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Acquisition of novel resistance genes is a key driver of multidrug resistance in the nosocomial pathogen Acinetobacter baumannii. To investigate the DNA uptake ability among clinical A. baumannii strains, a planktonic salt-free transformation assay was developed. A total of 142 clinical A. baumannii isolates with divergent genetic distance were selected, and 86 of them belong to international clonal lineage II (ICL2). Using this new transformation assay, 38% of the clinical A. baumannii isolates were natural competent. Among the multidrug-resistant (MDR) isolates, the transformable isolates all belonging to the ICLs, and showed significant higher transformation frequency compared with sensitive isolates. In addition, some of the ICL2 isolates triggered competence much earlier than the sensitive isolates with similar transformation frequencies. This may give them more opportunities to obtain successful transformation in their natural environment and provides an important clue to explain the severe drug resistance and clinical successfulness of ICL2.

Candida krusei is a notable pathogenic fungus that causes invasive candidiasis, mainly due to its natural resistance to fluconazole. However, to date, there is limited research on the genetic population features of C. krusei. We developed a set of microsatellite markers for this organism, with a cumulative discriminatory power of 1,000. Using these microsatellite loci, 48 independent C. krusei strains of clearly known the sources, were analyzed. Furthermore, susceptibility to 9 antifungal agents was determined for each strain, by the Clinical and Laboratory Standards Institute broth microdilution method. Population structure analyses revealed that C. krusei could be separated into two clusters. The cluster with the higher genetic diversity had wider MIC ranges for six antifungal agents. Furthermore, the highest MIC values of the six antifungal agents belonged to the cluster with higher genetic diversity. The higher genetic diversity cluster might have a better adaptive capacity when C. krusei is under selection pressure from antifungal agents, and thus is more likely to develop drug resistance.

To explore the effects of gastric non-H. pylori Helicobacter species(NHPH) on the structure and potential function of gastric microbiota, we employed 16S rRNA gene sequencing on 164 gastric biopsy specimens from NHPH (H. suis, H. felis, H. salomonis) /H. pylori coinfection individuals, H. pylori monoinfection individuals and healthy controls. The results demonstrated that marked structural and functional variations between H. pylori mono- and coinfection samples (HPHS, HPHF, HPHM). The changes in bacterial structure induced by NHPH are mainly attributed to their ability of gastric acid secretion inhibition as well as bacterial chemotaxis. Both the HPHS and HPHF groups showed significant increases in phylotype richness and significant decreases in β diversity, but this trend was not found in HPHM group. Regarding the top five phyla and top thirty-five genera, the HPHS and HPHF groups had similar variation trends in relative abundance. The increased relative abundance levels of the genera Vibrio, Pseudoalteromonas, Photobacterium, and Clostridium were associated with increases in predicted signal transduction/metabolic pathways among the three coinfection groups. The relative abundance levels of bacteria involved in the formation of N-nitroso compounds were significantly decreased in the HPHS and HPHF groups (e.g., Streptococcus, Neisseria, Haemophilus, Veillonella, Clostridium, etc.). The significantly decreased relative abundance levels of the phyla Firmicutes and Bacteroidetes in the HPHS and HPHF groups were associated with the observed increases in predicted lipid metabolism pathways. The results in this study implied that NHPH can arouse the variation of structure and function of gastric microbiota, which may pave the way to further research on the pathogenesis of gastric diseases.