Characterization of Salmonella Typhimurium isolates from domestically acquired infections in Finland by phage typing, antimicrobial susceptibility testing, PFGE and MLVA

Background: Salmonella enterica spp. enterica serotype Typhimurium (STM) is the most common agent of domestically acquired salmonellosis in Finland. Subtyping methods which allow the characterization of STM are essential for effective laboratory-based STM surveillance and for recognition of outbreaks. This study describes the diversity of Finnish STM isolates using phage typing, antimicrobial susceptible testing, pulsed-field gel electrophoresis (PFGE) and multilocus variable-number tandem repeat analysis (MLVA), and compares the discriminatory power and the concordance of these methods. Results: A total of 375 sporadic STM isolates were analysed. The isolates were divided into 31 definite phage (DT) types, dominated by DT1 (47 % of the isolates), U277 (9 % of the isolates) and DT104 (8 % of the isolates). Of all the isolates, 62 % were susceptible to all the 12 antimicrobials tested and 11 % were multidrug resistant. Subtyping resulted in 83 different XbaI-PFGE profiles and 111 MLVA types. The three most common XbaI-PFGE profiles (STYM1, STYM7 and STYM8) and one MLVA profile with three single locus variants accounted for 56 % and 49 % of the STM isolates, respectively. The studied isolates showed a genetic similarity of more than 70 % by XbaI-PFGE. In MLVA, 71 % of the isolates lacked STTR6 and 77 % missed STTR10p loci. Nevertheless, the calculated Simpson's diversity index for XbaI-PFGE was 0.829 (95 % CI 0.792-0.865) and for MLVA 0.867 (95 % CI 0.835-0.898). However, the discriminatory power of the 5-loci MLVA varied among the phage types. The highest concordance of the results was found between XbaI-PFGE and phage typing (adjusted Wallace coefficient was 0.833 and adjusted Rand coefficient was 0.627). Conclusions: In general, the calculated discriminatory power was higher for genotyping methods (MLVA and XbaI-PFGE) than for phenotyping methods (phage typing). Overall, comparable diversity indices were calculated for PFGE and MLVA (both DI > 0.8). However, MLVA was phage type dependent providing better discrimination of the most common phage types. Furthermore, 5-loci MLVA was a less laborious method and easier to interpret than XbaI-PFGE. Thus, the laboratory-based surveillance of the Finnish human STM infections has been conducted with a combination of phage typing, antimicrobial susceptibility testing and 5-loci MLVA since January 2014.Peer reviewe

Novel Microbiological and Spatial Statistical Methods to Improve Strength of Epidemiological Evidence in a Community-Wide Waterborne Outbreak

Peer reviewe

Antibacterial Effects of Extracts of Pinus sylvestris and Picea abies against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Streptococcus pneumoniae

Pine heartwood, sapwood, and spruce extracts were tested against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecalis (VRE), Escherichia coli O157:H7, and Streptococcus pneumoniae. The bacterial strains were cultured in a broth with and without the wood extracts. Also, the antibacterial effect of the extracts was studied by performing the antimicrobial sensitivity test method on agar plates. Both pine extracts had a clear antibacterial effect on MRSA, VRE, and S. pneumoniae. Only pine sapwood extract had an effect on E. coli and it was weaker than on other strains. Spruce showed a clear antibacterial effect on S. pneumoniae and a weaker effect on MRSA and VRE. The results suggest that these wood species have potential as surface materials in hospital and day care environments

Antibacterial effects of wood structural components and extractives from pinus sylvestris and picea abies on methicillin-resistant Staphylococcus aureus and Escherichia coli O157

Antibacterial properties of wood structural components and extractives were investigated against methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli O157:H7 by placing bacterial inoculum on the model surfaces and incubating them for 2, 4, and 24 h. After incubation, the amount of viable bacteria on the surfaces was studied. The film coverage and thickness were evaluated with atomic-force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The extracts were analyzed with gas chromatography-mass spectrometry (GC-MS). The results showed that films fully covered the glass surfaces. The XPS results confirmed the analysis of GC-MS, which revealed more similarities between the extractives of pine heartwood and spruce heartwood than between pine heartwood and pine sapwood. Only the pine heartwood extract showed an antibacterial effect against E. coli O157:H7. In contrast, MRSA was susceptible to all of the extracts and milled wood lignin (MWL).Peer reviewe

Pine heartwood and glass surfaces: easy method to test the fate of bacterial contamination

