Salmonella enterica– Mechanisms of fluoroquinolone and macrolide resistance

Salmonella enterica – Fluorokinoloni- ja makrolidiresistenssimekanisimit Vakavia salmonellainfektioita on pitkään hoidettu fluorokinoloniantibiooteilla, kuten siprofloksasiinilla. Fluorokinolonien runsas käyttö niin ihmisillä kuin eläimilläkin on kuitenkin johtanut fluorokinoloniresistenttien salmonellakantojen lisääntymiseen. Vuoteen 2002 asti kaikki matalan tason fluorokinoloniresistenssiä ilmentävät salmonellakannat olivat resistenttejä nalidiksiinihapolle, joka on vanha ensimmäisen polven kinoloniantibiootti jota ei enää käytetä infektioiden hoidossa. Vuonna 2003 havaitsimme aivan uudentyyppisen resistenssifenotyypin salmonelloissa. Kaikki uuden fenotyypin kannat osoittivat matalaa fluorokinoloniresistenssiä (MIC ≥0.125 mg/L), mutta useat kannat olivat yllättäen aikaisempaa herkempiä nalidiksiinihapolle (MIC ≤32 mg/L). Ilmiöllä on suuri merkitys salmonellan antibioottiherkkyyksien määrittämisessä, sillä jos kanta on ollut nalidiksiinihapolle herkkä, sitä on pidetty herkkänä myös fluorokinoloneille. Väitöskirjatyössä määritettiin vuosina 2003–2007 Suomessa kerättyjen kotimaisten ja ulkomaalaisten S. enterica -kantojen fluorokinoloniresistenssiä sekä tutkittiin uuden salmonellafenotyypin epidemiologiaa ja resistenssimekanismeja. Lisäksi tutkittiin salmonellan hoidossa mahdollisesti käyttökelpoisen makrolidiantibioottijohdannaisen, atsitromysiinin tehoa salmonelloihin ja erityisesti matalaa fluorokinoloniresistenssiä ilmentäviin kantoihin. Tutkimuksessa havaittiin, että matalaa fluorokinoloniresistenssiä osoittavien salmonellakantojen määrä vähenee. Lasku oli voimakkainta Kaakkois-Aasiasta tuoduissa kannoissa. Uusi resistenssifenotyyppi on plasmidivälitteinen ja qnr-geenit olivat ainoa plasmidivälitteinen kinoloniresistenssimekanismi, joka kannoista löydettiin. Myöskään kromosomaalisten gyrA, gyrB ja parE -geenien QRDR-alueelta ei löydetty fluorokinoloniresistenssiä aiheuttavia mutaatioita. Transformaatiolla osoitettiin qnr-plasmidien olevan siirtyviä ja uusi resistenssifenotyyppi saatiin ilmennettyä myös herkässä vastaanottajakannassa. Nämä tulokset osoittavat, että vaikka S. enterican qnr-fenotyyppi on toistaiseksi levinnyt pääasiassa Kaakkois-Aasiaan, se siirtyy helposti bakteerista toiseen ja tulee todennäköisesti aiheuttamaan hoito-ongelmia myös muualla maailmassa. Uudentyyppinen qnr-fenotyyppi voi olla vaikea havaita perinteisellä herkkyysmäärityksellä. Siksi laboratorioissa tulisi aina määrittää sekä siprofloksasiiniettä nalidiksiinihappoherkkyydet. Atsitromysiinin osoitettiin olevan herkkyysmääritysten mukaan tehokas salmonelloja kohtaan mukaanlukien matala-asteista fluorokinoloniresistenssiä ilmentävät bakteerikannat.Salmonella enterica – Mechanisms of fluoroquinolone and macrolide resistance Severe Salmonella infections are usually treated with fluoroquinolones, like ciprofloxacin. Along with the extensive use of fluoroquinolones both in humans and veterinary medicine, there has been a reduction in the fluoroquinolone susceptibility among the Salmonella enterica isolates. Before 2002, all isolates with reduced fluoroquinolone susceptibility were highly resistant to nalidixic acid, a first generation quinolone which is no longer used in the treatment of infections. In 2003, a new quinolone resistance phenotype of S. enterica was detected. These non-classical quinolone resistance phenotype isolates showed reduced susceptibility to ciprofloxacin (MIC ≥0.125 mg/L), but were susceptible or only low-level resistant to nalidixic acid (MIC ≤32 mg/L). This phenomenon has a great significance in fluoroquinolone susceptibility testing, since previously all Salmonella strains that were susceptible to nalidixic acid, were considered to be susceptible to ciprofloxacin as well. In this thesis, the incidence of reduced fluoroquinolone susceptibility among domestic and foreign S. enterica isolates collected during 2003–2007 was determined and the epidemiology and resistance mechanisms of the non-classical quinolone resistance phenotype were investigated. Also the in vitro activity of azithromycin was determined, with the aim to find an alternative for the fluoroquinolone treatment of salmonellosis. The results of this study show that reduced fluoroquinolone susceptibility among foreign S. enterica isolates decreased significantly during the study period. The decrease was the most prevalent in Southeast Asia. The non-classical quinolone resistance phenotype was shown to be plasmid-mediated and all isolates belonging to this phenotype were qnrpositive. No other plasmid-mediated quinolone resistance (PMQR) determinants were found and the isolates were also negative for all fluoroquinolone resistance causing mutations in the QRDR of the chromosomal gyrA, gyrB and pare genes. A transformation assay revealed that the qnr plasmids were transferable and the novel phenotype reproducible in vitro. These results indicate that although the qnr phenotype in S. enterica is concentrated so far, in Southeast Asia, the novel phenotype is readily transferable and therefore treatment problems will occur also in the other parts of the world. The qnr phenotype isolates might be hard to identify with conventional screening tests. Thus, laboratories should examine both ciprofloxacin and nalidixic acid susceptibility. Finally, azithromycin proved to be in vitro active against S. enterica isolates including those with reduced fluoroquinolone susceptibility, suggesting that it may be a useful alternative for the treatment of multiresistant Salmonella isolates.Siirretty Doriast

