In vitro activity of caspofungin against planktonic and sessile Candida sp. cells

Candida sp. may be regarded as one of the leading etiologic agents of hospital-acquired infections, including those related with the indwelling medical devices, which become colonized by the yeasts, accompanied by biofilm formation. In this paper we assayed in vitro susceptibility to caspofungin of planktonic and sessile cells of nasopharyngeal isolates of Candida sp. Two types of biomaterials were used - silicone elastomer-coated latex urinary Foley catheter and PCV Thorax catheter. The minimal inhibitory concentrations (MIC) of caspofungin for planktonic Candida sp. cells ranged from 0.008 to 0.031 mg/l, while the minimal fungicidal concentrations (MFC) from 0.008 to 0.062 mg/l, with MFC/MIC ratios ≤2. The minimal concentration of caspofungin preventing adhesion process of Candida sp. on both biomaterials ranged from 0.004 to 0.031 mg/l, while preventing biofilm formation from 0.004 to 0.062 mg/l. In contrast, much higher minimal concentrations of caspofungin were needed to eradicate the mature biofilm (0.25 to >8 mg/l). In all cases, drug concentrations depended on the strain and the biomaterial used. Our preliminary data suggest that caspofungin, showing good anti-adherent activity in vitro against Candida sp., appears to be a potential agent rather for prophylaxis of the yeast infections associated with biomaterials but not for their treatment.