[Staphylococcus aureus: new and old antimicrobial agents]. / Staphylococcus aureus: nuevos y antiguos antimicrobianos.

The objective of the study was to evaluate the susceptibility to old and new antimicrobial agents against hospital-acquired oxacillin-resistant Staphylococcus aureus (HA-ORSA), community-acquired oxacillin-resistant S. aureus (CA-ORSA), and oxacillin-susceptible S. aureus(OSSA). The minimum inhibitory concentration of different antimicrobial agents against 118 S. aureus consecutive and prospective isolates was studied by the CLSI agar dilution method. In ORSA isolates without accompanying resistance, the mecA gene, the Panton-Valentine leukocidin gene (PVL), and the gamma-hemolysin gene were determined by PCR, and the SCC cassette mec gene by multiplex PCR. Out of the 118 isolates, 44 were HA-ORSA, 16 were CA-ORSA, and 58 corresponded to OSSA. The HA-ORSA isolates presented simultaneous resistance to erythromycin, clindamycin, gentamicin, ciprofloxacin, levofloxacin, and moxifloxacin whereas all of them were susceptible to tigecycline (TIG), vancomycin, teicoplanin and linezolid (LZD). The CA-ORSA isolates were only resistant to OXA and presented susceptibility to all the antimicrobial agents assayed. In all of them, the mec-A gene, the PVL gene, the gamma-hemolysin gene and the SCC cassette mec type IV gene were detected. With the OSSA and CA-ORSA isolates, all the non-beta-lactam antimicrobial agents assayed exhibited excellent in vitro activity. However, in the HA-ORSA isolates, only the old antimicrobial agents such as glycopeptides, doxyciclin, rifampin, and trimethoprim-sulfamethoxazole and the new antimicrobial agents LZD and TIG, presented good in vitro activity. The ORSA phenotype without accompanying resistance was highly predictive of CA-ORSA as confirmed by a positive SCC cassette mec type IV.

[Microbiological and epidemiological evaluation of carbapenem-resistant Acinetobacter baumannii clones isolated at an intensive care unit of a University Hospital in Buenos Aires city]. / Evaluación microbiol6gica y epidemiológica de los clones de Acinetobacter baumannii resistentes a los carbapenemes aislados en la unidad de cuidados intensivos de un Hospital Universitario de la ciudad de Buenos Aires.

From June to December 2004, thirty-three carbapenem-resistant Acinetobacter baumannii isolates recovered from twenty nine patients at the intensive care unit in Hospital de Clínicas, Universidad de Buenos Aires, were studied. The isolates were categorized by molecular methods as: clone I (n = 14), clone IV (n = 7), clone III (n = 6), clone VI (n = 3), clone II (n = 2) and clone X (n = 1). Twenty one isolates were recovered from lower respiratory tract samples, 11 of which belonged to clone I. Clone III isolates were mainly recovered from non-respiratory samples (5/6). Clone IV isolates were recovered from patients not receiving previous imipenem therapy. The majority of the isolates belonging to clones I and IV were able to survive on inert materials for more than 5 days, whereas adhesion to catheters was observed in isolates belonging to clones I and III, especially in those related to bacteremia. Clone III isolates showed colistin, gentamicin and levofloxacin susceptibility, whereas clone I isolates and most from clone IV were only susceptible to colistin and tetracyclines.

Evaluación microbiológica y epidemiológica de los clones de Acinetobacter baumannii resistentes a los carbapenemes aislados en la unidad de cuidados intensivos de un Hospital Universitario de la ciudad de Buenos Aires / Microbiological and epidemiological evaluation of carbapenem-resistant Acinetobacter baumannii clones isolated at an intensive care unit of a University Hospital in Buenos Aires city

