Joint effect of surfactants and cephalexin on the formation of Escherichia coli filament.

Both antibiotics and surfactants commonly exist in natural environment and have generated great concerns due to their biological influence on the ecosystem. A major concern lies in the capacity of antibiotics to induce bacterial filaments formation, which has potential health risks. However, their joint effect is not clear so far. Here, we studied the joint effect of cephalexin (Cex), a typical antibiotic, and differently charged surfactants on the formation of E. coli filaments. Three kinds of surfactants characterized by different charges were used: cationic surfactant (CTAB), anionic surfactant (SDS) and nonionic surfactant (Tween). Data showed that Cex alone caused the formation of E. coli filaments, elongating their maximum profile from ca. 2 µm (a single E. coli cell) to tens of micrometers (an E. coli filament). A joint use of surfactants with Cex could produce even longer E. coli filaments, elongating the maximum length of the bacteria to larger than 100 µm. The capacity order of different surfactants under their optimum concentrations to produce elongated E. coli filaments was Tween > SDS > CTAB. The E. coli filaments were characterized with a normal DNA distribution and a good cell membrane integrity. We measured the stiffness of bacterial cell wall by atomic force microscopy and correlated the elongation capacity of the E. coli filaments to the stiffness of cell wall. Zeta potential measurement indicated that inserting into or being bound to the cell surface in a large quantity was tested not to be the major way that surfactants interacted with bacteria.

The long-term impact of cefalexin on organic substrate degradation and microbial community structure in EGSB system.

In order to investigate long-term effect of cefalexin (CFX) on the performance of expanded granular sludge bed (EGSB) system and microbial community structure, two 1.47 L EGSB reactors E1 and E2 were designed and run for 224 days treating with synthetic antibiotic wastewater. For the purpose of comparison, E1 was fed with synthetic antibiotic industry wastewater with CFX added as the test reactor, while, E2 was fed without any CFX added as the control reactor (E2). The addition of CFX resulted in the continual increasing of soluble COD (sCOD) and accumulation of VFAs in the effluent of E1 system. Besides, it was found that the accumulation of CFX by-products D-1, D-2 and D-3 was negative correlation with sCOD removal efficiency. Furthermore, the microbial community structures were also investigated. For the bacterial community, Gelria and Syntrophorhabdus which can ferment propionate and other organic pollutants as their substrate were obviously enriched in E1 system. For the archaea, there was more functional diversity in E1 system than in E2 system. Furthermore, fungi also played an important role on the removal of complex organics in E1 system.

Electrochemical mineralization of cephalexin using a conductive diamond anode: A mechanistic and toxicity investigation.

The contamination of surface and ground water by antibiotics is of significant importance due to their potential chronic toxic effects to the aquatic and human lives. Thus, in this work, the electrochemical oxidation of cephalexin (CEX) was carried out in a one compartment filter-press flow cell using a boron-doped diamond (BDD) electrode as anode. During the electrolysis, the investigated variables were: supporting electrolyte (Na2SO4, NaCl, NaNO3, and Na2CO3) at constant ionic strength (0.1 M), pH (3, 7, 10, and without control), and current density (5, 10 and 20 mA cm-2). The oxidation and mineralization of CEX were assessed by high performance liquid chromatography, coupled to mass spectrometry and total organic carbon. The oxidation process of CEX was dependent on the type of electrolyte and on pH of the solution due to the distinct oxidant species electrogenerated; however, the conversion of CEX and its hydroxylated intermediates to CO2 depends only on their diffusion to the surface of the BDD. In the final stages of electrolysis, an accumulation of recalcitrant oxamic and oxalic carboxylic acids, was detected. Finally, the growth inhibition assay with Escherichia coli cells showed that the toxicity of CEX solution decreased along the electrochemical treatment due to the rupture of the ß-lactam ring of the antibiotic.

Temperature rise and microplastics interact with the toxicity of the antibiotic cefalexin to juveniles of the common goby (Pomatoschistus microps): Post-exposure predatory behaviour, acetylcholinesterase activity and lipid peroxidation.

