Hemolytic and Antimicrobial Activities of a Series of Cationic Amphiphilic Copolymers Comprised of Same Centered Comonomers with Thiazole Moieties and Polyethylene Glycol Derivatives.

A series of well-defined antimicrobial polymers composed of comonomers bearing thiazole ring (2-(((2-(4-methylthiazol-5-yl)ethoxy)carbonyl)oxy)ethyl methacrylate monomer (MTZ)) and non-hemotoxic poly(ethylene glycol) side chains (poly(ethylene glycol) methyl ether methacrylate (PEGMA)) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. By post-polymerization functionalization strategy, polymers were quaternized with either butyl or octyl iodides to result in cationic amphiphilic copolymers incorporating thiazolium groups, thus with variable hydrophobic/hydrophilic balance associated to the length of the alkylating agent. Likewise, the molar percentage of PEGMA was modulated in the copolymers, also affecting the amphiphilicity. The antimicrobial activities of these cationic polymers were determined against Gram-positive and Gram-negative bacteria and fungi. Minimum inhibitory concentration (MIC) was found to be dependent on both length of the alkyl hydrophobic chain and the content of PEGMA in the copolymers. More hydrophobic octylated copolymers were found to be more effective against all tested microorganisms. The incorporation of non-ionic hydrophilic units, PEGMA, reduces the hydrophobicity of the system and the activity is markedly reduced. This effect is dramatic in the case of butylated copolymers, in which the hydrophobic/hydrophilic balance is highly affected. The hemolytic properties of polymers analyzed against human red blood cells were greatly affected by the hydrophobic/hydrophilic balance of the copolymers and the content of PEGMA, which drastically reduces the hemotoxicity. The copolymers containing longer hydrophobic chain, octyl, are much more hemotoxic than their corresponding butylated copolymers.

Activity of doripenem against extended-spectrum beta-lactamase-producing Enterobacteriaceae and Pseudomonas aeruginosa isolates.

The in vitro activity of doripenem was evaluated against a recent collection of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae and Pseudomonas aeruginosa isolates (201 ESBL-producing Enterobacteriaceae [153 Escherichia coli and 48 Klebsiella pneumoniae] and 201 P. aeruginosa). Comparator agents included amikacin, tobramycin, ciprofloxacin, cefepime, cefotaxime, ceftazidime piperacillin-tazobactam, imipenem, and meropenem. Both doripenem and meropenem inhibited 100% of the ESBL-producing Enterobacteriaceae at 4 microg/mL. Doripenem is active against ESBL-producing Enterobacteriaceae and P. aeruginosa isolates. Its activity is similar to that of meropenem and slightly better than that of imipenem. The results of this study suggest that doripenem could be an alternative therapeutic agent for infections caused by these organisms.

[Comparative study of the susceptibility to daptomycin and other antimicrobials against Staphylococcus spp. resistant to methicillin and Enterococcus spp. using Wider, E-test, and microdilution methods]. / Estudio comparativo de Wider, E-test y microdilución para la determinación de la sensibilidad a daptomicina y otros tres antimicrobianos de aislamientos clínicos de Staphylococcus spp. resistentes a meticilina y Enterococcus spp.

The human and material costs of inappropriate antimicrobial therapy are high. This study was designed to search for a rapid, simple and effective antimicrobial susceptibility test capable of identifying the best treatment strategy against microorganisms causing hospital infections showing resistance or reduced susceptibility to the more traditional antibiotics. The tests compared were the E-test, an automated test (Wider) and broth microdilution ( as the reference test), to determine the susceptibility to vancomycin, teicoplanin, linezolid and daptomycin of clinical isolates of methicillin resistant Staphylococcus aureus (MRSA), methicillin resistant coagulase negative Staphylococcus spp. and Enterococccus spp. The E-test and Wider methods showed good agreement with the reference method indicating their reliability for routine susceptibility testing of staphylococci and enterococci against vancomycin, teicoplanin, linezolid and daptomycin. Notwithstanding, when faced with a serious enterococcal infection, the MIC of daptomycin should be more accurately determined using a reference technique such as broth microdilution.

[In vitro activities of colistin combinations against Pseudomonas aeruginosa isolated from the intensive care unit]. / Actividad in vitro de terapia combinada con colistina frente a Pseudomonas aeruginosa aisladas en Unidad de Cuidados Intensivos.

Introduction. As the number of multidrug-resistant strains of Pseudomonas aeruginosa has risen in the intensive care unit (ICU) of the San Carlos Clinic Hospital, 12 consecutive isolates from different patients were collected to determine the possibility of an epidemic outbreak caused by the spread of a single strain. We determined the antimicrobial susceptibility to the most common agents used in the treatment of infections caused by this bacteria. The results of susceptibility studies suggest that different strains of P. aeruginosa are responsible for the respiratory tract infections in ICU. Methods. The clonal relationship between the isolates using was determined using BOX and ERIC primers by means of repetitive sequence-based polymerase chain reaction (rep-PCR). The in vitro activity of these strains against colistin, rifampicin, doxicycline and azythromycin was studied to determine in which cases the combination of colistin with any of the other three antibiotics was synergistic. Results. Sensitivity studies point out the presence of several strains of P. aeruginosa as the causal agents of respiratory infections produced by this microorganism in the ICU. Combinations of colistin with doxycicline and colistin with azithromycin were synergistic for some isolates in the synergy studies. Discussion. Clonal studies reveal the presence of five different clones among our isolates. Therefore we can conclude that there was no outbreak of P. aeruginosa in the ICU. Synergistic activity of combinations of colistin plus azithromycin, colistin plus doxicycline and colistin plus rifampicin was less than expected and a high percentage of indifferent results was observed.

