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- Mihaylova, Sashka A, et al.
(författare)
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Analyses of clinically-relevant isolates of Stenotrophomonas spp.
- 2007
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Ingår i: Proceedings of the 26th Annual General Meeting of the European Culture Collections’ Organization; A0264.
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Konferensbidrag (refereegranskat)abstract
- Objectives: The identification of clinical isolates of Stenotrophomonas spp. to the species level, using a polyphasic approach of phenotypic and genotypic methods, and the determination and comparison of the in vitro responses to various classes of antimicrobial agents by these isolates. Previous studies have suggested a marked diversity among clinical, as well as environmental, isolates of Stenotrophomonas spp. and they represent a significant threat within hospital settings, particularly for patients in ICUs and other immunocompromised conditions. Isolates characterised as putative Stenotrophomonas spp. from Pleven University Hospital were analysed in detail. The predominant source of the isolates was respiratory tract and two thirds of patients were admitted to ICUs. Isolates were examined, using the VITEK 2 compact system, CCUG phenotypic characterisation panels and sequencing and analyses of the genes for 16S rRNA and gyrB. The in vitro responses of isolates to 10 antibiotics (azlocillin, piperacillin, ceftazidime, imipenem, meropenem, ampicillin-sulbactam, piperacillin-tazobactam, gentamicin, amikacin and ciprofloxacin) were evaluated, using the disc diffusion method, according to guidelines of the Clinical and Laboratory Standards Institute. The commercial VITEK 2 system defined all isolates as S. maltophilia, with probabilities of identifications varying from 92 to 99%, and “good”, “very good” or “excellent” confidence. Results from conventional phenotypic testing confirmed identifications for isolates as S. maltophilia or S. rhizophila. DNA sequencing and analyses further defined the species affiliations of isolates of the genus Stenotrophomonas. Previous reports have indicated that Stenotrophomonas spp. exhibit resistance to a broad range of antibiotics. More than 90% of examined isolates were observed to be resistant to imipenem, meropenem and ampicillin-sulbactam, more than 80% were resistant to azlocillin, piperacillin and piperacillin-tazobactam. The only beta-lactam antibiotic with an indication of better activity was ceftazidime. Among the ten antimicrobial agents tested, ciprofloxacin demonstrated the highest activity, as evaluated by diameter zone of growth inhibition. Conclusions: The VITEK 2 compact system identified all isolates to the genus level. However, conventional phenotypic testing may be more effective for species differentiation. Analysis of DNA gene sequencing allows further precise taxonomic identification. Ciprofloxacin could be a drug of choice for therapy of infections caused by Stenotrophomonas spp.
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| 2. |
- Mihaylova, Sashka A, et al.
(författare)
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In vitro activity of antimicrobial agents against extended-spectrum-beta-lactamase-producing enteric bacteria isolated from urine specimens
- 2009
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Ingår i: FEMS 2009 - 3rd Congress of European Microbiologists.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Objectives: To apply detailed phenotypic and genotypic analyses on extended-spectrum-beta-lactamase (ESBL)-producing clinical isolates. To determine in vitro activities of 14 antimicrobial agents and access these data with respect to treatment choice. Methods: One hundred strains were collected from urine samples of patients from Pleven University Hospital, Bulgaria, from January to December 2008. Patient ages: one month to 85 years. Two thirds were male. At the time of sampling, 50 patients were in Urology department, 23 were in Nephrology department, 8 were in Pediatric department, and 19 were in other departments. Double disc and Combination disc tests were applied for ESBL confirmation. ESBL-types were determined, using a multiplex PCR assay for CTX, TEX, SHV and OXA types. In vitro activities of fosfomycin, imipenem, meropenem, ertapenem, amoxicillin/clavulanic acid, piperacillin/tazobactam, gentamicin, amikacin, tigecycline, colistin, nalidixic acid, nitrofurantoin, ciprofloxacin and levofloxacin were determined by the disk diffusion method, according to guidelines of the CLSI. Results: All strains were confirmed to be members of the Enterobacteriaceae and to be ESBL producers. All strains were susceptible to the three carbapenems tested. Eighty-eight percent of the strains were susceptible to tigecycline, 74% were susceptible to amikacin, 64% were susceptible to piperacillin/tazobactam and 63% were susceptible to nitrofurantoin. More than 70% of the strains tested were resistant or intermediately susceptible to amoxicillin/clavulanic acid, gentamicin, nalidixic acid, ciprofloxacin and levofloxacin. Conclusions: Correlation was found between phenotypic and genotypic methods for detection of ESBL-producing bacteria. Carbapenems demonstrated excellent in vitro activity against strains of ESBL-positive enteric bacteria isolated in a Bulgarian university hospital. Tigecycline, amikacin, piperacillin/tazobactam, nitrofurantoin should also be considered as treatment options.
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| 3. |
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| 4. |
- Svensson, Liselott A, et al.
(författare)
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Stenotrophomonas species differentiation by MLSA of gyrB and rpoD and identification of isolates from clinical and environmental samples
- 2009
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Ingår i: FEMS 2009 - 3rd Congress of European Microbiologists.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Background: Stenotrophomonas species are commonly observed in clinical and environmental samples. S. maltophilia is associated with respiratory infections, is recognized as the third most common nosocomial Gram-negative, non-fermenting bacterium and is isolated from a range of environmental ecosystems, often exhibiting biodegradation and other biotechnological potential. Identification of Stenotrophomonas spp. is famously problematic, due to lack of phenotypic markers, as well as limited 16S rRNA gene sequence differentiation. Objectives: The aim of this study was to determine the applicability of “house-keeping” genes gyrB and rpoD as biomarkers for species-level differentiation within Stenotrophomonas. Methods: Selected regions from gyrB and rpoD of Stenotrophomonas spp., including all type strains, were amplified by PCR and sequenced, for comparative analyses. Results: Comparative sequence analyses of targeted regions of gyrB and rpoD enabled effective resolution of all species in Stenotrophomonas. Dissimilarities between the sequences of the type strains of S. maltophilia and other Stenotrophomonas spp. ranged from 10.2 – 14.7 % (gyrB) and 13.0 – 21.7 % (rpoD). Inter-species sequence dissimilarities of gyrB and rpoD ranged from 7.2 % --18.0 % and from 5.5 % - 22.8%, respectively. Compared with Stenotrophomonas spp. 16S rRNA gene sequence dissimilarities, (0.9 – 3.1 %), both house keeping genes exhibit better capacity for reliably differentiating Stenotrophomonas species. Clinical isolates identified as S. maltophilia were analysed by gyrB and rpoD sequence analyses. These data elucidated high levels of sequence dissimilarities among isolates, bringing into question the identifications determined by traditional methods, as well as the resolution of the taxonomy of Stenotrophomonas. These questions are being addressed in more detail. Conclusions: Analyses of house-keeping genes gyrB and rpoD exhibited effective species-level differentiation for Stenotrophomonas, which can be applied, in combination with 16S rRNA gene sequence analyses to provide an MLSA strategy for genotypic analyses for reliable identifications of isolates from clinical and environmental samples.
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