Structural and Biochemical Features of OXA-517: a Carbapenem and Expanded-Spectrum Cephalosporin Hydrolyzing OXA-48 Variant.

OXA-48-producing Enterobacterales have now widely disseminated throughout the world. Several variants have now been reported, differing by just a few amino-acid substitutions or deletions, mostly in the region of the loop ß5-ß6. As OXA-48 hydrolyzes carbapenems but lacks significant expanded-spectrum cephalosporin (ESC) hydrolytic activity, ESCs were suggested as a therapeutic option. Here, we have characterized OXA-517, a natural variant of OXA-48- with an Arg214Lys substitution and a deletion of Ile215 and Glu216 in the ß5-ß6 loop, capable of hydrolyzing at the same time ESC and carbapenems. MICs values of E. coli expressing blaOXA-517 gene revealed reduced susceptibility to carbapenems (similarly to OXA-48) and resistance to ESCs. Steady-state kinetic parameters revealed high catalytic efficiencies for ESCs and carbapenems. The blaOXA-517 gene was located on a ca. 31-kb plasmid identical to the prototypical IncL blaOXA-48-carrying plasmid except for an IS1R-mediated deletion of 30.7-kb in the tra operon. The crystal structure of OXA-517, determined to 1.86 Å resolution, revealed an expanded active site compared to that of OXA-48, which allows for accommodation of the bulky ceftazidime substrate. Our work illustrates the remarkable propensity of OXA-48-like carbapenemases to evolve through mutation/deletion in the ß5-ß6 loop to extend its hydrolysis profile to encompass most ß-lactam substrates.

Clinical Course and Outcome of Community-Acquired Bacterial Meningitis in Cancer Patients.

The aim of the study was to determine the course and outcome of bacterial meningitis (BM) in patients with cancer. We retrospectively reviewed files of patients with community-acquired BM, hospitalized in a single neuroinfection center between January 2010 and December 2017. There were 209 patients included in the analysis: 28 had cancer (9 women, 19 men; median age 76, IQR 67-80 years) and 181 were cancer-free (76 women, 105 men; median age 52, IQR 33-65 years) and constituted the control group. Cancer patients, compared with controls, were more likely to present with seizures (25% vs. 8%, p = 0.019), scored higher on the Sequential Organ Failure Assessment, and had a higher mortality rate (32% vs. 13%, p = 0.025). Further, cancer patients were less likely (64% vs. 83%, p = 0.033) to present with two or more out of four clinical manifestations of BM (pyrexia, neck stiffness, altered mental status, and headache) and had a lower white blood cell (WBC) count than non-cancer controls. In multiple regression analysis, the presence of bacterial meningitis in cancer patients was independently associated only with older age (p = 0.001) and lower WBC count (p = 0.007), while mortality was associated with lower Glasgow Coma Score (p = 0.003). In conclusion, bacterial meningitis in cancer patients is characterized by atypical symptoms and high mortality, which requires physicians' vigilance and a prompt investigation of cerebrospinal fluid in suspected cases. However, multiple regression analysis suggests that differences in clinical presentation and outcomes of bacterial meningitis between cancer and cancer-free patients may also be attributable to other factors, such as age differences.

Chronic alcohol abuse affects the clinical course and outcome of community-acquired bacterial meningitis.

The aim of the study was to determine the effect of chronic alcohol abuse on the course and outcome of bacterial meningitis (BM). We analyzed records of patients with BM who were hospitalized between January 2010 and December 2017 in the largest neuroinfection center in Poland. Out of 340 analyzed patients, 45 (13.2%) were alcoholics. Compared with non-alcoholics, alcoholics were more likely to present with seizures (p < 0.001), scored higher on the Sequential Organ Failure Assessment (SOFA) (p = 0.002) and lower on the Glasgow Coma Scale (GCS) (p < 0.001), and had worse outcome as measured by the Glasgow Outcome Score (GOS) (p < 0.001). Furthermore, alcoholics were less likely to complain of headache (p < 0.001) and nausea/vomiting (p = 0.005) and had lower concentration of glucose in cerebrospinal fluid (CSF) (p = 0.025). In the multiple logistic regression analysis, alcoholism was associated with lower GCS (p = 0.036), presence of seizures (p = 0.041), male gender (p = 0.042), and absence of nausea/vomiting (p = 0.040). Furthermore, alcoholism (p = 0.031), lower GCS score (p = 0.001), and higher blood urea concentration (p = 0.018) were independently associated with worse outcome measured by GOS. Compared with non-alcoholics, chronic alcohol abusers are more likely to present with seizures, altered mental status, and higher SOFA score and have an increased risk of unfavorable outcome. In multivariate analysis, seizures and low GCS were independently associated with alcoholism, while alcoholism was independently associated with worse outcome.

