Indwelling Medical Devices Research Articles

Clinical trial of CATH TAG: An innovative new device to reduce infections associate with indwelling medical devices

7% of hospital patients will develop an HAI, many of these infections are associated with indwelling medical devices. To reduce the risk of infection, most hospitals have guidelines recommending removal of indwelling medical devices either at a specified time or as soon as the device is not required. However, complying with these guidelines remains a major challenge for hospitals.

Ochrobactrum anthropi: An emerging pathogen causing meningitis with sepsis in a neurotrauma patient.

Ochrobactrum anthropi is an unusual emerging pathogen especially in the hospital environment. Most of the reported cases are nosocomially acquired infections in patients with various indwelling and invasive medical devices, such as central venous catheters and drainage tubes. We report a case of nosocomially transmitted invasive catheter related septicaemia with meningitis due to O. anthropi, in an elderly immunocompetent male with a head trauma admitted to a level -1 trauma centre. This report describes clinical and microbiological characteristics of rare pathogen and also highlights the importance of rapid identification, susceptibility testing of such opportunistic pathogens in trauma settings and its unique antibiotic susceptibility profiles. This requires prompt treatment with timely intervention, and appropriate antimicrobial therapy, alongside adherence to strict infection control practices.

Role of Biofilm in Cerebrospinal Fluid Shunt Infections: A Study at Tertiary Neurocare Center from South India.

Introduction:Biofilms are the source of persistent infections of many pathogenic microbes. They are responsible for nosocomial infection and also associated with many surgical conditions including indwelling medical devices such as ventriculoperitoneal shunt. A significant problem encountered in shunt procedures is obstruction followed by infection, with infection rate ranging from 2% to 27%, often with poor outcome.Materials and Methods:This study was conducted in the Department of Neuromicrobiology at a tertiary neuroinstitute for 6 months from July 1 to December 31, 2014. The samples comprised cerebrospinal fluid (CSF) from suspected cases of shunt infections. Laboratory diagnosis of causative agent was established by adopting standard procedures. Then, isolates were evaluated for production of biofilm by tissue culture plate (TCP) method and tube method.Results:Of the 1642 shunt CSF samples obtained from neurosurgery, 14.79% were culture positive which yielded 254 isolates. About 51.97% were Gram-negative bacilli (GNB), 46.46% were Gram-positive cocci (GPC), and 1.57% were Candida albicans. Among GNB, nonfermenters were the most common (51.52%) followed by Pseudomonas aeruginosa (15.9%). Among GPC, coagulase-negative Staphylococci were 88.13%, out of which 43.26% were methicillin-resistant. Other GPC were Enterococcus spp. (4.24%), Staphylococcus aureus (5.08%), and Streptococcus spp. (2.54%). Among all isolates, 120 were tested for biofilm production, out of which 57.5% were biofilm producers and 42.5% were nonproducers.Conclusions:TCP was the better method to detect biofilm. Most of the biofilm producers were resistant pathogens.

Clinical trial of CATH TAG: An innovative new device to reduce infections associated with indwelling medical devices

•A new device, CATH TAG, was used in to improve compliance with peripheral intravenous catheter (PIVC) removal policy. •Point prevalence studies were performed at the start and end of a four-week trial. •Use of CATH TAG was associated with a reduction in PIVC dwell times that were either unknown or greater than 72 hours.

Staphylococcus aureus biofilm: a complex developmental organism.

Chronic biofilm-associated infections caused by Staphylococcus aureus often lead to significant increases in morbidity and mortality, particularly when associated with indwelling medical devices. This has triggered a great deal of research attempting to understand the molecular mechanisms that control S. aureus biofilm formation and the basis for the recalcitrance of these multicellular structures to antibiotic therapy. The purpose of this review is to summarize our current understanding of S. aureus biofilm development, focusing on the description of a newly-defined, five-stage model of biofilm development and the mechanisms required for each stage. Importantly, this model includes an alternate view of the processes involved in microcolony formation in S. aureus and suggests that these structures originate as a result of stochastically regulated metabolic heterogeneity and proliferation within a maturing biofilm population, rather than a subtractive process involving the release of cell clusters from a thick, unstructured biofilm. Importantly, it is proposed that this new model of biofilm development involves the genetically programmed generation of metabolically distinct subpopulations of cells, resulting in an overall population that is better able to adapt to rapidly changing environmental conditions.

