In vitro interaction of usnic acid in combination with antimicrobial agents against methicillin-resistant Staphylococcus aureus clinical isolates determined by FICI and ΔE model methods

The in vitro antimicrobial activities of usnic acid were evaluated in combination with five therapeutically available antibiotics, using checkerboard microdilution assay against methicillin-resistant clinical isolates strains of Staphylococcus aureus. MIC??, MIC??, as well as MBC?? and MBC??, were evaluated. A synergistic action was observed in combination with gentamicin, while antagonism was observed with levofloxacin. The combination with erythromycin showed indifference, while variability was observed for clindamycin and oxacillin. Data from checkerboard assay were analysed and interpreted using the fractional inhibitory concentration index (FICI) and the response surface approach using the ΔE model. Discrepancies were found between both methods for some combinations. These could mainly be explained by the failure of FIC approach, being too much subjective and sensitive to experimental errors. These findings, beside confirm the well known antimicrobial activity of usnic acid, suggest, however, that this substance might be a good candidate for the individuation of novel templates for the development of new antimicrobial agents or combinations of drugs for chemotherapy.     

Dissection of events in the resistance to β-lactam antibiotics mediated by the protein BlaR1 from Staphylococcus aureus

A heterologous expression system was used to evaluate activation of BlaR1, a sensor/signal transducer protein of Staphylococcus aureus with a central role in resistance to β-lactam antibiotics. In the absence of other S. aureus proteins that might respond to antibiotics and participate in signal transduction events, we documented that BlaR1 fragmentation is autolytic, that it occurs in the absence of antibiotics, and that BlaR1 directly degrades BlaI, the gene repressor of the system. Furthermore, we disclosed that this proteolytic activity is metal ion-dependent and that it is not modulated directly by acylation of the sensor domain by β-lactam antibiotics.     

Historical presence of the sturgeon Acipenser sturio in the Rhône basin determined by the analysis of ancient DNA cytochrome b sequences

Sturgeon disappeared from the Rhône River in the mid 70’s without certitude about which species it was and about the existence of a sympatry between European sturgeon, Acipenser sturio, and Adriatic sturgeon, A. naccarii, in this watershed. In order to reach a reliable specific determination of this extinct sturgeon population, archaeozoological remains of the Jardin d’Hiver in Arles city, on the Rhône river banks, were genetically analysed, following strict criteria of authentication for the ancient DNA work. The rich collection of Arles sturgeon bone remains stems from human activities between the 6th and the 2nd Century BC. Sequences of 86 bp of the cytochrome b gene were obtained on four bones, from different anatomical parts of the fish and from different archaeological layers. All gave A. sturio diagnostic sequences. This preliminary analysis is an essential first step in the project of sturgeon reintroduction in the Rhône River. Thus, further analyses on a larger sample are necessary to comfort this result and to solve the question of sympatry with A. naccarii.     

Impacts of global changes and extreme hydroclimatic events on macroinvertebrate community structures in the French Rhône River

We assessed the temporal changes in and the relationships between the structures of the macroinvertebrate communities and the environmental conditions of the French Rhône River (the river from Lake Geneva to the Mediterranean Sea) over the last 20 years (1985–2004). Multisite environmental and biological datasets were analysed using multiple CO-inertia analysis (MCOA) and Procrustean analysis. Changes in environmental conditions were mainly marked by an improvement in water quality between 1985 and 1991 and by an increase in water temperature from 1985 onwards due to climate change. Improvement in water quality seemed to delay changes in community structures under global warming. We then observed trends in community structures coupled with high temperatures and a decrease in oxygen content. Interestingly, we observed both gradual changes and rapid switches in community states. These shifts seemed coupled to extreme hydroclimatic events (i.e. pulse disturbances). Floods and the 2003 heatwave enhanced the development of eurytolerant and invasive taxa which were probably able to take advantage of gradual warming environmental conditions. Despite various site-specific “press” constraints (e.g. hydropower schemes, nuclear power plants), similar changes in community structures were observed along the French Rhône River. Such consistency in temporal processes at large geographical scales underlined the strength of hydroclimatic constraints on community dynamics compared to specific local disturbances. Finally, community structures did not show any sign of recovery, and their relative sensitivities to extreme hydroclimatic events seemed to increase with time. Thus, our results suggest that global changes may reduce the resilience of current community states.     

