Browsing by Subject "biofilm"

Most bacteria live as biofilms (99%), which is a population of cells attached to a natural or artificial surface and encased in self-produced exopolysaccharide matrix. The extracellular polymeric substances (EPS) in the matrix can vary greatly between species in chemical and physical properties, but primarily it consists of water, polysaccharides, proteins, nucleic acids and absorbed nutrients from the surrounding area. Biofilm formation appears to be a survival strategy of bacteria and the main purpose of the biofilm matrix is to protect the bacteria. In nature, biofilms have been found in variety of different environments, including humans. Bacterial biofilms demonstrate a decreased susceptibility to antimicrobial agents and several mechanisms have been proposed to be involved in this tolerance. One of the reasons why chronic infections develop is that the immune response fails to remove the biofilm. Most of the bacterial infections currently in developed countries are biofilm related and these infections are often recalcitrant and difficult to eradicate with available treatments. In addition to chronic infections, the treatment of acute infections is shadowed by increasing problems with highly resistant bacteria. The presence of dormant persisters in biofilms accounts for their tolerance to antimicrobials and likely are responsible for latent and chronic infections, such as tuberculosis. Persistence is not primarily an active mechanism of antibiotic tolerance, but a dormant state of the bacteria avoiding the mechanism of action of most antibiotics. Persisters form stochastically only in small numbers, and more relevant physiological explanation is related to the stress responses of the cells. Persisters are distinguish phenotypic variants of the normal population and it is not a heritable feature, as no mutations occur. The dormant, persistent state of the bacteria is largely responsible for the multidrug tolerance of recalcitrant infections. Biofilm cause various diseases in humans, as bacteria are able to attach to practically any surface, such as teeth, heart valves, lungs, middle ear, artificial prosthetics and instruments. Biofilms growing on prosthetic joints can cause also serious infections, which are painful for the patient with high risks for complications, expensive and laborious to replace. Biofilm infections are difficult to treat and a huge burden in the healthcare. Many acute infections can be cured with conventional antibiotic therapies, but this is not case with recalcitrant, chronic infections. B. cenocepacia belongs to the B. cepacia complex (Bcc) which consist of 20 closely related and phenotypically similar species. This species was chosen for this study because of its natural tolerance to antibiotics and ability to form biofilms easily. This species causes fatal lung infections in cystic fibrosis patients, and there is no treatment for it other than inadequate combination antibiotic treatment and lung transplant. In this thesis, a promising method was developed and validated for detecting anti-persister activity against B. cenocepacia. The assay is based on measuring the levels of ATP present in the cultures after treatment and it can be used quantify remaining persisters using B. cenocepacia biofilms. Utilizing the method validated, it was confirmed that mitomycin C is an effective anti-persister compound against highly tolerant B. cenocepacia biofilms even at low concentrations. Doxycycline was found to be ineffective against B. cenocepacia biofilms, although the bacteria are susceptible to it in planktonic form, and ciprofloxacin was proved to be effective at very high concentrations.

Quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) spectroscopy are methods measuring mass changes on solid surface. During measurement fluid flows over sensor. The aim of this study was to find out if it's possible to culture a biofilm using QCM and SPR methods and compare biofilms with those cultured in test tubes under static fluid conditions. Enrofloxacin antibiotic was tested against biofilm cultured in SPR. Biofilms were imaged electron microscopically. Bacteria used were Staphylococcus pseudintermedius and Corynebacterium auriscanis and a combination of those. Biofilm was successfully cultured by both methods repeatably. S.pseudintermedius formed a biofilm, but C.auriscanis didn't. Together S.pseudintemedius and C.auriscanis formed thicker biofilm than S.pseudintermedius alone. There were difference between biofilms depending on culturing conditions. Biofilm covered the surface quicker and bacterial density was higher under flowing conditions than static fluid. The growth of biofilm was ceased during enrofloxacin feeding, but not destroyed. Growth continued after stopping enrofloxacin feeding. QCM and SPR methods are suitable for culturing biofilms. They measure mass changes on solid surface but tell nothing about the architecture of biofilm. QCM and SPR could be good methods for studying compounds destroying biofilm matrix or trying to find coating materials to prevent bacterial adhesion.

