4,556 research outputs found
A KLUYVERA-CRYOCRESCENS STRAIN FROM A GALLBLADDER INFECTION
No full textThe isolation and the identification of a pure-culture Kluyvera cryocrescens
strain in a gall.bladder pus specimen from a 76-year-old woman vcith acute cholecystitis
is described. This is the first Teported recovery of a K. cryocrescens
strain from such a sample
Modified Mc Conkey medium which allows simple and reliable identification of Providencia stuartii.
No full textCoping with antibiotic resistance: contributions from genomics
No full textAntibiotic resistance is a public health issue of global dimensions with a significant impact on morbidity, mortality and healthcare-associated costs. The problem has recently been worsened by the steady increase in multiresistant strains and by the restriction of antibiotic discovery and development programs. Recent advances in the field of bacterial genomics will further current knowledge on antibiotic resistance and help to tackle the problem. Bacterial genomics and transcriptomics can inform our understanding of resistance mechanisms, and comparative genomic analysis can provide relevant information on the evolution of resistant strains and on resistance genes and cognate genetic elements. Moreover, bacterial genomics, including functional and structural genomics, is also proving to be instrumental in the identification of new targets, which is a crucial step in new antibiotic discovery programs
Low doses of Tetracycline trigger the E. coli growth: a case of hormetic response
No full textHormesis is a biphasic dose-response relationship, occurring when low concentrations of toxic agents elicit apparent improvements. In this work, the ability of sub-inhibitory concentrations of Tetracycline to induce hormetic response in a model organism was investigated. To this aim a reference strain of Escherichia coli, MG1655, was exposed to six decreasing doses of Tetracycline (between 0.12 and 0.00375 μg/ml), much lower than the Minimal Inhibitory Concentration (4 μg/ml). An hormetic increase was observed at the intermediate concentrations (0.015-0.03 μg/ml) of the tested range. The Colony Forming Unit number, indeed, rose up to 141% and 121% as compared to the control. At the highest (0.12 μg/ml) and lowest (0.00375 μg/ml) concentrations a slight decrease in CFU number was found. Results demonstrated that, in Escherichia coli, low concentrations of Tetracycline bias the bacterial numerical increase through a hormetic response; the dose-response curve describing this numerical increase is an U-inverted curve. Furthermore, these data confirm that hormesis is common to many - if not all - living systems, including bacteria; they underline the relevance of a deepened knowledge of both the effects and the possible consequences of exposure to low doses of contaminants
Gli Invisibili antagonisti: i batteri contro l'uomo
No full textAnche se sono una sparuta minoranza, rispetto all’immenso mondo microbico, i batteri patogeni offrono una panoramica vastissima di strategie, adattamenti, soluzioni sofisticate per interagire con noi e con le nostre difese e cercare di conquistarsi la persistenza in un ambiente, i nostri tessuti, dove ottenere nutrimento. La cosa però è meno facile di quel che sembri e gli invisibili antagonisti devono fare non poca fatica per avere successo. Alcuni si sono specializzati, altri approfittano delle occasioni, qualcuno cerca di venire a compromessi e a volte ci riesce, ma tutti hanno sviluppato, lungo la loro evoluzione, dei sistemi eleganti per “cavarsela” e forniscono un argomento di studio affascinante. Le figure, frutto del mio personale diletto, vogliono offrire un aiuto per fissare nella memoria concetti e nozioni: sono la prima ad essere cosciente che la batteriologia non è proprio facilissima da ricordare. E poiché conoscere i propri avversari è sempre un vantaggio, questo testo è dedicato ai nostri invisibili antagonisti, con rispetto
Gli Invisibili compagni: i microbi e l'ambiente
No full textI microrganismi sono ovunque: invisibili compagni di vita, molto più spesso nel bene che nel male. Agli invisibili compagni è dunque dedicato questo testo e al loro modo di vivere, reagire e interagire; agli ambienti in cui reazioni e interazioni hanno luogo, e all’uso che di esse si può fare per proteggere e migliorare l’ambiente.
Sono anche incluse una breve panoramica sui metodi e le tecniche più usate, e un “glossario”, che descrive in breve le caratteristiche e la collocazione tassonomica di tutti i microrganismi citati nel testo. Le illustrazioni (frutto del mio personale diletto) sono poco convenzionali ma studiate per comunicare in modo immediato i concetti e aiutare a fissarli nella memoria
The use of Escherichia coli bearing a phoN gene for the removal of uranium and nickel from aqueous flows
No full textA Citrobacter sp. originally isolated from metal-polluted soil accumulates heavy metals via metalphosphate deposition utilizing inorganic phosphate liberated via PhoN phosphatase activity. Further strain development was limited by the non-transformability of this environmental isolate. Recombinant Escherichia coli DH5 alpha bearing cloned phoN or the related phoC acquired metal-accumulating ability, which was compared with that of the Citrobacter sp. with respect to removal of uranyl ion (UO2(2+)) from dilute aqueous flows and its deposition in the form of polycrystalline hydrogen uranyl phosphate (HUO2PO4). Subsequently, HUO2PO4-laden cells removed Ni2+ from dilute aqueous flows via intercalation of Ni2+ into the HUO2PO4 lattice. Despite comparable acid phosphatase activity in all three strains, the E. coli DH5 alpha (phoN) construct was superior to Citrobacter N14 in both uranyl and nickel accumulation, while the E. coli DH5 alpha (phoC) construct was greatly inferior in both respects. Expression of phosphatase activity alone is not the only factor that permits efficient and prolonged metal phosphate accumulation, and the data highlight possible differences in the PhoN and PhoC phosphatases, which are otherwise considered to be related in many respects
A NEW APPROACH TO USE OF BACTERIOLYTIC ENZYMES AS A TOOL FOR SPECIES IDENTIFICATION - SELECTION OF SPECIES-SPECIFIC INDICATOR STRAINS WITH BACTERIOLYTIC ACTIVITY TOWARDS ENTEROCOCCUS STRAINS
No full textWe describe the bacteriolytic activity of 377 group D Enterococcus isolates expressed towards 25 Enterococcus strains belonging to different species and Micrococcus luteus ATCC 4698. Of the 26 indicator strains used to reveal bacteriolytic activity, 5 were lysed by all of the strains of some species and were not lysed by all of the strains of other species. The use of these indicator strains allowed us to devise a new method to differentiate group D Enterococcus strains, based on qualitative analysis (lysis or no lysis of the indicator strains) of bacteriolytic activity. The bacteriolytic patterns obtained fell into six bacteriolytic groups corresponding (98% agreement) to species or groups of enterococci as determined by a comparison with data from a phenetic similarity study
ORTHO-NITROPHENYL-BETA-D-GALACTOPYRANOSIDE UREASE INDOLE BROTH, A NEW COMPOSITE TUBE MEDIUM FOR SALMONELLA SCREENING
No full textA new composite broth medium combining o-nitrophenyl-i-D-galactopyranoside (ONPG) and urease and
indole tests in a single tube is described. High-level agreement with individual conventional tests was recorded
in comparative studies with 2,412 cultures of members of the family Enterobacteriaceae, i.e., 100% agreement
with the exception of Hafnia spp. (96.3% agreement) for the ONPG test and Citrobacter, Enterobacter, and
Hafnia spp. (75, 86.4, and 98.2% agreement, respectively) for the urease test. The new medium seems
especially promising as a screen for Salmonella subgroup I which encompasses most pathogenic Salmonella
species other than the Arizona subgroup
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