Molecular diversity of quinolone resistance in genetically related clinical isolates of Staphylococcus aureus and susceptibility to newer quinolones.

The genes encoding topoisomerases (gyrA and grlA) and the norA promoter of 100 fluoroquinolone-susceptible and -resistant Staphylococcus aureus clinical isolates obtained in two geographically distant hospitals were analysed. The relationship between mutations found and the susceptibility to newer quinolones was determined. Thirty-nine strains were grouped in seven clones by pulsed-field gel electrophoresis (PFGE). The remaining 61 strains were classified as unrelated strains. In three clones, all strains showed the same grlA-gyrA-norA mutation profiles. Strains in the rest of the groups showed different mutation profiles, even though PFGE indicated that they possessed genetically similar populations. One cluster showed a high level of diversity; five different mutation profiles were detected in the six isolates belonging to this pattern. Two isolates had a Glu84 to Lys mutation in grlA and another isolate had this mutation combined with a Ser84 to Leu mutation in gyrA. Combination of a Ser80 to Phe mutation in grlA and a Ser84 to Leu in gyrA was found in the two other isolates. One of these also had a thymine to a guanine transversion at a position 89 nucleotides upstream of the norA start codon in the norA promoter. These results show that fluoroquinolone resistance in clinical S. aureus strains does not necessarily result from the spread of resistant clones. Fluoroquinolone resistance may develop independently in strains belonging to the same PFGE pattern by accumulation of different mutations over a quinolone-susceptible ancestor wild type or single grlA mutant.

[In vitro activity of new quinolones against clinical strains of Staphylococcus aureus of the wild type and with mutations characterized by gyrA, gyrB and grlA]. / Actividad in vitro de nuevas quinolonasfrente a cepas clínicas de Staphylococcus aureussilvestres y con mutaciones caracterizadasen gyrA, gyrB y grlA.

The aim of this study was to determine the in vitro activity of five quinolones against clinical strains of methicillin-susceptible and -resistant Staphylococcus aureus clinical isolates characterized at the molecular level with respect to the presence of mutations in genes coding for resistance to quinolones (grlA, gyrA and gyrB). The relationship between the mutations found and the activities of these quinolones was also analyzed. Trovafloxacin was the most active against methicillin-susceptible S. aureus and showed good activity against methicillin-resistant S. aureus, with a MIC90 of 2 mg/l. The grlA-gyrA double mutation was the most frequent (55% of the strains). Single mutation in grlA was detected only in 5% of strains; 39% of strains showed a wild-type genotype. The grlA-gyrA double mutants presented a high level of resistance against the fluoroquinolones tested except for trovafloxacin, with the MIC ranging between 0.5 and 4 mg/l. Wild-type strains were susceptible to all the fluoroquinolones tested and the single grlA mutants had a low level of quinolone resistance but were still below the breakpoint for resistance. Trovafloxacin and sparfloxacin were less affected by this mutation.

Resultados histeroscópicos en pacientes tratadas con tamoxifeno / Histeroscopical results on tamoxifen-treated patients

El tamoxifeno es la terapia coadyuvante prescrita con más frecuencia en mujeres con cáncer de mama. Objetivo: valoración de los hallazgos histeroscópicos en mujeres con cáncer de mama en tratamiento con tamoxifeno durante un tiempo superior a seis meses, cuando se ha encontrado patología endometrial en la ecografía transvaginal de screening o la paciente ha presentado síntomas. Diseño del estudio: estudio retrospectivo de 73 pacientes con cáncer de mama en tratamiento con tamoxifeno sometidas a una histeroscopia diagnóstica Resultados: La media de edad de las pacientes fue de 62,28 años; de éstas el 89 por ciento fueron postmenopáusicas. La principal indicación para realizar la histeroscopia fue la sospecha ecográfica de patología endometrial (82 por ciento), seguido de la metrorragia postmenopáusica (13,7 por ciento).El hallazgo ecográfico más frecuente fue la presencia de un endometrio engrosado (75,3 por ciento). Los hallazgos histeroscópicos por orden de frecuencia fueron: histeroscopia normal, pólipos, hiperplasia quistica y atrofia endometrial. No hubo ningún caso de adenocarcinoma (AU)

Actividad in vitro de nuevas quinolonasfrente a cepas clínicas de Staphylococcus aureussilvestres y con mutaciones caracterizadasen gyrA, gyrB y grlA / In vitro activity of new quinolones against clinical strainsof Staphylococcus aureus of the wild type and with mutations characterized by gyrA, gyrB and grlA

