Analysis of carbapenemase resistance genes and their homology in multi-drug resistant Acinetobacter baumannii / 中国热带医学

@#Abstract: Objective　To analyze the genotype of carbapenemase resistance genes and their genetic homology in multidrug-resistant Acinetobacter baumannii, and to provide a theoretical basis for guiding the rational use of antibiotics and controlling the prevalence of nosocomial infections. Methods A total of 83 multidrug-resistant Acinetobacter baumannii isolated from patients in the intensive care unit (ICU) and environmental specimens in the Sixth People's Hospital of Nantong from July 2020 to December 2021 were collected. The bacteria were identified and subjected to drug sensitivity tests using the BioMérieux DL96-Ⅱ automatic bacterial identification susceptibility system. The carbapenemase-related drug resistance gene types were detected using the polymerase chain reaction (PCR) method, and clones were analyzed by pulsed field gel electrophoresis (PFGE). Results The types of 83 ICU Acinetobacter baumannii specimens include sputum (43 strains), broncholavage fluid (20 strains), and surfaces of objects such as ventilators (20 strains). The resistance rates of all strains to imipenem, tetracycline, gentamicin, amikacin and ciprofloxacin were 100%, 32.5%, 38.6%, 41.0% and 77.1% respecitively, while the resistance rates to others such as ticarcillin and clavulanate were greater than 95%. All strains carried were detected to carry OXA-23 and OXA-51 genes, while OXA-24, OXA-58, IMP-1, VIM, IMP-4, SIM and NDM-1 resistance genes were all negative. PFGE homology analysis confirmed that 83 strains of Acinetobacter baumannii, with counts of 12, 18, 12, 13, 10, 6, 7, 5 respectively, mainly A, B, C, D, E clones, the rest were sporadic clones. Conclusions The carbapenem resistant Acinetobacter baumannii isolated from our ICU are widely drug-resistant to commonly used antimicrobial drugs, with B clone strain being the major prevalent strain. Carrying OXA-23 and OXA-51 genes may be an important reason for the resistance of Acinetobacter baumannii to carbapenem antibiotics in our ICU. Rational use of antimicrobial drugs, enhanced monitoring of bacterial resistance, and effective control of the generation and further spread of drug-resistant strains should be emphasized.

Recent Advances on the Metal-Organic Frameworks-Based Biosensing Methods for Cancer Biomarkers Detection.

Sensitive and selective detection of cancer biomarkers is crucial for early diagnosis and treatment of cancer, one of the most dangerous diseases in the world. Metal-organic frameworks (MOFs), a class of hybrid porous materials fabricated through the assembly of metal ions/clusters and organic ligands, have attracted increasing attention in the sensing of cancer biomarkers, due to the advantages of adjustable size, high porosity, large surface area and ease of modification. MOFs have been utilized to not only fabricate active sensing interfaces but also arouse a variety of measurable signals. Several representative analytical technologies have been applied in MOF-based biosensing strategies to ensure high detection sensitivity toward cancer biomarkers, such as fluorescence, electrochemistry, electrochemiluminescence, photochemistry and colorimetric methods. In this review, we summarized recent advances on MOFs-based biosensing strategies for the detection of cancer biomarkers in recent three years based on the categories of metal nodes, and aimed to provide valuable references for the development of innovative biosensing platform for the purpose of clinical diagnosis.

The diagnostic value of combined detection of microRNA-155, TNF-α and IL-37 for active pulmonary tuberculosis in the elderly.

OBJECTIVE: To identify a panel of potential biomarkers consisting of microRNA-155 (miR-155), tumor necrosis factor-alpha (TNF-α), interleukin-37 (IL-37) for the diagnosis of active pulmonary tuberculosis (PTB) infection in elderly patients. METHODS: The serum expression of miR-155 and TNF-α in patients was measured by RT-qPCR, and the serum IL-37 level was determined by ELISA. The correlation between their expression and the features of active PTB patients was also analyzed. The AUCs of miR-155, TNF-α and IL-37 in diagnosing active PTB was calculated according to the ROC curves. The sensitivity, specificity and Youden's index of the three biomarkers alone or in combination for the active PTB diagnosis in the elderly were assessed. RESULTS: miR-155, TNF-α, and IL-37 were overexpressed in the sera of elderly patients with active PTB. miR-155, TNF-α and IL-37 serum levels were enhanced in the elderly patients with pulmonary and extrapulmonary TB relative to those with PTB only, and in patients with active TB infection in both lungs compared to those with unilateral lung infection. The AUCs of miR-155, TNF-α and IL-37 for the diagnosis of active PTB were 0.7920, 0.8734 and 0.7398, respectively. The combination of these three improved the sensitivity of the diagnosis (84.78%). CONCLUSION: miR-155, TNF-α and IL-37 were overexpressed in elderly patients with active PTB. The combined detection of serum miR-155/TNF-α/IL-37 expression has potential to serve as a diagnostic tool for active PTB in the elderly.

Studies of the mechanism of an antibacterial peptide (cecropinA-magainin) on methicillin-resistant Staphylococcus aureus membranes.

As bacterial resistance becomes increasingly common, a new hybrid peptide, cecropinA-magainin (KWALSKEGPGKFLGKKKKF), has been developed that can kill a broad spectrum of bacteria without damaging human cells. The mechanism of antibacterial toxicity for the hybrid peptides is unknown. Herein, we investigate the localization of the hybrid peptide in methicillin-resistant Staphylococcus aureus (MRSA). The minimum inhibitory concentration was 64 µg/mL. The hybrid peptides could enhance the hydrophobicity of MRSA. Dye leakage experiments showed that the hybrid peptides caused dye leakage from liposomes. The hybrid peptides influenced the permeability of the outer membrane and plasma membrane of MRSA. After cecropinA-magainin treatment of MRSA, the membrane ultrastructure was damaged and the concentration of K+ increased. Ultimately, the peptide destroyed the integrity of the bacterial cell membrane, allowing the dye propidium iodide to enter the cytoplasm. Therefore, the hybrid antibacterial peptide can kill MRSA.

[CecropinA-magainin, a new hybrid antibacterial peptide against meticillin-resistant Staphylococcus aureus].

OBJECTIVE: To study the mechanism of cecropinA-mangainin treatment on the meticillin-resistant Staphylococcus anreus biofilms. METHODS: The activity of the hybrid antibacterial peptide against Staphylococcus anreus was evaluated by the minimum inhibitory concentration (MIC) test and its effect on the bacteria membrane changes were observed through transmission electron microscope. The concentration of K+ of the tested bacterial liquid after interact with antibacterial peptide was detected with atomic absorption spectrometer. The changes of the treated bacteria biofilm was also evaluated by using flow cytometry. RESULTS: The results demonstrated that the MIC of the peptide against Staphylococcus aureus was 64 microg/mL. The ultrastructure changes of the meticillin-resistant Staphylococcus anreus membrane and the rising concentration of intracellular K+ were observed. And increased number of PI positive cells was also observed after hybrid antibacterial peptide treatmennt. CONCLUSION: The hybrid antibacterial peptide could kill the meticillin-resistant Staphylococcus anreus by damage the treated bacteria membrane.