Listeria monocytogenes on yksi yleisimmistä Suomessa esiintyvistä ruokamyrkytyspatogeeneistä. Pastöroimattomat maitotuotteet ovat merkittävä riskielintarvikeryhmä. Raakamaitoon L. monocytogenes voi päätyä esimerkiksi utareen pinnalta huonon lypsyhygienian seurauksena, mutta tartuntareittinä voi myös toimia lypsylaitteistoon tai maitotankkiin muodostuneet biofilmit. Biofilmin avulla bakteerit kiinnittyvät tiukasti alustaansa ja samalla ne suojautuvat mekaanisilta ja kemiallisilta puhdistustoimenpiteiltä. Biofilmit ovat usein erittäin vaikeita saneerata elintarviketuotantolinjoista. Tavoitteenamme oli kartoittaa maidon alkutuotannosta eristettyjen L. monocytogenes –kantojen kiinnittymistä ja biofilminmuodostusta kuoppalevyillä. Valitsimme yhteensä 79 L. monocytogenes -isolaattia (53 eri genotyyppiä), jotka olivat peräisin neljän lypsykarjatilan maidosta, lypsylaitteiston suodattimista ja navettaympäristöstä. Lisäksi tutkittiin referenssikannat ATCC 19115 ja EGD-e. Isolaateille tehtiin kiinnittymiskoe, jossa niitä kasvatettiin kuoppalevyllä vähäravinteisessa elatusaineessa 30 °C:ssa 24 ja 48 tunnin ajan. Tämän jälkeen kuoppalevy pestiin puhtaaksi irtonaisista bakteerisoluista tislatulla vedellä ja pohjaan kiinnittyneet bakteerisolut värjättiin 0,1 % kristallivioletilla. Väri liuotettiin 95 % etanoliin ja kuoppalevyjen absorbanssi mitattiin spektrofotometrin avulla. Kullekin isolaatiolle tehtiin kolme kiinnittymiskoetta ja jokaisessa kokeessa oli mukana kolme teknistä toistoa. Negatiivisena kontrollina käytettiin elatusainetta, johon ei lisätty bakteeria. L. monocytogenes -isolaattien absorbanssimittausten keskiarvo oli 24 tunnin kasvatuksen jälkeen 0,1915 (0,1468 – 0,2477) ja 48 tunnin kasvatuksen jälkeen 0,2266 (0,1694 – 0,3661). Referenssikannan ATCC 19115 mittaustulokset eivät merkitsevästi eronneet muiden isolaattien tuloksista, mutta EGD-e:n absorbanssi oli 48 tunnin mittauksessa keskimäärin suurempi kuin muiden isolaattien. Sivelynäytteistä eristettyjen isolaattien mittaustulokset olivat 48 tunnin jälkeen merkitsevästi suurempia (p<0,01) kuin maitonäytteistä eristettyjen isolaattien. Sivelynäytteistä eristettyjen isolaattien kasvuympäristöt ovat siis sellaisia, joissa runsaasta biofilminmuodostuksesta on hyötyä bakteereille. Maitonäytteiden isolaatit eivät ole kasvuympäristössään hyötyneet tästä ominaisuudesta, ja siksi niiden biofilminmuodostus on heikompaa. Tulosten valossa on perusteltua, että L. monocytogenes -kantojen kasvuympäristön ja biofilminmuodostuskyvyn mahdollista yhteyttä selvittäisiin tarkemmin.

The aim of this thesis was to study and develop the process hygiene of the new R1 bottling line at Altia Rajamäki alcoholic beverage plant. The products bottled on the line are mainly low- and non-alcoholic beverages that have limited amount of previously studied knowledge about the efficiency of hygienic practices of their production. In addition, the microbiological quality of the products’ raw materials was studied, and an attempt was made to identify the microbes occurring in the products and on the production line. The literature review deals with the legislation of food industry and the microbiological risks related to various types of beverages and their processing. In the experimental part of the thesis the microbiological hygiene of the bottling process was studied by collecting samples from the surfaces of the bottling line using mainly the microbiological swabbing method. The microbiological analyses of the bottled products were conducted by filtering the sample to a filter paper. Various culture mediums and antibiotics were also tested to identify the bacteria from yeasts and molds. 16S rRNA gene sequencing was used to identify the bacteria frequently occurring in the analyses. DNA isolation and PCR were conducted at the University of Helsinki and the gene sequencing was carried out by the Institute of Biotechnology. Sequence alignment was made using BLAST. The public version of the thesis lacks the confidential information which is provided only for Altia Oyj. Based on the results, the process hygiene of the R1 bottling line is sufficient in case the hygienic practices are followed. No significant microbiological growth was observed in the process hygiene samples. However, endospore producing bacteria were found in the products and these bacteria were presumed to originate from the raw materials of the products or from storage tanks and pipelines of these raw materials. Four bacterial genera, which frequently occurred in the products, were successfully identified. Nevertheless, based on the literature, it was noticed that these bacteria are not able to spoil alcoholic beverages nor to grow in the conditions of bottled products. However, some of these bacteria can substantially form biofilm.

