Effects of three veterinary antibiotics and their binary mixtures on two green alga species.

The individual and combined toxicities of chlortetracycline (CTC), oxytetracycline (OTC) and enrofloxacin (ENF) have been examined in two green algae representative of the freshwater environment, the international standard strain Pseudokichneriella subcapitata and the native strain Ankistrodesmus fusiformis. The toxicities of the three antibiotics and their mixtures were similar in both strains, although low concentrations of ENF and CTC + ENF were more toxic in A. fusiformis than in the standard strain. The toxicological interactions of binary mixtures were predicted using the two classical models of additivity: Concentration Addition (CA) and Independent Action (IA), and compared to the experimentally determined toxicities over a range of concentrations between 0.1 and 10 mg L-1. The CA model predicted the inhibition of algal growth in the three mixtures in P. subcapitata, and in the CTC + OTC and CTC + ENF mixtures in A. fusiformis. However, this model underestimated the experimental results obtained in the OTC + ENF mixture in A. fusiformis. The IA model did not predict the experimental toxicological effects of the three mixtures in either strain. The sum of the toxic units (TU) for the mixtures was calculated. According to these values, the binary mixtures CTC + ENF and OTC + ENF showed an additive effect, and the CTC + OTC mixture showed antagonism in P. subcapitata, whereas the three mixtures showed synergistic effects in A. fusiformis. Although A. fusiformis was isolated from a polluted river, it showed a similar sensitivity with respect to P. subcapitata when it was exposed to binary mixtures of antibiotics.

Effects of six antibiotics and their binary mixtures on growth of Pseudokirchneriella subcapitata.

The effect of ampicillin (AMP), amoxicillin (AMX), cephalotin (CEP), ciprofloxacin (CPF), gentamycin (GEN), and vancomycin (VAN) have been examined individually and as binary mixtures, on a non-target aquatic organism, the green alga Pseudokichneriella subcapitata. The ß-lactam antibiotics AMP and AMX were not toxic to the alga at concentrations up to 2000 mgl(-1) (less than 10% of algal growth inhibition), whereas the fluoroquinolone CPF, and the aminoglycoside GEN were the most toxic antibiotics, with an EC50=11.3 ± 0.7 mgl(-1) and 19.2 ± 0.5 mgl(-1), respectively. The cephalosporin CEP and the glycopeptide VAN were less toxic than the last two mentioned, showing an EC50>600 mgl(-1) and 724 ± 20 mgl(-1), respectively. The toxicological interactions of binary mixtures were predicted by the two classical models of additivity: concentration addition (CA) and independent action (IA), and compared to the experimentally determined toxicities over a range of concentrations between 1 and 50 mgl(-1). In all cases a clear synergistic effect was observed, showing that single compound toxicity data are not adequate for the prediction of aquatic toxicities of antibiotic mixtures. Risk assessment was performed by calculating the ratio between predicted environmental concentrations (PEC) and the predicted no effect concentration (PNEC). All the antibiotics tested, excepting GEN, have a potential ecological risk, taking into account the PEC of hospital effluents from Buenos Aires, Argentina. These risks increase when antibiotics are present in binary mixtures.

