Proton-coupled transport mechanism of the efflux pump NorA.

Efflux pump antiporters confer drug resistance to bacteria by coupling proton import with the expulsion of antibiotics from the cytoplasm. Despite efforts there remains a lack of understanding as to how acid/base chemistry drives drug efflux. Here, we uncover the proton-coupling mechanism of the Staphylococcus aureus efflux pump NorA by elucidating structures in various protonation states of two essential acidic residues using cryo-EM. Protonation of Glu222 and Asp307 within the C-terminal domain stabilized the inward-occluded conformation by forming hydrogen bonds between the acidic residues and a single helix within the N-terminal domain responsible for occluding the substrate binding pocket. Remarkably, deprotonation of both Glu222 and Asp307 is needed to release interdomain tethering interactions, leading to opening of the pocket for antibiotic entry. Hence, the two acidic residues serve as a "belt and suspenders" protection mechanism to prevent simultaneous binding of protons and drug that enforce NorA coupling stoichiometry and confer antibiotic resistance.

Molecular basis for Nse5-6 mediated regulation of Smc5/6 functions.

The Smc5/6 complex (Smc5/6) is important for genome replication and repair in eukaryotes. Its cellular functions are closely linked to the ATPase activity of the Smc5 and Smc6 subunits. This activity requires the dimerization of the motor domains of the two SMC subunits and is regulated by the six non-SMC subunits (Nse1 to Nse6). Among the NSEs, Nse5 and Nse6 form a stable subcomplex (Nse5-6) that dampens the ATPase activity of the complex. However, the underlying mechanisms and biological significance of this regulation remain unclear. Here, we address these issues using structural and functional studies. We determined cryo-EM structures of the yeast Smc5/6 derived from complexes consisting of either all eight subunits or a subset of five subunits. Both structures reveal that Nse5-6 associates with Smc6's motor domain and the adjacent coiled-coil segment, termed the neck region. Our structural analyses reveal that this binding is compatible with motor domain dimerization but results in dislodging the Nse4 subunit from the Smc6 neck. As the Nse4-Smc6 neck interaction favors motor domain engagement and thus ATPase activity, Nse6's competition with Nse4 can explain how Nse5-6 disfavors ATPase activity. Such regulation could in principle differentially affect Smc5/6-mediated processes depending on their needs of the complex's ATPase activity. Indeed, mutagenesis data in cells provide evidence that the Nse6-Smc6 neck interaction is important for the resolution of DNA repair intermediates but not for replication termination. Our results thus provide a molecular basis for how Nse5-6 modulates the ATPase activity and cellular functions of Smc5/6.

Contamination dynamics of personal protective equipment (PPE) by SARS-CoV-2 RNA in a makeshift hospital with COVID-19 positive occupants.

Background: Personal protective equipment (PPE) helps protect healthcare workers (HCWs) from infection and prevents cross-contamination. Knowledge of the contamination dynamics of PPE during the management of COVID-19 patients in a makeshift hospital is limited. Aim: To describe the rate of SARS-CoV-2 contamination in PPE and to assess the change of contamination at different time points. Methods: HCWs were followed up for up to 4 hours with hourly collection of swab samples from PPE surfaces in a makeshift COVID-19 hospital setting. Swabs were tested using quantitative reverse transcription polymerase chain reaction (RT-qPCR) for SARS-CoV-2 RNA. Results: SARS-CoV-2 was detected on 50.9% of the 1620 swabbed samples from 9 different sites of full-body PPE worn by HCWs. The proportion of sites contaminated with SARS-CoV-2 RNA varied from 10.6% to 95.6%. Viral RNA was most frequently detected from the sole of the outer foot cover (95.6%) and least frequently on the face shield (10.6%). The median Ct values among positive samples were 34.20 (IQR, 32.61-35.22) and 34.05 (IQR, 32.20-35.39) for ORF1ab and N genes, respectively. The highest rate of contamination with SARS-CoV-2 RNA for the PPE swab samples was found after 3 hours of use. The positive rate of outer surface of HEPA filters from air supply device was 82.1% during the full capacity period of the makeshift hospital. Conclusion: A higher rate of contamination was identified at 3 hours after the entrance to the COVID-19 patient care area. Virus-containing aerosols were trapped in the HEPA filter of air supply equipment, representing a potential protective factor against infection to HCWs.