Antimicrobial Peptides for the Control of Biofilm Formation

Antimicrobial peptides (AMPs) are an abundant and varied group of molecules recognized as the most ancient components of the innate immune system. They are found in a wide group of organisms including bacteria, plants and animals as a defense mechanism against different kinds of infectious pathogens. Over the past two decades, a fast-growing number of AMPs have been identified/designed and their wide-spectrum antimicrobial activity has been deeply investigated. In recent years, there has been an increasing interest in the use of AMPs as alternative anti-biofilm molecules for the control of biofilm-related infections. Biofilms are sessile communities of microbial cells embedded in a self-produced matrix and characterized by a low metabolic activity. Due to their peculiar physiological properties, bacteria/fungi in biofilms result more resistant to conventional antibiotic therapies compared with their planktonic counterparts. AMPs may be a promising strategy to combat biofilm-related infections, as many of them target the microbial membrane, thus being potentially effective also on metabolically inactive cells. Investigations conducted so far evidenced that these peptides may be active in either eradicating established biofilms or preventing their formation, depending on the specific molecule. Here we present a detailed review of the literature describing the latest results of both in vitro and in vivo experiments aimed at evaluating AMP potential usage in biofilm control. In addition, we provide the reader with an overview on AMP local delivery systems, and we discuss their potential application in the coating of medical indwelling devices.

Surface modification strategies for combating catheter-related complications: recent advances and challenges.

Indwelling medical devices such as catheters are a ubiquitous and indispensable component in modern medical practice for improving therapeutic outcomes for patients. Yet at the same time, they can be a cause of healthcare-associated infections contributing to patient morbidity and mortality, and healthcare costs. Other surface-related complications can also arise from interactions of the catheter with biological components in the in vivo environment. This review summarizes the progress made in the development of antimicrobial surfaces, and the application of surface modification strategies to three important classes of catheters: urinary catheters, intravascular catheters and peritoneal dialysis catheters. The review also provides a perspective on the challenges in translating favorable developments from in vitro studies into similar clinical outcomes.

Effect of Chlorhexidine and Sodium Hypochlorite on Staphylococcus aureus Biofilm

Biofilm is a matrix in which a microorganism encases in it and survives environmental stresses. It help the organisms to resist the antibiotics and disinfectant, chronic biofilm associated infection lead to significant increase in morbidity and mortality especially patient with indwelling medical devices. The objective of this research was to analyze the effectiveness of chlorhexidine, sodium hypochlorite and antimicrobial activity of methicillin and vancomycin against biofilm of isolated strains of Staphylococcus aureus isolated from different clinical samples. The results revealed that most biofilm strains were sensitive to vancomycin, some strains were sensitive some were moderate resist and some were resist to methicillin. In comparing different concentrations (0.3%, 0.2%, 0.15% and 0.075%) of chlorhexidine among time interval (1 min, 3 min and 5 min) concentrations showed significant decrease in biofilm formation in association with time; P value (0.001, 0.001, 0.000 and 0.000, respectively). Different concentrations (5%, 4%, 2.5% and 1.25%) of sodium hypochlorite also tested through the same time intervals; concentrations showed significant decrease in biofilm in association with time; P value (0.000, 0.000, 0.000 and 0.000, respectively).

Microbial Contamination of hemodialysis Catheter Tips among Renal Failure Patients in Brack Hospital, Southwestern Libya

Indwelling Medical Devices are significant in patient care and, critical patients easily become infect-able microbial contamination. The isolate and identify the bacterial biofilm that contaminated indwelling catheter tips for renal dialysis machines among patients and the associated resistance of antibiotics in Brack Hospital. One hundred of catheter tips were collected from patients. 2 inches of the distal tip of the catheter were clipped directly into a sterile broth. The culture was by rolling the tip across blood agar and incubated aerobically at 37C° for 18-24 hours. Bacterial isolates were Staphylococcus aureus 33%, Bacillus spp. 9.7%, Klebsiella. pneumoniae 8.3%, Escherichia. coli 8.3%, Staphylococcus albus 8.3%, Enterobacter aerogenes 8.3% Enterobacter spp. 6.9%, Proteus mirabilis 6.9%, Klebsiella ozaenae 6.9%, and Acinetobacter 2.7%. The resistance was 100% against Ampicillin. The 100% were resistant to Ceftazidime, Aztreonam but variable with the others and 100% sensitive to Imipenem with statistically significantly difference (P = 0.00).

