Rapid and ultrasensitive detection of pathogen-associated biomarkers is vital for the early diagnosis and therapy of bacterial infections. Herein, we developed a close-packed and ordered Au@AgPt array coupled with a cascade triggering strategy for surface-enhanced Raman scattering (SERS) and colorimetric identification of the Staphylococcus aureus biomarker micrococcal nuclease (MNase) in serum samples. The trimetallic Au@AgPt nanozymes can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) molecules to SERS-enhanced oxidized TMB (oxTMB), accompanied by the color change from colorless to blue. In the presence of S. aureus, the secreted MNase preferentially cut the nucleobase AT-rich regions of DNA sequences on magnetic beads (MBs) to release alkaline phosphatase (ALP), which subsequently mediated the oxTMB reduction for inducing the colorimetric/SERS signal fade away. Using this "on-to-off" triggering strategy, the target S. aureus can be recorded in a wide linear range with a limit of detection of 38 CFU/mL in the colorimetric mode and 6 CFU/mL in the SERS mode. Meanwhile, the MNase-mediated strategy characterized by high specificity and sensitivity successfully discriminated between patients with sepsis (n = 7) and healthy participants (n = 3), as well as monitored the prognostic progression of the disease (n = 2). Overall, benefiting from highly active and dense "hot spot" substrate, MNase-mediated cascade response strategy, and colorimetric/SERS dual-signal output, this methodology will offer a promising avenue for the early diagnosis of S. aureus infection.

Objective:To identify and characterize one Spiroplasma strain (designated as DGKH1) isolated from the blood of a patient with sepsis. Methods:The traditional bacterial culture, staining, morphological observation, physiological and biochemical identification, 16S rRNA gene sequencing, phylogenetic analysis, genome sequencing, and the genome-related index analysis were performed to accurately determine the taxonomic status of the strain DGKH1. Antibiotic susceptibility testing was performed using a specific kit for culturing and testing Ureaplasma urealyticum/ Metamycoplasma hominis. Results:The strain DGKH1 could weakly grow on Columbia blood agar, chocolate agar, and Haemophilus chocolate 2 agar. However, it did not grow in liquid culture medium containing tetracycline (4 μg/ml), doxycycline (1 μg/ml), minocycline (1 μg/ml), josamycin (2 μg/ml), roxithromycin (1 μg/ml), clarithromycin (1 μg/ml), or telithromycin (1 μg/ml). DGKH1 resembling Metamycoplasma hominis formed "fried egg-like colonies" on Mycoplasma solid culture medium. DGKH1 could not be stained by Gram staining. When observed under transmission electron microscopy (TEM) using phosphate buffer as the matrix, the bacteria were spiral-shaped. Results of 16S rRNA gene sequence alignment showed that DGKH1 was highly similar (99.85%) to Spiroplasma eriocheiris CCTCC M 207170 T. However, the urea decomposition test was positive, which was different from all of the known Spiroplasma species. The phylogenetic analysis based on whole genome showed that DGKH1 was clustered in a small branch along with Spiroplasma eriocheiris CCTCC M 207170 T. However, the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the two strains were 94.14% and 56.00%, respectively, both below the threshold for prokaryotic species identification. Conclusions:DGKH1 represented a potential new species of genus Spiroplasma, closely related to Spiroplasma eriocheiris. Some microbiological characteristics of DGKH1 were similar to Mycoplasmas. However, the natural host and epidemiological data of DGKH1 need to be further studied.

Objective To evaluate the application of time to positivity (TTP)in differential diagnosis of intracranial infection caused by coagulase-negative Staphylococcus (CNS).Methods One hundred and twenty-four adult patients with positive CNS isolated from cerebrospinal fluid (CSF)including 70 cases with intracranial infection and 54 cases of CSF contamination,who were admitted in Xiangya Hospital of Central South University during January to December 201 5,were retrospectively analyzed.The difference of TTP between two groups was compared,receiver operating characteristic (ROC)curve was analyzed and the area under the ROC curve (AUC)was calculated.The application of TTP in differential diagnosis of CNS infection was evaluated.SPSS 1 8.0 software was used to analyze the data.Results TTP in intracranial infection group was shorter than that in CSF contamination group [(23.5 ±7.5 )h vs. (37.6 ±1 0.5)h,t =-8.71 7,P =0.000].The AUC of TTP was 0.854.Taking the cut-off value of 27.94 h,the sensitivity,specificity,positive and negative predictive values in differentiation of two groups were 72.7%,91 .4%,90.0% and 72.2%,respectively.There were statistically differences in TTP of Staphylococcus epidermidis,Staphylococcus haemolyticus and Staphylococcus capitis between two groups (Z =-4.496,-2.322 and -2.399,respectively,P <0.05 or <0.01 ).Conclusion TTP can be used to discriminate early intracranial infection and CSF contamination caused by CNS,and also can identify intracranial infection caused by different categories of CNS.