A close look onto structural models and primary ligands of metallo-ß-lactamases.

ß-Lactamases are hydrolytic enzymes capable of opening the ß-lactam ring of antibiotics such as penicillin, thus endowing the bacteria that produce them with antibiotic resistance. Of particular medical concern are metallo-ß-lactamases (MBLs), with an active site built around coordinated Zn cations. MBLs are pan-reactive enzymes that can break down almost all classes of ß-lactams, including such last-resort antibiotics as carbapenems. They are not only broad-spectrum-reactive but are often plasmid-borne (e.g., the New Delhi enzyme, NDM), and can spread horizontally even among unrelated bacteria. Acquired MBLs are encoded by mobile genetic elements, which often include other resistance genes, making the microbiological situation particularly alarming. There is an urgent need to develop MBL inhibitors in order to rescue our antibiotic armory. A number of such efforts have been undertaken, most notably using the 3D structures of various MBLs as drug-design targets. Structure-guided drug discovery depends on the quality of the structures that are collected in the Protein Data Bank (PDB) and on the consistency of the information in dedicated ß-lactamase databases. We conducted a careful review of the crystal structures of class B ß-lactamases, concluding that the quality of these structures varies widely, especially in the regions where small molecules interact with the macromolecules. In a number of examples the interpretation of the bound ligands (e.g., inhibitors, substrate/product analogs) is doubtful or even incorrect, and it appears that in some cases the modeling of ligands was not supported by electron density. For ten MBL structures, alternative interpretations of the original diffraction data could be proposed and the new models have been deposited in the PDB. In four cases, these models, prepared jointly with the authors of the original depositions, superseded the previous deposits. This review emphasizes the importance of critical assessment of structural models describing key drug design targets at the level of the raw experimental data. Since the structures reviewed here are the basis for ongoing design of new MBL inhibitors, it is important to identify and correct the problems with ambiguous crystallographic interpretations, thus enhancing reproducibility in this highly medically relevant area.

Usefulness of SOFA score and artesunate - based treatment in severe malaria ­ a single center study

INTRODUCTION: This study was conducted to assess the usefulness of the guidelines of treatment recommended in Malaria diagnosis and treatment guideline published by University College London Hospitals-NHS Foundation Trust on 26th June 2013, usefulness of artesunate-based therapy and usefulness of SOFA (sepsis-related organ failure assessment) score in treatment of severe malaria. Severe malaria is usually caused by Plasmodium falciparum and most of the time fulfills the criteria of sepsis which are specified in the new definition of sepsis. The other malaria species are commonly considered to be the cause of mild course of malaria, however more and more cases of severe malaria are reported in the course of tertian fever malaria caused by Plasmodium vivax and in the disease caused by Plasmodium knowlesi. MATERIALS AND METHODS: Fourteen patients with malaria were hospitalized in the Department of Adults' Infectious Diseases and in the Intensive Care Unit of the Hospital for Infectious Diseases in Warsaw between December 2013 and April 2017. All patients were treated according to Malaria diagnosis and treatment guideline UCLH. RESULTS: Thirteen patients in our study fulfilled the criteria of severe malaria. All fourteen patients presented with a SOFA score ≥2 points. Intravenous artesunate was administered to all patients in doses recommended in the UCLH guidelines. All patients presented with thrombocytopenia and elevated level of D-Dimers. The main factor influencing the dynamics of SOFA score was thrombocytopenia. All the patients fully recovered without any complications. CONCLUSIONS: The malaria treatment guidelines used in the Department for Infectious Diseases in Adults and in the Intensive Care Unit of the Hospital for Infectious Diseases in Warsaw in years 2013-2017 are effective. In assessing the severity of malaria SOFA score is useful especially as a warning of possibility of a severe course of the disease.