Disinfectant-resistant bacteria in Buenos Aires city hospital wastewater

Large quantities of disinfectants are used in hospitals, externally on human skin or to eliminate microorganisms from inanimate objects. After use, residual quantities of these products reach the wastewater, exposing the bacteria that survive in hospital wastewaters to a wide range of biocides that could act as a selective pressure for the development of resistance. Increasing attention has been directed recently to the resistance of bacteria to disinfectants. The aim of this paper was to determine the disinfectant bacterial resistance pattern of the microflora released to the urban sewer system by hospital effluents. The characterization of the waste water microflora was performed by determination of the CFU of heterotrophic bacteria, fecal indicator bacteria, Pseudomonas sp. and Staphylococcus sp., in a Buenos Aires hospital effluent. The bacterial resistance to the disinfectants more frequently used in the hospital practice, glutaraldehyde, chlorhexidine and povidone-iodine, was then evaluated. Disinfectant resistant bacterial strains were isolated and typified. Between 10³ and 10(6) chlorexidine resistant bacteria/100 mL were isolated from the samples. Bacteria resistant to other disinfectants ranged between 10³ and 10(4) /100 mL. The bacterial population resistant to desinfectants to was mainly composed by Enterobacteriaceae, Staphylococcus spp, and Bacillus spp, which are highly associated to nosocomial infections. The results obtained show that the hospital effluents are of importance in the bacterial resistance selection process, particularly in the case of disinfectants.

Os hospitais utilizam uma grande quantidade de desinfetantes para eliminar microorganismos tanto da pele humana como de superfícies inanimadas. Após sua utilização, esses produtos podem chegar ao esgoto em quantidades residuais. A pressão seletiva exercida pelos antimicrobianos nos efluentes hospitalares propicia a disseminação de linhagens resistentes. Além dos antibióticos, os desinfetantes podem atuar como agentes seletivos de linhagens resistentes aos antimicrobianos. Este trabalho teve como objetivo o estudo do perfil da resistência aos desinfetantes das bactérias lançadas na rede de esgoto pelo efluente hospitalar. Na caracterização microbiológica do efluente do Hospital de Clínicas Buenos Aires, determinou-se a concentração de bactérias heterotróficas, bactérias indicadoras fecais, Pseudomonas sp. e Staphylococcus sp. presentes. A resistência aos desinfetantes empregados no hospital, glutaraldeído, iodo povidona, e clorexidina foi então avaliada. Verificou-se a existência de bactérias resistentes à clorexidina em número variando de 10³ a 10(6) bactérias/100 mL e de bactérias resistentes a outros desinfetantes em uma faixa de variação de 10³ a 10(4) bactérias/100 mL. Bactérias dos gêneros Staphylococcus e Bacillus, e da família Enterobacteriaceae, envolvidas em infecções hospitalares, apresentaram resistência aos desinfetantes testados. Estes resultados indicam que as águas residuárias de hospitais desempenham um papel de grande relevância na disseminação de linhagens bacterianas resistentes aos desinfetantes no meio aquático.

Genotoxicity of maleic hydrazide, acridine and DEHP in Allium cepa root cells performed by two different laboratories.

The purpose of this paper was to compare the results of the Allium cepa chromosome aberration assay between two laboratories under the same test protocol and at the same time, use chemicals and onions obtained in their own homeland. For this study three chemicals were selected: di(2-ethylhexyl)phthalate (DEHP), maleic hydrazide, and acridine. Both laboratories found genotoxicity with a positive dose-response relationship for maleic hydrazide and acridine. However, for DEHP the results were quite different--one of the laboratories found this compound not genotoxic but the other found a positive response. Although the comparative study was inconclusive for DEHP, it was successful for the maleic hydrazide, acridine and also for the positive control (methyl methanesulfonate). Further studies need to be performed in the case of DEPH.

Estudio de la genotoxicidad resultante de una mezcla de origen ambiental mediante dos sistemas bacterianos / Study of the genotoxicity of environmental complex mixtures with two bacterial tests

El ensayo de Ames, que permite estudiar la genotoxicidad de conpuestos químicos mediante la reversión de mutaciones en cepas de Salmonella typhimurium, y el ensayo con Bacillus subtilis rec-, que utiliza con el mismo fin mutantes deficientes en procesos de reparación del ADN, fueron empleados para estudiar mezclas complejas de origen ambiental. Muestras de tierras contaminadas con residuos de la industria petroquímica se sometieron a una extracción secuencial con éter etílico y metanol. Dichos solventes se evaporaron y el residuo se redisolvió en dimetilsulfóxido. Los extractos así obtenidos no mostraron efectos mutagénicos para las cepas de Salmonella typhimurium TA98 y TA100 si bien en esta última se observó una marcada toxicidad inducida por el extracto éter de la parcela 1. Cuando este extracto se ensayó con el sistema de Bacillus subtilis rec-evidenció una clara relación dosis de extracto-respuesta genotóxica. Los resultados obtenidos con ambos sistemas biológicos permitieron estimar que la toxicidad genética resultante de la mezcla ensayada sería del tipo de la de los compuestos intercalantes al ADN

