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Trichosporonosis is an uncommon but frequently fatal mycosis in immunocompromised patients 8 and 91.7%, respectively). Well over half of these were suffering from acute leukemia (68 and 84% of patients with Trichosporon sp. and G. capitatum infections, respectively). Crude mortality rates were 77% for Trichosporon spp. and 55.7% for G. capitatum. The optimal therapy for trichosporonosis has yet to be identified; however, in vitro experiences are providing encouraging evidence of the potential role of the new triazoles, in particular, voriconazole.

Trichosporon asahii is the most common cause of fatal disseminated trichosporonosis, frequently associated with indwelling medical devices. Despite the use of antifungal drugs to treat trichosporonosis, infection is often persistent and is associated with high mortality. This drove our interest in evaluating the capability of T. asahii to form a biofilm on biomaterial-representative polystyrene surfaces through the development and optimization of a reproducible T. asahii-associated biofilm model. Time course analyses of viable counts and a formazan salt reduction assay, as well as microscopy studies, revealed that biofilm formation by T. asahii occurred in an organized fashion through four distinct developmental phases: initial adherence of yeast cells (0 to 2 h), germination and microcolony formation (2 to 4 h), filamentation (4 to 6 h), and proliferation and maturation (24 to 72 h). Scanning electron microscopy and confocal scanning laser microscopy revealed that mature T. asahii biofilms (72-h) displayed a complex, heterogeneous three-dimensional structure, consisting of a dense network of metabolically active yeast cells and hyphal elements completely embedded within exopolymeric material. Antifungal susceptibility testing demonstrated a remarkable rise in the MICs of sessile T. asahii cells against clinically used amphotericin B, caspofungin, voriconazole, and fluconazole compared to their planktonic counterparts. In particular, T. asahii biofilms were up to 16,000 times more resistant to voriconazole, the most active agent against planktonic cells (MIC, 0.06 g/ml). Our results suggest that the ability of T. asahii to form a biofilm may be a major factor in determining persistence of the infection in spite of in vitro susceptibility of clinical isolates.Candida species are the most common cause of disseminated nosocomial fungal infections (34). Invasive infections by rarer opportunistic fungal pathogens, however, have recently emerged as a significant problem in treatment of immunocompromised patients (8, 34).In particular, disseminated life-threatening Trichosporon infection is becoming increasingly common in patients with underlying hematological malignancies, extensive burns, solid tumors, and AIDS, accounting for approximately 10% of all confirmed cases of disseminated fungal infections (8,12,14,(32)(33)(34). Likewise, nonimmunosuppressed patients have suffered from Trichosporon infections associated with ophthalmologic surgery, infections of prosthetic devices, intravenous drug abuse, and peritoneal dialysis (1, 17, 21).Trichosporon beigelii was formerly considered the causative agent in trichosporonosis, but recent taxonomic findings based on partial sequences of large-subunit rRNA and DNA relatedness (9, 29, 30) revealed that T. beigelii actually consists of six distinct pathogenic Trichosporon species.In particular, Trichosporon asahii is the major cause of disseminated or deep-seated trichosporonosis (12,30). Although most of the reported cases of hematogenous T. asahii infections occurred in patie...

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...

Organisms in the genus Kocuria are Gram-positive, coagulase-negative, coccoid actinobacteria belonging to the family Micrococcaceae, suborder Micrococcineae, order Actinomycetales. Sporadic reports in the literature have dealt with infections by Kocuria species, mostly in compromised hosts with serious underlying conditions. Nonetheless, the number of infectious processes caused by such bacteria may be higher than currently believed, given that misidentification by phenotypic assays has presumably affected estimates of the prevalence over the years. As a further cause for concern, guidelines for therapy of illnesses involving Kocuria species are lacking, mostly due to the absence of established criteria for evaluating Kocuria replication or growth inhibition in the presence of antibiotics. Therefore, breakpoints for staphylococci have been widely used throughout the literature to try to understand this pathogen's behaviour under drug exposure; unfortunately, this has sometimes created confusion, thus higlighting the urgent need for specific interpretive criteria, along with a deeper investigation into the resistance determinants within this genus. We therefore review the published data on cultural, genotypic and clinical aspects of the genus Kocuria, aiming to shed some light on these emerging nosocomial pathogens. IntroductionThe genus Kocuria was named after Miroslav Kocur, a Slovakian microbiologist, and belongs to the family Micrococcaceae, suborder Micrococcineae, order Actinomycetales, class Actinobacteria (Takarada et al., 2008;Zhou et al., 2008;Lee et al., 2009;Stackebrandt et al., 1995). It includes Gram-positive, strictly aerobic (a few exceptions are Kocuria kristinae, which is facultatively anaerobic, Kocuria marina, which may grow in 5 % CO 2 , and Kocuria rhizophila strain DC2201, which can proliferate anaerobically), catalasepositive, coagulase-negative, non-haemolytic cocci. These are also non-encapsulated, non-endospore-forming, non-halophilic, mesophilic, non-motile and Voges-Proskauer (production of indole and acetoin)-negative, and do not possess mycolic or teichoic acids. Kocuria species can be differentiated from other members of the Actinomycetales based on the presence of galactosamine and glucosamine as main cell wall amino sugars, the peptidoglycan type L-Lys-Ala 3/4 , the fatty acid anteisio-C 15 : 0 , the polar lipids diphosphatidylglycerol and phosphatidylglycerol, MK-7(H 2 ) and MK-8(H 2 ) as major menaquinones and a DNA G+C content of 60.0-75.3 mol%, depending on the species. Organisms in the genus are environmental bacteria, as well as human skin and oropharynx mucosa commensals; nevertheless, they can be responsible for infectious processes which mostly complicate severe underlying diseases. Owing to misidentification by phenotypic typing over the years, clinical syndromes caused by these agents are believed to be rare; however, the prevalence of such infectious pathologies is presumably higher and will surely increase in the coming years, as soon as genome-based identification i...