Se ha estudiado la actividad in vitro de cinco fluoroquinolonas frente a cepas clínicas de Staphylococcus aureus, sensibles y resistentes a la meticilina, caracterizadas desde el punto de vista genético respecto a la existencia de mutaciones en los genes causantes de la resistencia a las quinolonas (grlA, gyrA y gyrB). También se comprobó el efecto de estas mutaciones en la actividad de las quinolonas. El trovafloxacino apareció como el más activo de los antimicrobianos estudiados frente a S. aureus sensibles a la meticilina (SASM), presentando también una buena actividad frente a los resistentes a ésta (SARM), con una CMI90 de 2 mg/l. El patrón más frecuente fue la doble mutación gyrA y grlA (55 por ciento de las cepas), siendo mucho menos frecuente la mutación únicamente en grlA (5 por ciento). El 39 por ciento de las cepas presentaron un genotipo silvestre. Las cepas con doble mutación presentaron altos grados de resistencia a todas las fluoroquinolonas probadas excepto a trovafloxacino, con un rango de CMI de 0,5-4 mg/l. Las cepas silvestres fueron sensibles a todas las quinolonas ensayadas; en las cinco cepas con mutación en grlA se observó un ligero aumento de las CMI para todos los antimicrobianos, aunque siempre por debajo del punto de corte que determina resistencia. Las quinolonas menos afectadas por esta mutación fueron trovafloxacino y esparfloxacino (AU)

In vitro activities of 13 fluoroquinolones against Staphylococcus aureus isolates with characterized mutations in gyrA, gyrB, grlA, and norA and against wild-type isolates.

The in vitro activities of 13 fluoroquinolones (FQs) were tested against 90 Staphylococcus aureus clinical isolates: 30 wild type for gyrA, gyrB, grlA and norA and 60 with mutations in these genes. Clinafloxacin (CI-960), sparfloxacin, and grepafloxacin were the most active FQs against wild-type isolates (MICs at which 90% of isolates were inhibited, 0.06 to 0.1 microgram/ml). Mutations in grlA did not affect the MICs of newer FQs. grlA-gyrA double mutations led to higher MICs for all the FQs tested. Efflux mechanisms affected the newer FQs to a much lesser extent than the less recently developed FQs.

In vitro activity of eight fluoroquinolones against multiresistant Stenotrophomonas maltophilia.

We studied the activity of eight fluoroquinolones (norfloxacin, ciprofloxacin, grepafloxacin, trovafloxacin, gatifloxacin, clinafloxacin, PD-117596 and PD-138312) against 58 multiresistant Stenotrophomonas maltophilia clinical strains. Norfloxacin was the least active drug (MIC(90) = 128 mg/l). Grepafloxacin, trovafloxacin and gatifloxacin activity was moderately higher (MIC(90) = 8 mg/l) than ciprofloxacin (MIC(90) = 16 mg/l). The best activity was shown by clinafloxacin and PD-138312 (MIC(90) = 4 mg/l). The most resistant strains showed similar MICs against all the fluoroquinolones tested. The highest increase of activity of newer fluoroquinolones was observed against the most sensitive strains.

In vitro activities of beta-lactam-beta-lactamase inhibitor combinations against Stenotrophomonas maltophilia: correlation between methods for testing inhibitory activity, time-kill curves, and bactericidal activity.

The activities of ampicillin, ampicillin-sulbactam, amoxicillin, amoxicillin-clavulanic acid, ticarcillin, ticarcillin-clavulanic acid, piperacillin, piperacillin-tazobactam, aztreonam, and aztreonam-clavulanic against Stenotrophomonas maltophilia strains for which the MICs of penicillins and commercially available beta-lactam-beta-lactamase inhibitor combinations were higher than the breakpoints usually recommended for Pseudomonas aeruginosa in commercially available broth microdilution methods were tested by the agar diffusion, agar dilution, and broth microdilution methods. Time-kill curve studies were performed when discrepancies between these methods were observed. The MICs obtained by the commercially available broth microdilution method, the agar dilution method, and the broth microdilution method were almost identical. Twenty-five percent of the strains tested showed inhibition diameters of > or =15 mm for ticarcillin-clavulanic acid, and 43.7% of the strains tested showed inhibition diameters of > or =18 mm for piperacillin-tazobactam by the agar diffusion method. The time-kill curves for these strains confirmed the results obtained by dilution methods. Aztreonam-clavulanic acid (2:1) at concentrations of < or =16 microg/ml inhibited all of these strains (MIC range, 1 to 16 microg/ml). The time-kill curves confirmed this activity. The addition of piperacillin to this combination did not modify the MICs. The combination aztreonam-clavulanic acid-ticarcillin was two- to fourfold more active than aztreonam-clavulanic acid alone. We studied the inhibitory and bactericidal activities of the two most active combinations (aztreonam-clavulanic acid and aztreonam-clavulanic acid-ticarcillin) against the standard inoculum and 10 and 50 times the standard inoculum. Inoculum modifications did not modify the MICs. Both combinations showed good bactericidal activity against the standard inoculum. With 10 times the standard inoculum, minimum bactericidal concentration (MBC) results were heterogeneous (for 55% of the strains, MBCs were between the MIC and 4-fold the MIC, and for 45% of the strains MBCs were between 8- and >32-fold the MIC). With 50 times the standard inoculum, MBCs were at least 32-fold the MICs for all the strains tested.