Molecular Epidemiology of Klebsiella pneumoniae from Clinical Bovine Mastitis in Northern Area of China,2018–2019

Klebsiella pneumoniae(K.pneumonia,KpⅠ)is a predominate inducement of bovine mastitis,which is associated with high mortality and milk yield reduction.However,data is lacking on the molecular characteristics of bovine K.pneumoniae,limiting the risk assessment of its transmission through the food chain.Herein,we investigated the prevalence of K.pneumoniae in 6301 clinical mastitis(CM)milk samples from dairy cattle in northern area of China.In total,183 K.pneumoniae isolates were recovered,with detection rates of 3.0% and 2.8% in 2018 and 2019,respectively.Like human clinical K.pneumoniae,all CM K.pneumoniae isolates belonged to one of three phylogroups:KpⅠ(n=143),Klebsiella.quasipneumoniae subsp.similipneumoniae(KpⅡ-B)(n=37),and Klebsiella variicola(KpⅢ)(n=3).We detected the extendedspectrum β-lactamase-encoding genes bla_(SHV-2a),blac_(CTX-M-14),and bla_(CTX-M-15),as well as clpC,lpfA,lacI,lacZ,lacY,and the fecABDEIR operon in the KpⅠ isolates,which may contribute to their pathogenicity and host adaptability in cows.The high prevalence of KpⅠ in dairy farms may be problematic,as it showed relatively higher rates of antibiotic resistance and virulence gene carriage than the KpⅡ-B and KpⅢ isolates.Furthermore,we observed distinct differences in population structure between CM-and human infection-associated KpⅠ isolates,with the genes associated with invasive infection in humans rarely being observed in bovine isolates,indicating that few CM-associated K.pneumoniae isolates pose a threat to human health.Nevertheless,bovine KpⅡ-B isolates shared a high level of nucleotide sequence identity with isolates from human infections and frequently carried the nitrogen-fixation gene nif,suggesting an association between KpⅡ-B isolates from cattle and humans,and plant-derived bacteria.

Climate change in the Hongliujing area of Lop Nur over the past 200 years revealed by the stable oxygen isotopes of Tamarix cones

The layers of Tamarix cones within sedimentary deposits in arid regions have significant chronological and paleoenvironmental implications.Here,we compare the δ^(18)O values of Tamarix cones in the Hongliujing area of Lop Nur with meteorological data for the Ruoqiang meteorological station for 1960-2019 AD.Linear regression analysis was used to reconstruct the average temperature for April and the precipitation for November in the Hongliujing area over the past 200 years.The results showed that the δ^(18)O values were significantly negatively correlated with the temperature for February,April,May,August,December,and with the annual mean temperature;significantly negatively correlated with the precipitation for February and April;significantly negatively correlated with the sunshine hours for March and May;significantly positively correlated with the sunshine hours for February,July,August,October,and December,and with the annual mean values;and significantly correlated with the relative humidity for April,July,August,September,October,and November,and with the annual mean values.Based on the δ^(18)O record of the past 200 years,the Hongliujing area experienced two warm-wet periods(1874-1932 and 2004-2019 AD)and two cold-dry periods(1832–1873 and 1933-2003 AD).Thus,the climate was characterized by alternating warm-wet and cold-dry conditions.Wavelet analysis revealed three main cycles:45 years,29 years,and 14 years.