BACKGROUND Increasing incidence rates of invasive Streptococcus dysgalactiae subspecies equisimilis (iSDSE) have been detected worldwide. AIM We aimed to investigate iSDSE infection incidence rates in Denmark during 2014–2024, and characterise the genomic population structure of a subset of iSDSE isolates and their antimicrobial resistance (AMR). METHODS Using national register data, we estimated overall and sex-/age-stratified iSDSE incidences during 2014–2024, by retrospectively identifying cases of invasive infections with group C and G streptococci or S. dysgalactiae (including specified as subspecies equisimilis). From the voluntary national beta-haemolytic streptococci laboratory surveillance system, whole-genome-sequenced isolates from August 2020−September 2022 were used to investigate the iSDSE genomic population structure. Susceptibility to penicillin, erythromycin and clindamycin was determined and AMR genes identified. RESULTS During 2014–2024, iSDSE incidence rates increased significantly (linear trend analysis p < 0.001) with mean annual incidence ranging between 10.3 and 16.4 per 100,000, peaking in 2023. Incidence was higher in males, increasing with older age. Nearly 75% of the 1,223 iSDSE isolates belonged to four of 14 genetic clusters. Sequence types (STs) ST20 and ST17 were most prevalent, while emm-type stG62647, a variant associated internationally with higher virulence, dominated. All isolates were phenotypically susceptible to penicillin but approximately 10% were respectively erythromycin and clindamycin resistant. High erythromycin resistance prevalence (57%; 39/68), coinciding with gene ermA, occurred in one genetic cluster. CONCLUSION The findings illustrate the need for national registry-based surveillance to detect epidemiological changes and potential outbreaks. Further, continuous genomic surveillance can monitor the occurrence and expansion of genetic clades and AMR genes.

Background Staphylococcus epidermidis is a ubiquitous member of the healthy skin and mucous microbiota but is also an opportunistic pathogen responsible for various infections, often treated with antibiotics like rifampicin. Resistance to rifampicin in S. epidermidis arises primarily through nonsynonymous mutations in the rpoB gene. Objectives To investigate the prevalence of rpoB mutations and their association with phenotypic rifampicin resistance in clinical S. epidermidis isolates from Denmark, France, and Sweden. Methods All clinical isolates (N = 942) were whole-genome sequenced to identify mutations in rpoB and subsequently linked to phenotypic rifampicin resistance based on antimicrobial susceptibility testing. Results A total of 64 (6.8%) isolates were resistant to rifampicin. They carried all mutational changes in the rifampicin resistance-determining region (RRDR). Among 12 identified nonsynonymous mutations, 11 were exclusively observed in resistant strains, including novel mutations not previously described in S. epidermidis. Conclusions This study highlights the diverse genetic variants of rpoB associated with rifampicin resistance in clinical S. epidermidis isolates, including novel mutations. The strong correlation between mutational changes in RRDR and phenotypic resistance reinforces the role of rpoB mutations as a primary mechanism of resistance in clinical isolates.

BACKGROUND:Recent studies have reported an increasing prevalence of penicillin-susceptible Staphylococcus aureus (PSSA) worldwide. The reliability of disc diffusion testing for detecting penicillin-resistance has been questioned, and the molecular epidemiology of PSSA has not been studied to the same extent as that of MRSA strains. OBJECTIVES:To investigate the reliability of the disc diffusion method for detecting penicillin-resistance in S. aureus, and to examine the prevalence and molecular epidemiology of PSSA in bloodstream infections. METHODS:A total of 258 bacteraemic isolates obtained from one geographic region in Sweden during 2018-2019 were analysed using the disc diffusion test to detect penicillin-resistance, and genome sequenced to examine the prevalence of the blaZ gene and the molecular epidemiology of PSSA. RESULTS:Phenotypic susceptibility to penicillin correlated strongly with the absence of the blaZ gene, with nearly 98% concordance. The prevalence of PSSA among patients with bacteraemia was 35.1%, highlighting the need for penicillin-susceptibility testing. Additionally, population structure analyses revealed substantial genetic diversity, underscoring the complexity of the PSSA epidemiology. The PSSA belonged to diverse clonal lineages, with CC5 and CC45 dominating our cohort, similar to findings in Spain, Australia, and other parts of Sweden. However, our study revealed a higher prevalence of CC12 compared with other regions, underscoring the importance of local epidemiological surveillance. CONCLUSIONS:These findings validate the reliability of EUCAST's disc diffusion method, showing a high prevalence of PSSA, and provide insight into the genetic underpinnings of penicillin-susceptibility in S. aureus.