Exposure of Bacterial Biofilms to Electrical Current Leads to Cell Death Mediated in Part by Reactive Oxygen Species.

Bacterial biofilms may form on indwelling medical devices such as prosthetic joints, heart valves and catheters, causing challenging-to-treat infections. We have previously described the ‘electricidal effect’, in which bacterial biofilms are decreased following exposure to direct electrical current. Herein, we sought to determine if the decreased bacterial quantities are due to detachment of biofilms or cell death and to investigate the role that reactive oxygen species (ROS) play in the observed effect. Using confocal and electron microscopy and flow cytometry, we found that direct current (DC) leads to cell death and changes in the architecture of biofilms formed by Gram-positive and Gram-negative bacteria. Reactive oxygen species (ROS) appear to play a role in DC-associated cell death, as there was an increase in ROS-production by Staphylococcus aureus and Staphylococcus epidermidis biofilms following exposure to DC. An increase in the production of ROS response enzymes catalase and superoxide dismutase (SOD) was observed for S. aureus, S. epidermidis and Pseudomonas aeruginosa biofilms following exposure to DC. Additionally, biofilms were protected from cell death when supplemented with antioxidants and oxidant scavengers, including catalase, mannitol and Tempol. Knocking out SOD (sodAB) in P. aeruginosa led to an enhanced DC effect. Microarray analysis of P. aeruginosa PAO1 showed transcriptional changes in genes related to the stress response and cell death. In conclusion, the electricidal effect results in death of bacteria in biofilms, mediated, at least in part, by production of ROS.

Clonality, virulence and the occurrence of genes encoding antibiotic resistance among Staphylococcus warneri isolates from bloodstream infections.

Coagulase-negative Staphylococcuswarneri is an opportunistic pathogen capable of causing several infections, especially in patients with indwelling medical devices. We evaluated the virulence-associated properties of 23 clinical isolates recovered from blood specimens. In addition, the carriage of biofilm-associated genes, as well as antibiotic-resistant genes, was identified. S. warneri isolates appeared to be clonally unrelated and revealed a high degree of genetic diversity. All isolates revealed adhesion to epithelial cells, and 43.5 % of strains invaded the cells. Moreover, 52 % of isolates formed biofilm in vitro. PCR analysis demonstrated the presence of the ica operon, in two of the 12 biofilm-positive isolates. This indicated that biofilm formation, in this species, is not restricted to strains harbouring icaADBC genes, encoding polysaccharide intercellular adhesion. Analysis by confocal laser scanning microscopy revealed that biofilm-forming strains formed a three-dimensional structure, composed of mainly living cells. All strains revealed cell-contact cytotoxicity that was strongly associated with biofilm formation. Moreover, cell-free supernatants, of 95 % of the isolates, expressed a cytotoxic activity which caused the destruction of HeLa cells. S. warneri capable of forming biofilm carried significantly more genes encoding resistance to beta-lactams, aminoglicosides and macrolide-lincosamide streptogramin B antibiotics than biofilm-negative isolates. We have shown that tigecycline/rifampicin is effective against bacteria growing as a biofilm. The biofilm inhibitory concentration range of tigecycline/rifampicin was ≤1 µg ml-1. Results indicated that S. warneri have the ability to adhere, form biofilm, invade and destroy epithelial cells, which could be important mechanisms contributing to the development of diseases.

Structure-Function Analyses of a Staphylococcus epidermidis Autoinducing Peptide Reveals Motifs Critical for AgrC-type Receptor Modulation.

Staphylococcus epidermidis is frequently implicated in human infections associated with indwelling medical devices due to its ubiquity in the skin flora and formation of robust biofilms. The accessory gene regulator (agr) quorum sensing (QS) system plays a prominent role in the establishment of biofilms and infection by this bacterium. Agr activation is mediated by the binding of a peptide signal (or autoinducing peptide, AIP) to its cognate AgrC receptor. Many questions remain about the role of QS in S. epidermidis infections, as well as in mixed-microbial populations on a host, and chemical modulators of its agr system could provide novel insights into this signaling network. The AIP ligand provides an initial scaffold for the development of such probes; however, the structure-activity relationships (SARs) for activation of S. epidermidis AgrC receptors by AIPs are largely unknown. Herein, we report the first SAR analyses of an S. epidermidis AIP by performing systematic alanine and d-amino acid scans of the S. epidermidis AIP-I. On the basis of these results, we designed and identified potent, pan-group inhibitors of the AgrC receptors in the three S. epidermidis agr groups, as well as a set of AIP-I analogs capable of selective AgrC inhibition in either specific S. epidermidis agr groups or in another common staphylococcal species, S. aureus. In addition, we uncovered a non-native peptide agonist of AgrC-I that can strongly inhibit S. epidermidis biofilm growth. Together, these synthetic analogs represent new and readily accessible probes for investigating the roles of QS in S. epidermidis colonization and infections.