Monitoring Prevalence and Persistence of Environmental Contamination by SARS-CoV-2 RNA in a Makeshift Hospital for Asymptomatic and Very Mild COVID-19 Patients.

Objective: To investigate the details of environmental contamination status by SARS-CoV-2 in a makeshift COVID-19 hospital. Methods: Environmental samples were collected from a makeshift hospital. The extent of contamination was assessed by quantitative reverse transcription polymerase chain reaction (RT-qPCR) for SARS-CoV-2 RNA from various samples. Results: There was a wide range of total collected samples contaminated with SARS-CoV-2 RNA, ranging from 8.47% to 100%. Results revealed that 70.00% of sewage from the bathroom and 48.19% of air samples were positive. The highest rate of contamination was found from the no-touch surfaces (73.07%) and the lowest from frequently touched surfaces (33.40%). The most contaminated objects were the top surfaces of patient cubic partitions (100%). The median Ct values among strongly positive samples were 33.38 (IQR, 31.69-35.07) and 33.24 (IQR, 31.33-34.34) for ORF1ab and N genes, respectively. SARS-CoV-2 relic RNA can be detected on indoor surfaces for up to 20 days. Conclusion: The findings show a higher prevalence and persistence in detecting the presence of SARS-CoV-2 in the makeshift COVID-19 hospital setting. The contamination mode of droplet deposition may be more common than contaminated touches.

Fully automated multi-grid cryoEM screening using Smart Leginon.

Single-particle cryo-electron microscopy (cryoEM) is a swiftly growing method for understanding protein structure. With increasing demand for high-throughput, high-resolution cryoEM services comes greater demand for rapid and automated cryoEM grid and sample screening. During screening, optimal grids and sample conditions are identified for subsequent high-resolution data collection. Screening is a major bottleneck for new cryoEM projects because grids must be optimized for several factors, including grid type, grid hole size, sample concentration, buffer conditions, ice thickness and particle behavior. Even for mature projects, multiple grids are commonly screened to select a subset for high-resolution data collection. Here, machine learning and novel purpose-built image-processing and microscope-handling algorithms are incorporated into the automated data-collection software Leginon, to provide an open-source solution for fully automated high-throughput grid screening. This new version, broadly called Smart Leginon, emulates the actions of an operator in identifying areas on the grid to explore as potentially useful for data collection. Smart Leginon Autoscreen sequentially loads and examines grids from an automated specimen-exchange system to provide completely unattended grid screening across a set of grids. Comparisons between a multi-grid autoscreen session and conventional manual screening by 5 expert microscope operators are presented. On average, Autoscreen reduces operator time from ∼6 h to <10 min and provides a percentage of suitable images for evaluation comparable to the best operator. The ability of Smart Leginon to target holes that are particularly difficult to identify is analyzed. Finally, the utility of Smart Leginon is illustrated with three real-world multi-grid user screening/collection sessions, demonstrating the efficiency and flexibility of the software package. The fully automated functionality of Smart Leginon significantly reduces the burden on operator screening time, improves the throughput of screening and recovers idle microscope time, thereby improving availability of cryoEM services.

Smart data collection for CryoEM.

This report provides an overview of the discussions, presentations, and consensus thinking from the Workshop on Smart Data Collection for CryoEM held at the New York Structural Biology Center on April 6-7, 2022. The goal of the workshop was to address next generation data collection strategies that integrate machine learning and real-time processing into the workflow to reduce or eliminate the need for operator intervention.

Cryo-EM structure of DNA-bound Smc5/6 reveals DNA clamping enabled by multi-subunit conformational changes.