Transfers between a eutrophic ecosystem,the river Rhône,and an oligotrophic ecosystem,the north-western Mediterranean Sea

Transfer processes from a eutrophic ecosystem, the river Rhône, to an oligotrophic environment, the north-west Mediterranean Sea, were studied during the winter period, when inputs of dissolved and particulate matter are at their highest.During a cruise carried out in February 1987, salinity, temperature, turbidity, nutrients, pigments, suspended particulate matter and particulate carbon and nitrogen were measured in surface and subsurface waters near the Rhône outlet.For most of the parameters the results show that during this period a simple dilution process occurs in the river plume of the Rhône without adsorption, desorption, precipitation or biological uptake, contrary to recordings for some other rivers. All the nutrients discharged into the sea by the Rhône are available for utilization by marine phytoplankters.     

Bacteriophage types of methicillin--resistant Staphylococcus aureus strains isolated in 2005-2006 in the Gdańsk area and their resistance to other antibiotics

The phage type of 38 methicillin--resistant Staphylococcus aureus strains isolated from clinical samples in 5 hospitals in the Gdańsk area in 2005-2007 was determined and antibiotic resistance of obtained phage types was analysed. Phage typing was performed using set of 10 phages as following: MR8, MR12, MR25, 30, 33, 38, M3, M5, 622, 56B. Drug resistance was determined by the disc--diffusion method. There were 12 phage types observed. The most frequent (28.9%) was 56B type which was present in 3 hospitals and in one hospital was found to be predominated. The studied strains were most frequent (23.7%) resistant to erythromycin, clindamycin, ciprofloxacin, trimethoprim/sulfamethoxazole, tetracycline and gentamicin. This resistance pattern predominated in strains belonging to 56B type.     

Oligochaete drift in a large river (French Upper Rhône): the effect of life cycle and discharge

In the framework of a macroinvertebrate drift study, the oligochaete community was analysed over one year (1989) at six sites located in a partly impounded reach of the Upper Rhône River (France). Drift composition between sites was somewhat affected by the environmental conditions. These differences were caused by significant deviations in drift rates (P < 0.05) of endobenthic oligochaetes and non-swimming Naididae. There was no significant difference (P > 0.05) among the swimming Naididae. As the latter strongly dominated, global spatial differences in the drift were weak. Temporal changes constituted the main source of variability in drifting oligochaetes. Life cycles and reproductive ecology of four major swimming Naidid species, Nais elinguis, Stylaria lacustris, Nais christinae, and Nais barbata, explained most of the drift structure over the year. Hydrological fluctuations also affected drift structure, both for swimming and non-swimming species. Taxon richness and relative abundance in the drift were very similar to those obtained in the river benthos from a reference reach previously studied. There was a lack of stygobiont and stygophilous species that are frequent in area of groundwater seepage. Biological and environmental implications of oligochaete drift are stressed. The drift phenomenon is appropriated to provide ecological informations on oligochaete communities in fast flowing and deep, large rivers.     

Genetic diversity and antimicrobial resistance? in Streptococcus agalactiae strains recovered from female carriers in the Bucharest area

For the first time, we used multilocus sequence typing (MLST) to understand how Romanian group B streptococcus (GBS) strains fit into the global GBS population structure. Colonising isolates recovered from adult human females were tested for antibiotic resistance, were molecularly serotyped based on the capsular polysaccharide synthesis (cps) gene cluster and further characterised using a set of molecular markers (surface protein genes, pilus-encoded islands and mobile genetic elements inserted in the scpB-lmb intergenic region). Pulsed-field gel electrophoresis was used to complement the MLST clonal distribution pattern of selected strains. Among the 55 strains assigned to six cps types (Ia, Ib, II-V), 18 sequence types (STs) were identified by MLST. Five STs represented new entries to the MLST database. The prevalent STs were ST-1, ST-17, ST-19 and ST-28. Twenty molecular marker profiles were identified. The most common profiles (rib+GBSi1+PI-1, rib+GBSi1+PI-1, PI-2b and alp2/3+PI-1, PI-2a) were associated with the cps III/ST-17 and cps V/ST-1 strains. A cluster of fluoroquinolone-resistant strains was detected among the cps V/ST-19 members; these strains shared alp1 and IS1548 and carried PI-1, PI-2a or both. Our results support the usefulness of implementing an integrated genotyping system at the reference laboratory level to obtain the reliable data required to make comparisons between countries.     