Streptococcus agalactiae infection in cancer patients: a five-year study.

Although the highest burden of Streptococcus agalactiae infections has been reported in industrialized countries, studies on the characterization and epidemiology are still limited in developing countries and implementation of control strategies remains undefined. The aim of this retrospective study was to assess the epidemiological, clinical, and microbiological aspects of S. agalactiae infections in cancer patients treated at a Reference Brazilian National Cancer Institute - INCA, Rio de Janeiro, Brazil. We reviewed the clinical and laboratory records of all cancer patients identified as having invasive S. agalactiae disease during 2010-2014. The isolates were identified by biochemical analysis and tested for antimicrobial susceptibility. A total of 263 strains of S. agalactiae were isolated from cancer patients who had been clinically and microbiologically classified as infected. S. agalactiae infections were mostly detected among adults with solid tumors (94%) and/or patients who have used indwelling medical devices (77.2%) or submitted to surgical procedures (71.5%). Mortality rates (in-hospital mortality during 30 days after the identification of S. agalactiae) related to invasive S. agalactiae infections (n = 28; 31.1%) for the specific category of neoplasic diseases were: gastrointestinal (46%), head and neck (25%), lung (11%), hematologic (11%), gynecologic (4%), and genitourinary (3%). We also found an increase in S. agalactiae resistance to erythromycin and clindamycin and the emergence of penicillin-less susceptible isolates. A remarkable number of cases of invasive infections due to S. agalactiae strains was identified, mostly in adult patients. Our findings reinforce the need for S. agalactiae control measures in Brazil, including cancer patients.

Studies on prevalence of biofilm associated genes and primary observation on sasX gene in clinical isolates of coagulase negative staphylococci (CoNS).

Coagulase negative staphylococci (CoNS) are nosocomial pathogens that cause indwelling medical device associated infections due to its biofilm forming potential and multiple antibiotic resistance. The current study focused on species identification, antibiotic resistance profile and molecular basis of biofilm formation and attachment of CoNS isolated from clinical samples. Along with this, molecular screening for mecA and newly identified surface colonization protein encoded by sasX gene was also conducted. S. epidermidis (n = 19, 47%) was identified as the most prevalent CoNS species and very interestingly two biofilm forming, mecA positive S. epidermidis isolates were found to carry all the biofilm associated genes screened in this study, which indicates its potential to form the strong biofilm. Another novel observation of the study is the detection of sasX gene in one biofilm positive S. epidermidis isolate. The study also identified one doxycycline resistant mecA positive, multidrug resistant S. haemolyticus isolate. In conclusion, the study signifies the existence of multiple biofilm related genes, multidrug resistance and the presence of sasX gene among clinical isolates of CoNS.

Bacteria-responsive multilayer coatings comprising polycationic nanospheres for bacteria biofilm prevention on urinary catheters

This work reports on the development of infection-preventive coatings on silicone urinary catheters that contain in their structure and release on demand antibacterial polycationic nanospheres. Polycationic aminocellulose conjugate was first sonochemically processed into nanospheres to improve its antibacterial potential compared to the bulk conjugate in solution (ACSol). Afterward the processed aminocellulose nanospheres (ACNSs) were combined with the hyaluronic acid (HA) polyanion to build a layer-by-layer construct on silicone surfaces. Although the coating deposition was more effective when HA was coupled with ACSol than with ACNSs, the ACNSs-based coatings were thicker and displayed smoother surfaces due to the embedment of intact nanospheres. The antibacterial effect of ACNSs multilayers was 40% higher compared to ACSol coatings. This fact was further translated into more effective prevention of Pseudomonas aeruginosa biofilm formation. The coatings were stable in the absence of bacteria, whereas their disassembling occurred gradually during incubation with P. aeruginosa, and thus eradicate the biofilm upon release of antibacterial agents. Only 5 bilayers of HA/ACNSs were sufficient to prevent the biofilm formation, in contrast to the 10 bilayers of ACSol required to achieve the same effect. The antibiofilm efficiency of (HA/ACNSs)10 multilayer construct built on a Foley catheter was additionally validated under dynamic conditions using a model of the catheterized bladder in which the biofilm was grown during seven days. Statement of SignificanceAntibacterial layer-by-layer coatings were fabricated on silicone that efficiently prevents Pseudomonas aeruginosa biofilm formation during time beyond the useful lifetime of the currently employed urinary catheters in medical practice. The coatings are composed of intact, highly antibacterial polycationic nanospheres processed from aminated cellulose and bacteria-degrading glycosaminoglycan hyaluronic acid. The importance of incorporating nanoscale structures within bacteria-responsive surface coatings to impart durable antibacterial and self-defensive properties to the medical indwelling devices is highlighted.

