Revealing the Interaction Mechanism between Mycobacterium tuberculosis GyrB and Novobiocin, SPR719 through Binding Thermodynamics and Dissociation Kinetics Analysis.

With the rapid emergence of drug-resistant strains of Mycobacterium tuberculosis (Mtb), various levels of resistance against existing anti-tuberculosis (TB) drugs have developed. Consequently, the identification of new anti-TB targets and drugs is critically urgent. DNA gyrase subunit B (GyrB) has been identified as a potential anti-TB target, with novobiocin and SPR719 proposed as inhibitors targeting GyrB. Therefore, elucidating the molecular interactions between GyrB and its inhibitors is crucial for the discovery and design of efficient GyrB inhibitors for combating multidrug-resistant TB. In this study, we revealed the detailed binding mechanisms and dissociation processes of the representative inhibitors, novobiocin and SPR719, with GyrB using classical molecular dynamics (MD) simulations, tau-random acceleration molecular dynamics (τ-RAMD) simulations, and steered molecular dynamics (SMD) simulations. Our simulation results demonstrate that both electrostatic and van der Waals interactions contribute favorably to the inhibitors' binding to GyrB, with Asn52, Asp79, Arg82, Lys108, Tyr114, and Arg141 being key residues for the inhibitors' attachment to GyrB. The τ-RAMD simulations indicate that the inhibitors primarily dissociate from the ATP channel. The SMD simulation results reveal that both inhibitors follow a similar dissociation mechanism, requiring the overcoming of hydrophobic interactions and hydrogen bonding interactions formed with the ATP active site. The binding and dissociation mechanisms of GyrB with inhibitors novobiocin and SPR719 obtained in our work will provide new insights for the development of promising GyrB inhibitors.

A metabolomics perspective on clorobiocin biosynthesis: discovery of bromobiocin and novel derivatives through LC-MSE-based molecular networking.

Clorobiocin is a well-known, highly effective inhibitor of DNA gyrase belonging to the aminocoumarin antibiotics. To identify potentially novel derivatives of this natural product, we conducted an untargeted investigation of clorobiocin biosynthesis in the known producer Streptomyces roseochromogenes DS 12.976 using LC-MSE, molecular networking, and analysis of fragmentation spectra. Previously undescribed clorobiocin derivatives uncovered in this study include bromobiocin, a variant halogenated with bromine instead of chlorine, hydroxylated clorobiocin, carrying an additional hydroxyl group on its 5-methyl-pyrrole 2-carboxyl moiety, and two other derivatives with modifications on their 3-dimethylallyl 4-hydroxybenzoate moieties. Furthermore, we identified several compounds not previously considered clorobiocin pathway products, which provide new insights into the clorobiocin biosynthetic pathway. By supplementing the medium with different concentrations of potassium bromide, we confirmed that the clorobiocin halogenase can utilize bromine instead of chlorine. The reaction, however, is impeded such that non-halogenated clorobiocin derivatives accumulate. Preliminary assays indicate that the antibacterial activity of bromobioin against Bacillus subtilis and efflux-impaired Escherichia coli matches that of clorobiocin. Our findings emphasize that yet unexplored compounds can be discovered from established strains and biosynthetic gene clusters by means of metabolomics analysis and highlight the utility of LC-MSE-based methods to contribute to unraveling natural product biosynthetic pathways. IMPORTANCE: The aminocoumarin clorobiocin is a well-known gyrase inhibitor produced by the gram-positive bacterium Streptomyces roseochromogenes DS 12.976. To gain a deeper understanding of the biosynthetic pathway of this complex composite of three chemically distinct entities and the product spectrum, we chose a metabolite-centric approach. Employing high-resolution LC-MSE analysis, we investigated the pathway products in extracted culture supernatants of the natural producer. Novel pathway products were identified that expand our understanding of three aspects of the biosynthetic pathway, namely the modification of the noviose, transfer and methylation of the pyrrole 2-carboxyl moiety, and halogenation. For the first time, brominated products were detected. Their levels and the levels of non-halogenated products increased in medium supplemented with KBr. Based on the presented data, we propose that the enzyme promiscuity contributes to a broad product spectrum.

In Vitro Evaluation of Anti-Parasitic Activities of Quinolone-Coumarin Hybrids Derived from Fluoroquinolones and Novobiocin Against Toxoplasma gondii.