Prior knowledge or freedom of interpretation? A critical look at a recently published classification of "novel" Zn binding sites.

In a recently published article (Yao, Flight, Rouchka, and Moseley, Proteins 2015;83:1470-1487) the authors proposed novel Zn coordination patterns in protein structures, apparently discovered using an unprejudiced approach to the information collected in the Protein data Bank (PDB), which they advocated as superior to the prior-knowledge-informed paradigm. In our assessment of those propositions we demonstrate here that most, if not all, of the "new" coordination geometries are fictitious, as they are based on incorrectly interpreted protein crystal structures, which in themselves are often not error-free. The flaws of interpretation include partial or wrong Zn sites, missed or wrong ligands, ignored crystal symmetry and ligands, etc. In conclusion, we warn against using this and similar meta-analyses that ignore chemical and crystallographic knowledge, and emphasize the importance of safeguarding structural databases against bad apples. Proteins 2016; 84:770-776. © 2016 Wiley Periodicals, Inc.

Structure of a complete four-domain chitinase from Moritella marina, a marine psychrophilic bacterium.

X-ray crystallography reveals chitinase from the psychrophilic bacterium Moritella marina to be an elongated molecule which in addition to the catalytic ß/α-barrel domain contains two Ig-like domains and a chitin-binding domain, all linked in a chain. A ligand-binding study using NAG oligomers showed the enzyme to be active in the crystal lattice and resulted in complexes of the protein with oxazolinium ion (the reaction intermediate) and with NAG2, a reaction product. The characteristic motif DXDXE, containing three acidic amino-acid residues, which is a signature of type 18 chitinases, is conserved in the enzyme. Further analysis of the unliganded enzyme with the two protein-ligand complexes and a comparison with other known chitinases elucidated the roles of other conserved residues near the active site. Several features have been identified that are probably important for the reaction mechanism, substrate binding and the efficiency of the enzyme at low temperatures. The chitin-binding domain and the tryptophan patch on the catalytic domain provide general affinity for chitin, in addition to the affinity of the binding site; the two Ig-like domains give the protein a long reach over the chitin surface, and the flexible region between the chitin-binding domain and the adjacent Ig-like domain suggests an ability of the enzyme to probe the surface of the substrate, while the open shallow substrate-binding groove allows easy access to the active site.

Crystallographic analysis of a thermoactive nitrilase.

The nitrilase superfamily is a large and diverse superfamily of enzymes that catalyse the cleavage of various types of carbon-nitrogen bonds using a Cys-Glu-Lys catalytic triad. Thermoactive nitrilase from Pyrococcus abyssi (PaNit) hydrolyses small aliphatic nitriles like fumaro- and malononitryl. Yet, the biological role of this enzyme is unknown. We have analysed several crystal structures of PaNit: without ligands, with an acetate ion bound in the active site and with a bromide ion in the active site. In addition, docking calculations have been performed for fumaro- and malononitriles. The structures provide a proof for specific binding of the carboxylate ion and a general affinity for negatively changed ligands. The role of residues in the active site is considered and an enzymatic reaction mechanism is proposed in which Cys146 acts as the nucleophile, Glu42 as the general base, Lys113/Glu42 as the general acid, WatA as the hydrolytic water and Nζ_Lys113 and N_Phe147 form the oxyanion hole.

Flexible loops of New Delhi metallo-ß-lactamase modulate its activity towards different substrates.

