion. S. aureus was isolated in 1681 children. Among these, 107 harboured MRSA. Fifty-one children were colonized or infected by CO-MRSA, 20% of whom had no healthcare exposure. Twelve infants <3 months old and five cystic fibrosis patients were colonized. None of the 22 infected patients (59% with acute otitis media and 36% with skin and soft tissue infections (SSTIs)) required hospitalization. Two-thirds of them failed to respond to empirical antibiotic therapy. The 37 characterized CO-MRSA strains were genetically diverse. Most of them had healthcare-associated genotypes. Only six strains were PVL-positive, all of which were ciprofloxacin-susceptible and more common in children with SSTIs (p 0.001). CO-MRSA remains uncommon in our paediatric population. So far, there is no need to modify the empirical treatment of common S. aureus infections. Monitoring of MRSA rates in S. aureus CO infections remains mandatory, and further investigation is warranted to establish the source of colonization in young infants.

Prospective evaluation of Coris Influ-A&B Respi-Strip and of BinaxNOW Influenza A&B assay against viral culture and real-time PCR assay for detection of 2009 pandemic influenza A/H1N1v in Belgian patients.

PURPOSE: Evaluation of the performance of two rapid (15') antigen detection tests (RAT), BinaxNOW Influenza A&B and Coris Influ-A&B Respi-Strip for the detection of A(H1N1)v2009. STUDY DESIGN: Between July 2009 and November 2009, 4105 respiratory specimens from patients with influenza-like illness attending seven public hospitals in Brussels were prospectively examined by two immunochromatographic RAT, followed by viral culture and/or specific real-time RT-PCR. RESULTS: Samples consisted predominantly of nasopharyngeal aspirates (NPA-41%), nasopharyngeal (NPS-37%) and throat swabs (TS-14%). The sensitivity and specificity of Coris RAT and BinaxNOW RAT were 36.6% and 99.7%, and 47% and 98.7% respectively compared to culture; and 33.7% and 99.6%; and 46.5% and 98.8% compared to RT-PCR. Significant differences in sensitivity could be observed when splitting up the samples by sample type and patient's age. NPA gave by far the highest sensitivities: 51.1- 62% for Coris compared to culture and 62.6-78.4% for BinaxNOW. Sensitivities in paediatric NPS varied less between different hospitals (34-41.9%) being still much higher than in adult NPS (11.4-20%). TS resulted in unsatisfactory results: 13% sensitivity in children and 10.5% in adults. CONCLUSIONS: Both RAT showed excellent specificities, but insufficient sensitivities. Consequently, negative results should be confirmed. NPA are clearly superior to NPS orTS, and they stay the sample of choice for viral diagnosis.

Differences in nasopharyngeal bacterial carriage in preschool children from different socio-economic origins.

A prospective cohort study of preschool healthy children (3-6 years old) from two distinct socio-economic settings in the Brussels area, Belgium, was conducted during the years 2006-2008. The objectives were to evaluate nasopharyngeal colonization by Streptococcus pneumoniae, Staphylococcus aureus, Moraxella catarrhalis and Haemophilus influenzae at the time of PCV7 vaccine introduction and to assess the socio-economic level impact on flora composition and antibiotic resistance. Three hundred and thirty-three children were included and a total of 830 nasopharyngeal samples were collected together with epidemiological data. Pneumococcal serotypes and antibiotic resistance profiles were determined. Risk factors for carriage and bacterial associations were analysed by multivariate logistic regression. Carriage rates were high for all pathogens. Fifty per cent of the children were colonized at least once with S. aureus, 69% with S. pneumoniae, 67% with M. catarrhalis and 83% with H. influenzae. PCV7 uptake was higher among children from a higher socio-economic setting and S. pneumoniae serotypes varied accordingly. Children from lower socio-economic schools were more likely to carry M. catarrhalis, S. aureus and antibiotic-resistant S. pneumoniae, including a high proportion of non-typeable pneumococcal strains. Positive associations between S. pneumoniae and H. Influenza, between H. influenzae and M. catarrhalis and between H. influenzae and S. aureus were detected. Our study indicates that nasopharynx flora composition is influenced not only by age but also by socio-economic settings. A child's nasopharynx might represent a unique dynamic environment modulated by intricate interactions between bacterial species, host immune system and PCV7 immunization.