Bacterial surface layers (S-layers) usually consist of a single protein or glycoprotein species and they form the outermost layer of many bacteria. Three S-layer protein genes have been found in Lactobacillus brevis ATCC 14869, but the expression of only two of them, slpB and slpD, has been described in planktonic conditions. Preliminary results have suggested that the third gene, slpC, may be expressed in biofilm cells. The aim of this thesis was to study the expression of S-layer protein genes slpB, slpC and slpD in the different growth modes of L. brevis ATCC 14869. Surface proteins were detached both chemically for SDS-PAGE analysis and enzymatically for surfaceome analysis by LC-MS/MS and label-free quantification (LFQ). Messenger RNA transcript levels of the S-layer protein genes were analyzed by reverse transcriptase droplet digital PCR (RT-ddPCR). The expression of all three S-layer protein genes slpB, slpC and slpD was confirmed in the study. In the surfaceome analysis, SlpD was the most abundant protein detected on the cell surface, representing more than a third of all identified proteins, whereas SlpB and SlpC were less abundant. The S-layer proteins were detected by gel electrophoresis. Transcripts of all three genes were observed; slpD transcript amounts were the highest, whereas slpB and slpC transcript amounts were lower. The S-layer proteins and their transcripts were present in equal amounts in biofilm and planktonic cells. In this study, SlpC expression is demonstrated for the first time in L. brevis ATCC 14869. The expression of slpB, slpC and slpD was at the same level in biofilm and planktonic cells.

Periodontitis is a globally significant disease which destroys the attachment tissues and alveolar bone of teeth, eventually leading to tooth loss. Biofilms, the most intrinsic lifestyle of bacteria, play a pivotal role in the occurrence of this disease. Periodontal biofilms can be treated with topically administered chlorhexidine and strain-specific antibiotics. However, these antimicrobials do not offer solutions for periodontal attachment tissue and alveolar bone loss. Some therapeutical alternatives for these conventional treatments have been investigated. In numerous studies, periodontitis is treated successfully (increased attachment and/or alveolar bone levels) with topically and systemically administered bisphosphonates. Furthermore, a topically administered bone graft substitute (bioactive glass) has shown to improve periodontal parameters. In addition, bioactive glass has known antimicrobial and anti-biofilm effects. Moreover, a few bisphosphonates have shown antimicrobial activity against some bacterial strains. Hence, both bisphosphonates and bioactive glass are promising materials for dental applications, also raising interest in their combination. Indeed, it could be hypothesized that this combination product could simultaneously treat both the underlying cause (biofilms) and consequences (alveolar bone and attachment tissue loss) of periodontitis. Open research questions remain for the combination product. Is the anti-biofilm effect enhanced when bioactive glass is combined with bisphosphonates? Moreover, do bisphosphonates have intrinsic anti-biofilm properties? These questions are investigated in this thesis, which is a continuation of a recent doctoral dissertation. In this dissertation, a clodronate-bioactive glass combination product was studied by applying it into periodontal pockets. However, anti-biofilm effects were not assessed. In this thesis, a close examination is carried out on these effects, utilizing relevant biofilm models. The aims of this work were to investigate anti-biofilm effects of bisphosphonates (alendronate, clodronate, etidronate, risedronate and zoledronate) (i) alone, administered as solutions and (ii) combined with bioactive glass S53P4. Optimization of the used assay methods (96-well plate assay, Static Biofilm method) was performed. The anti-biofilm effects of bisphosphonate solutions were screened in the 96-well plate assay using a model organism Staphylococcus aureus Newman and a periodontopathogen Aggregatibacter actinomycetemcomitans ATCC 33384. After this, experiments were conducted with bisphosphonate-bioactive glass combinations. The experiments were performed with a single-specie (A. actinomycetemcomitans ATCC 33384) dental biofilm model based on the Static Biofilm method. The model mimics conditions encountered by periodontal bacteria in the oral cavity. In this part, bisphosphonate particle sizes were measured to determine a suitable control material. In addition to bacterial experiments, pH measurements were carried out to gain an insight to a possible anti-biofilm mechanism. Bisphosphonates administered as stand-alone compounds did not have an effect on either the Gram-positive model organism (S. aureus Newman) or the Gram-negative periodontopathogen (A. actinomycetemcomitans ATCC 33384). In contrast, most combinations of bisphosphonate-bioactive glass revealed a statistically significant increase in anti-biofilm effect on A. actinomycetemcomitans ATCC 33384. The combinations were compared to a control composed of inert glass and bioactive glass. In these assay conditions, the risedronate-bioactive glass-combination was the most effective (significant statistical difference, p < 0.05). Other combinations also reduced biofilms (significant statistical differences, p < 0.05), with the exception of clodronate-bioactive glass, where the change was not statistically significant. The most effective combinations (containing risedronate and etidronate) subjected the biofilms to a period of low pH. Conversely, the least effective combination (clodronate-bioactive glass) rapidly became alkaline, similarly to the control compounds (inert glass and bioactive glass). Thus, anti-biofilm efficacy could be connected to lowered pH. This observation is supported by recent literature where A. actinomycetemcomitans has been deemed highly sensitive to acidity. However, establishing the anti-biofilm rank order of bisphosphonate-bioactive glass combinations would benefit from experiments with equal bisphosphonate particle sizes.