Paal S. Andersen

The B form of dihydroorotate dehydrogenase from Lactococcus lactis consists of two different subunits, encoded by the pyrDb and pyrK genes, and contains FMN, FAD, and [FeS] redox centers.

The B form of dihydroorotate dehydrogenase from Lactococcus lactis (DHOdehase B) is encoded by the pyrDb gene. However, recent genetic evidence has revealed that a co-transcribed gene, pyrK, is needed to achieve the proper physiological function of the enzyme. We have purified DHOdehase B from two strains of Escherichia coli, which harbored either the pyrDb gene or both the pyrDb and the pyrK genes of L. lactis on multicopy plasmids. The enzyme encoded by pyrDb alone (herein called the δ-enzyme) was a bright yellow, dimeric protein that contained one molecule of tightly bound FMN per subunit. The δ-enzyme exhibited dihydroorotate dehydrogenase activity with dichloroindophenol, potassium hexacyanoferrate(III), and molecular oxygen as electron acceptors but could not use NAD+. The DHOdehase B purified from the E. coli strain that carried both the pyrDb and pyrK genes on a multicopy plasmid (herein called the δκ-enzyme) was quite different, since it was formed as a complex of equal amounts of the two polypeptides, i.e. two PyrDB and two PyrK subunits. The δκ-enzyme was orange-brown and contained 2 mol of FAD, 2 mol of FMN, and 2 mol of [2Fe-2S] redox clusters per mol of native protein as tightly bound prosthetic groups. The δκ-enzyme was able to use NAD+ as well as dichloroindophenol, potassium hexacyanoferrate(III), and to some extent molecular oxygen as electron acceptors for the conversion of dihydroorotate to orotate, and it was a considerably more efficient catalyst than the purified δ-enzyme. Based on these results and on analysis of published sequences, we propose that the architecture of the δκ-enzyme is representative for the dihydroorotate dehydrogenases from Gram-positive bacteria.

Genome Sequence of Staphylococcus aureus Strain 11819-97, an ST80-IV European Community-Acquired Methicillin-Resistant Isolate

The European methicillin-resistant Staphylococcus aureus (MRSA) clone ST80-IV has historically dominated community-associated infections in major parts of Europe and is a lineage strongly linked to skin and soft tissue infections. Here, we report the genome sequence of an ST80-IV representative, 11819-97, isolated from a skin infection in Denmark in 1997.

Staphylococcus aureus Bacteremia in Children Aged 5-18 Years—Risk Factors in the New Millennium

Objectives To assess the association between comorbidities and Staphylococcus aureus bacteremia in children aged 5‐18 years, thus, in children with a matured immune system. Further, we aimed to identify presumably healthy children acquiring bacteremia. Study design By cross‐linking nationwide registries, we consecutively included all children born from 1995 onward at their 5‐year birthday or date of immigration during 2000‐2015. We examined incidence rate ratios (IRR) between preselected exposures and microbiologically verified S aureus bacteremia (reference = children without exposure) using Poisson regression models. Results We followed 1 109 169 children in 2000‐2015 during which 307 children (incidence rate: 3.7 per 100 000 person‐years) acquired S aureus bacteremia (methicillin‐resistant S aureus = 8; 2.6%). Children without known comorbidities or recent contact with the healthcare system comprised 37.1% of infected children. The highest IRRs were observed in children undergoing dialysis or plasmapheresis (IRR = 367.2 [95% CI) = 188.5‐715.3]), children with organ transplantation (IRR = 149.5 [95% CI = 73.9‐302.2]), and children with cancer (IRR = 102.9 [95% CI = 74.4‐142.2]). Positive associations also were observed in children with chromosomal anomalies (IRR = 7.16 [95% CI = 2.96‐17.34]), atopic dermatitis (IRR = 4.89 [95% CI = 3.11‐7.69]), congenital heart disease (IRR = 3.14 [95% CI = 1.92‐5.11]), and in children undergoing surgery (IRR = 3.34 [95% CI = 2.59‐4.28]). Neither premature birth nor parental socioeconomic status was associated with increased disease rates. Conclusions S aureus bacteremia is uncommon in children between 5 and 18 years of age. Risk factors known from the adult population, such as dialysis, plasmapheresis, organ transplantation, and cancer, were associated with the highest relative rates. However, prematurity and parental socioeconomic status were not associated with increased rates. Approximately one‐third of infected children were presumably healthy.

Nasal and pharyngeal carriage of methicillin-resistant Staphylococcus sciuri among hospitalised patients and healthcare workers in a Serbian university hospital

There has been a paucity of data on methicillin-resistant Staphylococcus sciuri (MRSS) epidemiology in European healthcare settings. The aim of the study was to determine the prevalence of nasal and pharyngeal carriage and diversity of MRSS among inpatients and healthcare workers (HCWs) in the largest healthcare centre in Serbia, and to assess performance of different methods for MRSS screening. Nasal and pharyngeal swabs were obtained from 195 patients and 105 HCWs in different departments. Each swab was inoculated directly onto MRSA-ID, oxacillin-resistance screening agar and mannitol salt agar (MSA) with 2 mg/L of oxacillin. After inoculation, each swab was dipped in Mueller-Hinton broth with 6.5% NaCl and after overnight incubation, subcultured onto oxacillin-MSA. Characterisation of isolated MRSS strains was determined by antimicrobial susceptibility testing, PFGE, SCCmec typing and antimicrobial resistance genes detection. MRSS nasal and pharyngeal carriage rate was high (5%) in our hospital and department-variable. PFGE revealed a possible cross-transmission of MRSS between a patient and an HCW, and dissemination across hospital wards. All analysed isolates were multidrug resistant. Fusidic acid resistance was discovered in 93.7% of isolates, but fusA mutations in EF-G and fusB/C genes were not detected. SCCmec regions of MRSS contained elements of classic methicillin-resistant S. aureus type III. Broth enrichment prior to isolation on oxacillin-MSA was superior to direct cultivation on different media with a sensitivity/specificity of 100% and 88.5%, respectively. MRSS is a significant coloniser of patients and HCWs in the hospital. Further research is needed to investigate the clinical significance of the bacterium in our settings.