AKTIVITAS ANTIBAKTERI EKSTRAK KASAR SPONS Agelas clathrodes TERHADAP BAKTERI PATOGENIK IKAN Vibrio parahaemolyticus

Bakteri Vibrio parahaemolyticus adalah bakteri patogenik Gram negatif yang tersebar luas di lingkungan laut dan estuari di seluruh dunia. Pada ikan, strain V. parahaemoliticus patogenik menyebabkan vibrosis dengan dampak seperti kematian 100% pada larva maupun ikan-ikan budidaya ukuran konsumsi sedangkan pada manusia dapat menyebabkan gastroenteritis atau diare akut. Salah satu upaya untuk mengatasi masalah infeksi bakteri strain V. parahaemoliticus patogenik ini adalah antibiotik. Pada kanyataannya penggunaan antibiotik dapat meningkatkan kasus resistensi antibiotik. Krisis resistensi antibiotik telah memunculkan kesadaran menggunakan antibiotik dari bahan alami untuk mengobati penyakit ikan, hewan lainnya atau manusia salah satunya dari ekstrak spons A. clathordes. Itulah sebabnya, dalam penelitian ini aktivitas antibakteri spons A. clathordes akan diuji terhadap bakteri patogen ikan V. parahaemolythicus. Pengujian akan menggunakan media TSA yang dikultur dengan biakan V. parahaemolythicus. Kertas cakram ditempatkan pada media kemudian ditetesi dengan (ekstark 1.0, 10.0, 100.0 mg/mL; tetrasiklin; methanol), setiap perlakuan dilakukan 3 kali ulangan. Hasil pengukuran zona hambat kemudian dievaluasi dengan mengkategorikan zona hambat sebagai berikut <9 mm (tidak aktif), 9-12 mm (kurang aktif), 13-18 mm (aktif) dan >18 mm (sangat aktif) dan ditabulasikan pada sebuah tabel. Hasil penelitian menunjukan aktivitas antibakteri A. clathrodes terhadap V. parahaemoliticus bertambah dengan naiknya konsentrasi. Meskipun zona hambat pada tiga konsentrasi masih lebih kecildibandingkan dengan zona hambat dari antibiotik pembanding, zona hambat ekstrak-ekstrak kasar itu tergolong sangat akti

Variations in TcdB Activity and the Hypervirulence of Emerging Strains of Clostridium difficile

Hypervirulent strains of Clostridium difficile have emerged over the past decade, increasing the morbidity and mortality of patients infected by this opportunistic pathogen. Recent work suggested the major C. difficile virulence factor, TcdB, from hypervirulent strains (TcdBHV) was more cytotoxic in vitro than TcdB from historical strains (TcdBHIST). The current study investigated the in vivo impact of altered TcdB tropism, and the underlying mechanism responsible for the differences in activity between the two forms of this toxin. A combination of protein sequence analyses, in vivo studies using a Danio rerio model system, and cell entry combined with fluorescence assays were used to define the critical differences between TcdBHV and TcdBHIST. Sequence analysis found that TcdB was the most variable protein expressed from the pathogenicity locus of C. difficile. In line with these sequence differences, the in vivo effects of TcdBHV were found to be substantially broader and more pronounced than those caused by TcdBHIST. The increased toxicity of TcdBHV was related to the toxin's ability to enter cells more rapidly and at an earlier stage in endocytosis than TcdBHIST. The underlying biochemical mechanism for more rapid cell entry was identified in experiments demonstrating that TcdBHV undergoes acid-induced conformational changes at a pH much higher than that of TcdBHIST. Such pH-related conformational changes are known to be the inciting step in membrane insertion and translocation for TcdB. These data provide insight into a critical change in TcdB activity that contributes to the emerging hypervirulence of C. difficile

Comparative genomic analysis of toxin-negative strains of Clostridium difficile from humans and animals with symptoms of gastrointestinal disease

Background: Clostridium difficile infections (CDI) are a significant health problem to humans and food animals. Clostridial toxins ToxA and ToxB encoded by genes tcdA and tcdB are located on a pathogenicity locus known as the PaLoc and are the major virulence factors of C. difficile. While toxin-negative strains of C. difficile are often isolated from faeces of animals and patients suffering from CDI, they are not considered to play a role in disease. Toxin-negative strains of C. difficile have been used successfully to treat recurring CDI but their propensity to acquire the PaLoc via lateral gene transfer and express clinically relevant levels of toxins has reinforced the need to characterise them genetically. In addition, further studies that examine the pathogenic potential of toxin-negative strains of C. difficile and the frequency by which toxin-negative strains may acquire the PaLoc are needed. Results: We undertook a comparative genomic analysis of five Australian toxin-negative isolates of C. difficile that lack tcdA, tcdB and both binary toxin genes cdtA and cdtB that were recovered from humans and farm animals with symptoms of gastrointestinal disease. Our analyses show that the five C. difficile isolates cluster closely with virulent toxigenic strains of C. difficile belonging to the same sequence type (ST) and have virulence gene profiles akin to those in toxigenic strains. Furthermore, phage acquisition appears to have played a key role in the evolution of C. difficile. Conclusions: Our results are consistent with the C. difficile global population structure comprising six clades each containing both toxin-positive and toxin-negative strains. Our data also suggests that toxin-negative strains of C. difficile encode a repertoire of putative virulence factors that are similar to those found in toxigenic strains of C. difficile, raising the possibility that acquisition of PaLoc by toxin-negative strains poses a threat to human health. Studies in appropriate animal models are needed to examine the pathogenic potential of toxin-negative strains of C. difficile and to determine the frequency by which toxin-negative strains may acquire the PaLoc

WSES guidelines for management of Clostridium difficile infection in surgical patients

In the last two decades there have been dramatic changes in the epidemiology of Clostridium difficile infection (CDI), with increases in incidence and severity of disease in many countries worldwide. The incidence of CDI has also increased in surgical patients. Optimization of management of C difficile, has therefore become increasingly urgent. An international multidisciplinary panel of experts prepared evidenced-based World Society of Emergency Surgery (WSES) guidelines for management of CDI in surgical patients.Peer reviewe

Tennyson and Geology: Poetry and Poetics

This book offers new interpretations of Tennyson’s major poems along-side contemporary geology, and specifically Charles Lyell’s Principles of Geology (1830-3). Employing various approaches, from close readings both poetic and geological texts, historical contextualisation and the application of Bakhtin’s concept of dialogism, this book demonstrates, not only the significance of geology for Tennyson’s poetry, but the vital import of Tennyson’s poetics in explicating the implications of geology for the nineteenth century and beyond. Gender ideologies in The Princess (1847) are read via High Miller’s geology, while Lyell’s writings are examined for their significance for In Memoriam’s (1851) form. Maud’s (1855) figuration of fossil remains is read along-side methods in comparative anatomy, while Bakhtinian theory is applied to In Memoriam and Maud to demonstrate Tennyson’s remarkable production of a Lyellian and ‘uniformitarian’ poetics. This book will appeal to students and scholars of literature and science, the history of science and of ideas and Bakhtin scholars

Races and populations of maize in Yugoslavia

This is the most extensive and the most complete study of genetic characteristics of populations in the Yugoslav corn collection conducted so far, using isozymes as gene markers