To describe the clinical characteristics of exogenous episodes of endophthalmitis from which Staphylococcus epidermidis was isolated by vitreous cultures. We also explored the genomic traits of these S. epidermidis isolates and their relatedness to S. epidermidis originating from carriers and from prosthetic joint infections in the same geographical region. S. epidermidis isolated from cases of exogenous endophthalmitis (n = 33) were genome sequenced. Clinical features were retrospectively collected from medical records. The isolates were compared with previously sequenced S. epidermidis isolates from the nares of healthy individuals (n = 151) and from prosthetic joint infections (n = 138). The most common ophthalmological procedure preceding the endophthalmitis was a posterior segment surgery (76

BACKGROUND AND OBJECTIVES:Staphylococcus epidermidis is a major cause of prosthetic joint infections (PJIs). Multidrug resistant (MDR), hospital-adapted clones constitute most cases globally, though regional differences in lineage dissemination likely exist. The aim was to explore the population structure of S. epidermidis from PJIs in Sweden and France, with a focus on the presence of antimicrobial resistance (AMR). METHODS:This study included genome sequence data from 191 clinical S. epidermidis isolates collected from patients with PJI in central Sweden (2007-16; n = 138) and the Lyon region in France (2015-20; n = 53). RESULTS:Hospital-adapted lineages with a high burden of AMR dominated the cases in both countries. However, the ST2 lineage was significantly more prevalent in Sweden (43% versus 11% in France), while ST5 and ST87 were more common in France (55% versus 10% in Sweden). ST215 was only present in Sweden (25%). A significantly higher prevalence of streptogramin resistance genes [vat(B), vga(A), vga(B)] was found in French (26%) versus Swedish (2%) isolates. These genes were present in all ST87 isolates and in 20% of the French ST5 isolates. The erm(C) gene (resistance to streptogramin A, macrolides and lincosamides) was also more common in the French isolates (77% versus 55% of Swedish isolates), and so was the fusidic acid resistance gene fusB (France: 66%, Sweden: 39%). CONCLUSIONS:This study highlights significant regional differences in S. epidermidis variants causing PJI. Despite similar MDR levels, certain AMR genes, particularly those related to streptogramin resistance, were significantly more prevalent among French isolates. This suggests that S. epidermidis undergoes local adaptation to region-specific antibiotic usage.

Denmark has monitored invasive pneumococcal diseases (IPD) for decades, observing shifts in serotype prevalence, partly due to pneumococcal conjugate vaccines in children. The COVID-19 pandemic and the Danish government's 2020 vaccination program with the 23-valent pneumococcal polysaccharide vaccine (PPV23) for older adults further influenced IPD epidemiology. This study explores the dynamics of Global Pneumococcal Sequence Clusters (GPSCs) in Denmark from 2019 to 2023 using whole-genome sequencing (WGS) on IPD isolates from all age groups received at Statens Serum Institut (SSI). Serotyping, multilocus sequence typing (MLST), GPSC identification, and phylogenetic analysis to assess clonal relationships were conducted. Of the 1,999 sequenced isolates, representing 93.3% of reported cases, 79 different GPSCs were identified, with GPSC3, GPSC12, and GPSC19 being dominant. GPSC3/ST53 (serotype 8) declined significantly from 24.6% in 2019 to 14.4% in 2023 (p < 0.05), whereas GPSC12/ST180 (serotype 3) increased significantly from 8.2% to 15.1% (p < 0.05). The PPV23 vaccine and pandemic restrictions decreased IPD incidence, particularly for vaccine-covered serotypes, yet serotype 3 remained problematic, indicating challenges in achieving broad serotype coverage. Although pneumococcal vaccination and pandemic-related public health measures influenced the distribution of serotypes and sequence types (STs), only two dominant GPSCs showed clear changes over time. This reflects that a single GPSC can encompass multiple serotype-ST combinations, including both vaccine-covered and non-vaccine variants. As a result, while GPSCs provide a useful high-level overview of pneumococcal lineages, they may lack the resolution needed to detect finer-scale shifts in serotype-ST composition, especially those critical for evaluating vaccine impact and identifying emerging clones.

