Pseudomonas Aeruginosa is a Gram-negative bacterium which can form biofilms, increasing its resistance against antibiotics and the host immune system. Polysaccharides are an integral part of this... Show morePseudomonas Aeruginosa is a Gram-negative bacterium which can form biofilms, increasing its resistance against antibiotics and the host immune system. Polysaccharides are an integral part of this biofilm, one of these polysaccharides is called Psl. PslG is a glycosidase, able to cleave this polysaccharide, Psl, into smaller fragments. This decreases the antibiotic resistance of P. Aeruginosa. Interestingly PslG is produced by P. Aeruginosa itself, where it is found on the synthesis gene of Psl. The exact effects of PslG remain partly unknown. Moreover, only hypotheses have been made as to why P. Aeruginosa expresses such an enzyme. Here we have developed a set of activity-based probes based on Psl to discover the mode of action of PslG. Subsequently, a set of inhibitors have been designed based on the Psl motive and the mechanism of action of PslG. PslG was then co-crystallized with the inhibitors in order to study their binding interactions. Show less
A prosthetic joint infection (PJI) is a severe complication after arthroplasty. From the current thesis, three main conclusion can be drawn regarding diagnosis and treamtent of PJI. (a) Accurate... Show moreA prosthetic joint infection (PJI) is a severe complication after arthroplasty. From the current thesis, three main conclusion can be drawn regarding diagnosis and treamtent of PJI. (a) Accurate self-monitoring of postoperative wounds after joint implantation helped elucidate the course of wound leakage and its association with acute prosthetic joint infections. (b) The collection of clinical data on different antimicrobial treatment strategies provided insight into the effectiveness of different treatment options for patients with a prosthetic joint infection. In this thesis, we report that personalized antimicrobial treatment for prosthetic joint infections is possible without compromising the effectiveness of treatment. (c) this thesis describes the role and importance of new anti-persister drugs against biofilm-associated infections. We developed a biofilm model that closely resembles the clinic of a prosthetic joint infection. Based on the results described in this thesis, future research will be aimed at better understanding the pathogenesis of biofilms. This should ultimately lead to better treatment options for patients with a prosthetic joint infection. Show less
Aims: Here we used a mature seven -day biofilm model of Staphylococcus aureus, exposed to antibiotics up to an additional seven days, to establish the effectiveness of either mechanical cleaning or... Show moreAims: Here we used a mature seven -day biofilm model of Staphylococcus aureus, exposed to antibiotics up to an additional seven days, to establish the effectiveness of either mechanical cleaning or antibiotics or non-contact induction heating, and which combinations could eradicate S. aureus in mature biofilms. Methods: Mature biofilms of S. aureus (ATCC 29213) were grown on titanium alloy (Ti6Al4V) coupons for seven days and were subjected to the following treatments or their combinations: antibiotics, mechanical cleaning, or heat shock by induction heating of 60 & DEG;C for one minute. Experiments were repeated at least five times. Results: In the untreated biofilm, growth up to 1.8x1011 colony-forming units (CFU)/cm2 was observed. Treatment with ciprofloxacin, flucloxacillin, vancomycin, cefuroxime, and amoxicillin all with rifampicin gave 6.0 log, 6.1 log, 1.4 log, 4.8 log, and 3.6 log reduction in CFU/cm2, respectively. Mechanical cleaning alone resulted in 4.9 log reduction and induc-tion heating in 7.3 log reduction. There was an additional effect of ciprofloxacin, fluclox-acillin, and induction heating when used in combinations. There was no additional effect for mechanical cleaning. No bacterial growth could be detected after induction heating followed by seven days of ciprofloxacin with rifampicin. Conclusion: Mechanical cleaning, antibiotics, and non-contact induction heating reduced the bacterial load of mature S. aureus biofilms with approximately 5 log or more as a single treatment. The effect of mechanical cleaning on mature S. aureus biofilms was limited when used in combination with antibiotics and/or induction heating. Show less
Background: Clostridioides difficile is the most common causative agent of antibiotic-acquired diarrhea in hospitalized patients associated with substantial morbidity and mortality. The global... Show moreBackground: Clostridioides difficile is the most common causative agent of antibiotic-acquired diarrhea in hospitalized patients associated with substantial morbidity and mortality. The global epidemic of CDI (Clostridioides difficile infection) began in the early 20th century with the emergence of the hypervirulent and resistant ribotype 027 strains, and requires an urgent search for new therapeutic agents. Objective: The aim of this study is to investigate the antibacterial activity of the three essential oils isolated from spice herbs (wild oregano, garlic and black pepper) against C. difficile clinical isolates belonging to 6 different PCR ribotypes and their potential inhibitory effect on the biofilm production in in vitro conditions. Results: Wild oregano essential oil showed strong inhibitory activity in concentrations 0.02-1.25 mg/mL and bactericidal activity in concentrations from 0.08 to 10 mg/mL. Garlic essential oil was effective in the concentration range of 0.02-40 mg/mL, and 0.16 -> 40 mg/mL. MIC and MBC for black pepper oil ranged from 0.04 to 40 mg/mL, and 0.08 -> 40 mg/mL, respectively. All the tested oils reduced in vitro biofilm production, with the best activity of oregano oil. Conclusion: Essential oils of wild oregano, black pepper and garlic are candidates for adjunctive therapeutics in the treatment of CDI. Oregano oil should certainly be preferred due to the lack of selectivity of action in relation to the ribotype, the strength of the produced biofilm and/or antibiotic-susceptibility patterns.(c) 2022 Elsevier Ltd. All rights reserved. Show less
