Cross-Contamination Risk of Dental Tray Adhesives: An In Vitro Study.

BACKGROUND: The aim of this study was to investigate the risk of cross-contamination in dental tray adhesives with reusable brush systems. METHODS: Four dental tray adhesives with different disinfectant components were examined for risk as a potential transmission medium for Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Streptococcus oralis, and Candida albicans. Bacterial and fungal strains were mixed with artificial saliva. The contaminated saliva was intentionally added to tray adhesive liquid samples. At baseline and up to 60 min, 100 microliters of each sample were collected and cultivated aerobically on Columbia and Sabouraud agar for 24 or 48 h, respectively. RESULTS: At baseline, contamination with Staphylococcus aureus and Candida albicans could be identified in three out of four adhesives. In the subsequent samples, low counts of up to 20 colony-forming units per milliliter could be observed for Staphylococcus aureus. All other strains did not form colonies at baseline or subsequently. Adhesives with isopropanol or ethyl acetate as disinfectant additives were most effective in preventing contamination, while adhesives with hydrogen chloride or acetone as a disinfectant additive were the least effective. CONCLUSION: Within 15 min, the tested adhesives appeared to be sufficiently bactericidal and fungicidal against all microorganisms tested.

Discrimination of Human Pathogen Clostridium Species Especially of the Heterogeneous C. sporogenes and C. botulinum by MALDI-TOF Mass Spectrometry.

Clostridium species cause several local and systemic diseases. Conventional identification of these microorganisms is in part laborious, not always reliable, time consuming or does not always distinguish different species, i.e., C. botulinum and C. sporogenes. All in, there is a high interest to find out a reliable, powerful and rapid method to identify Clostridium spp. not only on genus but also on species level. The aim of the present study was to identify Clostridium spp. strains and also to find differences and metabolic groups of C. botulinum by Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS). A total of 123 strains of Clostridium spp. (C. botulinum, n = 40, C. difficile, n = 11, C. tetani, n = 11, C. sordellii, n = 20, C. sporogenes, n = 18, C. innocuum, n = 10, C. perfringens, n = 13) were analyzed by MALDI-TOF MS in combination with methods of multivariate statistical analysis. MALDI-TOF MS analysis in combination with methods of multivariate statistical analysis was able to discriminate between the different tested Clostridium spp., even between species which are closely related and difficult to differentiate by traditional methods, i.e., C. sporogenes and C. botulinum. Furthermore, the method was able to separate the different metabolic groups of C. botulinum. Especially, E gene-positive C. botulinum strains are clearly distinguishable from the other species but also from those producing other toxin types. Thus, MALDI-TOF MS represents a reliable and above all quick method for identification of cultivated Clostridium species.

Rapid identification of oral Actinomyces species cultivated from subgingival biofilm by MALDI-TOF-MS.

BACKGROUND: Actinomyces are a common part of the residential flora of the human intestinal tract, genitourinary system and skin. Isolation and identification of Actinomyces by conventional methods is often difficult and time consuming. In recent years, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has become a rapid and simple method to identify bacteria. OBJECTIVE: The present study evaluated a new in-house algorithm using MALDI-TOF-MS for rapid identification of different species of oral Actinomyces cultivated from subgingival biofilm. DESIGN: Eleven reference strains and 674 clinical strains were used in this study. All the strains were preliminarily identified using biochemical methods and then subjected to MALDI-TOF-MS analysis using both similarity-based analysis and classification methods (support vector machine [SVM]). The genotype of the reference strains and of 232 clinical strains was identified by sequence analysis of the 16S ribosomal RNA (rRNA). RESULTS: The sequence analysis of the 16S rRNA gene of all references strains confirmed their previous identification. The MALDI-TOF-MS spectra obtained from the reference strains and the other clinical strains undoubtedly identified as Actinomyces by 16S rRNA sequencing were used to create the mass spectra reference database. Already a visual inspection of the mass spectra of different species reveals both similarities and differences. However, the differences between them are not large enough to allow a reliable differentiation by similarity analysis. Therefore, classification methods were applied as an alternative approach for differentiation and identification of Actinomyces at the species level. A cross-validation of the reference database representing 14 Actinomyces species yielded correct results for all species which were represented by more than two strains in the database. CONCLUSIONS: Our results suggest that a combination of MALDI-TOF-MS with powerful classification algorithms, such as SVMs, provide a useful tool for the differentiation and identification of oral Actinomyces.