Staphylococci include both nasal commensals and opportunistic pathogens, globally responsible for a large proportion of infection-related deaths, especially in S. aureus carriers. To understand staphylococcal temporal dynamics within the nasal microbiota, we employed Staphylococcus-targeted sequencing in two cohorts from Denmark and Germany. We identified two major staphylococcal community state types (sCSTs)-one dominated by S. aureus and one dominated by S. epidermidis-and eight subgroups defined by co-colonizing coagulase-negative staphylococci. The distribution of sCSTs was similar between the two cohorts. Predominance of either S. aureus or S. epidermidis was highly persistent over time, whereas co-colonizing staphylococcal species were transient with varying stability among the sCST subgroups. Detection of S. aureus by culture was positively associated with absolute abundance by qPCR. S. aureus domination was diminished when Dolosigranulum and Corynebacterium co-occurred. Our findings could inform efforts to reduce S. aureus nasal colonization and infection.

Neisseria meningitidis can be a human commensal in the upper respiratory tract but is also capable of causing invasive diseases such as meningococcal meningitis and septicaemia. No specific genetic markers have been detected to distinguish carriage from disease isolates. The aim here was to find genetic traits that could be linked to phenotypic outcomes associated with carriage versus invasive N. meningitidis disease through a bacterial genome-wide association study (GWAS). In this study, invasive N. meningitidis isolates collected in Sweden (n=103) and carriage isolates collected at Örebro University, Sweden (n=213) 2018–2019 were analysed. The GWAS analysis, treeWAS, was applied to single-nucleotide polymorphisms (SNPs), genes and k-mers. One gene and one non-synonymous SNP were associated with invasive disease and seven genes and one non-synonymous SNP were associated with carriage isolates. The gene associated with invasive disease encodes a phage transposase (NEIS1048), and the associated invasive SNP glmU S373C encodes the enzyme N-acetylglucosamine 1-phosphate (GlcNAC 1-P) uridyltransferase. Of the genes associated with carriage isolates, a gene variant of porB encoding PorB class 3, the genes pilE/pilS and tspB have known functions. The SNP associated with carriage was fkbp D33N, encoding a FK506-binding protein (FKBP). K-mers from PilS, tbpB and tspB were found to be associated with carriage, while k-mers from mtrD and tbpA were associated with invasiveness. In the genes fkbp, glmU, PilC and pilE, k-mers were found that were associated with both carriage and invasive isolates, indicating that specific variations within these genes could play a role in invasiveness. The data presented here highlight genetic traits that are significantly associated with invasive or carriage N. meningitidis across the species population. These traits could prove essential to our understanding of the pathogenicity of N. meningitidis and could help to identify future vaccine targets.

A highly virulent sub-lineage of the Streptococcus pyogenes M1 clone has been rapidly expanding throughout Denmark since late 2022 and now accounts for 30% of the new invasive group A streptococcal infections. We aimed to investigate whether a shift in variant composition can account for the high incidence rates observed over winter 2022/23, or if these are better explained by the impact of COVID-19-related restrictions on population immunity and carriage of group A Streptococcus.

IntroductionThis study aimed to investigate the epidemiology, serotype distribution, phenotypical antibiogram, and molecular resistance gene characteristics of invasive Haemophilus influenzae infections in Denmark from 2014 to 2022. Additionally, the potential impact of outdoor temperature and COVID-19 restrictions on the epidemiology of H. influenzae was assessed.Materials and methodsInvasive H. influenzae isolates were received from patients with positive culture results from cerebrospinal fluid, blood, or other sterile sites. Sample data were obtained from the Danish laboratory surveillance system/MiBa database, and whole-genome sequencing (WGS) was performed on the isolates. The incidence rates and distribution of H. influenzae cases were analyzed, and antibiotic susceptibility were assessed.ResultsA total of 1,007 invasive H. influenzae cases were identified, with serotyping conducted for 752 (74.7%) isolates. The median incidence per year of H. influenzae was 2.0 cases per 100,000, with the highest incidence in 2014 and the lowest in 2020. The majority of H. influenzae isolates were non-typeable H. influenzae (NTHi), while the most prominent serotypes were serotype f followed by serotype b. Bacteremia cases accounted for the majority (88.6%) of occurrences, although meningitis cases showed an increasing trend during the time period. The age group 85+ exhibited the highest incidence. The implementation of COVID-19 preventive interventions in 2020 resulted in a significant reduction in H. influenzae incidence, which returned to pre-COVID levels in 2021. A negative correlation was observed between monthly H. influenzae cases and outdoor temperature. An overall level of genetic beta-lactamase resistance of 26.3% was observed divided into 10.6% beta-lactamase-positive ampicillin-resistant (gBLPAR), 13.6% beta-lactamase-negative ampicillin-resistant (gBLNAR) and 2.1% beta-lactamase-positive amoxicillin clavulanate-resistant (gBLPACR). Other non-beta-lactam resistance traits were detected in 7.6% of isolates (primarily aminoglycoside-modifying enzymes).ConclusionThe overall incidence of H. influenzae in Denmark returned to stable levels after the COVID-19 epidemic, with NTHi strains dominating. The COVID-19 preventive interventions led to a major reduction in incidence. A significant negative correlation between the incidence of H. influenzae and temperature was observed. The study revealed an overall genetic beta-lactam resistance rate of 26.3%, and the concordance between genotypic and phenotypic beta-lactam resistance was high (98.2%).

