ABSTRACT
Many sea-level residents suffer from acute mountain sickness (AMS) when first visiting altitudes above 4,000 m. Exercise tolerance also decreases as altitude increases. We observed exercise capacity at sea level and under a simulated hypobaric hypoxia condition (SHHC) to explore whether the response to exercise intensity represented by physiological variables could predict AMS development in young men. Eighty young men from a military academy underwent a standard treadmill exercise test (TET) and biochemical blood test at sea level, SHHC, and 4,000-m altitude, sequentially, between December 2015 and March 2016. Exercise-related variables and 12-lead electrocardiogram parameters were obtained. Exercise intensity and AMS development were investigated. After exposure to high altitude, the count of white blood cells, alkaline phosphatase and serum albumin were increased (P < 0.05). There were no significant differences in exercise time and metabolic equivalents (METs) between SHHC and high-altitude exposures (7.05 ± 1.02 vs. 7.22 ± 0.96 min, P = 0.235; 9.62 ± 1.11 vs. 9.38 ± 1.12, P = 0.126, respectively). However, these variables were relatively higher at sea level (8.03 ± 0.24 min, P < 0.01; 10.05 ± 0.31, P < 0.01, respectively). Thus, subjects displayed an equivalent exercise tolerance upon acute exposure to high altitude and to SHHC. The trends of cardiovascular hemodynamics during exercise under the three different conditions were similar. However, both systolic blood pressure and the rate-pressure product at every TET stage were higher at high altitude and under the SHHC than at sea level. After acute exposure to high altitude, 19 (23.8%) subjects developed AMS. Multivariate logistic regression analysis showed that METs under the SHHC {odds ratio (OR) 0.355 per unit increment [95% confidence intervals (CI) 0.159-0.793], P = 0.011}, diastolic blood pressure (DBP) at rest under SHHC [OR 0.893 per mmHg (95%CI 0.805-0.991), P = 0.030], and recovery DBP 3 min after exercise at sea level [OR 1.179 per mmHg (95%CI 1.043-1.333), P = 0.008] were independently associated with AMS. The predictive model had an area under the receiver operating characteristic curve of 0.886 (95%CI 0.803-0.969, P < 0.001). Thus, young men have similar exercise tolerance in acute exposure to high altitude and to SHHC. Moreover, AMS can be predicted with superior accuracy using characteristics easily obtainable with TET.
ABSTRACT
BACKGROUND: Carbapenemase-producing Klebsiella pneumoniae (CP-Kp) poses distinct clinical challenges due to extensively drug resistant (XDR) phenotype, and sequence type (ST) 11 is the most dominant blaKPC-2-bearing CP-Kp clone in China. The purpose of this current retrospective study was to explore the genetic factors associated with the success of XDR CP-Kp ST11 strains circulated in the intensive care unit (ICU) of a Chinese tertiary hospital. METHODS: Six ST11 XDR CP-Kp strains were identified between May and December 2014 and validated by minimum inhibitory concentration examination, polymerase chain reaction, and pyrosequencing. The six ST11 XDR CP-Kp, as well as three multi-drug resistant (MDR) and four susceptible strains, were sequenced using single-molecule real-time method. Comprehensively structural and functional analysis based on comparative genomics was performed to identify genomic characteristics of the XDR ST11 CP-Kp strains. RESULTS: We found that ST11 XDR blaKPC-2-bearing CP-Kp strains isolated from inpatients spread in the ICU of the hospital. Functionally, genes associated with information storage and processing of the ST11 XDR CP-Kp strains were more abundant than those of MDR and susceptible strains, especially genes correlative with mobile genetic elements (MGEs) such as transposons and prophages. Structurally, eleven large-scale genetic regions taken for the unique genome in these ST11 XDR CP-Kp strains were identified as MGEs including transposons, integrons, prophages, genomic islands, and integrative and conjugative elements. Three of them were located on plasmids and eight on chromosomes; five of them were with antimicrobial resistance genes and eight with adaptation associated genes. Notably, a new blaKPC-2-bearing ΔΔTn1721-blaKPC-2 transposon, probably transposed and truncated from ΔTn1721-blaKPC-2 by IS903D and ISKpn8, was identified in all six ST11 XDR CP-Kp strains. CONCLUSION: Our findings suggested that together with clonal spread, MGEs identified uniquely in the ST11 XDR CP-Kp strains might contribute to their formidable adaptability, which facilitated their widespread dissemination in hospital.