Two accessory loop regions that are present in numerous variants of New Delhi metallo-ß-lactamases (NDM) are important for the enzymatic activity. The first one is a flexible loop L3 that is located near the active site and is thought to play an important role in the catalytic process. The second region, Ω loop is located close to a structural element that coordinates two essential zinc ions. Both loops are not involved in any specific interactions with a substrate. Herein, we investigated how the length and hydrophobicity of loop L3 influence the enzymatic activity of NDMs, by analyzing mutants of NDM-1 with various deletions/point mutations within the L3 loop. We also investigated NDM variants with sequence variations/artificial deletions within the Ω loop. For all these variants we determined kinetic parameters for the hydrolysis of ampicillin, imipenem, and a chromogenic cephalosporin (CENTA). None of the mutations in the L3 loop completely abolished the enzymatic activity of NDM-1. Our results suggest that various elements of the loop play different roles in the hydrolysis of different substrates and the flexibility of the loop seems necessary to fulfill the requirements imposed by various substrates. Deletions within the Ω loop usually enhanced the enzymatic activity, particularly for the hydrolysis of ampicillin and imipenem. However, the exact role of the Ω loop in the catalytic reaction remains unclear. In our kinetic tests, the NDM enzymes were inhibited in the ß-lactamase reaction by the CENTA substrate. We also present the X-ray crystal structures of the NDM-1, NDM-9 and NDM-12 proteins.

Advanced age and increased CRP concentration are independent risk factors associated with Clostridioides difficile infection mortality.

Clostridioides difficile (C.difficile) is a Gram-positive, spore-forming, toxin-producing anaerobic bacillus, which is one of the most common causes of health-care-associated infection developed mainly by elderly patients. The objective of this study was to assess mortality among the patients of the Hospital for Infectious Diseases in Warsaw related to C.difficile infection. Analysis was conducted of 1638 records reporting the medical histories of patients hospitalized for the first time due to Clostridioides difficile infection (CDI) in the Hospital for Infectious Diseases in Warsaw from 2010 to 2017. The inclusion criteria were any (principal or secondary) discharge diagnosis code for CDI according to ICD-10 and being an adult (≥ 18 years). 108 out of 1638 (7%) of the patients died. The median age in this group was 83 years. The largest number of deaths (90%) occurred in the group of patients aged 65 years or older and 81-90 years old (53% of all the deaths). In the multivariate logistic regression model relevant only to the age groups, not to sepsis-age over 80 and over 90 were independent predictors of death, increasing the risk of death by 3.4 and 1.8 times, respectively. The result of the receiver operating curve (ROC) analysis determined the age of 77 years as the threshold value, indicating the increased risk of death (AUC 0.727, standard error 0.025, 95% CI 0.678-0.776, p < 0.0001). In addition, other quantitative variables, namely CRP, creatinine and leucocytes were studied and turned out to be independent death predictors as well. The diagnosis of sepsis increased the risk of death fourfold (OR = 4.042; 95% Cl 2.4-6.7; p < 0.001). Increased inflammatory parameters, namely CRP and white blood cell count, advanced age, particularly over the age of 80, as well as a diagnosis of sepsis are independent risk factors for death and could be used as predictive markers of poor outcome in CDI.

Structural Insight into DNA-Dependent Activation of Human Metalloprotease Spartan.

The DNA-dependent metalloprotease Spartan (SPRTN) cleaves DNA-protein crosslinks (DPCs) and protects cells from DPC-induced genome instability. Germline mutations of SPRTN are linked to human Ruijs-Aalfs syndrome (RJALS) characterized by progeria and early-onset hepatocellular carcinoma. The mechanism of DNA-mediated activation of SPRTN is not understood. Here, we report the crystal structure of the human SPRTN SprT domain bound to single-stranded DNA (ssDNA). Our structure reveals a Zn2+-binding sub-domain (ZBD) in SprT that shields its active site located in the metalloprotease sub-domain (MPD). The narrow catalytic groove between MPD and ZBD only permits cleavage of flexible substrates. The ZBD contains an ssDNA-binding site, with a DNA-base-binding pocket formed by aromatic residues. Mutations of ssDNA-binding residues diminish the protease activity of SPRTN. We propose that the ZBD contributes to the ssDNA specificity of SPRTN, restricts the access of globular substrates, and positions DPCs, which may need to be partially unfolded, for optimal cleavage.

The clinical course and outcome of Listeria monocytogenes meningitis: A retrospective single center study.