Haemophilus influenzae is a gram-negative coccobacillus known to cause respiratory and invasive infections. It can possess a polysaccharide capsule that can be categorized into six different serotypes (i.e., Hia, Hib, Hic, Hid, Hie, and Hif) and non-encapsulated strains that are defined as non-typeable. Furthermore, H. influenzae can be characterized into eight biotypes (I-VIII). Traditionally, isolates have been serotyped and biotyped using phenotypic methods; however, these methods are not always reliable. In this study, we evaluate the use of whole-genome sequencing (WGS) for national surveillance and characterization of clinical Danish H. influenzae isolates. In Denmark, all clinical invasive isolates between 2014 and 2021 have been serotyped using a traditional phenotypic latex agglutination test as well as in silico serotyped using the in silico programs "hinfluenzae_capsule_characterization" and "hicap" to compare the subsequent serotypes. Moreover, isolates were also biotyped using a phenotypic enzyme test and the genomic data for the detection of the genes encoding ornithine, tryptophan, and urease. The results showed a 99-100% concordance between the two genotypic approaches and the phenotypic serotyping, respectively. The biotyping showed a 95% concordance between genotyping and phenotyping. In conclusion, our results show that in a clinical surveillance setting, in silico serotyping and WGS-based biotyping are a robust and reliable approach for typing clinical H. influenzae isolates.

The newly found Omicron SARS-CoV-2 variant of concern has rapidly spread worldwide. Omicron carries numerous mutations in key regions and is associated with increased transmissibility and immune escape. The variant has recently been divided into four subvariants with substantial genomic differences, in particular between Omicron BA.1 and BA.2. With the surge of Omicron subvariants BA.1 and BA.2, a large number of reinfections from earlier cases has been observed, raising the question of whether BA.2 specifically can escape the natural immunity acquired shortly after a BA.1 infection. To investigate this, we selected a subset of samples from more than 1,8 million cases of infections in the period from November 22, 2021, until February 11, 2022. Here, individuals with two positive samples, more than 20 and less than 60 days apart, were selected. From a total of 187 reinfection cases, we identified 47 instances of BA.2 reinfections shortly after a BA.1 infection, mostly in young unvaccinated individuals with mild disease not resulting in hospitalization or death. In conclusion, we provide evidence that Omicron BA.2 reinfections do occur shortly after BA.1 infections but are rare.

1AbstractThe Omicron SARS-CoV-2 variant of concern (VOC lineage B.1.1.529), which became dominant in many countries during early 2022, includes several subvariants with strikingly different genetic characteristics. Several countries, including Denmark, have observed the two Omicron subvariants: BA.1 and BA.2. In Denmark the latter has rapidly replaced the former as the dominant subvariant.Based on nationwide Danish data, we estimate the transmission dynamics of BA.1 and BA.2 following the spread of Omicron VOC within Danish households in late December 2021 and early January 2022.Among 8,541 primary household cases, of which 2,122 were BA.2, we identified a total of 5,702 secondary infections among 17,945 potential secondary cases during a 1-7 day follow-up period. The secondary attack rate (SAR) was estimated as 29% and 39% in households infected with Omicron BA.1 and BA.2, respectively.We found BA.2 to be associated with an increased susceptibility of infection for unvaccinated individuals (Odds Ratio (OR) 2.19; 95%-CI 1.58-3.04), fully vaccinated individuals (OR 2.45; 95%-CI 1.77-3.40) and booster-vaccinated individuals (OR 2.99; 95%-CI 2.11-4.24), compared to BA.1. We also found an increased transmissibility from unvaccinated primary cases in BA.2 households when compared to BA.1 households, with an OR of 2.62 (95%-CI 1.96-3.52). The pattern of increased transmissibility in BA.2 households was not observed for fully vaccinated and booster-vaccinated primary cases, where the OR of transmission was below 1 for BA.2 compared to BA.1.We conclude that Omicron BA.2 is inherently substantially more transmissible than BA.1, and that it also possesses immune-evasive properties that further reduce the protective effect of vaccination against infection, but do not increase its transmissibility from vaccinated individuals with breakthrough infections.