Structural maintenance of chromosomes (SMC) complexes are essential for chromatin organization and functions throughout the cell cycle. The cohesin and condensin SMCs fold and tether DNA, while Smc5/6 directly promotes DNA replication and repair. The functions of SMCs rely on their abilities to engage DNA, but how Smc5/6 binds and translocates on DNA remains largely unknown. Here, we present a 3.8 Å cryogenic electron microscopy (cryo-EM) structure of DNA-bound Saccharomyces cerevisiae Smc5/6 complex containing five of its core subunits, including Smc5, Smc6, and the Nse1-3-4 subcomplex. Intricate interactions among these subunits support the formation of a clamp that encircles the DNA double helix. The positively charged inner surface of the clamp contacts DNA in a nonsequence-specific manner involving numerous DNA binding residues from four subunits. The DNA duplex is held up by Smc5 and 6 head regions and positioned between their coiled-coil arm regions, reflecting an engaged-head and open-arm configuration. The Nse3 subunit secures the DNA from above, while the hook-shaped Nse4 kleisin forms a scaffold connecting DNA and all other subunits. The Smc5/6 DNA clamp shares similarities with DNA-clamps formed by other SMCs but also exhibits differences that reflect its unique functions. Mapping cross-linking mass spectrometry data derived from DNA-free Smc5/6 to the DNA-bound Smc5/6 structure identifies multi-subunit conformational changes that enable DNA capture. Finally, mutational data from cells reveal distinct DNA binding contributions from each subunit to Smc5/6 chromatin association and cell fitness. In summary, our integrative study illuminates how a unique SMC complex engages DNA in supporting genome regulation.

Supramolecular Assembly of Single-Tail ssDNA-Amphiphiles through π-π Interactions.

In this work, we demonstrate the formation of supramolecular architectures from the assembly of single-tail single stranded DNA (ssDNA)-amphiphiles. Short ssDNA sequences of 10 nucleotides that were either unstructured or formed G-quadruplex secondary structures were conjugated to a single 4-(hexadecyloxy)benzamide tail, either directly or through a polycarbon (C12) spacer. Conjugation of the ssDNA to the tail did not interfere with the G-quadruplex secondary structure of the ssDNA sequence. The ssDNA-amphiphiles self-assembled into ellipsoidal micelles, vesicles, nanotapes, and nanotubes. These nanotubes appeared to be formed by the rolling up of nanotapes. The increase of the hydrophobic block of the ssDNA-amphiphiles through the addition of a C12 spacer led to an increase in wall thickness and nanotube diameter. The presence of π-π interactions, through the benzoic group, was verified via X-ray diffraction (XRD) and played a critical role in the formation of the different nanostructures. In contrast, ssDNA-amphiphiles with a single heptadecanoic acid tail self-assembled only into ellipsoidal micelles.

Better, Faster, Cheaper: Recent Advances in Cryo-Electron Microscopy.

Cryo-electron microscopy (cryo-EM) continues its remarkable growth as a method for visualizing biological objects, which has been driven by advances across the entire pipeline. Developments in both single-particle analysis and in situ tomography have enabled more structures to be imaged and determined to better resolutions, at faster speeds, and with more scientists having improved access. This review highlights recent advances at each stageof the cryo-EM pipeline and provides examples of how these techniques have been used to investigate real-world problems, including antibody development against the SARS-CoV-2 spike during the recent COVID-19 pandemic.

A Localized Enantioselective Catalytic Site on Short DNA Sequences and Their Amphiphiles.