National survey of molecular epidemiology of Staphylococcus aureus colonization in Belgian cystic fibrosis patients.

OBJECTIVES: Epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) is poorly defined in cystic fibrosis (CF) patients, and S. aureus detection may be hampered by the presence of small colony variants (SCVs). We conducted a multicentre survey to determine the prevalence of S. aureus and MRSA colonization in Belgian CF patients and characterize the phenotype and clonal distribution of their staphylococcal strains. METHODS: S. aureus isolated from CF patients attending nine CF centres were collected. Oxacillin resistance was detected by oxacillin agar screen and mecA PCR. Antibiotic susceptibility was tested by microdilution. MRSA strains were genotyped by PFGE and SCCmec typing and compared with hospital-associated MRSA strains. RESULTS: Laboratories used a diversity of sputum culture procedures, many of which appeared substandard. S. aureus was isolated from 275/627 (44%) CF patients (20% to 72% by centre). The prevalence of SCV colonization was 4%, but SCVs were almost exclusively recovered from patients in two centres performing an SCV search. Phenotypically, 14% of S. aureus isolates were oxacillin-resistant: 79% carried mecA and 19% were SCVs lacking mecA. The mean prevalence of 'true' MRSA colonization was 5% (0% to 17% by centre). By PFGE typing, 67% of CF-associated MRSA were related to five epidemic clones widespread in Belgian hospitals. CONCLUSIONS: This first survey of S. aureus colonization in the Belgian CF population indicated a diversity in local prevalence rates and in proportion of oxacillin-resistant and SCV phenotypes, probably related to variation in bacteriological methods. These findings underscore the need for standard S. aureus detection methods and MRSA control policies in Belgian CF centres.

Polyclonal emergence and importation of community-acquired methicillin-resistant Staphylococcus aureus strains harbouring Panton-Valentine leucocidin genes in Belgium.

OBJECTIVES: Worldwide spread of a limited number of Panton-Valentine leucocidin (PVL) -producing methicillin-resistant Staphylococcus aureus (MRSA) clones has been reported in various communities. The objective of this study was to describe the molecular characteristics of the first PVL-positive MRSA strains isolated in Belgium. METHODS: Clinical MRSA isolates (n = 41) collected from 2002 to 2004 from Belgian patients were investigated for the PVL gene by PCR. PVL-positive isolates were genotyped by PFGE, staphylococcal cassette chromosome mec (SCCmec) typing, spa sequence typing, accessory gene regulator (agr) polymorphism and multi-locus sequence typing (MLST). Susceptibility to 14 antimicrobials was determined by the disc diffusion method. Genes encoding resistance to tetracyclines, aminoglycosides and macrolide-lincosamide-streptogramin were determined by PCR. RESULTS: Sixteen isolates carried lukS-lukF genes that encode the PVL toxin. All but one isolate were community-acquired. Three patients reported recent travel to North Africa and South America. They were associated with skin or soft tissue infections, bacteraemia and peritonitis. By molecular typing, they belonged to five genotypes: ST80-SCCmec IV, ST8-SCCmec IV, ST30-SCCmec IV, ST153-SCCmec IV and ST88-SCCmec IV. They belonged to the agr type 3 except for ST8 strains, which showed agr type 1. All isolates were susceptible to fluoroquinolones. Approximately, half of them were resistant to tetracycline, fusidic acid and kanamycin. Tetracycline-resistant strains harboured the tet(K) gene and resistance to kanamycin was associated with the aph3'-IIIa gene. The single erythromycin-resistant isolate harboured msr(A/B) genes conferring the M resistance phenotype. CONCLUSIONS: These results indicate the recent emergence and sporadic importation into Belgium of PVL-positive community-associated MRSA strains belonging to five distinct clones.