Extraintestinal pathogenic Escherichia coli (ExPEC) is a globally distributed pathogen, with uropathogenic E. coli (UPEC) and sepsis-associated E. coli (SEPEC) pathotypes particularly involved in human and companion animal disease, while avian pathogenic pathotype (APEC) severely impact poultry health and production. Similarities between APEC from poultry/meat and human ExPEC suggest that some APEC lineages may have zoonotic potential. ExPEC sequence type 73 (ST73) and its clonal complex (CC) are increasing causes of urinary tract infections and sepsis, but its role in zoonotic disease is less well understood. Here, we analyzed the genome sequences of 25 E. coli isolates from Brazil (11 APEC and 14 UPEC) from two time periods, from poultry producing areas and hospitals in the same geographical regions. Isolates were compared to 558 publicly available ST73/CC73 global sequences. Brazilian APEC harbored virulence factors associated with UPEC/SEPEC such as sfa, cnf1, vat, usp, hlyA, iron acquisition and protectins/serum resistance systems, while lacking some common APEC markers and widespread multidrug resistance. Analysis of core genome MLST and SNP phylogenetic trees indicated evolutionary relationships between subgroups of the Brazilian APEC to two contemporary Brazilian UPEC isolates from the same region, and one Brazilian UPEC available from another study. Phylogenies showed a non-host, geographical, or pathotype specificity, with APEC isolates clustering closely with international human UPEC, SEPEC. The remaining Brazilian UPEC grouped within human clusters. Collectively, this suggests a zoonotic potential for subgroups of Brazilian APEC from the ST73 lineage that could contaminate poultry products and subsequently cause human infection.

42 The newly found Omicron SARS-CoV-2 variant of concern has rapidly spread worldwide. 43 Omicron carries numerous mutations in key regions and is associated with increased 44 transmissibility and immune escape. The variant has recently been divided into four 45 subvariants with substantial genomic differences, in particular between Omicron BA.1 and 46 BA.2. With the surge of Omicron subvariants BA.1 and BA.2, a large number of reinfections 47 from earlier cases has been observed, raising the question of whether BA.2 specifically can 48 escape the natural immunity acquired shortly after a BA.1 infection. 49 To investigate this, we selected a subset of samples from more than 1,8 million cases of 50 infections in the period from November 22, 2021, until February 11, 2022. Here, individuals 51 with two positive samples, more than 20 and less than 60 days apart, were selected. 52 From a total of 187 reinfection cases, we identified 47 instances of BA.2 reinfections shortly 53 after a BA.1 infection, mostly in young unvaccinated individuals with mild disease not 54 resulting in hospitalization or death. 55 In conclusion, we provide evidence that Omicron BA.2 reinfections do occur shortly after 56 BA.1 infections but are rare. 57 58 59 Introduction 60 Since the first report of a new SARS-CoV-2 variant of concern (VOC), Omicron (Pango 61 lineage B.1.1.529), on November 19, 2021, this VOC has rapidly disseminated globally and 62 now dominates in many countries. Omicron carries more than 30 mutations and deletions in 63 the spike gene compared to the original Wuhan strain and is associated with increased 64 transmissibility and immune escape. Studies indicate that the Omicron variant results in 65 less severe disease outcomes than Delta. Currently, Omicron is subdivided into four 66 subvariants, BA.1, BA.1.1, BA.2 and BA.3, where BA.1 is the dominating Omicron 67 subvariant worldwide (https://outbreak.info), and in Europe Omicron is estimated to account 68 for about 70% of all reported cases. In Denmark, we have observed a dramatic increase in 69 Omicron BA.2 case number since the beginning of early 2022, and BA.2 now accounts for 70 88% of all cases. Omicron BA.2 case numbers are also increasing in countries like the United 71 Kingdom, South Africa and Norway currently. Omicron BA.1 and BA.2 differ by up to 40 72 non-synonymous mutations and deletions including key mutations in the N-terminal and the 73 receptor binding domains of the spike gene, both regions that influence the immune response. 74 The diversity between Omicron BA.1 and BA.2 in the spike protein exceeds the variation 75 between the Wuhan and the Alpha variant. With the surge of both BA.1 and BA.2, a large 76 number of reinfections, as defined by the European Centre for Disease Prevention and 77 Control (ECDC) as two positive tests >60 days apart, has been observed, raising the question 78 if BA.2 can escape the natural immunity acquired shortly after a BA.1 infection, and if so, 79 whether these cases are associated with changes in disease severity. 80 Using whole genome sequencing (WGS), we investigate whether Omicron BA.2 reinfections 81 occurred within 20-60 days following initial infections with BA.1 in the time period when 82 these two subvariants emerged and became dominant in Denmark. Here we present evidence 83 that Omicron BA.2 reinfections indeed do occur relatively shortly after a BA.1 infection, 84 causing mostly mild disease in unvaccinated young individuals. 85 86 Methods 87 Epidemiological information 88 For the SARS-CoV-2 cases, we obtained data up to and including February 15, 2022, from 89 the Danish COVID-19 surveillance which includes information from multiple national 90 . CC-BY 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 22, 2022. ; https://doi.org/10.1101/2022.02.19.22271112 doi: medRxiv preprint