BACKGROUND: The aim of the study was to determine clinical manifestations and outcome of Listeria monocytogenes meningitis (LM) and to compare with other forms of bacterial meningitis (BM). MATERIAL AND METHODS: We analyzed records of all adult patients with BM who were hospitalized between January 2010 and December 2017 in the largest neuroinfection center in Poland. RESULTS: Out of 343 analyzed patients with BM 24 were diagnosed to have LM. Patients with LM were older compared to patients with other forms of BM (62 years vs. 57 years, p=0.039), were more likely to have cancer (16.7% vs. 4.7%, p=0.045), receive immunosuppressive treatment (45.8% vs. 10.7%, p<0.001), or be immunocompromised in any way (62.5% vs. 35.5%, p=0.016). Blood tests showed lower WBC (10.7 × 103 cells/µl vs. 15.5 × 103 cells/µl, p=0.004), C-reactive protein (150 mg/L vs. 221 mg/L, p=0,019) and procalcitonin (1.27 ng/mL vs. 3.78 ng/mL, p=0.003) in LM group. Analysis of cerebrospinal fluid showed lower cell count (531.5 cells/µL vs. 1100 cells/µL, p<0.001) and lower chloride (113 mmol/L vs. 117 mmol/L, p=0.036) in patients with LM. In the multiple logistic regression analysis, immunosuppressive therapy was the only variable independently associated with LM (OR:8.72, CI 95%:1.41-64.34, p=0.024). CONCLUSIONS: LM is associated with older age, cancer and immunosuppressive therapy. However, in multivariate analysis only immunosuppressive therapy turned out to be an independent risk factor for LM.

The crystal and solution studies of glucosamine-6-phosphate synthase from Candida albicans.

Glucosamine 6-phosphate (GlcN-6-P) synthase is an ubiquitous enzyme that catalyses the first committed step in the reaction pathway that leads to formation of uridine 5'-diphospho-N-acetyl-D-glucosamine (UDP-GlcNAc), a precursor of macromolecules that contain amino sugars. Despite sequence similarities, the enzyme in eukaryotes is tetrameric, whereas in prokaryotes it is a dimer. The activity of eukaryotic GlcN-6-P synthase (known as Gfa1p) is regulated by feedback inhibition by UDP-GlcNAc, the end product of the reaction pathway, whereas in prokaryotes the GlcN-6-P synthase (known as GlmS) is not regulated at the post-translational level. In bacteria and fungi the enzyme is essential for cell wall synthesis. In human the enzyme is a mediator of insulin resistance. For these reasons, Gfa1p is a target in anti-fungal chemotherapy and in therapeutics for type-2 diabetes. The crystal structure of the Gfa1p isomerase domain from Candida albicans has been analysed in complex with the allosteric inhibitor UDP-GlcNAc and in the presence of glucose 6-phosphate, fructose 6-phosphate and an analogue of the reaction intermediate, 2-amino-2-deoxy-d-mannitol 6-phosphate (ADMP). A solution structure of the native Gfa1p has been deduced using small-angle X-ray scattering (SAXS). The tetrameric Gfa1p can be described as a dimer of dimers, with each half similar to the related enzyme from Escherichia coli. The core of the protein consists of the isomerase domains. UDP-GlcNAc binds, together with a metal cation, in a well-defined pocket on the surface of the isomerase domain. The residues responsible for tetramerisation and for binding UDP-GlcNAc are conserved only among eukaryotic sequences. Comparison with the previously studied GlmS from E. coli reveals differences as well as similarities in the isomerase active site. This study of Gfa1p focuses on the features that distinguish it from the prokaryotic homologue in terms of quaternary structure, control of the enzymatic activity and details of the isomerase active site.

A novel approach to genome-wide association analysis identifies genetic associations with primary biliary cholangitis and primary sclerosing cholangitis in Polish patients.

