Seyhan Ulusoy

Evaluation of different methods to detect oxacillin resistance in Staphylococcus aureus and their clinical laboratory utility

Methicillin-resistant Staphylococcus aureus strains (MRSA) are major human pathogens responsible for nosocomial and serious community-acquired infections worldwide. Methicillin resistance in S. aureus is primarily mediated by a modified penicillin-binding protein (PBP2a) encoded by the mecA gene, which is not present in susceptible strains [1–3]. Several additional gene products, such as those encoded by fem (factor essential for methicillin resistance) genes and auxiliary genes, can also contribute to MRSA resistance [1, 2, 4]. Rapid and accurate identification of MRSA is necessary for therapeutic and epidemiological purposes. Currently, several methods are available for detecting oxacillin resistance including phenotypic methods, such as disk diffusion, E-test and broth dilution tests, and genotypic methods that detect the mecA gene [1, 5, 6]. PCR amplification of the mecA gene has been used successfully and is presently considered the gold standard for detecting methicillin resistance in S. aureus [1]. Detection of oxacillin resistance using phenotypic methods is problematic because of variation in the degree of mecA gene expression in heterogeneous populations of MRSA; thus, routine oxacillin disk diffusion tests often fail to detect heterogeneous MRSA populations. The Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards) has consequently recommended use of the cefoxitin disk diffusion test rather than the oxacillin disk diffusion test [7]. In the study presented here, the performance and utility of several different methods for detecting MRSA was evaluated. PCR for detecting the mecA gene was used as the gold standard assay against which we compared oxacillin and cefoxitin disk diffusion tests and the GenoType MRSA molecular genetic assay (Hain Lifescience, Nehren, Germany) for detecting MRSA. The objective was to determine whether these disk diffusion tests and GenoType MRSA could detect all MRSA as accurately as mecA PCR and to evaluate their suitability as routine methods for detecting oxacillin resistance in S. aureus in clinical microbiology laboratories. GenoType MRSA is a new DNA-based strip assay kit designed to detect oxacillin resistance in S. aureus. Its performance is based on amplification of a 71 bp fragment of the mecA gene and an 85 bp sequence highly specific for S. aureus and subsequent hybridization of the denatured amplicons to their complementary sequences coated on DNA strips. A total of 224 isolates of S. aureus collected from patients of Suleyman Demirel University Hospital were included in this study. The isolates were collected from different clinical specimens and at different times. All strains were identified using biochemical procedures. Reference strains included ATCC33591 (MRSA) and ATCC29213 (MSSA). Disk diffusion tests were performed for each of the 224 isolates using the following method recommended by the National Committee for Clinical Laboratory Standards [7]: 1 μg oxacillin disks (Oxoid, Basingstoke, UK) were incubated at 35°C and at 30°C on Mueller-Hinton agar (Difco, Detroit, MI, USA) with and without 2% NaCl, and 30 μg cefoxitin disks (Oxoid) were incubated at 35°C on Mueller-Hinton agar. After incubation, inhibition zone sizes for oxacillin and cefoxitin were noted and compared. For cefoxitin, isolates showing a zone of inhibition of ≤19 mm were considered Eur J Clin Microbiol Infect Dis (2006) 25:410–412 DOI 10.1007/s10096-006-0153-8

RF hydrazine plasma modification of chitosan for antibacterial activity and nanofiber applications

Chitosan nano powders were modified using RF hydrazine plasma produced at low pressure (26.66Pa) with 13.56MHz frequency at a power of 100W for 30min. Characterization and investigation of the properties of plasma-modified chitosan (PMCh) and non-modified chitosan (Ch) were carried out using an optical monochromator, FTIR, florescence analysis, TGA, SEM, and X-ray techniques. FTIR spectra of PMCh indicated a band broadening at 3436cm(-1) that confirmed increasing functional groups based on H-bonding. The number of NH(2) groups was determined from fluorescence analysis. TGA analysis shows that the moisture absorption is three times higher in the PMCh structure. Ch and PMCh in PVA solutions were used to produce nanofibers by the electrospinning method; average fiber diameters were 480 and 280nm for Ch and PMCh, respectively. It was found that the antibacterial effect of PMCh is better than the Ch for Gram-positive strains.