SARS coronavirus 2 (SARS-CoV-2) continues to evolve and new variants emerge. Using nationwide Danish data, we estimate the transmission dynamics of SARS-CoV-2 Omicron subvariants BA.1 and BA.2 within households. Among 22,678 primary cases, we identified 17,319 secondary infections among 50,588 household contacts during a 1–7 day follow-up. The secondary attack rate (SAR) was 29% and 39% in households infected with Omicron BA.1 and BA.2, respectively. BA.2 was associated with increased susceptibility of infection for unvaccinated household contacts (Odds Ratio (OR) 1.99; 95%–CI 1.72-2.31), fully vaccinated contacts (OR 2.26; 95%–CI 1.95–2.62) and booster-vaccinated contacts (OR 2.65; 95%–CI 2.29–3.08), compared to BA.1. We also found increased infectiousness from unvaccinated primary cases infected with BA.2 compared to BA.1 (OR 2.47; 95%–CI 2.15–2.84), but not for fully vaccinated (OR 0.66; 95%–CI 0.57–0.78) or booster-vaccinated primary cases (OR 0.69; 95%–CI 0.59–0.82). Omicron BA.2 is inherently more transmissible than BA.1. Its immune-evasive properties also reduce the protective effect of vaccination against infection, but do not increase infectiousness of breakthrough infections from vaccinated individuals.

Background Atopic dermatitis (AD) patients have an altered skin bacterial community, with an abundance of Staphylococcus aureus associated with flares, highlighting that microbial organisms may be important for disease exacerbation. Despite strong evidence of association between bacterial skin colonisation and AD, very limited knowledge regarding the eukaryotic microbial community, including fungi and ectoparasites, in AD exists. In this study, we compared the skin and nasal eukaryotic microbial community between adult AD patients ( n = 55) and non-AD healthy controls ( n = 45) using targeted 18S rRNA amplicon sequencing. Analysis was based on the presence or absence of eukaryotic microorganisms. Results The cutaneous composition of the eukaryotic microbial community and the alpha-diversity differed significantly between AD patients and non-AD individuals, with increased species richness on AD skin. Alpha-diversity and beta-diversity were similar on lesional and non-lesional skin of patients. The ectoparasite Demodex folliculorum and the yeast Geotrichum candidum were significantly more prevalent on the skin of AD patients. The prevalence of D. folliculorum on lesional skin was greater among patients recently treated with topical corticosteroid. Malassezia was one of the most frequently detected genera at all sites, with M. globosa and M. restricta being the most prevalent. M. restricta was under represented in the anterior nares of AD patients as compared to the non-AD control population. Conclusion Significant differences in the eukaryotic microbial communities were found between AD patients and non-AD individuals, with the most striking finding being the significantly overrepresentation of D. folliculorum on AD skin. Whether D. folliculorum can contribute to skin inflammation in AD needs further investigation.