Actividad in vitro de terapia combinada con colistina frente a Pseudomonas aeruginosa aisladas en Unidad de Cuidados Intensivos / In vitro activities of colistin combinations against Pseudomonas aeruginosa isolated from the intensive care unit

Introducción. Ante el incremento de aislados de Pseudomonasaeruginosa multirresistentes en la Unidad de CuidadosIntensivos (UCI) del Hospital Clínico San Carlos deMadrid y para determinar la posibilidad de que se tratase deun brote epidémico causado por la diseminación de unaúnica cepa, se recogieron 12 muestras consecutivas de distintospacientes que fueron identificadas y a las que posteriormentese determinó su sensibilidad a los antibióticosutilizados habitualmente para el tratamiento de las infeccionesproducidas por este microorganismo.Métodos. Mediante la amplificación de secuencia basadaen la reacción en cadena de la polimerasa (repetitive sequence-based polymerase chain reaction, rep-PCR) se determinó larelación clonal entre los aislados utilizando los primers BOX yERIC y se estudió la actividad in vitro frente a estas cepas decolistina, rifampicina, doxiciclina y azitromicina para determinaren qué casos la combinación de colistina con alguno de losotros tres antibióticos presentaba actividad sinérgica.Resultados. Los estudios de sensibilidad apuntan a la presenciade varias cepas de P. aeruginosa como responsables delas infecciones respiratorias producidas por este microorganismoen la UCI, hecho que fue corroborado mediante los estudiosclonales realizados. En los estudios de sinergia las asociacionesde colistina con doxiciclina y con azitromicina presentaron actividadsinérgica para alguno de los aislados.Discusión. Los resultados de los estudios clonales revelanla presencia de cinco clones diferentes entre los aisladosseleccionados, por lo que podemos concluir que no se tratade un brote de P. aeruginosa en la UCI. La actividad sinérgicade la asociación de colistina con azitromicina, doxiciclinay rifampicina ha sido menor de la esperada y se observa unelevado porcentaje de resultados indiferentes (AU)

Introduction. As the number of multidrug-resistantstrains of Pseudomonas aeruginosa has risen in the intensivecare unit (ICU) of the San Carlos Clinic Hospital,12 consecutive isolates from different patients were collectedto determine the possibility of an epidemic outbreakcaused by the spread of a single strain. We determinedthe antimicrobial susceptibility to the most commonagents used in the treatment of infections caused by thisbacteria. The results of susceptibility studies suggest thatdifferent strains of P. aeruginosa are responsible for therespiratory tract infections in ICU.Methods. The clonal relationship between the isolatesusing was determined using BOX and ERIC primersby means of repetitive sequence-based polymerase chainreaction (rep-PCR). The in vitro activity of these strainsagainst colistin, rifampicin, doxicycline and azythromycinwas studied to determine in which cases the combinationof colistin with any of the other three antibioticswas synergistic.Results. Sensitivity studies point out the presence ofseveral strains of P. aeruginosa as the causal agents ofrespiratory infections produced by this microorganism inthe ICU. Combinations of colistin with doxycicline andcolistin with azithromycin were synergistic for some isolatesin the synergy studies.Discussion. Clonal studies reveal the presence of fivedifferent clones among our isolates. Therefore we canconclude that there was no outbreak of P. aeruginosa inthe ICU. Synergistic activity of combinations of colistinplus azithromycin, colistin plus doxicycline and colistinplus rifampicin was less than expected and a high percentageof indifferent results was observed (AU)

m-Xylylenediamine determination in the official EU aqueous food simulants.

European Union directive 90/128/EEC prescribes a specific migration limit of 0.05 mg/kg for the aliphatic diamine m-xylylenediamine (m-XDA) into food or food simultants, but there is no generally accepted method of analysis available for compliance testing with the given restriction. A method is described for the determination of m-XDA monomer in the following food simulants: distilled water, 3% (w/v) acetic acid, and 15% (v/v) ethanol. The method is appropriate for the quantitative determination of m-XDA at a minimum level of 0.020 mg/kg in these food simulants. Detection limits are in the range of 0.004 to 0.010 mg m-XDA per kilogram food simulant (depending on the type of food simulant). The method should also be applicable to other aqueous food simulants. m-XDA in aqueous simulant test samples is determined by high-performance liquid chromatography with fluorescence detection following derivatization with fluorescamine. Quantitation is relative to external standards. The identity of m-XDA may be confirmed by the presence of a second peak in the chromatograms obtained from samples derivatized with less fluorescamine or by comparison with authentic samples.