Agent Petri Nets Framework for Modeling <i>Staphylococcus epidermidis</i> Biofilm Formation

This Staphylococcus epidermidis has been discovered as the most frequent germ detected during indwelling medical devices infection. This fact is well attached with the ability of this bacterium to form structured layered population known as biofilm. Inside S. epidermidis biofilm, bacterial cells present more different behavior than in their planktonic counterpart. This paper describes the thriving application of Petri net theory for modeling of interaction between different regulations actors leading S. epidermidis to switch from Planctonik to Biofilm. Indeed this biologic system is very sensible and has dangerous effect. We propose Agent Petri Nets model to describe and analyze the process of formation of Biofilm molecule. This model presents a formal framework based on Multi Agents system characteristics.

Assessment of Microbicidal Activity of Atmospheric Pressure Non- Thermal Plasma Against Planktonic and Biofilm Forms

Background:Atmospheric pressure non-thermal plasma (APNTP) is a promising, relatively novel method for destroying microorganisms either in planktonic or biofilm form, alternative to “conventional” methods which have numerous drawbacks. Aim of the work: To assess the microbicidal activity of atmospheric pressure non-thermal plasma (APNTP) on planktonic and biofilm forms. Subjects and methods: This study was performed on Staphylococcus aureus (S. aureus), coagulase negative staphylococci (CoNS), Pseudomonas (P.) aeruginosa and Escherichia (E.) coli isolates from patients with indwelling medical devices associated infections in different intensive care units (ICUs), Zagazig University Hospitals. Detection of biofilm forming ability of these isolates was done by tube method (TM). Planktonic and biofilm counterpart of selected biofilm forming isolates were exposed to APNTP for different durations to assess the biocidal efficacy of plasma on both microbial forms by colony forming unit (CFU) count and/or 2,3-Bis-(2-Methoxy-4-Nitro-5- Sulfophenyl)-2H-Tetrazolium-5-Carboxanilide (XTT), assay. APNTP morphological changes in E. coli and S. aureus were assessed by transmission electron microscopic (TEM) imaging. Results: APNTP treatment of S. aureus, E. coli suspensions caused progressive reduction in surviving bacterial count and metabolic activity with increasing treatment duration and at 180 seconds of exposure complete sterilization achieved. Similar but more prolonged effect was detected on CoNS and P. aeruginosa suspensions. Its exposure for 240 seconds was needed for their complete sterilization. There was no difference between bacterial percentage reduction calculated by CFU count and XTT assay except in P. aeruginosa suspension for 60 seconds. No observed difference between APNTP effect on planktonic gram positive (GP) and gram negative (GN) bacteria. On the other hand, GN bacterial biofilm was more resistant to APNTP than GP bacterial biofilm. TEM showed that in both S. aureus and E. coli there were significant morphological changes after exposure to plasma. Conclusion: The efficacy of APNTP was proved for in vitro decontamination of planktonic and biofilm forms of S. aureus, CoNS, P. aeruginosa and E. coli that are responsible for many healthcare-acquired infections (HCAIs).

Toward Infection-Resistant Surfaces: Achieving High Antimicrobial Peptide Potency by Modulating the Functionality of Polymer Brush and Peptide.