Species-specific detection of Chlamydia psittaci is challenging and all published PCR tests have so far shown deficiencies in specificity or sensitivity. The present investigation reports on the development of a species-specific real-time PCR assay for C. psittaci. The test is based on an 84 bp indel in a gene of unknown function that is unique to C. psittaci. The Cps-indel84-PCR assay was validated on a wide range of chlamydial and other bacterial strains as well as on clinical samples from animals and humans in two different diagnostic laboratories in Germany and Denmark. Furthermore, the test was employed for investigating samples from racing pigeon flocks in Denmark. The evaluation showed that the Cps-indel84-PCR assay has excellent test characteristics and is a highly reliable method for identifying C. psittaci in clinical samples both from humans and animals.

Staphylococcus epidermidis, ubiquitous in the human nasal and skin microbiota, is a common causative microorganism in prosthetic joint infections (PJIs). A high proportion of PJI isolates have been shown to harbor genetic traits associated with resistance to/tolerance of agents used for antimicrobial prophylaxis in joint arthroplasties. These traits were found within multidrug-resistant S. epidermidis (MDRSE) lineages of multiple genetic backgrounds. In this study, the aim was to study whether MDRSE lineages previously associated with PJIs are present in the nasal and skin microbiota of patients planned for arthroplasty surgery but before hospitalization. We cultured samples from nares, inguinal creases, and skin over the hip or knee (dependent on the planned procedure) taken two weeks (median) prior to admittance to the hospital for total joint arthroplasty from 66 patients on agar plates selecting for methicillin resistance. S. epidermidis colonies were identified and tested for the presence of mecA. Methicillin-resistant S. epidermidis (MRSE) were characterized by Illumina-based whole-genome sequencing. Using this method, we found that 30/66 (45%) of patients were colonized with MRSE at 1–3 body sites. A subset of patients, 10/66 (15%), were colonized with MDRSE lineages associated with PJIs. The qacA gene was identified in MRSE isolates from 19/30 (63%) of MRSE colonized patients, whereas genes associated with aminoglycoside resistance were less common, found in 11/30 (37%). We found that MDRSE lineages previously associated with PJIs were present in a subset of patients’ pre-admission microbiota, plausibly in low relative abundance, and may be selected for by the current prophylaxis regimen comprising whole-body cleansing with chlorhexidine-gluconate containing soap. To further lower the rate of S. epidermidis PJIs, the current prophylaxis may need to be modified, but it is important for possible perioperative MDRSE transmission events and specific risk factors for MDRSE PJIs to be investigated before reevaluating antimicrobial prophylaxis.

Objectives: The intestinal parasite Dientamoeba fragilis is a common colonizer of children in Denmark. Metronidazole has been used to reduce gastrointestinal symptoms in children colonized with D fragilis. We aimed to identify gut microbiota changes associated with D fragilis carrier status and metronidazole treatment of D fragilis-positive children. Methods: The fecal microbiota of 275 fecal samples from children treated with metronidazole (n = 48) or placebo (n = 48) were characterized by ribosomal DNA sequencing. Samples collected before (T1), 2 weeks after (T2), and 8 weeks (T5) after treatment were included. Seventy fecal samples from 70 age-matched parasite-negative children served as controls. Results: The abundance of 24 bacterial genera differed significantly according to D fragilis carrier status, with Flavonifractor being remarkably more abundant in children testing negative for D fragilis. Eight bacterial genera changed significantly in abundance in children losing versus keeping D fragilis after metronidazole treatment. Of these, 7 returned to pretreatment (T1) levels at T5. Meanwhile, the abundance of Flavonifractor continued to differ at T5, whereas for Ruminococcus the abundance only remained high in children who were D fragilis-negative at T2 and T5. Increases in Hungatella, Sutterella, and Streptococcus abundances observed at T2 were specific to metronidazole exposure and hence independent of D fragilis colonization. Conclusions: This study revealed that specific bacterial genera were associated with D fragilis colonization. Metronidazole treatment had a short-term impact on the abundance of some bacterial genera, with most of these reverting to pretreatment levels 8 weeks after completed treatment.