Near East mtDNA haplotype variants in Roman cattle from Augusta Raurica, Switzerland, and in the Swiss Evolène breed

Typical Near East mitochondrial haplotypes of the T2 lineage were found in one cattle metacarpus sample from the Roman period and in two present-day Evolène cattle in Switzerland. Sequences from eight additional Evolène and four Raetian Grey aligned to the European haplotype T3. Analysis of nucleotide diversity within the mitochondrial D-loop of both studied Swiss cattle breeds revealed high haplotype diversity and similar diversity to a European cattle reference group. Mitochondrial T3 haplotypes radiated star-like from two similarly frequent haplotypes, possibly indicating two different expansion routes. The breed structure of Evolène cattle can be explained either by an introduction of diverse female lineages from the domestication centre or by later admixture. The introduction of the Near East lineage to Switzerland must have happened during the Roman time or earlier.     

Characterisation of virulence genes in methicillin susceptible and resistant Staphylococcus aureus isolates from a paediatric population in a university hospital of Medellín, Colombia

Virulence and antibiotic resistance are significant determinants of the types of infections caused by Staphylococcus aureus and paediatric groups remain among the most commonly affected populations. The goal of this study was to characterise virulence genes of methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) strains isolated from a paediatric population of a Colombian University Hospital during 2009. Sixty MSSA and MRSA isolates were obtained from paediatric patients between zero-14 years. We identified the genes encoding virulence factors, which included Panton-Valentine leucocidine (PVL), staphylococcal enterotoxins A-E, exfoliative toxins A and B and toxic shock syndrome toxin 1. Typing of the staphylococcal chromosome cassette mec (SCCmec) was performed in MRSA strains. The virulence genes were more diverse and frequent in MSSA than in MRSA isolates (83% vs. 73%). MRSA strains harboured SCCmec types IVc (60%), I (30%), IVa (7%) and V (3%). SCCmec type IVc isolates frequently carried the PVL encoding genes and harboured virulence determinants resembling susceptible strains while SCCmec type I isolates were often negative. PVL was not exclusive to skin and soft tissue infections. As previously suggested, these differences in the distribution of virulence factor genes may be due to the fitness cost associated with methicillin resistance.     

Comparison of solutes, nutrients, and bacteria inputs from two types of groundwater to the Rhône river during an artificial drought

Solute, nutrient and bacterial inputs to the River Rhône from the interstitial habitat of a gravel bar and the floodplain aquifer were investigated during an artificial drought. Eight springs were investigated: four groundwater-fed springs in the floodplain, located at the bottom of the bank; and four interstitial-fed springs located at the downstream end of a gravel bar. During this period, the inflows of groundwater to the river represented an average input of 0.77 mg l^–1 of nitrogen (of which 93.3% were nitrates), 0.0187 mg l^–1 of total phosphorus (of which 42.2% was orthophosphate), 3.56 mg l^–1 of silica, 2.315 ± 0.703 mg l^–1 of dissolved organic carbon (DOC, of which 47% was biodegradable) and 7.3 × 10⁴ ± 3.7 × 10⁴ bacteria per ml (of which 8.8% were active). Silica, DOC, biodegradable DOC, and bacteria concentrations displayed temporal variations during the study, which seem to be linked to the biological activity of the groundwater biofilm. There was a strong heterogeneity between the two types of groundwater that flow to the river: concentrations of calcium and alkalinity were higher in bank springs than in gravel bars springs. In these latters, sulfate, sodium, nitrogen, phosphorus were significantly higher.     

Expression of δ-toxin by Staphylococcus aureus mediates escape from phago-endosomes of human epithelial and endothelial cells in the presence of β-toxin

Staphylococcus aureus is able to invade non-professional phagocytes by interaction of staphylococcal adhesins with extracellular proteins of mammalian cells and eventually resides in acidified phago-endosomes. Some staphylococcal strains have been shown to subsequently escape from this compartment. A functional agr quorum-sensing system is needed for phagosomal escape. However, the nature of this agr dependency as well as the toxins involved in disruption of the phagosomal membrane are unknown. Using a novel technique to detect vesicular escape of S. aureus, we identified staphylococcal virulence factors involved in phagosomal escape. Here we show that a synergistic activity of the cytolytic peptide, staphylococcal δ-toxin and the sphingomyelinase β-toxin enable the phagosomal escape of staphylococci in human epithelial as well as in endothelial cells. The agr dependency of this process can be directly explained by the location of the structural gene for δ-toxin within the agr effector RNAIII.     