Clinical evaluation of an automated, rapid mariPOC antigen test in screening of symptomatics and asymptomatics for SARS-CoV-2 infection

A novel automated mariPOC SARS-CoV-2 antigen test was evaluated in a Health Care Center Laboratory among symptomatic and asymptomatic individuals seeking SARS-CoV-2 testing. According to the national testing strategy, reverse transcription polymerase chain reaction (RT-PCR) was used as a reference method. A total of 962 subjects were included in this study, 4.8% (46/962) of their samples were SARS-CoV-2 RT-PCR-positive, and 87% (40/46) of these were from symptomatics. Among the symptomatics, the overall sensitivity of the mariPOC SARS-CoV-2 test was 82.5% (33/40), though the sensitivity increased to 97.1% (33/34) in samples with a C-t < 30. The mariPOC SARS-CoV-2 test detected two of six PCR-positive samples among the asymptomatics, four cases that remained antigen test negative had C-t values between 28 and 36. The specificity of the mariPOC SARS-CoV-2 test was 100% (916/916). The evaluation showed that the mariPOC SARS-CoV-2 rapid antigen test is very sensitive and specific for the detection of individuals who most probably are contagious

Antibacterial Activity of Electrodeposited Copper and Zinc on Metal Injection Molded (MIM) Micropatterned WC-CO Hard Metals

Antibacterial activity of electrodeposited copper and zinc both on flat and micropatterned hard metal tungsten carbide-cobalt (WC-Co) specimens was studied. Tribological wear was applied on electrodeposited specimens: coatings were completely removed from flat surfaces whereas only top of the micropillars was exposed to wear for the micropatterned specimens protecting the functional metal coating in between the micropillars. The growth of Staphylococcus aureus (S. aureus) Gram-positive bacterial species was studied on the specimens using a touch test mimicking bacterial transfer from the surfaces. Copper coated specimens prevented bacterial growth completely independent of wear or surface structure, i.e., even residual traces of copper were sufficient to prevent bacterial growth. Zinc significantly suppressed the bacterial growth both on flat and micropatterned specimens. However, adhesion of zinc was low resulting in an easy removal from the surface by wear. The micropatterned zinc specimens showed antibacterial activity as electrodeposited zinc remained intact on the sample surface between the micropillars. This was sufficient to suppress the growth of S. aureus. On the contrary, the flat zinc coated surfaces did not show any antibacterial activity after wear. Our results show that micropatterned hard metal specimens can be used to preserve antibacterial activity under tribological wear