PURPOSE: Toxoplasmosis is caused by the parasite Toxoplasma gondii (T. gondii). In immunocompetent individuals, the infection is often asymptomatic; however, in expectant mothers and those with immune system deficiencies, complications may arise. Consequently, there is a need for new drugs that cause minimal damage to host cells. The purpose of this study was to investigate the in vitro antiparasitic efficacy of quinolone-coumarin hybrids QC1-QC12, derived from quinolone antibacterials and novobiocin, against T. gondii. METHODS: The derivatives were compared with novobiocin and ciprofloxacin during testing, with pyrimethamine used as a positive control. We conducted the MTT assay to examine the anti-toxoplasmic effects of the test compounds and novobiocin. Evaluation included the infection and proliferation indices, as well as the size and number of plaques, based on the viability of both healthy and infected cells. RESULTS: The in vitro assays revealed that QC1, QC3, QC6, and novobiocin, with selectivity indices (SIs) of 7.27, 13.43, and 8.23, respectively, had the least toxic effect on healthy cells and the highest effect on infected cells compared to pyrimethamine (SI = 3.05). Compared to pyrimethamine, QC1, QC3, QC6, and novobiocin Without having a significant effect on cell viability, demonstrated a significant effect on reducing in both infection index and proliferation index, in addition to reducing the quantity and dimensions of plaques ( P < 0.05). CONCLUSION: Based on our results, QC1, QC3, QC6, and novobiocin due to their significant therapeutic effects could be considered as potential new leads in the development of novel anti-Toxoplasma agents.

Influence of novobiocin on gama-irradiation G0-lymphocytes as analyzed by cytogenetic endpoints

Experiments with novobiocin (NB) post-treatment were performed to verify its effect on the frequencies of micronuclei (MN) and chromosomal aberrations (CA) induced by g-irradiation (0.75, 1.5 and 3.0 Gy) in human lymphocytes at G0-phase. The frequencies of MN significantly decreased by 44 and 50 per cent, for the treatment with NB 50 µg/ml (30-min pulse) after radiation doses of 1.5 and 3.0 Gy, respectively. However, CA frequencies were not significantly affected. No significant effect on CA was observed when lymphocyte cultures were exposed to a single dose of 2.0 Gy at the G0-phase and posttreated with 25 µg/ml NB for three hours either immediately after irradiation (G0-phase) or after 24 h (S-phase). The significant suppressive effect of NB on MN frequencies supports the hypothesis that NB interaction with chromatin increases access to DNA repair enzymes.

Identificaçäo presuntiva de Staphylococcus saprophyticus através de método automatizado / Presumptive identification of Staphylococcus saprophyticus using an automated method

Os autores propöem novo método automatizado para verificaçäo do comportamento de estafilococos coagulase negativa à novobiocina, através do sistema MS-2 (Abbott Laboratories, Diagnostics Div., Irving, Texas). A nova técnica automatizada possibilita o teste de um maior número de espécimes em um tempo médio de 99 minutos, apresentando 100% de concordância com o método tradicional de cultura

Aislamiento de Staphylococcus xylosus, asociado con vulvo-vaginitis pediatrica / Isolation of Staphylococcus xylosus associated with pediatric vulvovaginitis

A traves de procedimientos bacteriologicos sencillos pero conlcuyentes, se aisla el 13-07-1994 estaphylococcus excylosus en un proceso cronico de vulvo-vaginitis (muestra 442/1994) siendo la base de este procedimiento el esquema propuesto por Kloos y Schleifer. El antibiograma (KIRBI-BAUER) demostro sensibilidad a Rifampicina, Cefradina, Ciprofloxacina, Gentamicina, Oxacilina y resistencia a la ampicilina, lincomicina y eritromicina, en concordancia con otros resultados internacionales previos. Es pertinente desarrollar este tipo de pruebas en Bolivia para delimitar el espectro epidemiologicos de este y otros ESTAPHYLOCOCCUS COAGULASA NEGATIVOS (CNS)

Contaminación bacteriana y presencia de Sinorhizobium meliloti en aguas de los canales de riego del río Neuquén / Bacterial contamination and presence of Sinorhizobium meliloti in irrigation canal water from the NeuquUn River

