Atypical Class 1 Integron Coexists with Class 1 and Class 2 Integrons in Multi-Drug Resistant Shigella flexneri Isolates from China
CURRENT MICROBIOLOGY
Authors: Zhu, Jing Yuan; Duan, Guang Cai; Yang, Hai Yan; Fan, Qing Tang; Xi, Yuan Lin
Abstract
The antimicrobial resistance and the character of integrons were determined in 58 Shigella flexneri strains isolated from China. All isolates were multi-drug resistant and found to carry integrons of class 1 (94.8%), class 2 (100%), or both (94.8%). No intI3 was detected. The typical class 1 integrons were found in conjugative plasmids and could be transferred to the recipient E. coli DH5 alpha. The gene cassettes of typical class 1 integrons dfrA17-aadA5 and dfrA12-orfF-aadA2 were detected in 54 strains (93.1%) and 1 strain, respectively. Atypical class 1 integrons located on the chromosome with gene cassettes bla (oxa-30)-aadA1 were detected in 55 isolates (94.8%). All the intI2 positive isolates carried gene cassettes dfrA1-sat1-aadA1. To our knowledge, this is the first report that atypical and typical class 1 integrons coexisted with class 2 integron in multi-drug resistant S. flexneri strains.
ADH1 promotes Candida albicans pathogenicity by stimulating oxidative phosphorylation
INTERNATIONAL JOURNAL OF MEDICAL MICROBIOLOGY
Authors: Song, Yanjun; Li, Shuixiu; Zhao, Yajing; Zhang, Yishan; Lv, Yan; Jiang, Yuanying; Wang, Yan; Li, Dongmei; Zhang, Hong
Abstract
Objective: Alcohol dehydrogenase I is encoded by ADH1 in Candida albicans, and is one of the key enzymes in fungal metabolism by which it catalyzes the conversion from acetaldehyde to ethanol. The role of the associated protein Adh1p, encoded by ADHI in fungal pathogenicity has not been thoroughly studied despite its near ubiquity in the fungal kingdom. Using C. albicans as a model, this study proposes to determine the possible pathogenic roles for ADH1 and its possible underlying mechanisms. Methods: The SAT1 flipper strategy was used to construct the ADHI deletion mutant. Growth curves and spot assay were used to compare growth and cell viability of the mutant to wild type C. albicans. Three host model systems (infected mice, C. elegans, and G. mellonella) were used to investigate the effects of ADH1 deletion in vivo on C. albicans pathogenicity. Then, adhesion, hyphal formation, biofilm formation, cell surface hydrophobicity (CSH) and RT-qPCR were performed to investigate the effects of ADHI deletion in vitro on C. albicans virulence. Finally, Xfe 96 seahorse assay, ROS level, mitochondrial membrane potential, and intracellular ATP content were used to determine the effects of ADH1 deletion on bioenergetics. Results: ADH1 deletion has no effects on the growth and cell viability of C. albicans, but significantly prolongs survival time in each of the three host models, decreases fungal burden in kidney and liver, and lessens pathological tissue damage (P < 0.05). In addition, ADH1 deletion significantly increases CSH and reduces C. albicans virulence in terms of adhesion, hyphal formation and biofilm formation in accord with the downregulation of virulence-related genes such as ALS1, ALS3, HWP1, and CSH1 (P < 0.05). For bioenergetics, ADH1 deletion has no obvious effect on glycolysis, but a lack of ADHI significantly increases ROS levels and decreases mitochondrial membrane potential and intracellular ATP content even through the mitochondrial oxygen consumption rate and NADH/NAD(+) ratio are elevated (P < 0.05). Conclusion: Our results suggest that the fermentative enzyme ADHI is required for the pathogenicity of C. albicans under one of the presumed mechanisms viaits effects on oxidative phosphorylation activities in mitochondria.