The goal of this study was to investigate the toxicity of cefalexin to Pomatoschistus microps juveniles in relation to the presence of microplastics in the water and temperature rise. After acclimatization, groups of wild juveniles were exposed for 96h to artificial salt water (control), microplastics alone (0.184mg/l), cefalexin alone (1.3-10mg/l) and in mixture with microplastics (cefalexin: 1.3-10mg/l; microplastics: 0.184mg/l) at 20 and 25°C. Effect criteria were mortality, post-exposure predatory performance (PEPP), acetylcholinesterase activity (AChE) and lipid peroxidation levels (LPO). At 20°C, concentrations of cefalexin alone≥5mg/l significantly reduced PEPP (up to 56%; 96h-EC50=8.4mg/l), indicating toxicity of the antibiotic to juveniles after short-term exposure to water concentrations in the low ppm range. At 20°C, fish exposed to microplastics alone did not have significant differences in any of the parameters tested relative to the control group but tended to have an inhibition of the PEPP (23%) and AChE (21%); at 25°C, microplastics alone caused mortality (33%) and PEPP inhibition (28%). Thus, microplastics are toxic to P. microps juveniles. At 20°C, under simultaneous exposure to cefalexin and microplastics, the PEPP was significantly reduced (at cefalexin concentrations≥1.25mg/l). Moreover, at 25°C, the toxicity curves of cefalexin (PEPP based), alone and in mixture with microplastics, were significantly different (p<0.05; 96h-EC50 of 3.8 and 5.2mg/l, respectively), and the integrated data analysis indicated significant interactions between the two substances for all biomarkers. Thus, the presence of microplastics in the water influenced the toxicity of cefalexin. The rise of water temperature (from 20°C to 25°C), increased the microplastics-induced mortality (from 8 to 33%), and the inhibitory effects of cefalexin on the PEPP (up to 70%). Significant differences (p<0.05) between the toxicity curves of cefalexin alone at distinct temperatures were found, with a lower 96h-EC50 at 25°C (3.8mg/l) than at 20°C (8.4mg/l). Moreover, at 25°C, increases of AChE activity (14%) and LPO (72%) in fish exposed to the mixture treatment containing the highest cefalexin concentration were found, and the integrated analysis of data indicated significant interactions between cefalexin and temperature for PEPP, and among all stressors for LPO. Thus, the temperature rise increased the toxicity of microplastics and of cefalexin, alone and in mixture with microplastics, to P. microps juveniles. These findings raise concern on the long-term exposure of wild populations to complex mixtures of pollutants, likely decreasing their fitness, and highlight the need of more research on the combined effects of widely used pharmaceuticals, microplastics and temperature increase on wild species to improve environmental and human risk assessments of chemicals and their safe use under a global warming scenario.

Kill rate of mastitis pathogens by a combination of cefalexin and kanamycin.

AIM: To assess the bacterial killing rate produced by a combination of cefalexin and kanamycin at two different concentration ratios. METHODS AND RESULTS: Time-kill kinetics of cefalexin and kanamycin, individually and in combination, were determined against one strain each of Escherichia coli, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae and Streptococcus uberis. The combination was tested using two fixed ratios (cefalexin : kanamycin ratios of 1·25 : 1 and 1 : 2·3) and two concentrations of each ratio. Time-kill curves produced with either ratio were quite similar. Against most bacterial species, higher concentrations produced faster kill. In all cases, the combination of cefalexin and kanamycin showed faster and greater kill at lower antibiotic concentrations than those observed with either drug alone. CONCLUSIONS: The combination of cefalexin and kanamycin results in a fast initial killing of major mastitis pathogens at both concentration ratios. SIGNIFICANCE AND IMPACT OF THE STUDY: The combination of cefalexin and kanamycin achieved rapid bacterial kill at concentrations and ratios that can be achieved in vivo following intramammary infusion of a mastitis treatment.

Histological examinations of chief and parietal cells of the rat gastric glands after experimental administration of cephalexin and ethanol.

The experiment was carried out on Wistar rat males weighting about 200 g. Animals from experimental group I received 20% ethanol for drinking (ad libitum), animals from experimental group II--cephalexin in the dose of 42 mg/24 h, animals from experimental group III--cephalexin and ethanol in mentioned doses. After 10 days animals were decapitated and specimens of the stomach were taken from the greater curvature. It was stated that 10-day administration of 20% ethanol causes hyperemia of the gastric mucous membrane and the decrease of secretory activity of the glands. On the contrary, cephalexin causes the increase of secretory activity of chief and parietal cells. Concomitant administration of ethanol and cephalexin damages the gastric mucous membrane causing its narrowing, flattening of gastric pits and atrophy of secretory cells in the glands.