BACKGROUND: Primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are forms of hepatic autoimmunity, and risk for both diseases has a strong genetic component. This study aimed to define the genetic architecture of PBC and PSC within the Polish population. METHODS: Subjects were 443 women with PBC, 120 patients with PSC, and 934 healthy controls recruited from Gastroenterology Departments in various Polish hospitals. Allelotyping employed a pooled-DNA sample-based genome-wide association study (GWAS) approach, using Illumina Human Omni2.5-Exome BeadChips and the following novel selection criteria for risk loci: blocks of at least 10 single nucleotide polymorphisms (SNPs) in strong linkage disequilibrium, where the distance between each adjacent SNP pair in the block was less than 30 kb, and each SNP was associated with disease at a significance level of P < 0.005. A selected index SNP from each block was validated using TaqMan SNP genotyping assays. RESULTS: Nineteen and twenty-one SNPs were verified as associated with PBC and PSC, respectively, by individual genotyping; 19 (10/9, PBC/PSC) SNPs reached a stringent (corrected) significance threshold and a further 21 (9/12, PBC/PSC) reached a nominal level of significance (P < 0.05 with odds ratio (OR) > 1.2 or < 0.83), providing suggestive evidence of association. The SNPs mapped to seven (1p31.3, 3q13, 6p21, 7q32.1, 11q23.3, 17q12, 19q13.33) and one (6p21) chromosome region previously associated with PBC and PSC, respectively. The SNP, rs35730843, mapping to the POLR2G gene promoter (P = 1.2 × 10-5, OR = 0.39) demonstrated the highest effect size, and was protective for PBC, whereas for PSC respective SNPs were: rs13191240 in the intron of ADGRB3 gene (P = 0.0095, OR = 0.2) and rs3822659 (P = 0.0051, OR = 0.236) along with rs9686714 (P = 0.00077, OR = 0.2), both located in the WWC1 gene. CONCLUSIONS: Our cost-effective GWAS approach followed by individual genotyping confirmed several previously identified associations and discovered new susceptibility loci associated with PBC and/or PSC in Polish patients. However, further functional studies are warranted to understand the roles of these newly identified variants in the development of the two disorders.

Primary biliary cirrhosis in the era of liver transplantation.

Primary biliary cirrhosis (PBC) is an autoimmune disease of the liver, characterized by the presence of antimitochondrial antibodies (AMA) and progressive immune-mediated destruction of biliary ductules, which lead to cirrhosis. Theories of the PBC etiopathogenesis assume that the disease develops secondarily as an improper immunological reaction to undefined environmental and/or infectious factors in genetically predisposed individuals. Ursodeoxycholic acid (UDCA) is the only drug recommended to treat PBC; it delays the progression of liver disease, but remains only a symptomatic treatment. In the advanced stage of PBC, the treatment of choice is liver transplantation (LTx). Nowadays, PBC is the third indication for LTx, after viral-related and alcoholic liver cirrhosis. Unfortunately, PBC recurs in 21-37% of patients at 10 years after LTx, and in 43% at 15 years after LTx, with the median time to recurrence of 3-5.5 years. Diagnosis of recurrent PBC (rPBC) is based on the liver histopathology. Although various risk factors of rPBC have been investigated, the cause of the recurrence is not clear. There is no specific treatment of rPBC. Together with immunosuppression after LTx, UDCA remains the treatment of choice. New diagnostic technologies (e.g., genomics, proteomics, cell-based therapy, and clinical study of the rPBC patients) may be helpful in understanding the pathogenesis of PBC and the development of new treatment modalities.

Atypical presentation of invasive pulmonary aspergillosis in a liver transplant recipient.

BACKGROUND: Invasive pulmonary aspergillosis (IPA) occurs in 1% to 8% of liver transplant recipients. It is one of the most frequent life-threatening fungal infections in immunocompromised patients, with a reported mortality rate of approximately 60%. CASE REPORT: We present the case of an 18-year-old man who underwent liver transplantation (LT) in January 2004 due to multifocal hepatoblastoma (HBL) and was diagnosed with IPA 3 years after LT. Because of a single pulmonary nodule of the left lung found in chest computed tomography (CT) 4 weeks after LT, the patient received adjuvant chemotherapy. A control chest CT performed in September 2004 did not reveal any pathological changes. A subsequent examination in May 2006 demonstrated a pulmonary lesion situated in the 10th segment of the left lung, which was confirmed by PET in October 2006. In March 2007 the patient underwent videothoracoscopic complete resection of the lesion. Histopathological examination revealed IPA and subsequent 3-month antifungal treatment with voriconazole resulted in 5 years of recurrence-free survival. CONCLUSIONS: We conclude that any stable solitary pulmonary lesion in a transplant recipient needs to be resected in order to allow a definitive diagnosis and prevent disease dissemination such as IPA in our patient.