Low levels of β-lactam antibiotics induce extracellular DNA release and biofilm formation in Staphylococcus aureus.

UNLABELLED: Subminimal inhibitory concentrations of antibiotics have been shown to induce bacterial biofilm formation. Few studies have investigated antibiotic-induced biofilm formation in Staphylococcus aureus, an important human pathogen. Our goal was to measure S. aureus biofilm formation in the presence of low levels of β-lactam antibiotics. Fifteen phylogenetically diverse methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) strains were employed. Methicillin, ampicillin, amoxicillin, and cloxacillin were added to cultures at concentrations ranging from 0× to 1× MIC. Biofilm formation was measured in 96-well microtiter plates using a crystal violet binding assay. Autoaggregation was measured using a visual test tube settling assay. Extracellular DNA was quantitated using agarose gel electrophoresis. All four antibiotics induced biofilm formation in some strains. The amount of biofilm induction was as high as 10-fold and was inversely proportional to the amount of biofilm produced by the strain in the absence of antibiotics. MRSA strains of lineages USA300, USA400, and USA500 exhibited the highest levels of methicillin-induced biofilm induction. Biofilm formation induced by low-level methicillin was inhibited by DNase. Low-level methicillin also induced DNase-sensitive autoaggregation and extracellular DNA release. The biofilm induction phenotype was absent in a strain deficient in autolysin (atl). Our findings demonstrate that subminimal inhibitory concentrations of β-lactam antibiotics significantly induce autolysin-dependent extracellular DNA release and biofilm formation in some strains of S. aureus. IMPORTANCE: The widespread use of antibiotics as growth promoters in agriculture may expose bacteria to low levels of the drugs. The aim of this study was to investigate the effects of low levels of antibiotics on bacterial autoaggregation and biofilm formation, two processes that have been shown to foster genetic exchange and antibiotic resistance. We found that low levels of β-lactam antibiotics, a class commonly used in both clinical and agricultural settings, caused significant autoaggregation and biofilm formation by the important human pathogen Staphylococcus aureus. Both processes were dependent on cell lysis and release of DNA into the environment. The effect was most pronounced among multidrug-resistant strains known as methicillin-resistant S. aureus (MRSA). These results may shed light on the recalcitrance of some bacterial infections to antibiotic treatment in clinical settings and the evolution of antibiotic-resistant bacteria in agricultural settings

Towards development of a prototype high-temperature latent heat storage unit as an element of a RES-based energy system (part 2)

This paper presents an experimental study performed with the general aim of defining procedures for calculation and optimization of shell-and-tube latent thermal energy storage unit with metals or metal alloys as PCMs. The experimental study is focused on receiving the exact information about heat transfer between heat transfer fluid (HTF) and phase change material (PCM) during energy accumulation process. Therefore, simple geometry of heat transfer area was selected. Two configurations of shell-and-tube thermal energy storage (TES) units were investigated. The paper also highlights the emerging trend (reflected in the literature) with respect to the investigation of metal PCM-based heat storage units in recent years and shortly presents unique properties and application features of this relatively new class of PCMs

Impact of treated sewage on sewagetreatment plant in Myślenice on the quailty of their receiver

Artykuł zawiera analizę i ocenę wpływu ścieków oczyszczonych w oczyszczalni w Myślenicach w latach 2008 - 2011, na skład fizyczno-chemiczny oraz jakość wód ich odbiornika - rzeki Raby. Pracę wykonano na podstawie zebranych oraz statystycznie opracowanych wyników badań, obejmujących ilość i skład ścieków oczyszczonych, odprowadzanych do Raby, a także skład wód odbiornika w przekrojach Stróże i Osieczany, znajdujących się odpowiednio powyżej i poniżej punktu zrzutu ścieków oczyszczonych. Zakres wskaźników zanieczyszczeń oznaczanych w ściekach i wodzie obejmował: zawiesinę ogólną, BZT5 , ChZTCr, fosfor ogólny oraz azot ogólny. Na podstawie wykonanych badań stwierdzono, że oczyszczalnia ścieków w Myślenicach, w latach 2008 - 2011, funkcjonowała prawidłowo, ponieważ oczyszczone na niej ścieki, spełniały wymogi pozwolenia wodno-prawnego, co przekładało się bezpośrednio na skuteczną ochronę przed zanieczyszczeniem wód ich odbiornika. Ponadto stwierdzono, że w obu badanych przekrojach skład fizyczno-chemiczny wód Raby był do siebie zbliżony. Potwierdziły to wyniki zastosowanego testu U Mann'a-Whitney'a, które nie wykazały statystycznie istotnych różnic pomiędzy średnimi wartościami stężeń analizowanych wskaźników zanieczyszczeń. Ścieki oczyszczone, odprowadzane z oczyszczalni w Myślenicach do rzeki Raby nie przyczyniają się do pogorszenia jakości jej wód.The article contains analysis and evaluation of the impact of clean sewage on sewage treatment plant in Myślenice, in the period 2008 - 201,1 on the physico-chemical composition and water quality of the receiver - river Raba. The analysis conducted based on collected and statistical research: amount and composition of clean sewage and composition of the water receiver in cross-section: Stróże (above of inflow clean sewage) and Osieczany (below of inflow clean sewage). The following pollution index were tested: total suspended solids, BOD5, CODCr, total nitrogen and total phosphorus. Based on obtained results its concluded that in period 2008 - 2011 sewage treatment plant was working properly, what explain quality of clean sewage. What reflected in directly protection of receiver water against pollution. Moreover, based on the results of U Mann Whitney test, concluded that in the both cross-section, composition of the water of Raba river was similar, what explain the results of this test, which didn't show statistically significant differences between average values of concentrations analyzed indicators of pollutions. Based on obtained results its concluded that sewage treatment plant in Myślenice doesn't negatively impact on quality of the water receiver -Raba river