We investigated the in vitro effects of seven fluoroquinolones (ciprofloxacin, grepafloxacin, levofloxacin, moxifloxacin, norfloxacin, ofloxacin, and rufloxacin), compared to those of trimethoprim-sulfamethoxazole (SXT) and ceftazidime on total biomass and cell viability of Stenotrophomonas maltophilia biofilm. S. maltophilia attached rapidly to polystyrene, within 2 h of incubation, and then biofilm formation increased over time, reaching maximum growth at 24 h. In the presence of fluoroquinolones at one-half and one-fourth the MIC, biofilm biomass was significantly (P < 0.01) reduced to 55 to 70% and 66 to 76% of original mass, respectively. Ceftazidime and SXT did not exert any activity. Biofilm bacterial viability was significantly reduced by all antibiotics tested at one-half the MIC. At one-fourth the MIC all antibiotics, except levofloxacin, significantly reduced viability. Treatment of preformed biofilms with bactericidal concentrations (500, 100, and 50 g/ml) of all fluoroquinolones caused, except for norfloxacin, significant reduction of biofilm biomass to 29.5 to 78.8, 64.1 to 83.6, and 70.5 to 82.8% of original mass, respectively. SXT exerted significant activity at 500 g/ml only. Ceftazidime was completely inactive. Rufloxacin exhibited the highest activity on preformed biofilm viability, significantly decreasing viable counts by 0.6, 5.4, and 17.1% at 500, 100, and 50 g/ml, respectively. Our results show that (i) subinhibitory (one-half and one-fourth the MIC) concentrations of fluoroquinolones inhibit adherence of S. maltophilia to polystyrene and (ii) clinically achievable concentrations (50 and 100 g/ml) of rufloxacin are able to eradicate preformed S. maltophilia biofilm.The use of synthetic materials for temporary or permanent implantation-i.e., central venous catheters, urinary catheters, intraocular lenses, and prosthetic heart valves-has been accompanied by the emergence of implant-associated infection. The bacterial infections following colonization and biofilm formation on these prosthetic materials represent the principal cause of morbidity in patients undergoing prosthetic implantation (6). The production of extracellular slime or glycocalyx is a crucial factor in the adherence of bacteria and their protection from host defense mechanisms and effects of antimicrobial agents. It has become clear that biofilm-grown cells express properties distinct from those of planktonic cells, one of which is an increased resistance to antimicrobial agents. Standard antimicrobial treatments typically fail to eradicate biofilms, which can result in chronic infection and the need for surgical removal of afflicted areas.Stenotrophomonas maltophilia is being reported with increasing frequency as an important nosocomial pathogen. It is an opportunistic pathogen colonizing patients in intensive care settings, especially those with underlying debilitating conditions such as immunosuppression, malignancies, and implantation of foreign devices (catheters, respiratory therapy equipment, etc.). Bacterial adherenc...

Time-kill and postantifungal effect (PAFE) of amphotericin B, caspofungin, fluconazole, and voriconazole were determined against clinical isolates of Candida guilliermondii, Candida kefyr, and Candida lusitaniae. Azoles displayed fungistatic activity and no measurable PAFE, regardless of the concentration tested. Amphotericin B and caspofungin demonstrated concentration-dependent fungicidal activity, although amphotericin B only produced a significant dose-dependent PAFE against all isolates tested.Invasive fungal infections are important causes of morbidity and mortality in immunosuppressed patients (10). Although C. albicans, C. glabrata, C. parapsilosis, and C. tropicalis account for the majority of Candida bloodstream infections, recent epidemiologic trends indicate a shift toward infections by the less frequently isolated non-albicans Candida (NAC) species (12). Among NAC species, C. kefyr, C. guilliermondii, and C. lusitaniae are rare causes of invasive infections but are increasingly encountered among severely immunosuppressed patients occurring in nosocomial clusters and/or exhibiting innate or acquired resistance to one or more established antifungal agents, often related to intravascular catheters and breaks in infection control precautions (3-5, 11, 12, 14).Currently, knowledge of the in vitro pharmacodynamic characteristics of C. kefyr, C. guilliermondii, and C. lusitaniae is poor and limited to amphotericin B (AMB) and voriconazole (VRC) only (7,15). Therefore, we conducted time-kill and postantifungal effect (PAFE) studies with AMB, caspofungin, fluconazole (FLC), and VRC against bloodstream isolates of C. guilliermondii, C. kefyr, and C. lusitaniae from neutropenic patients.Antifungal agents. Stock solutions of AMB (Sigma-Aldrich SRL, Milan, Italy), caspofungin (Merck Sharp & Dohme Italia SpA, Rome, Italy), FLC (Pfizer Inc., New York, N.Y.), and VRC (Pfizer) were prepared in RPMI 1640 medium (Sigma) buffered to a pH of 7.0 with 0.165 M morpholinepropanesulfonic acid (MOPS) buffer (Sigma) and stored at Ϫ80°C until use. Antifungals were solubilized in sterile water, except AMB in dimethyl sulfoxide (Sigma).Test isolates. Six Candida isolates were obtained from the Clinical Microbiology Service, Department of Hematology and Oncology, "Spirito Santo" Hospital, Pescara, Italy, for use in this study: two strains each of C. guilliermondii (337 and 555), C. kefyr (240 and 270), and C. lusitaniae (325 and 447) were selected for testing.Antifungal susceptibility testing. The MIC for each isolate was determined, in triplicate, by broth microdilution techniques as outlined by the National Committee for Clinical Laboratory Standards (17). The endpoint was defined as 50% inhibition of visible growth for azoles and complete inhibition of visible growth for AMB and caspofungin.Time-kill. Before the time-kill studies were initiated, antifungal carryover effects were examined. Briefly, 100 l of a standardized suspension (1 ϫ 10 3 CFU/ml) of each isolate were added to either 900 l of sterile water with (sample) or w...