A DNA-based artificial metalloenzyme (ArM) consisting of a copper(II) complex of 4,4'-dimethyl-2,2'-bipyridine (dmbipy-Cu) bound to double-stranded DNA (dsDNA) as short as 8 base pairs with only 2 contiguous central pairs (G for guanine and C for cytosine) catalyzes the highly enantioselective Diels-Alder reaction, Michael addition, and Friedel-Crafts alkylation in water. Molecular simulations indicate that these minimal sequences provide a single site where dmbipy-Cu is groove-bound and able to function as an enantioselective catalyst. Enantioselective preference inverts when d-DNA is replaced with l-DNA. When the DNA is conjugated to a hydrophobic tail, the obtained ArMs exhibit enantioselective performance in a methanol-water mixture superior to that of non-amphiphilic dsDNA, and dsDNA-amphiphiles with more complex G•C-rich sequences.

ssDNA nanotubes for selective targeting of glioblastoma and delivery of doxorubicin for enhanced survival.

Effective treatment of glioblastoma remains a daunting challenge. One of the major hurdles in the development of therapeutics is their inability to cross the blood-brain tumor barrier (BBTB). Local delivery is an alternative approach that can still suffer from toxicity in the absence of target selectivity. Here, we show that nanotubes formed from self-assembly of ssDNA-amphiphiles are stable in serum and nucleases. After bilateral brain injections, nanotubes show preferential retention by tumors compared to normal brain and are taken up by glioblastoma cells through scavenger receptor binding and macropinocytosis. After intravenous injection, they cross the BBTB and internalize in glioblastoma cells. In a minimal residual disease model, local delivery of doxorubicin showed signs of toxicity in the spleen and liver. In contrast, delivery of doxorubicin by the nanotubes resulted in no systemic toxicity and enhanced mouse survival. Our results demonstrate that ssDNA nanotubes are a promising drug delivery vehicle to glioblastoma.

Genetic diversity and transmission patterns of Burkholderia pseudomallei on Hainan island, China, revealed by a population genomics analysis.

Burkholderia pseudomallei is a Gram-negative soil-dwelling bacillus that causes melioidosis, a frequently fatal infectious disease, in tropical and subtropical regions. Previous studies have identified the overall genetic and evolutionary characteristics of B. pseudomallei on a global scale, including its origin and transmission routes. However, beyond its known hyperendemicity foci in northern Australia and Southeast Asia, the distribution and genetic characteristics of B. pseudomallei in most tropical regions remain poorly understood, including in southern China. Here, we sequenced the genomes of 122 B. pseudomallei strains collected from Hainan, an island in southern China, in 2002-2018, to investigate the population structure, relationships with global strains, local epidemiology, and virulence and antimicrobial-resistance factors. A phylogenetic analysis and hierarchical clustering divided the Hainan strains into nine phylogenic groups (PGs), 80 % of which were concentrated within five major groups (group 1: corresponding to minor sequence types [STs], 12.3 %; group 3: ST46 and ST50, 31.1 %; group 9: ST58, 13.1 %; group 11: ST55, 8.2 %; group 15: mainly ST658, 15.6%). A phylogenetic analysis that included global strains suggested that B. pseudomallei in Hainan originated from Southeast Asian countries, transmitted in multiple historical importation events. We also identified several mutual transmission events between Hainan and Southeast Asian countries in recent years, including three importation events from Thailand and Singapore to Hainan and three exportation events from Hainan to Singapore, Malaysia, and Taiwan island. A statistical analysis of the temporal distribution showed that the Hainan strains of groups 3, 9, and 15 have dominated the disease epidemic locally in the last 5 years. The spatial distribution of the Hainan strains demonstrated that some PGs are distributed in different cities on Hainan island, and by combining phylogenic and geographic distribution information, we detected 21 between-city transmission events, indicating its frequent local transmission. The detection of virulence factor genes showed that 56 % of the Hainan strains in group 1 encode a B. pseudomallei-specific adherence factor, boaB, confirming the specific pathogenic characteristics of the Hainan strains in group 1. An analysis of the antimicrobial-resistance potential of B. pseudomallei showed that various kinds of alterations were identified in clinically relevant antibiotic resistance factors, such as AmrR, PenA and PBP3, etc. Our results clarify the population structure, local epidemiology, and pathogenic characteristics of B. pseudomallei in Hainan, providing further insight into its regional and global transmission networks and improving our knowledge of its global phylogeography.

