Evolutionary Analyses of Staphylococcus aureus Identify Genetic Relationships between Nasal Carriage and Clinical Isolates

Nasal carriage of Staphylococcus aureus has long been hypothesized to be a major vector for the transmission of virulent strains throughout the community. To address this hypothesis, we have analyzed the relatedness between a cohort of nasal carriage strains and clinical isolates to understand better the genetic conformity therein. To assess the relatedness between nasal carriage and clinical isolates of S. aureus, a genetic association study was conducted using multilocus sequence typing (MLST) and typing of the hypervariable regions of clumping factor and fibronectin binding protein genes. At all loci analyzed, genetic associations between both nasal carriage and clinical isolates were observed. Computational analyses of MLST data indicate that nasal carriage and clinical isolates belong to the same genetic clusters (clades), despite differences in sequence type assignments. Genetic analyses of the hypervariable regions from the clumping factor and fibronectin binding protein genes revealed that not only do clinically relevant strains belong to identical genetic lineages as the nasal carriage isolates within our cohort, but they also exhibit 100% sequence similarity within these regions. The findings of this report indicate that strains of S. aureus being carried asymptomatically throughout the community via nasal colonization are genetically related to those responsible for high levels of morbidity and mortality

An international comparison of Retinopathy of Prematurity grading performance within the Benefits of Oxygen Saturation Targeting (BOOST) II trials. International variation in ROP grading.

PurposeTo investigate whether the observed international differences in retinopathy of prematurity (ROP) treatment rates within the Benefits of Oxygen Saturation Targeting (BOOST) II trials might have been caused by international variation in ROP disease grading.MethodsGroups of BOOST II trial ophthalmologists in UK, Australia, and New Zealand (ANZ), and an international reference group (INT) used a web based system to grade a selection of RetCam images of ROP acquired during the BOOST II UK trial. Rates of decisions to treat, plus disease grading, ROP stage grading, ROP zone grading, inter-observer variation within groups and intra-observer variation within groups were measured.ResultsForty-two eye examinations were graded. UK ophthalmologists diagnosed treat-requiring ROP more frequently than ANZ ophthalmologists, 13.9 (3.49) compared to 9.4 (4.46) eye examinations, P=0.038. UK ophthalmologists diagnosed plus disease more frequently than ANZ ophthalmologists, 14.1 (6.23) compared to 8.5 (3.24) eye examinations, P=0.021. ANZ ophthalmologists diagnosed stage 2 ROP more frequently than UK ophthalmologists, 20.2 (5.8) compared to 12.7 (7.1) eye examinations, P=0.026. There were no other significant differences in the grading of ROP stage or zone. Inter-observer variation was higher within the UK group than within the ANZ group. Intra-observer variation was low in both groups.ConclusionsWe have found evidence of international variation in the diagnosis of treatment-requiring ROP. Improved standardisation of the diagnosis of treatment-requiring ROP is required. Measures might include improved training in the grading of ROP, using an international approach, and further development of ROP image analysis software.Eye advance online publication, 28 July 2017; doi:10.1038/eye.2017.150