A survey of the changes in populations of heterotrophic bacteria, coliform microorganisms and S. meliloti was conducted in samples taken from the water irrigation channels of the NeuquUn River (Argentina). Fifty-six water samples were collected during the spring-summer seasons of 1997-1999 years. Both the heterotrophic plate count bacterial and the number of coliforms oscillated between 110-5050 CFU/ml and 8-1400 CFU/100 ml, respectively, during the period this study was carried out. Fecal coliforms were detected in 91.1 of the water samples investigated. Moreover, the results showed that S. meliloti capable of nodulating alfalfa (Medicago sativa L.) Cuf 101 were present in 68 of the water samples and in effectiveness studies, no isolate out of 25 evaluated could be classified as superior N fixers. That is, they did not produce plants equal in weight to nitrate-grown plants (KNO3 0.05). All the S. meliloti strains were resistant to novobiocin and bacitracin, while 72 of the microsymbionts demonstrated resistance to between seven and ten antibiotics. Results presented in this study showed that irrigation waters of the NeuquUn river could act as dispersal agents of both ineffective S. meliloti strains and thermotolerant coliform bacteria.(AU)

Infecciones por S. cohnii: A propósito de 7 casos / Staphylococcus chonii infection: Report of seven cases

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Susceptibilidad a antimicrobianos de cepas de estafilococos coagulasa positivos aisladas de mastitis bovina en la cuenca lechera central de la Argentina / Antimicrobial sensitivity of coagulase-positive staphylococcal strains isolated from bovine mastitis in the central dairy catchment area of Argentina

The activity of antimicrobial agents frequently used for treating bovine mastitis was determined against 101 coagulase-positive staphylococci isolated from bovine mammary secretion. The isolates were obtained from 39 dairy farms located in the central dairy area of Argentina. The disk diffusion method was used and the following antimicrobial agents were tested: penicillin, ampicillin, oxacillin, cephacetrile, penicillin + novobiocin, erythromycin, pirlimycin, novobiocin and neomycin. The highest levels of resistance were observed against penicillin and ampicillin (47.6), while the lowest against erythromycin (2), pirlimycin (4) and neomycin (2.9). No resistant strains against oxacillin, cephacetrile and penicillin + novobiocin were detected.(AU)

Significância etiológica e características de estafilococos coagulase-negativa isolados de processos infecciosos em recém-nascidos / Etiologic significance and characteristics of coagulase-negative staphylococci isolated from infectious among newborns

Os estafilococos coagulase-negativa (ECN), embora reconhecidos como saprófitas por muito tempo, têm emergido como agentes etiológicos de uma série de infecçöes, sendo atualmente os mais freqüentemente isolados em infecçöes hospitalares. Esses microrganismos apresentam elevado risco potencial de bacteremia nosocomial entre recém-nascidos com baixo peso ao nascimento, os quais geralmente säo imunologicamente imaturos e freqüentemente requerem procedimentos invasivos para a adminstraçäo de substâncias nutritivas e medicamentosas. O aumento da incidência de bacteremia nosocomial por ECN em neonatos nos últimos anos, tem sido também associado ao aumento da sobrevivência de crianças prematuras com peso ao nascimento menor que 1.500 g e à sua longa permanência no ambiente hospitalar. Contudo, como os ECN fazem parte da flora normal da pele, freqüentemente contaminam espécimes clínicos, sendo muitas vezes negligenciados por esse aspecto quanto à sua importância etiológica. Tendo em vista essas características, este estudo teve como objetivos avaliar a significância etiológica de estafilococos coagulase-negativa isolados de processos infecciosos em recém-nascidos da Unidade neonatal do Hospital das Clínicas da Faculdade de Medicina de Botucatu e a caracterizaçäo das linhagens quanto aos fatores de virulência e sensibilidade às drogas. As linhagens de ECN isoladas foram classificadas em significativas, suspeitas e contaminantes com base em uma série de dados clínicos e laboratoriais. Das 117 linhagens de ECN isoladas, 51 (43,6 por cento) foram classificadas como significativas, nove (7,7 por cento) como suspeitas e 57 (48,7 por cento) como contaminantes. Das 45 crianças com infecçäo por ECN, 37 (82,2 por cento) eram prematuras e 22 (48,9 por cento) com peso ao nascimento < 1500g. A maioria das crianças com infecçäo por ECN estavam submetidas a dois ou mais procedimentos invasivos (77,8 por cento), incluindo o uso de catéter (88,9 por cento), nutriçäo parenteral (66,7 por cento) e ventilaçäo mecânica (57,8 por cento). O Staphylococcus epidermidis foi a espécie mais frequentemente isolada (77,8 por cento) e mais associada com infecçäo (90,2 por cento) do que com contaminaçäo (68,4 por cento). Outras espécies de ECN, incluindo uma linhagem de S. haemolyticus, duas linhagens de S. lugdunensis, uma linhagem de S. simulans e uma linhagem de S. xylosis, também foram isoladas de crianças com evidência clínica de pneumonia, enterocolite necrosante ou sepse...