Entre junio y diciembre de 2004 se estudiaron 33 aislamientos de Acinetobacter baumannii resistentes a los carbapenemes, aislados de materiales clínicos de 29 pacientes internados en la unidad de cuidados intensivos del Hospital de Clínicas de la Universidad de Buenos Aires. La distribución clonal de esos aislamientos fue la siguiente: clon I (n = 14), clon IV (n = 7), clon III (n = 6), clon VI (n = 3), clon II (n = 2) y clon X (n = 1).Veintiún aislamientos se recuperaron de materiales del tracto respiratorio inferior, 11 de ellos pertenecieron al clon I. Casi todos los aislamientos pertenecientes al clon III (5/6) se recuperaron de materiales no respiratorios, y todos los del clon IV se recuperaron de pacientes que no recibieron imipenem. En los aislamientos pertenecientes a los clones I y III se observó una mayor adherencia a catéteres, principalmente en los asociados con bacteriemias. La mayoría de los aislamientos de los clones I y IV sobrevivieron en materiales inertes durante un período superior a los 5 días. La totalidad de los aislamientos del clon III fueron sensibles a colistina, gentamicina y levofloxacina, mientras que los del clon I y la mayoría de los del clon IV sólo fueron sensibles a colistina y tetraciclinas.

From June to December 2004, thirty-three carbapenem-resistant Acinetobacter baumannii isolates recovered from twenty nine patients at the intensive care unit in Hospital de Clínicas, Universidad de Buenos Aires, were studied. The isolates were categorized by molecular methods as: clone I (n = 14), clon IV (n = 7), clone III (n = 6), clone VI (n = 3), clone II (n = 2) and clone X (n = 1). Twenty one isolates were recovered from lower respiratory tract samples, 11 of which belonged to clon I. Clone III isolates were mainly recovered from non-respiratory samples (5/6). Clone IV isolates were recovered from patients not receiving previous imipenem therapy. The majority of the isolates belonging to clones I and IV were able to survive on inert materials for more than 5 days, whereas adhesion to catheters was observed in isolates belonging to clones I and III, especially in those related to bacteremia. Clone III isolates showed colistin, gentamicin and levofloxacin susceptibility, whereas clone I isolates and most from clone IV were only susceptible to colistin and tetracyclines.

[Sensitivity to colistin: evaluation of cut-off points available in disk diffusion test]. / Sensibilidad a colistín: evaluación de los puntos de corte disponibles en el antibiograma por difusión.

Infections produced by multidrug resistant organisms are one of the greatest problems in health centers. Often, only polymyxines show good activity "in vitro" against the carbapenem resistant gram-negative strains; but the National Committee for Clinical Laboratory Standards (NCCLS) documents do not currently provide interpretative criteria for testing the polymyxines. The antimicrobial activity of colistin, and the correlation between the agar dilution test and disk diffusion test were evaluated against 186 gram-negative strains isolated at the Hospital de Clínicas "José de San Martín" of Buenos Aires city. All susceptibility tests were performed according to the NCCLS recommendations. Were evaluated two breakpoints, NCCLS 1981 (< or = 8 mm and > or = 11 mm), and R. Jones 2001 (< or = 11 mm and > or = 14 mm). Discrepancies on interpretative category were found (0.5% minor; 2.2% major and 4.4% very major) with NCCLS 1981, and (18.9% minor; 3.8% major and 0.5% very major) with R. Jones 2001 criteria. Conclusions. In spite of the fact that the breakpoint used by R. Jones 2001 decreases the very major error but increases the minor error, according to our results we recommend the use of MIC methods to assist the therapeutic application of colistin; however resistance to colistin was not detected with zone diameters > or = 16 mm.

Sensibilidad a colistín: evaluación de los puntos de corte disponibles en el antibiograma por difusión / Susceptibility to colistin: evaluation of breakpoints available in disk diffusion test

Las infeccionesproducidas por microorganismos multirresistentes son uno de los mayores problemas en los centros asistenciales. Frecuentemente, sólo las polimixinas muestran actividad “in vitro” frente a aislamientos de bacilos gram-negativos resistentes a los carbapenemes. Sin embargo, el National Committee for Clinical Laboratory Standards (NCCLS) no incluye, actualmente, recomendaciones para la realización de las pruebas de sensibilidad para este grupo de antibióticos. Se determinóla actividad de colistín y la correlación entre las pruebas de difusión y dilución de este antibiótico frente a 186 aislamientos contemporáneos en el Hospital de Clínicas “José de San Martín”, siguiendo las recomendaciones generales del NCCLS. Se evaluaron dos puntos de corte: NCCLS 1981 (resistente £ 8 mm y sensible > 11mm) y R. Jones 2001 (resistente £ 11mm y sensible > 14mm). Utilizando el punto de corte del NCCLS 1981 se cometieron los siguientes errores: 0,5% “minor”; 2,2% “major” y 4,4% “very major”, mientras que con el propuesto por R. Jones 2001: 18,9% “minor”; 3,8% “major” y 0,5% “very major”. En conclusión, dado que el punto de corte utilizado por R. Jones 2001 disminuye el error “very major” pero aumenta el “minor” se recomienda la utilización de la concentración inhibitoria mínima (CIM) para confirmar la sensibilidad a colistín cuando sea usada en el tratamiento de infecciones, sin embargo no se detectó resistencia a colistín con halos de inhibición > a 16 mm.