The influence of experimental administration of ethanol and cephalexin on stomach mucous barrier of rat.

The Wistar rat males weighing approximately 200 g were administered 20% ethanol ad libitum during 10 days, cephalexin in the dose of 42 mg/24 h, and simultaneously ethanol and cephalexin in the above-mentioned doses. After 10 days the animals were decapitated and stomach specimens were taken from the major curvature region for examinations. They were fixed in 10% formalin, dehydrated and immersed in paraffin. For the purpose of estimation changes in activity of gastric gland mucous cells Mc Manus's PAS reaction was performed on 7 micro-thick sections. It was found that ethanol causes functional decrease in the activity of mucous cells. However, cephalexin increases the activity of superficial mucous cells and orifice mucous cells of gastric glands, and inhibits the activity of cervix mucous cells. A simultaneous administration of ethanol and cephalexin causes atrophic changes in gastric glands, and thereby strong reduction of mucous cells activity.

Histological changes of white rat kidney after experimental administration of ethanol and cephalexin.

The experiment was carried out on Wistar rat males weighing about 200 g. Animals from the control group received water and standard granulated fodder ad libitum. Animals from control group II received 20% ethanol ad libitum instead of water. Animals from experimental group I received cephalexin in the single dose of 42 mg/24h, Animals from experimental group II received cephalexin in the dose of 42 mg/24h and 20% ethanol ad libitum. After 10 days animals were decapitated. Histological examinations (H+E staining and PAS reaction) were made on 7 micro thick paraffin slices. It was stated that ethanol causes hyperemia of the renal parenchyma and cephalexin stimulates diuresis. However, concomitant administration of ethanol and cephalexin causes functional changes (inhibition of diuresis) and degenerative changes in capillary loops of some renal corpuscles apart from hyperemia.

Histological changes in the pancreas of white rats after administering cephalexin and ethanol.

The research was conducted on male Wistar rats weighing approximately 200 g. Animals of experimental group I were administered 20% ethyl alcohol for drinking, animals of experimental group II--cephalexin in the dose of 42 mg daily, animals of experimental group III--simultaneously alcohol and cephalexin in the mentioned doses. After 10 days the animals were guillotined and pancreas was taken for research. On paraffin sections 7 mu thick there were carried out H + E stain and PAS reaction aimed at discovering neutral mucopolysaccharides. After administering alcohol there was stated a decrease in the activity of exocrime cells and after administering of cephalexim--an increase in this activity. A simultaneous administration of ethyl alcohol and antibiotic causes trophic changes, which can be noticed as introductory, but at this stage--reversible, degenerative changes.

Ultrastructural changes of pancreas of white rats after experimental administration of ethanol and cephalexin.

The experiment was carried out on Wistar rat males weighting about 200 g. Animals from experimental group I received 20% ethanol for drinking (ad libitum), animals from experimental group II--cephalexin in the dose of 42 mg/24 h, animals from experimental group III--cephalexin and ethanol in the mentioned doses. After 10 days the animals were decapitated and pancreases were collected for ultrastructural examinations in electron microscope. The performed experiments showed that 10-day administration of ethanol causes mainly the decrease of amount of ribosomes and zymogen granules in pancreatic exocrine cells, whereas cephalexin causes increase of amount of these organelles. Administration of both ethanol and cephalexin causes reversible degenerative changes including distinct decreasing of the number of ribosomes, swelling of many mitochondria and the presence of myelinic structures inside cells.