Wooden surfaces in interior use hold potential for improving human health and wellbeing. The antibacterial properties of wood might reduce the possibility of cross-contamination from surfaces. In order to be able to control the hygienic quality of the wooden surface, the antibacterial effect should be better understood. The main aim of this thesis was to identify and evaluate the antibacterial properties of wood and its components.  Different methods were developed and used to study the antibacterial properties of Scots pine and Norway spruce, heartwood and sapwood. The solid wood surface showed clear antibacterial properties, even when the extractives had been removed with acetone. Studies with the extracts showed several human pathogens, including methicillin-resistant Staphylococcus aureus, to be susceptible to pine heartwood and sapwood in particular, and also, to some extent, spruce. Besides extractives, lignin was the only separate wood component showing antibacterial properties. Wood volatile organic compounds (VOCs), which were studied in gaseous form, showed an antibacterial effect against various human pathogens.  Several antibacterial compounds were found in all the extracts, however, they did not always explain the order of antibacterial activity between wood species. No single compound could alone explain the effect, hence the antibacterial effect derives either from different mechanisms in different species or from a synergistic effect. α-pinene and limonene could partly explain the antibacterial effect of the VOCs, but other components were also found to have an influence.  Wood was found to have various antibacterial parts and a diverse range of bacterial pathogens that were sensitive to it. These results offer a good ground for the exploitation of the hygienic properties of wood and a good starting point for enhancing them further. Additionally, the extracts showed promising qualities and they should be studied further in regard to resistant pathogens.Puupinnat sisätiloissa vaikuttavat positiivisesti ihmisten terveyteen ja hyvinvointiin. Puun antibakteeriset ominaisuudet saattavat vähentää pintojen kautta tapahtuvan kontaminaation todennäköisyyttä. Antibakteeristen ominaisuuksien parempi ymmärrys mahdollistaa puupintojen hygieenisen laadun paremman hallinnan. Tämän väitöskirjan päätavoite oli selvittää puun ja sen komponenttien antibakteerisia ominaisuuksia.  Männyn ja kuusen sydän- ja pintapuun antibakteerisuuden tutkimiseen käytettiin osin tätä työtä varten kehitettyjä menetelmiä. Puupinnan todettiin olevan antibakteerinen myös silloin, kun puun uuteaineet oli poistettu asetonilla. Uutteiden tarkempi tutkimus osoitti erityisesti männyn sydän- ja pintapuun, mutta jonkin verran myös kuusen uutteiden ehkäisevän useiden tautia aiheuttavien bakteereiden mm. metisilliinille resistentin Staphylococcus aureuksen (MRSA) kasvua. Uutteiden lisäksi ligniini oli ainoa erillinen komponentti, jolla todettiin antibakteerisia ominaisuuksia. Puusta haihtuvilla orgaanisilla yhdisteillä (VOC) todettiin antibakteerisia ominaisuuksia useita tautia aiheuttavia bakteerikantoja kohtaan.  Kaikissa uutteissa todettiin useita antibakteerisia yhdisteitä, mutta niiden määrä ei aina selittänyt eri puulajien antibakteerisuutta suhteessa toisiin puulajeihin. Mikään yksittäinen yhdiste ei yksin selittänyt antibakteerista vaikutusta, joten ilmiö johtuu joko eri puulajeilla eri mekanismeista tai synergisistä vaikutuksista. α-pineeni ja limoneeni selittivät osin VOCien antibakteerisia ominaisuuksia, mutta myös muilla yhdisteillä todettiin olevan vaikutusta.  Puun antibakteerisuuden todettiin johtuvan useista eri aineista ja tehoavan useisiin eri bakteereihin. Nämä tulokset tarjoavat hyvän lähtökohdan puun hygieenisten ominaisuuksien hyödyntämiseen ja niiden kehittämiseen. Uutteet osoittautuivat myös tehokkaiksi ja niiden ominaisuuksia erityisesti suhteessa resistentteihin bakteereihin kannattaisi tutkia lisää

Microbiological results of faecal samples from symptomatic patients of a waterborne outbreak in Vuorela, July 2012.

<p>Methods used were cultivation¹, PCR/RT-PCR² (polymerase chain reaction/reverse transcripition-PCR), EM³ (electron microscopy) and/or EIA⁴ (Enzyme Immunoassay). ⁵<i>Campylobacter jejuni</i> and ⁶EHEC O157:H7 (from one sample) and ⁷sapovirus GII.P3 were isolated from the samples.</p