Inhibition of Quorum Sensing–Regulated Behaviors by Scorzonera sandrasica

Many Gram-negative bacteria use N-acyl homoserine lactone signal molecules to monitor their own population density and coordinate gene regulation in a process called quorum sensing (QS). Increasing evidence implies that certain eukaryotes produce QS-inhibitory compounds. In this work, we tested 46 terrestrial plants materials for their ability to inhibit QS-regulated behaviors in different bacterial species. Plant materials were dried and extracted using different solvents. The chloroform-soluble compounds extracted from Scorzonera sandrasica were found to inhibit violacein production, a QS-regulated behavior in Chromobacterium violaceum. In addition, the chloroform extract was also able to inhibit QS-regulated carbapenem antibiotic production in Erwinia carotovora. Because the regulation of many bacterial processes is controlled by QS systems, the finding of natural compounds acting as QS inhibitors suggests an attractive tool to control and handle detrimental infections caused by human, animal, and plant pathogens.

Electrospun chitosan/PEDOT nanofibers.

Plasma-modified chitosan and poly(3,4-ethylenedioxythiophene) were blended to obtain conducting nanofibers with polyvinyl alcohol as a supporting polymer at various volumetric ratios by electrospinning method. Chemical compositions and molecular interactions among nanofiber blend components were determined using Fourier transform infrared spectroscopy (FTIR). The conducting blends containing plasma-modified chitosan resulted in a superior antibacterial activity and thinner fiber formation than those containing chitosan without plasma-modification. The obtained nanofiber diameters of plasma-modified chitosan were in the range of 170 to 200 nm and those obtained from unmodified chitosan were in the range of 190 to 246 nm. The electrical and electrochemical properties of nanofibers were also investigated by four-point probe conductivity and cyclic voltammetry measurements.

Objective and subjective performance evaluations of wet wipes including herbal components

In this study, wet wipes were produced for body applications with nonwoven fabrics consisting of polyester and cellulose (viscose and Tencel®). Fabrics were wetted by natural-based wetting solutions (rose water, olive oil) which were functionalized by sodium alginate and natural antibacterial agents (cinnamaldehyde and geraniol) without preservatives. Besides physical characteristics (weight, thickness, porosity, fiber orientation), bending rigidity, Handle-O-Meter measurements, and moisture management test parameters of the nonwoven fabrics were determined. Subjective hand and wiping performances of produced wipes were determined by subjective evaluations carried out on 10 female subjects. According to the results, 100% Tencel® and its blend with viscose have good absorption and moderate transfer characteristics. Polyester content up to 60% is acceptable for wet wipes for the body according to their liquid absorption, transfer, and subjective evaluation results if fabric weight is sufficient. Among the functionalized wetting solutions, antibacterial performance of the solution including olive oil, sodium alginate and cinnamaldehyde was the maximum and it has acceptable hand values according to objective Handle-O-Meter results and subjective evaluation results.

Atmospheric pen plasma sterilizing help paper surface

Cleaning process applied to microorganisms on any substance is called as sterilization. This process can be applied with different methods such as chemical (EtO), filtration (gases, liquids), temperature sterilizations etc. However, these methods have some drawbacks. Plasma sterilization is one of the rapidly developing technique in the study of disinfection because of its cheap, healthy and useful method. In this study, He aid-atmospheric plasma sterilizing is applied onto paper surface. We studied the use of non thermal helium plasma for sterilization of S. aureus and P. aeruginosa cells when applied the filter paper. The bacterial survival was evaluated in terms of the number of colony-forming units on agar plates. All of the S. aureus and P. aeruginosa cells (106 CFU/mL) are sterilized by helium plasma treatment for 5 minutes.

Atmospheric pressure plasma jet effects on sterilization of e. coli and s. aureus

In the recent days, since the epidemic spread of diseases, sterilization has become very important. Atmospheric pressure plasma jets which are used locally and effective results for sterilization procedures are popular. In this study, we produced atmospheric pressure plasma jet with helium flow and used for sterilization of Escherichia coli and Staphylococcus aureus. In the experiments, hundred-fold diluted 250 µlt McFarland bacteria were used in eppendorf tubes for plasma treatment. The effects of plasma treatment time (1, 2, 3 second), applied voltage frequency (5–10 kHz) and amplitude (Vpp 15–16 kV) on sterilization were investigated. Plasma current-voltage characteristics and optical emission results were given.