Discrimination of Enterobacteriaceae and Non-fermenting Gram Negative Bacilli by MALDI-TOF Mass Spectrometry.

Discrimination of Enterobacteriaceae and Non-fermenting Gram Negative Bacilli by MALDI-TOF Mass Spectrometry Matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) has proven to be an effective identification tool in medical microbiology. Discrimination to subspecies or serovar level has been found to be challenging using commercially available identification software. By forming our own reference database and using alternative analysis methods, we could reliably identify all implemented Enterobacteriaceae and non-fermenting gram negative bacilli by MALDI-TOF MS and even succeeded to distinguish Shigella sonnei from Escherichia coli (E. coli) and Salmonella enterica spp. enterica serovar Enteritidis from Salmonella enterica spp. enterica serovar Typhimurium. Furthermore, the method showed the ability to separate Enterohemorrhagic E. coli (EHEC) and Enteropathogenic E. coli (EPEC) from non-enteropathogenic E. coli.

In vitro activities of levofloxacin, gatifloxacin, moxifloxacin and garenoxacin against Bacteroides fragilis strains evaluated by kill kinetics.

This study was designed to investigate the killing activity of levofloxacin, gatifloxacin, moxifloxacin and garenoxacin against 12 Bacteroides fragilis strains by kill kinetics over time. MIC values were determined by Etest and by agar dilution. B. fragilis strains were divided according to their MIC values into two groups: one group with strains with MIC <8.0 µg ml(-1) and one group with strains with MIC ≥ 8.0 µg ml(-1). For kill kinetics over time, the strains with MIC <8.0 µg ml(-1) were incubated with the antibiotics at 0.5, 1, 2 and 4 times their MIC values. The strains with MIC ≥ 8.0 µg ml(-1) were incubated with 0.5, 1, 2, and 4 times the maximum achievable concentrations of the antibiotics in human plasma (Cmax). Among the strains with MIC <8.0 µg ml(-1) levofloxacin and gatifloxacin showed equal efficacy. The growth of the strains with MIC ≥ 8.0 µg ml(-1) was barely affected by levofloxacin, while gatifloxacin had bactericidal action when concentrations of 4 × C max were used. Moxifloxacin was more effective against both groups of strains compared with levofloxacin and gatifloxacin. Garenoxacin was the most active agent against all strains investigated. Due to the varying in vitro activity of the quinolones against obligate anaerobes the treatment with quinolones of patients with intra-abdominal infections needs intensive scrutiny.

A step towards the discrimination of beta-lactamase-producing clinical isolates of Enterobacteriaceae and Pseudomonas aeruginosa by MALDI-TOF mass spectrometry.

BACKGROUND: Matrix-Assisted Laser-Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) has already proven to be a powerful tool for species identification in microbiological laboratories. As adequate and rapid screening methods for antibiotic resistance are crucially needed, the present study investigated the discrimination potential of MALDI-TOF MS among extended-spectrum-beta-lactamase (ESBL) or metallo-beta-lactamases- (MBL) producing and the nonproducing strains of Escherichia coli (n=19), Klebsiella pneumoniae (n=19), and Pseudomonas aeruginosa (n=38), respectively. MATERIAL/METHODS: We used a MALDI-TOF MS protocol, usually applied for species identification, in order to integrate a screening method for beta-lactamases into the routine species identification workflow. The acquired spectra were analyzed by visual inspection, statistical similarity analysis and support vector machine (SVM) classification algorithms. RESULTS: Neither visual inspection nor mathematical similarity analysis allowed discrimination between spectra of beta-lactamase-producing and the nonproducing strains, but classification within a species by SVM-based algorithms could achieve a correct classification rate of up to 70%. CONCLUSIONS: This shows that MALDI-TOF MS has definite potential to discriminate antibiotic-resistant strains due to ESBL and MBL production from nonproducing strains, but this performance is not yet sufficiently reliable for routine microbiological diagnostics.