Interleukin Polymorphisms and Predisposition of Systemic Lupus Erythematosus: A Meta-Analysis.

BACKGROUND: It is plausible that interleukin polymorphisms may affect predisposition of autoimmune disorders such as systemic lupus erythematosus (SLE), but the results of so far published studies remain controversial. OBJECTIVES: The authors conducted this meta-analysis to clarify relationships between interleukin-1 (IL-1)/interleukin-4 (IL-4)/interleukin-6 (IL-6)/interleukin-10 (IL-10) polymorphisms and SLE by pooling the findings of eligible studies. METHODS: A comprehensive search of PubMed, EMBASE, Web of Science, and CNKI was endorsed by the authors to identify already published studies. Fifty-seven studies were found to be eligible for meta-analyses. RESULTS: The overall pooled meta-analyses yielded positive findings for IL-1A -889 C/T, IL-1B -31 T/C, IL-6 -174 G/C, IL-4 -590 C/T, and IL-10 -1,082 A/G polymorphisms. In addition, we also detected similar positive findings for IL-1B -511 C/T, IL-4 -590 C/T, IL-10 -592 A/C, IL-10 -819 C/T, and IL-10 -1,082 A/G polymorphisms in Asians, and such positive findings were also observed for IL-1A -889 C/T, IL-6 -174 G/C, and IL-10 -1,082 A/G polymorphisms in Caucasians. CONCLUSIONS: The meta-analyses' results suggest that IL-1A -889 C/T, IL-1B -31 T/C, IL-6 -174 G/C, IL-4 -590 C/T, and IL-10 -1,082 A/G polymorphisms might affect predisposition of SLE.

Integrative analysis reveals unique structural and functional features of the Smc5/6 complex.

Structural maintenance of chromosomes (SMC) complexes are critical chromatin modulators. In eukaryotes, the cohesin and condensin SMC complexes organize chromatin, while the Smc5/6 complex directly regulates DNA replication and repair. The molecular basis for the distinct functions of Smc5/6 is poorly understood. Here, we report an integrative structural study of the budding yeast Smc5/6 holo-complex using electron microscopy, cross-linking mass spectrometry, and computational modeling. We show that the Smc5/6 complex possesses several unique features, while sharing some architectural characteristics with other SMC complexes. In contrast to arm-folded structures of cohesin and condensin, Smc5 and Smc6 arm regions do not fold back on themselves. Instead, these long filamentous regions interact with subunits uniquely acquired by the Smc5/6 complex, namely the Nse2 SUMO ligase and the Nse5/Nse6 subcomplex, with the latter also serving as a linchpin connecting distal parts of the complex. Our 3.0-Å resolution cryoelectron microscopy structure of the Nse5/Nse6 core further reveals a clasped-hand topology and a dimeric interface important for cell growth. Finally, we provide evidence that Nse5/Nse6 uses its SUMO-binding motifs to contribute to Nse2-mediated sumoylation. Collectively, our integrative study identifies distinct structural features of the Smc5/6 complex and functional cooperation among its coevolved unique subunits.

Effect of an alkyl spacer on the morphology and internalization of MUC1 aptamer-naphthalimide amphiphiles for targeting and imaging triple negative breast cancer cells.