Using γ-emitting artificial radionuclides,released by nuclear plants,as markers of restricted movements by chub,Leuciscus cephalus,in a large river,the Lower Rhône

Synopsis On the basis that -emitting artificial radionuclides, present in nuclear plant radioactive wastes, can be considered as natural collective markers of fish living downstream from a radioactive discharge, we studied the restricted movements of chub in a reservoir on the Lower Rhône river where the Marcoule nuclear plant is located. A qualitative determination, based on the detection of specific radioelements in our samples originating from radioactive waste, and a quantitative determination of the cesium-137 concentration in the samples, were used to identify fish radioactively marked by the effluent. Individual measurements of -radioactivity in 49 adult chub captured at two stations, each 2 km long and 6 km apart, divided the fish into two distinct sub-units: one living downstream of the discharge pipe, in which 73% were marked, and the other upstream, in which 79% were not marked. Similar results were found in two neighbouring stations when we analysed previous radioecological measurements of -radioactivity in groups of chub. After combining all the data concerning chub, detailed information was obtained on the spatial stability of the chub population in the reservoir. Two spatially different stocks were found and each stock can be divided in two components: a sedentary component that remains in a restricted zone (its home range), and a mobile component that undertakes movements between the two zones.     

Demographic structure and life history traits of the common goby Pomatoschistus microps (Teleostei,Gobiidae) in a Mediterranean coastal lagoon (Rhône River delta,France)

Demographic structure and life history traits of the common goby Pomatoschistus microps were investigated in a brackish water lagoon of the Rhône River delta (Mediterranean Sea, southern France). The size frequency distribution and gonadosomatic index indicated that three different age groups occurred and reproduced successively in the lagoon, resulting in a long spawning period from March to September and a high investment in reproduction. This high investment in reproduction, which contrasts with that found in other mostly northern European populations, probably relates to the unpredictability of the gobyˈs environmental conditions.     

Evaluation of antimicrobial resistance among <Emphasis Type="Italic">Salmonella</Emphasis> and <Emphasis Type="Italic">Shigella</Emphasis> isolates in the University Hospital “St. George,” Plovdiv,Bulgaria

The aim of this work is to study the epidemiology and antimicrobial resistance to the most commonly used antibiotics for the treatment of acute gastroenteritis caused by Salmonella and Shigella at the largest Bulgarian hospital—University Hospital “St. George,” Plovdiv—for the period 2009–2013. Two hundred ninety strains were in vitro tested for resistance to 15 antimicrobial agents. The presence of extended-spectrum beta-lactamases (ESBLs) was demonstrated by a variety of specialized tests. For comparison, a collection of 28 strains submitted by the National Reference Laboratory (NRL) “Enteric Infections” at the National Center of Infectious and Parasitic Diseases (NCIPD), Sofia, was also tested for the production of ESBLs. In isolates, phenotypically demonstrated as ESBL producers, polymerase chain reaction (PCR) detection of the genes bla-CTX-M, bla-SHV, and bla-TEM was performed. Among the 290 tested isolates, only two— Salmonella serotype Livingstone and Shigella flexneri—were phenotypically proven to be ESBL producers. Only 4 strains from the collection of 28, submitted from the NRL “Intestinal Infections” in NCIPD, Sofia, were phenotypically confirmed as ESBL producers. The presence of the bla-CTX-M gene was detected in all of the tested strains (4 from NRL, NCIPD, Sofia, and 2 from the University Hospital St. George, Plovdiv), the bla-SHV gene only in strain S. Livingstone from Plovdiv, and the bla-TEM gene in two from Sofia and one (again S. Livingstone) from Plovdiv. In conclusion, Salmonella and Shigella isolates from patients hospitalized at the University Hospital St. George, Plovdiv, with acute gastroenteritis demonstrate good susceptibility to the most commonly used antibiotic agents, including azithromycin.