Evaluación de la nefrotoxicidad en la administración conjunta de cefalexina sódica y sulfato de gentamicina en perros / Evaluation of the nephrotoxicity of the administration of sodium dephalexin together with genramicin sulphate in dogs

Se utilizaron 16 perros clínicamente sanos de diferentes razas, con edades que fluctuaron entre 2 y 6 años. Se les dividió al azar en dos grupos: al A se la aplicó gentamicina cada 24 horas por vía intramuscular, y al grupo B se le administró gentamicina, de igual forma que A más 20 mg/kg de cefalexina por vía oral cada 8 horas. Se determinaron en los 16 perros las concentraciones plasmáticas de urea y creatinina (UC) basales, durante el tratamiento y semanalmente, por tres semanas, después de suspender la medicación. La administración de los medicamentos se continuó hasta 7 días o antes si se obtuvieron niveles plasmáticos de UC superiores a los normales. El análisis estadístico reveló que existe una disminución estadísticamente significativa únicamente de los valores plasmáticos de urea para el grupo B (P<0.05), pero este mismo grupo tardó más tiempo en regresar las concentraciones de UC a niveles basales. Estos resultados sugieren que la aplicación conjunta de cefalexina y gentamicina no incrementa la nefrotoxicidad que pudieran generar las dosis terapéuticas de gentamicina. Se discute la relevancia de los resultados para el tratamiento empírico de infecciones en perros

Toxicity of cephalosporins to fatty acid metabolism in rabbit renal cortical mitochondria.

UNLABELLED: Cephaloglycin (Cgl) and cephaloridine (Cld) are acutely toxic to the proximal renal tubule, in part because of their cellular uptake by a contraluminal anionic secretory carrier and in part through their intracellular attack on the mitochondrial transport and oxidation of tricarboxylic acid (TCA) cycle anionic substrates. Preliminary studies with Cgl have provided evidence of a role of fatty acid (FA) metabolism in its nephrotoxicity, and work with Cld has shown it to be a potent inhibitor of renal tubular cell and mitochondrial carnitine (Carn) transport. Studies were therefore done to examine the effects of Cgl and Cld on the mitochondrial metabolism of butyrate, the anion of a short-chain FA that does not require the Carn shuttle to enter the inner matrix, and the effects of Cgl on the metabolism of palmitoylcarnitine (PCarn), the Carn conjugate of a long-chain FA that does enter the mitochondrion by the Carn shuttle. The following was found: (1) Cgl reduced the oxidation and uptake of butyrate after in vitro (2000 micrograms/mL, immediate effect) and after in vivo (300 mg/kg body weight, 1 hr before killing) exposure; (2) Cld caused milder in vitro toxicity, and no significant in vivo toxicity, to mitochondrial butyrate metabolism; (3) like Cld, Cgl reduced PCarn-mediated respiration after in vivo exposure, but, unlike Cld, it did not inhibit respiration with PCarn in vitro; (4) the Carn carrier was stimulated slightly by in vitro Cgl but was unaffected by in vivo Cgl; (5) in vivo Cgl had no effect on mitochondrial free Carn or long-chain acylCarn concentrations in the in situ kidney; (6) Cgl increased the excretion of Carn minimally compared with the effect of Cld; and (7) cephalexin, a nontoxic cephalosporin, caused mild reductions of respiration with butyrate and PCarn during in vitro exposure, but stimulated respiration with both substrates after in vivo exposure. CONCLUSIONS: Cgl has essentially the same patterns of in vitro and in vivo toxicity against mitochondrial butyrate uptake and oxidation that both Cgl and Cld have against TCA-cycle substrates. Cld has little or no in vivo toxicity to mitochondrial butyrate metabolism, whereas in vivo Cgl is as toxic as Cld to respiration with PCarn. The greater overall in vivo toxicity of Cgl to mitochondrial FA metabolism, with lower cortical concentrations and AUCs than those of Cld, supports earlier evidence that Cld is less toxic than Cgl at the molecular level.

Renal cell type specificity of cephalosporin-induced cytotoxicity in suspensions of isolated proximal tubular and distal tubular cells.