Estudio de la genotoxicidad resultante de una mezcla de origen ambiental mediante dos sistemas bacterianos / Study of the genotoxicity of environmental complex mixtures with two bacterial tests

El ensayo de Ames, que permite estudiar la genotoxicidad de conpuestos químicos mediante la reversión de mutaciones en cepas de Salmonella typhimurium, y el ensayo con Bacillus subtilis rec-, que utiliza con el mismo fin mutantes deficientes en procesos de reparación del ADN, fueron empleados para estudiar mezclas complejas de origen ambiental. Muestras de tierras contaminadas con residuos de la industria petroquímica se sometieron a una extracción secuencial con éter etílico y metanol. Dichos solventes se evaporaron y el residuo se redisolvió en dimetilsulfóxido. Los extractos así obtenidos no mostraron efectos mutagénicos para las cepas de Salmonella typhimurium TA98 y TA100 si bien en esta última se observó una marcada toxicidad inducida por el extracto éter de la parcela 1. Cuando este extracto se ensayó con el sistema de Bacillus subtilis rec-evidenció una clara relación dosis de extracto-respuesta genotóxica. Los resultados obtenidos con ambos sistemas biológicos permitieron estimar que la toxicidad genética resultante de la mezcla ensayada sería del tipo de la de los compuestos intercalantes al ADN (AU)

[Genotoxicity resulting from a complex mixture of environmental origin using 2 bacterial systems]. / Estudio de la genotoxicidad resultante de una mezcla compleja de origen ambiental mediante dos sistemas bacterianos.

The genotoxicity of environmental complex mixtures was tested with Ames mutagenicity assay and with Bacillus subtilis rec assay for estimation of primary DNA damage. Soil samples obtained from an area contaminated with petrochemical wastes were sequentially extracted with ethyl ether and methanol. After evaporation to dryness the extracts were resuspended in dimethylsulfoxide for their use in biological tests. No mutagenic response was detected with the Ames test. Ether extract from parcel 1 showed an unusually high toxicity for Salmonella typhimurium TA100 and induced DNA damage in Bacillus subtilis with a clear relationship dose-genotoxic response. The analysis of the results obtained in both assays and the nature of the samples indicate that the genotoxicity detected in the complex mixture is compatible with the one caused by DNA intercalating compounds.

[Computer-assisted design and production of a femoral hip prosthesis]. / Conception et fabrication assistée par ordinateur d'une prothèse fémorale de hanche.

The authors believe that a better design of prosthetic femoral stem might reduce the incidence of loosening. They have developed a method to make a prosthesis precisely adapted to a patient. Two X-Rays, one antero-posterior and one lateral view are taken. Several bony points are precisely determined. The magnification of the X-Rays is calculated, using a metallic circular collar placed around the thigh. A computer analyses the X-Rays, bony points are numerated and the prostheses have a length, thickness and shape adapted to the patient's hip. A study of the pressures transmitted by the prostheses to the bone was made using geometrical models. Compared to conventional prostheses, a prosthesis made as an exact fit to the hip of the patient reduces the pressure applied on femoral cortex by two thirds. A prosthesis with a collar also allows reduction of pressure on the cortex by a degree of three to one. The personalized prosthesis obtained by the use of a computer appears to be a stage in progress towards a better fitting and more reliable prosthesis. Twenty five patients have been operated on with good short-term results.