Infections produced by multidrug resistant organisms are one of the greatest problems in health centers. Often, only polymyxines show good activity “in vitro” against the carbapenem resistant gram-negative strains; but the National Committee for Clinical Laboratory Standards (NCCLS) documents do not currently provide interpretative criteria for testing the polymyxines.The antimicrobial activity ofcolistin,and the correlation betweenthe agar dilution test and disk diffusion test were evaluated against 186 gram-negative strains isolated at the Hospital de Clínicas “José de San Martín” of Buenos Aires city. All susceptibility tests were performed according to the NCCLS recommendations. Were evaluated two breakpoints, NCCLS 1981 (£ 8mm and >11mm), and R. Jones 2001 (£ 11 mm and > 14 mm). Discrepancies on interpretative category were found (0.5% minor; 2.2% major and 4.4% very major) with NCCLS 1981, and (18.9% minor; 3.8% majorand 0.5% very major) with R. Jones 2001 criteria. Conclusions. In spite of the fact that the breakpoint used by R. Jones 2001decreases the very major error but increases the minor error, according to our results we recommend the use of MIC methods to assist the therapeutic application of colistin; however resistance to colistin was not detected with zone diameters > 16mm.

Sensibilidad a colistín: evaluación de los puntos de corte disponibles en el antibiograma por difusión. / [Sensitivity to colistin: evaluation of cut-off points available in disk diffusion test]

Infections produced by multidrug resistant organisms are one of the greatest problems in health centers. Often, only polymyxines show good activity [quot ]in vitro[quot ] against the carbapenem resistant gram-negative strains; but the National Committee for Clinical Laboratory Standards (NCCLS) documents do not currently provide interpretative criteria for testing the polymyxines. The antimicrobial activity of colistin, and the correlation between the agar dilution test and disk diffusion test were evaluated against 186 gram-negative strains isolated at the Hospital de Clínicas [quot ]José de San Martín[quot ] of Buenos Aires city. All susceptibility tests were performed according to the NCCLS recommendations. Were evaluated two breakpoints, NCCLS 1981 (< or = 8 mm and > or = 11 mm), and R. Jones 2001 (< or = 11 mm and > or = 14 mm). Discrepancies on interpretative category were found (0.5

minor; 2.2

major and 4.4

very major) with NCCLS 1981, and (18.9

minor; 3.8

major and 0.5

very major) with R. Jones 2001 criteria. Conclusions. In spite of the fact that the breakpoint used by R. Jones 2001 decreases the very major error but increases the minor error, according to our results we recommend the use of MIC methods to assist the therapeutic application of colistin; however resistance to colistin was not detected with zone diameters > or = 16 mm.

Effects of endothelin-3 on water and sodium excretion during extracellular volume expansion.

The aim of the present study was to elucidate the role of an IV dose of endothelin-3 (ET-3) (5 ng Kg-1 min-1) on mean arterial pressure (MAP), on diuresis and natriuresis in control and in volume expanded anesthetized rats. A systemic infusion of ET-3 in normal rats (Group I) increased MAP and produced a trend of increasing diuresis, without changes in natriuresis. A 10% body weight expansion (Group II) increased diuresis and natriuresis without changes in MAP. The simultaneous infusion of ET-3 and expansion with saline (Group III) resulted in an increase in MAP, an enhanced diuretic response, and a natriuresis of similar magnitude to that observed in Group II. These results suggest that the diuresis produced by a low dose of exogenous ET-3 in control rats, is independent of sodium excretion. Furthermore, the enhanced diuresis caused by ET-3 during expansion is greater than the addition of ET-3 and expansion effects, suggesting that new mechanisms are triggered in order to maintain volume and salt homeostasis in this state.