Nibberinga, P.H.; Goblyos, A.; Adriaans, A.E.; Cordfunke, R.A.; Ravensbergen, B.; Rietveld, M.H.; ... ; Ghalbzouri, A. el 2019
Skin bacterial colonization/infection is a frequent cause of morbidity in patients with chronic wounds and allergic/inflammatory skin diseases. This study aimed to develop a novel approach to... Show moreSkin bacterial colonization/infection is a frequent cause of morbidity in patients with chronic wounds and allergic/inflammatory skin diseases. This study aimed to develop a novel approach to eradicate meticillin-resistant Staphylococcus aureus (MRSA) from human skin. To achieve this, the stability and antibacterial activity of the novel LL-37-derived peptide P10 in four ointments was compared. Results indicate that P10 is chemically stable and antibacterial in hypromellose gel and Softisan-containing cream, but not in Cetomacrogol cream (with or without Vaseline), at 4 degrees C for 16 months. Reduction in MRSA counts on Leiden human epidermal models (LEMs) by P10 in hypromellose gel was greater than that of the peptide in Cetomacrogol cream or phosphate buffered saline. P10 did not show adverse effects on LEMs irrespective of the ointment used, while Cetomacrogol with Vaseline and Softisan cream, but not hypromellose gel or Cetomacrogol cream, destroyed MRSA-colonized LEMs. Taking all this into account, P10 in hypromellose gel dose-dependently reduced MRSA colonizing the stratum corneum of the epidermis as well as biofilms of this bacterial strain on LEMs. Moreover, P10 dose-dependently reduced MRSA counts on ex-vivo human skin, with P10 in hypromellose gel being more effective than P10 in Cetomacrogol and Softisan creams. P10 in hypromellose gel is a strong candidate for eradication of MRSA from human skin. (C) 2019 Elsevier B.V. and International Society of Chemotherapy. All rights reserved. Show less
Acinetobacter baumannii is an important nosocomial pathogen responsible for outbreaks of infection worldwide. The studies presented in this thesis aimed to gain further insight into the bacterial... Show moreAcinetobacter baumannii is an important nosocomial pathogen responsible for outbreaks of infection worldwide. The studies presented in this thesis aimed to gain further insight into the bacterial and host factors associated with the pathogenesis of A. baumannii to seek an explanation for the clinical success of A. baumannii. We demonstrated that both A. baumannii and less virulent Acinetobacter species can adhere to surfaces and form a biofilm, albeit with a wide variation among strains of each species. These results first of all show that a single strain is not representative for the species. Secondly, the presence of many virulence attributes in both clinically relevant and less-relevant strains indicates that the clinical success of A. baumannii cannot be explained by these virulence factors alone. Moreover, our results suggest that the outcome of infection depends mainly on the host. In this respect, a specific host innate immune response induced by different A. baumannii strains was associated with the outcome of A. baumannii pneumonia. Thus, the ability of certain A. baumannii strains to induce specific immune responses in susceptible hosts in combination with their metabolic versatility and a MDR phenotype are likely to be important features associated with the clinical success of this pathogen. Show less
Pseudomonas putida strain PCL1445 produces two cyclic lipopeptides, named putisolvins I and II, which represent a Novel class of biosurfactants. Putisolvins reduce the surface tension between... Show morePseudomonas putida strain PCL1445 produces two cyclic lipopeptides, named putisolvins I and II, which represent a Novel class of biosurfactants. Putisolvins reduce the surface tension between liquid and air, and disrupt already existing biofilms of several Pseudomonas sp., including those of the opportunistic human pathogen P. aeruginosa, and therefore offers opportunities for interesting application in the medical and industrial field. In this Ph.D Thesis, I describe the regulation of cyclic lipopeptide biosynthesis in P. putida. A dnaK gene and a GacA/GacS two-component signalling system were discovered and were shown to be involved in biosurfactants production. Given that DnaK is a heat-chock protein, we investigated the role of temperature on putisolvin production. The results showed that biosurfactant production in P. putida is up-regulated at low temperatures and that DnaK is required for putisolvin production. Bacteria co-ordinate their activities by producing and detecting small diffusible signal molecules (N-acylhomoserine lactones) which enable a population of organized bacteria to act as a community by forming a biofilm. Such a co-operative behaviour is named “quorum sensing” and plays a central role in the lifestyle of bacteria. P. putida PCL1445 was shown to produce N-acylhomoserine lactones which control the production of putisolvins and regulate biofilm formation. We hypothesise that the bacterial community co-ordinates the biosynthesis of putisolvin when nutrients become limiting resulting in a detachment of part of the bacterial cell population. In this Ph.D Thesis, Novel mechanisms for the regulation of cyclic lipopeptide biosynthesis are described, which contribute to the understanding of their role for bacterial proliferation in the rhizosphere. Show less
