Clonal outbreak of fluconazole-resistant (FLZR) Candida parapsilosis isolates have been reported in several countries. Despite being the second leading cause of candidemia, the azole resistance mechanisms and the clonal expansion of FLZR C. parapsilosis blood isolates have not been reported in Turkey. Herein, we consecutively collected the C. parapsilosis blood isolates (n=225) from the fifth largest hospital in Turkey (2007–2019), assessed their azole susceptibility pattern using CLSI M27-A3/S4, and sequenced ERG11 for all and MRR1, TAC1, and UPC2 for selected number of C. parapsilosis isolates. The typing resolution of two widely used techniques, AFLP and microsatellite typing (MST), and the biofilm production of FLZR isolates with/without Y132F were compared. Approximately 27% of isolates were FLZR (60/225), among which 90% (54/60) harboured known mutations in Erg11, including Y132F (24/60) and Y132F+K143R (19/60). Several mutations specific to FLZR isolates were found in MRR1, TAC1, and UPC2. AFLP clustered isolates into two clusters, while MST revealed several clusters. The majority of Y132F/Y132F+K143R isolates grouped in clonal clusters, which significantly expanded throughout 2007–2019 in neonatal wards. Candida parapsilosis isolates carrying Y132F were associated with significantly higher mortality and less biofilm production relative to other FLZR isolates. Collectively, we documented the first outbreak of FLZR C. parapsilosis blood isolates in Turkey. The MRR1, TAC1, and UPC2 mutations exclusively found in FLZR isolates establishes basis for future studies, which potentially broaden our knowledge on FLZR mechanisms in C. parapsilosis. MST should be a preferred method for clonal analysis of C. parapsilosis isolates in outbreak scenarios.

In vitro models that mimic in vivo host-pathogen interactions are needed to evaluate candidate drugs that inhibit bacterial virulence traits. We established a new approach to study Pseudomonas aeruginosa biofilm susceptibility on biotic surfaces, using a three-dimensional (3-D) lung epithelial cell model. P. aeruginosa formed antibiotic resistant biofilms on 3-D cells without affecting cell viability. The biofilm-inhibitory activity of antibiotics and/or the anti-biofilm peptide DJK-5 were evaluated on 3-D cells compared to a plastic surface, in medium with and without fetal bovine serum (FBS). In both media, aminoglycosides were more efficacious in the 3-D cell model. In serum-free medium, most antibiotics (except polymyxins) showed enhanced efficacy when 3-D cells were present. In medium with FBS, colistin was less efficacious in the 3-D cell model. DJK-5 exerted potent inhibition of P. aeruginosa association with both substrates, only in serum-free medium. DJK-5 showed stronger inhibitory activity against P. aeruginosa associated with plastic compared to 3-D cells. The combined addition of tobramycin and DJK-5 exhibited more potent ability to inhibit P. aeruginosa association with both substrates. In conclusion, lung epithelial cells influence the efficacy of most antimicrobials against P. aeruginosa biofilm formation, which in turn depends on the presence or absence of FBS.

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The objective of this study was the development of Ag-rich antibacterial coatings on titanium (Ti) to prevent post-operative infections. A series of Ag-doped TiO2 coatings were synthesized on Ti discs by plasma electrolytic oxidation (PEO) in an electrolyte containing Ag nanoparticles (AgNPs). The incorporation, distribution and chemical composition of the AgNPs on Ti were determined using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). The crystalline structure and wettability of the coating was characterized by X-ray diffraction (XRD) and water contact angle (WCA) analysis respectively. Surface roughness and hardness of the coating were examined using atomic force microscopy (AFM) and Knoop indentation test respectively, while silver ion release was quantified using inductively coupled plasma-mass spectroscopy (ICP-MS).Following PEO, the surface of the Ti substrate was converted to TiO2 composed of anatase and rutile phases. The SEM micrographs showed that the AgNPs were distributed throughout the oxide layer, without changing the morphology of the coating. The coatings also revealed an increased surface roughness, enhanced surface microhardness and improved surface wettability relative to untreated Ti substrates. Furthermore, the incorporation of Ag into the coating did not alter the phase component, surface roughness, microhardness and wettability. A series of in-vitro antibacterial assays indicated that increasing the number of AgNPs in the electrolyte led to excellent antibacterial activities, resulting in a complete reduction of Escherichia coli and a 6-log reduction of Staphylococcus aureus after 24 hours of incubation.