Bacterial infection associated with indwelling medical devices and implants is a major clinical issue, and the prevention or treatment of such infections is challenging. Antimicrobial coatings offer a significant step toward addressing this important clinical problem. Antimicrobial coatings based on tethered antimicrobial peptides (AMPs) on hydrophilic polymer brushes have been shown to be one of the most promising strategies to avoid bacterial colonization and have demonstrated broad spectrum activity. Optimal combinations of the functionality of the polymer-brush-tethered AMPs are essential to maintaining long-term AMP activity on the surface. However, there is limited knowledge currently available on this topic. Here we report the development of potent antimicrobial coatings on implant surfaces by elucidating the roles of polymer brush chemistry and peptide structure on the overall antimicrobial activity of the coatings. We screened several combinations of polymer brush coatings and AMPs constructed on nanoparticles, titanium surfaces, and quartz slides on their antimicrobial activity and bacterial adhesion against Gram-positive and Gram-negative bacteria. Highly efficient killing of planktonic bacteria by the antimicrobial coatings on nanoparticle surfaces, as well as potent killing of adhered bacteria in the case of coatings on titanium surfaces, was observed. Remarkably, the antimicrobial activity of AMP-conjugated brush coatings demonstrated a clear dependence on the polymer brush chemistry and peptide structure, and optimization of these parameters is critical to achieving infection-resistant surfaces. By analyzing the interaction of polymer-brush-tethered AMPs with model lipid membranes using circular dichroism spectroscopy, we determined that the polymer brush chemistry has an influence on the extent of secondary structure change of tethered peptides before and after interaction with biomembranes. The peptide structure also has an influence on the density of conjugated peptides on polymer brush coatings and the resultant wettability of the coatings, and both of these factors contributed to the antimicrobial activity and bacterial adhesion of the coatings. Overall, this work highlights the importance of optimizing the functionality of the polymer brush to achieve infection-resistant surfaces and presents important insight into the design criteria for the selection of polymers and AMPs toward the development of potent antimicrobial coating on implants.

Quorum-Quenching and Matrix-Degrading Enzymes in Multilayer Coatings Synergistically Prevent Bacterial Biofilm Formation on Urinary Catheters.

Bacteria often colonize in-dwelling medical devices and grow as complex biofilm communities of cells embedded in a self-produced extracellular polymeric matrix, which increases their resistance to antibiotics and the host immune system. During biofilm growth, bacterial cells cooperate through specific quorum-sensing (QS) signals. Taking advantage of this mechanism of biofilm formation, we hypothesized that interrupting the communication among bacteria and simultaneously degrading the extracellular matrix would inhibit biofilm growth. To this end, coatings composed of the enzymes acylase and α-amylase, able to degrade bacterial QS molecules and polysaccharides, respectively, were built on silicone urinary catheters using a layer-by-layer deposition technique. Multilayer coatings of either acylase or amylase alone suppressed the biofilm formation of corresponding Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. Further assembly of both enzymes in hybrid nanocoatings resulted in stronger biofilm inhibition as a function of acylase or amylase position in the layers. Hybrid coatings, with the QS-signal-degrading acylase as outermost layer, demonstrated 30% higher antibiofilm efficiency against medically relevant Gram-negative bacteria compared to that of the other assemblies. These nanocoatings significantly reduced the occurrence of single-species (P. aeruginosa) and mixed-species (P. aeruginosa and Escherichia coli) biofilms on silicone catheters under both static and dynamic conditions. Moreover, in an in vivo animal model, the quorum quenching and matrix degrading enzyme assemblies delayed the biofilm growth up to 7 days.

Candida tropicalis Biofilms: Biomass, Metabolic Activity and Secreted Aspartyl Proteinase Production.

According to epidemiological data, Candida tropicalis has been related to urinary tract infections and haematological malignancy. Several virulence factors seem to be responsible for C. tropicalis infections, for example: their ability to adhere and to form biofilms onto different indwelling medical devices; their capacity to adhere, invade and damage host human tissues due to enzymes production such as proteinases. The main aim of this work was to study the behaviour of C. tropicalis biofilms of different ages (24-120 h) formed in artificial urine (AU) and their ability to express aspartyl proteinase (SAPT) genes. The reference strain C. tropicalis ATCC 750 and two C. tropicalis isolates from urine were used. Biofilms were evaluated in terms of culturable cells by colony-forming units enumeration; total biofilm biomass was evaluated using the crystal violet staining method; metabolic activity was evaluated by XTT assay; and SAPT gene expression was determined by real-time PCR. All strains of C. tropicalis were able to form biofilms in AU, although with differences between strains. Candida tropicalis biofilms showed a decrease in terms of the number of culturable cells from 48 to 72 h. Generally, SAPT3 was highly expressed. C. tropicalis strains assayed were able to form biofilms in the presence of AU although in a strain- and time-dependent way, and SAPT genes are expressed during C. tropicalis biofilm formation.