Super-dominant pathobiontic bacteria in the nasopharyngeal microbiota as causative agents of secondary bacterial infection in influenza patients.

The source of secondary lower respiratory tract bacterial infections in influenza patients is not fully understood. A case-control study was conducted during the 2017-2018 influenza epidemic period in Beijing, China. Nasopharyngeal swabs were collected from 52 virologically confirmed influenza patients and 24 healthy medical staff. The nasopharyngeal microbiota taxonomic composition was analysed using high-throughput sequencing of the 16S rRNA gene V3-V4 regions. The super-dominant pathobiontic bacterial genus (SDPG) was defined as that accounting for >50% of sequences in a nasopharyngeal swab. We attempted to isolate bacteria of this genus from both nasopharyngeal swabs and lower-respiratory tract samples and analyse their genetic similarities. We observed a significantly lower taxonomy richness in influenza cases compared with healthy controls. A SDPG was detected in 61% of severe cases but in only 24% of mild cases and 29% of healthy controls. In 10 cases, the species isolated from lower-respiratory tract infection sites were identified as belonging to the nasopharyngeal microbiota SDPG. Genetically identical strains were isolated from both nasopharyngeal swabs and lower-respiratory tract infection sites, including 23 Acinetobacter baumannii strains from six severe cases, six Klebsiella pneumoniae strains from two severe cases, five Pseudomonas aeruginosa strains from one severe and one mild case, and four Corynebacterium striatum strains from two severe cases. The SDPG in the nasopharyngeal microbiota are the likely cause of subsequent infection in influenza patients.

Antibiotic Resistance and Azithromycin Resistance Mechanism of Legionella pneumophila Serogroup 1 in China.

Legionnaires' disease, caused by Legionella pneumophila, has been treated primarily with antibiotics. However, few reports have been published on antibiotic-resistant Legionella in China. Our aim was to determine the azithromycin resistance mechanism of L. pneumophila serogroup 1 in China. The sensitivities of 149 L. pneumophila serogroup 1 strains, isolated from clinical cases or environmental water in China from 2002 to 2016, to five antibiotics, including erythromycin, azithromycin, levofloxacin, moxifloxacin, and rifampin, were evaluated. The mechanisms of the resistance of L. pneumophila serogroup 1 to azithromycin were studied. The expression levels of efflux pump gene lpeAB and the MIC of azithromycin-resistant strains in the presence and absence of the efflux pump inhibitor carbonyl cyanide-chlorophenylhydrazone (CCCP) were determined. All 149 strains were sensitive to erythromycin, levofloxacin, moxifloxacin, and rifampin, among which 25 of the strains exhibited azithromycin resistance. These 25 strains, including strains of sequence type 1 (ST1), ST144, ST150, ST154, and ST629, were screened. Expression of lpeAB was responsible for the reduced azithromycin susceptibility in all 25 of these strains. The phenotypes of 25 strains with virulence were linked by evaluating the intracellular growth ability in mouse macrophage J774 cells. Among the 25 strains, 60% were more virulent than the ATCC 33152 reference strain. The results determined in our study represent data supporting the further study of the antibiotic sensitivity of L. pneumophila strains in China.

Sharp constant of Hardy operators corresponding to general positive measures.

We investigate a new kind of Hardy operator [Formula: see text] with respect to arbitrary positive measures µ and prove that [Formula: see text] is bounded on [Formula: see text] with an upper constant [Formula: see text]. Moreover, we characterize a sufficient condition about the measure which makes [Formula: see text] to be the [Formula: see text]-norm of [Formula: see text].

[High-resolution Variations of Oxygen and Hydrogen Isotopes of Precipitation and Feedback from Cave Water: An Example of Jiguan Cave, Henan].

The stable isotopes of atmospheric precipitation that affect the isotopes of speleothem and cave water are controlled by a variety of factors, such as temperature, rainfall amount, altitude, vapor source and others. Knowledge in the factors causing rainfall stable isotopes change is one of the keys to understanding the cave water stable isotopes change of monsoon-sensitive area in the north-south China intersection. The samples collected from 4 ground water sites in Jiguan Cave and the instantaneous heavy rain during Aug.4th-6th, 2015 were analyzed, and combined with the precipitation oxygen and hydrogen isotopes data for samples from almost 6 years (2009-2015) collected in Jiguan Cave of Luanchuan County in Henan Province, leading to the following findings:① The precipitation was divided into 2 stages with different vapor sources (high-altitude water vapor from the South China Sea and inland areas from near the ground to evaporate moisture) that could be recorded in the δ18O of single rainfall by HYSPLIT model. ② The evaporation of stage 2 masked the temperature effect to some extent, which also decreased the slope and intercept of LMWL and d-excess of precipitation. ③ The δ18O values feature of cave drip water in Jiguan Cave during this rainfall was mainly a response to the summer monsoon precipitation from sea source vapor. The cave drip water of Jiguan Cave responded to the heavy rain very quickly, and the time was ~3 h. The δ18O of drip became heavier when dripping rate increased and then decreased slowly. The same pattern could be found in underground river with slight delay, and the pool near the cave entrance reflected the difference of precipitation δ18O in two stages.