Despite decades of research, there are few targeted treatment options available for triple negative breast cancer (TNBC), leaving chemotherapy, and radiation treatment regimes with poor response and high toxicity. Herein aptamer-amphiphiles were synthesized which selectively bind to the mucin-1 (MUC1) glycoprotein that is overexpressed in TNBC cells. These amphiphiles have a fluorescent tail (1,8-naphthalimide or 4-nitro-1,8-naphthalimide) which enables self-assembly of the amphiphiles and allows for easy visualization without the requirement for further conjugation of a fluorophore. Interestingly, the length of the alkyl spacer (C4 or C12) between the aptamer and tail was shown to influence the morphology of the self-assembled structure, and thus its ability to internalize into the TNBC cells. While both the MUC1 aptamer-C4-napthalimide spherical micelles and the MUC1 aptamer-C12-napthalimide long cylindrical micelles showed internalization into MDA-MB-468 TNBC cells but not the noncancerous MCF-10A breast cells, the cylindrical micelles showed greatly enhanced internalization into the MDA-MB-468 cells. Similar patterns of enhanced binding and internalization were observed between the MUC1 aptamer-C12-napthalimide cylindrical micelles and SUM159 and MDA-MB-231 TNBC cells. The MUC1 aptamer cylindrical micelles were not toxic to the cells, and when used to deliver doxorubicin to the TNBC cells, were shown to be as cytotoxic as free doxorubicin. Moreover, a pharmacokinetic study in mice showed a prolonged systemic circulation time of the MUC1 aptamer cylindrical micelles. There was a 4.6-fold increase in the elimination half-life of the aptamer cylindrical micelles, and their clearance decreased 10-fold compared to the MUC1 aptamer spherical micelles. Thus, the MUC1 aptamer-C12-napthalimide nanofibers represent a promising vehicle that could be used for easy visualization and targeted delivery of therapeutic loads to TNBC cells.

[Single Center Analysis of Bloodstream Infection Clinical Characteristics and Prognosis in Patients with Hematological Malignancies in the Tropics].

OBJECTIVE: To analyze the characteristics, prognosis and risk factors of bloodstream infection in patients with hematological malignancies in the tropics, so as to provide evidence for the prevention and treatment of bloodstream infection. METHODS: The clinical features, blood culture results and prognosis of patients with bloodstream infection in patients with hematological malignancies admitted to Hainan Hospital of PLA General Hospital were retrospectively studied. RESULTS: The most common primary infection site of the 81 patients with hematological malignancies was lung (46.91%), followed by PICC (11.11%). The detection rate of Gram-positive bacteria and Gram-negative bacteria in the blood culture was 60.98% and 30.02%, respectively. Coagulase-negative staphylococci was the most common Gram-positive bacteria resulting in bloodstream infection in our study. Of the Gram-negatives, Klebsiella pneumoniae (34.38%) was predominant, followed by Escherichia coli (18.75%) and Pseudomonas aeruginosa (18.75%). Gram-positive bacteria was highly sensitive (100%) to vancomycin, linezolid and tigecycline. Study showed that Gram-negative bacteria had low sensitive to quinolones, in particular, the resistance rate of Escherichia coli to quinolones was as high as 83.33%. In terms of overall survival (OS), the 30-days OS of patients with Gram-negative and Gram-positive septicemia was 77.42% and 92.00%, respectively. There was no statistically significant difference between the two groups. Multivariate analysis revealed that septic shock (P=0.001, RR=269.27) was an independent risk factor for 30-day mortality, and remission status (P=0.027, RR=0.114) was an independent predictor of a favourable outcome of bloodstream infection in patients with hematological malignancies. CONCLUSION: Gram-positive bacteria are the main pathogens causing bloodstream infections in patients with hematological malignancies in the tropics. Improving the care of PICC is an important measure to reduce the incidence of bloodstream infection in patients with hematological malignancies in the tropics. A correct treatment relieving disease and effective prevention and treatment of septic shock can reduce mortality of patients with bloodstream infection in patients with hematological malignancies in the tropics.

Design of an Aptamer-Amphiphile for the Detection of ß-Lactoglobulin on a Liquid Crystal Interface.