We have developed an in vitro model for investigation of nephron heterogeneity and cell type-specific patterns of renal injury. To further validate our model and to study biochemical mechanisms of cephalosporin-induced injury, cytotoxicity of three cephalosporins was studied in freshly isolated proximal tubular (PT) and distal tubular (DT) cells from rat kidney. The three cephalosporins [cephaloridine (CPH), cephalexin (CXN), cephalothin (CTN)] were chosen because they exhibit varying degrees of nephrotoxicity in vivo and contain different functional groups. CPH produced greater amounts of lactate dehydrogenase release from PT cells than either CXN or CTN, indicating greater toxicity of CPH, which agrees with in vivo observations. DT cells were not affected by any of the cephalosporins. Thus, the cephem ring is sufficient to produce PT cell injury but the presence of other functional groups modifies toxicity. SKF-525A and alpha-tocopherol protected PT cells from both CPH and CTN, suggesting involvement of cytochrome P-450 metabolism and oxidative stress. Both PT and DT cells exhibited transport of CPH or CXN and transport of CPH into PT cells was inhibitable by probenecid, consistent with action of a specific carrier. Transport alone, therefore, cannot account for the cell type specificity pattern in vitro. Effects on intracellular glutathione status, malondaldehyde formation, and uncoupler-stimulated respiration were also investigated, and these generally correlated with cell type specificity patterns but not always with degree of cytotoxicity. These results validate further the isolated PT and DT cells as in vitro models to study cell type-specific renal injury and show a role for oxidative stress, cytochrome P-450 bioactivation, and mitochondrial dysfunction in cephalosporin-induced PT cell injury.

Detecting methicillin-resistant Staphylococcus epidermidis--disc diffusion, broth breakpoint or polymerase chain reaction?

Growth conditions are important for the expression of resistance to methicillin among staphylococci. Consequently a phenotypic susceptibility test has to be chosen carefully to avoid false susceptible results. In this study we wanted to devise rapid and simple phenotypic tests whose results completely correlate with the presence of the methicillin resistance gene, mecA. A simplified polymerase chain reaction (PCR) method not needing separate DNA extraction from the tested bacteria was used to amplify a 449 bp region of the mecA gene. One hundred and ten strains of S. epidermidis were tested. The results were in complete agreement with those from a broth tube breakpoint test, known to identify more strains as resistant than does the method recommended by NCCLS. In disc diffusion test it was possible to clearly distinguish resistant from susceptible strains by using discs containing oxacillin, cephalexin and cephradine. A 5 micrograms cephradine disc was further analysed by testing another 441 consecutive clinical isolates of staphylococci. All resistant coagulase-negative staphylococci grew out to the edge of this disc, whereas susceptible strains showed an inhibition zone at least 10 mm in diameter. The 5 micrograms cephradine disc is recommended for routine work. The PCR method and broth tube breakpoint test are both reliable reference methods.

Synthetic cephalosporins. II. The synthesis and oral activity of 7-[R-2-amino-2-(3-chloro-4-hydroxyphenyl)acetamido]-3-methylthio-3- cephem-4-carboxylic acid and related compounds.

A series of 3-methylthio-3-cephem-4-carboxylic acids were prepared to test their antibacterial activities, and 7-[R-2-amino-2-(3-chloro-4-hydroxyphenyl)acetamido]-3-methylthio-3-ce phe m-4- carboxylic acid was found to be a new orally active antibiotic.

[Assessment of the reproductive function of white rats exposed to cephalexin by inhalation]. / Otsenka sostoianiia reproduktivnoi funktsii belykh krys pri ingaliatsionnom vozdeistvii tsefaleksinom.

The embryotoxic and teratogenic effects of cefalexin were studied on Wistar albino rats subjected to inhalations of the antibiotic within the whole gravidity term. It was shown that in a concentration of 1.29 mg/m3 cefalexin did not increase the rate of fetus intrauterine death, had no unfavourable effect on the fetus and placenta development and did not induce anomalies in development of the fetus internal organs. The frequency of sensitization in the gravid and nongravid animals was the same. No signs of sensitization were detected in the litter of the rats treated with cefalexin inhalations.

Synthesis and antibacterial activities of new (alpha-hydrazinobenzyl)cephalosporins.

Some (alpha-hydrazinobenzyl)cephalosporins, I (R = Me, CH2OAc, Cl) and II (R = Me, CH2OAc), structurally related (formula; see text) to cephalexin, cephaloglycin, and cefaclor have been prepared and evaluated in vitro for their antimicrobial activity. The synthesis involves the condensation of the chloride hydrochloride III (R = H or Me) with the 7-aminocephem derivatives IV. The hydrazino compound I (R = Cl), an analogue of cefaclor, resulted in being the most active compound of the series.