Antimicrobial characterization of silver nanoparticle-coated surfaces by “touch test” method

Abstract: Bacterial infections, especially by antimicrobial resistant (AMR) bacteria, are an increasing problem worldwide. AMR is especially a problem with health care-associated infections due to bacteria in hospital environments being easily transferred from patient to patient and from patient to environment, and thus, solutions to prevent bacterial transmission are needed. Hand washing is an effective tool for preventing bacterial infections, but other approaches such as nanoparticle-coated surfaces are also needed. In the current study, direct and indirect liquid flame spray (LFS) method was used to produce silver nanoparticle-coated surfaces. The antimicrobial properties of these nanoparticle surfaces were evaluated with the “touch test” method against Escherichia coli and Staphylococcus aureus. It was shown in this study that in glass samples one silver nanoparticle-coating cycle can inhibit E. coli growth, whereas at least two coating cycles were needed to inhibit S. aureus growth. Silver nanoparticle-coated polyethylene (PE) and PE terephthalate samples did not inhibit bacterial growth as effectively as glass samples: three nanoparticle-coating cycles were needed to inhibit E. coli growth, and more than 30 coating cycles were needed until S. aureus growth was inhibited. To conclude, with the LFS method, it is possible to produce nanostructured large-area antibacterial surfaces which show antibacterial effect against clinically relevant pathogens. Results indicate that the use of silver nanoparticle surfaces in hospital environments could prevent health care-associated infections in vivo.</p

Characterization of flame coated nanoparticle surfaces with antibacterial properties and the heat-induced embedding in thermoplastic-coated paper

Silver nanoparticles deposited on surfaces can provide an antibacterial effect with potential uses in, for example, health-care settings. However, release of nanoparticles and their potential exposure to the environment is of concern. The current work demonstrates a continuous synthesis that simultaneously deposits silver nanoparticles onto plastic coated paper surface by utilizing the liquid flame spray (LFS) aerosol process. Heat from LFS is used to soften the thermoplastic paper surface, which enables partial and full embedding of the nanoparticles, thereby improving adhesion. The embedding is confirmed with atomic force and scanning electron microscopy, and the deposited silver amounts are quantified with X-ray photoelectron spectroscopy. The results suggest that embedding was more effective in PE-coated paper samples due to the lower glass transition temperature when compared to PET-coated paper samples. The antibacterial properties of the surfaces against E. coli and S. aureus were maintained and confirmed with a previously developed 'Touch-Test Method: The LFS process has the potential to be used for large-scale manufacturing of antibacterial surfaces with improved nanoparticle adhesion on appropriately chosen thermoplastic surfaces

Functionalization of TiO2 inverse opal structure with atomic layer deposition grown Cu for photocatalytic and antibacterial applications

TiO2 inverse opal (IO) structure surfaces were functionalized with a sub-monolayer amount of Cu by atomic layer deposition (ALD) and tested for photocatalytic and antimicrobial applications. Decomposition of acetylene (C2H2) into CO2 and reduction of CO2 into CH4 were tested in the gas phase and photodegradation of methylene blue (MB) was tested in the liquid phase. Antimicrobial activity was tested against Gram-positive Staphylococcus aureus (S. aureus) bacteria. ALD Cu without any post-deposition heat treatment (HT) decreased the photo degradation rate of both C2H2 and MB but improved the activity towards CO2 reduction. ALD Cu increased MB photodegradation rate and antimicrobial activity only after HT at 550 C, which was linked to the improved chemical stability Cu after the HT. The same HT decreased the activity towards CO2 reduction and decomposition of C2H2. The HT induced desorption of loosely bound ALD Cu+/2+ from the TiO2 IO surface and the remaining Cu+/2+ was reduced to Cu+. The photocatalytic and antimicrobial activity of TiO2 IO can be tailored by the addition of a sub-monolayer amounts of Cu with performance depending on the targeted reaction