An aptamer-amphiphile was designed that binds to ß-lactoglobulin (ß-LG), a major allergen from cow's milk. For this work, a 23-nucleotide ssDNA aptamer ß-LG-23, capable of forming antiparallel G-quadruplexes was used, and its specificity and binding affinity of 22 ± 2 nM for ß-LG were evaluated via enzyme-linked apta-sorbent assay (ELASA). The ß-LG-23 aptamer was synthesized as an amphiphile by conjugating it to a C16 double tail via different spacers, and the effect of the spacers on the binding affinity and secondary structure of the aptamer was investigated. From all amphiphiles tested, direct conjugation of the aptamer to the tail gave the lowest binding affinity to ß-LG (37 ± 2 nM), while maintaining the antiparallel G-quadruplex secondary structure of the aptamer. As a proof of concept, the ß-LG-23 aptamer-amphiphile was used to decorate the interface of a liquid crystal (LC) and effectively detected 10 nM or 0.18 ppm of ß-LG with a 20 min equilibration time, thus demonstrating that it has the potential to be used for fast and label-free detection of ß-LG.

ssDNA-amphiphile architecture used to control dimensions of DNA nanotubes.

Controlling the dimensions of DNA nanotubes is of great interest as they can be used in different applications ranging from functional elements in nanodevices to carriers for drug delivery. ssDNA-amphiphiles composed of a ssDNA headgroup, a hydrophobic dialkyl tail and a polycarbon spacer between the tail and the headgroup, self-assemble into hollow DNA nanotubes by forming bilayer nanotapes that transition from twisted nanotapes, to helical nanotapes, to nanotubes. The presence of the DNA nanotubes is verified via cryo-TEM and SAXS. We further explore the effect of the ssDNA secondary structure and tail length on the assembly of the ssDNA-amphiphiles. We demonstrate that the presence of intermolecular G-quadruplexes in the ssDNA sequence dictates the nanotube length. The nanotube diameter is controlled by the hydrophobic tail length, and coarse-grained molecular dynamics simulations are employed to elucidate the tail design impact on assembly.

[Single Center Analysis of Pathogenic Characteristics of Lung Candida Infection and Other Pathogenic Bacteria Infection in the Patients with Hemotological Maliglancies in the Tropical Region of Hainan].

OBJECTIVE: To analyze the infection characteristics of sputum and venous blood pathogen in the patients with hematological malignancies and respiratory symptom in the Hematology Department in tropical region and to investigate its drug-resistance so as to provide etiological evidence for clinical treatment. METHODS: The pathogens and their drug-resistance of 2466 samples in the patients with hematological malignancies and respiratory symptom in the Department were analyzed retrospectively from January 2013 to November 2017. The samples were collected from sputum and venous blood. RESULTS: The sputum sample culture in patients with hematologic diseases showed that 224 strains were isolated, out of them 98 strains (43.75%) were fungi mainly candida albicans (41 strains); and then 88 Gram-negative strains (39.28%), among them the main pathogenic bacteria were Escherichia coli(22 strains) and klebsiella Klebsiella pneumoniae(12 strains); and then 38 Gram-positive strains (16.96%), among them the main pathogeni-bacteria were Enteroccocus (14 strains) and Gram-positive bacilli (14 strains). The blood samples culture of patients with hematologic diseases showed that 61 strains were isolated, out of them the isolated rate of Gram-positive bactetia was higherst, which accounted for 55.74%(34/61), mainly including staphylococcus lominis (19 strains); and the isolated rate of Gram-negative bacteria was 44.26% (27/61), among them main pathogenic bacteria was Klebsiella pneumoniae (12 strains). The resistance test of pathogenic bacteria to drugs showed that the resistant rate of Gram-negative bacteria to tigecycline, imipenem and atl-962 duenner was lowest, while the Gram-positive pathogenic bacteria such as Enterococcus, Gram-positive bacilli and Staphylococcus aureus were sensitive to vancomycin, tigecycline and linezolid was high. CONCLUSION: the patients in hematology department are infected easily in the hospital in tropical region. The main pathogens are fungal strains in the respiratory tract of patients with hematological malignancy according to the sputum culture results. The clinician in tropical regions should choose suitable antibiotics for anti-infective therapy, which is different from the situation in North China or other northern areas.