Browsing by Author "McGee L"

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    Geochemical fingerprinting of Holocene tephras in the Willaumez Isthmus District of West New Britain, Papua New Guinea
    (The Australian Museum, 2021-05-12) Neall V; McGee L; Turner M; O'Neill T; Zernack A; Athens JS; Specht, J; Attenbrow, V; Allen, J
    Electron microprobe analyses were conducted on volcanic glasses extracted from Holocene tephra marker beds on the Willaumez isthmus in West New Britain, Papua New Guinea. These tephra beds are pivotal in the dating of a wide range of human artefacts and manuports found in the intervening buried soils, extending back over the last 40,000 years. Three major groups can be easily separated: W-K1 and 2; W-K3 and 4; and the Dakataua tephra. Of the remaining post-W-K4 tephras, most show slightly higher FeO and CaO and lower SiO2 contents than the W-K3 and 4 group, although there is some overlap. The combination of these geochemical data sets with the known stratigraphy and radiocarbon dates has helped resolve tephra correlation where these ashes become thin and less visually diagnostic or where pumice has been resorted and redeposited by the Kulu-Dulagi River.
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    Global Distribution of Invasive Serotype 35D Streptococcus pneumoniae Isolates following Introduction of 13-Valent Pneumococcal Conjugate Vaccine.
    (American Society for Microbiology, 2018-06-25) Lo SW; Gladstone RA; van Tonder AJ; Hawkins PA; Kwambana-Adams B; Cornick JE; Madhi SA; Nzenze SA; du Plessis M; Kandasamy R; Carter PE; Eser ÖK; Ho PL; Elmdaghri N; Shakoor S; Clarke SC; Antonio M; Everett DB; von Gottberg A; Klugman KP; McGee L; Breiman RF; Bentley SD
    A newly recognized pneumococcal serotype, 35D, which differs from the 35B polysaccharide in structure and serology by not binding to factor serum 35a, was recently reported. The genetic basis for this distinctive serology is due to the presence of an inactivating mutation in wciG, which encodes an O-acetyltransferase responsible for O-acetylation of a galactofuranose. Here, we assessed the genomic data of a worldwide pneumococcal collection to identify serotype 35D isolates and understand their geographical distribution, genetic background, and invasiveness potential. Of 21,980 pneumococcal isolates, 444 were originally typed as serotype 35B by PneumoCaT. Analysis of the wciG gene revealed 23 isolates from carriage (n = 4) and disease (n = 19) with partial or complete loss-of-function mutations, including mutations resulting in premature stop codons (n = 22) and an in-frame mutation (n = 1). These were selected for further analysis. The putative 35D isolates were geographically widespread, and 65.2% (15/23) of them was recovered after the introduction of pneumococcal conjugate vaccine 13 (PCV13). Compared with serotype 35B isolates, putative serotype 35D isolates have higher invasive disease potentials based on odds ratios (OR) (11.58; 95% confidence interval[CI], 1.42 to 94.19 versus 0.61; 95% CI, 0.40 to 0.92) and a higher prevalence of macrolide resistance mediated by mefA (26.1% versus 7.6%; P = 0.009). Using the Quellung reaction, 50% (10/20) of viable isolates were identified as serotype 35D, 25% (5/20) as serotype 35B, and 25% (5/20) as a mixture of 35B/35D. The discrepancy between phenotype and genotype requires further investigation. These findings illustrated a global distribution of an invasive serotype, 35D, among young children post-PCV13 introduction and underlined the invasive potential conferred by the loss of O-acetylation in the pneumococcal capsule.