[In vitro activity of linezolid against clinical isolates of methicillin-resistant Staphylococcus aureus]. / Actividad in vitro de la linezolida en aislamientos clínicos de Staphylococcus aureus resistentes a la meticilina.

In recent years, there has been a dramatic increase in the number of infections caused by multidrug-resistant Gram-positive microorganisms, making necessary the search for alternative antibacterial agents. Linezolid is a new synthetic antimicrobial agent with activity against multidrug-resistant Gram-positive cocci. The objective of this study was to determine the in vitro activity of linezolid against 74 clinical isolates of methicillin-resistant Staphylococcus aureus. Minimal inhibitory concentrations were determined by an agar dilution method following NCCLS criteria. Vancomycin, teicoplanin, rifampicin, trimethoprim-sulfamethoxazole and linezolid were studied at concentrations ranging from 128 to 0.008 mg/l. All of the isolates were susceptible to vancomycin, teicoplanin, and linezolid while four strains (5.4%) were resistant to rifampicin and five (6.7%) to trimethoprim-sulfamethoxazole. Linezolid showed excellent in vitro activity against 74 clinical isolates of methicillin-resistant Staphylococcus aureus with an MIC ranging from 0.25 to 2 mg/l

[In vitro activity of beta-lactam agents and beta-lactamase inhibitors in clinical isolates of Acinetobacter baumannii]. / Actividad in vitro de antibióticos betalactámicos e inhibidores de betalactamasas en aislamientos clínicos de Acinetobacter baumannii.

Acinetobacter is a Gram-negative coccobacillus frequently associated with nosocomial infections, especially pneumonia in patients using mechanical ventilators in ICUs. Many of the clinical isolates of Acinetobacter baumannii are now resistant to most antibiotics, including the betalactams, making these infections difficult to treat. We compared the in vitro activity of betalactam agents (ampicillin, piperacillin and ticarcillin), betalactamase inhibitors (clavulanic acid, sulbactam and tazobactam) alone and in combination with betalactam agents (amoxicillin-clavulanic acid, ampicillin-sulbactam, piperacillin-tazobactam and ticarcillin-clavulanic) against 156 clinical isolates of A. baumannii using an agar dilution method. In general, we observed a low susceptibility to the betalactam agents tested (ampicillin: 1.9% susceptibility; piperacillin: 10.2%; ticarcillin: 19.8%). We did not observe a significant reduction of the MIC in the combination of betalactam agents and betalactamase inhibitors; only ampicillin/sulbactam showed a high antimicrobial activity (84.6% compared to 14.1%, 37.8% and 33.9% for amoxicillin-clavulanic acid, piperacillin-tazobactam and ticarcillin-clavulanic acid, respectively). Sulbactam was the only betalactamase inhibitor which showed good in vitro activity, with a low MIC(50) and MIC(90) (8 and 32 mg/l, respectively) similar to ampicillin/sulbactam (2 and 16 mg/l, respectively). Sulbactam could be a good therapeutic alternative for the treatment of multiresistant A. baumannii infections.

Scedosporium apiospermum pneumonia after autologous bone marrow transplantation.

Although opportunistic infections after bone marrow transplantation (BMT) are very common, only five cases of Pseudallescheria boydii infection have been reported in the literature, two of which were autopsy findings. A case of Scedosporium apiospermum infection after BMT, treated initially with amphotericin B (total dose of 2.5 g) and then with itraconazole (for 25 days), is reported here. When the patient failed to improve, Scedosporium apiospermum pneumonia was diagnosed and therapy was changed. The patient was treated successfully with miconazole (600 mg/8h for 32 days) and ketoconazole (200 mg/8h for 7 days) plus surgery.