Introduction: One of the main causes of treatment failure in bacterial prosthetic joint infections (PJI) is biofilm formation. The topography of the biofilm may be associated with susceptibility to... Show moreIntroduction: One of the main causes of treatment failure in bacterial prosthetic joint infections (PJI) is biofilm formation. The topography of the biofilm may be associated with susceptibility to antimicrobial treatment. The aims of this study were to assess differences in topography of biofilms on different implant materials and the correlation thereof with susceptibility to antimicrobial treatment. Methods: Methicillin-resistant Staphylococcus aureus (MRSA) 7-day mature biofilms were generated on disks made from titanium alloys (Ti-6Al-7Nb and Ti-6Al-4V), synthetic polymer and orthopedic bone cement, commonly used in implant surgery. The surface topography of these implant materials and the biofilms cultured on them was assessed using atomic force microscopy. This provided detailed images, as well as average roughness (Ra) and peak-to-valley roughness (Rt) values in nanometers, of the biofilm and the material surfaces. Bacterial counts within biofilms were assessed microbiologically. Antimicrobial treatment of biofilms was performed by 24-h exposure to the combination of rifampicin and ciprofloxacin in concentrations of 1-, 5- and 10-times the minimal bactericidal concentration (MBC). Finally, treatment-induced differences in bacterial loads and their correlation with biofilm surface parameters were assessed. Results: The biofilm surfaces on titanium alloys Ti-6Al-7Nb (Ra = 186 nm) and Ti-6Al-4V (Ra = 270 nm) were less rough than those of biofilms on silicone (Ra = 636 nm). The highest roughness was observed for biofilms on orthopedic bone cement with an Ra of 1,551 nm. Interestingly, the roughness parameters of the titanium alloys themselves were lower than the value for silicone, whereas the surface of the bone cement was the roughest. Treatment with 1- and 5-times the MBC of antibiotics resulted in inter-material differences in colony forming units (CFU) counts, ultimately showing comparable reductions of 2.4-3.0 log CFU/mL at the highest tested concentration. No significant differences in bacterial loads within MRSA biofilms were observed between the various implant materials, upon exposure to increasing concentrations of antibiotics. Discussion: The surface parameters of MRSA biofilms were determined by those of the implant materials on which they were formed. The antibiotic susceptibility of MRSA biofilms on the various tested implant materials did not differ, indicating that the efficacy of antibiotics was not affected by the roughness of the biofilm. Show less
Objectives: While Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA), defined as CC398, is a well-known pathogen among those working with livestock, there are indications... Show moreObjectives: While Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA), defined as CC398, is a well-known pathogen among those working with livestock, there are indications that LA-MRSA prevalence among the general population is increasing. However, the clinical impact in urban areas remains unknown. The aim of this study was to assess the genetic epidemiology and clinical characteristics of LA-MRSA in an urban area with a limited livestock population. Methods: In this retrospective study, we evaluated LA-MRSA strains that were collected between 2014 and 2018 from patients who received clinical care in a single urban area in Netherlands. Patient files were assessed for livestock exposure data, clinical findings, and contact tracing information. Next-generation sequencing (NGS) analysis in combination with wgMLST was conducted to assess genetic diversity and relatedness and to detect virulence and resistance genes. Results: LA-MRSA strains were cultured from 81 patients, comprising 12% of all the MRSA strains found in seven study laboratories between 2014 and 2018. No livestock link was found in 76% of patients (n = 61), and 28% of patients (n = 23) had an infection, mostly of the skin or soft tissue. Contact tracing had been initiated in 14 cases, leading to the identification of two hospital transmissions: a cluster of 9 cases and one of 2 cases. NGS data were available for 91% (n = 75) of the patients. wgMLST confirmed the clusters detected via contact tracing (n = 2) and identified 5 additional clusters without a known epidemiological link. Relevant resistance and virulence findings included the PVL virulence gene (3 isolates) and tetracycline resistance (79 isolates). Conclusion: LA-MRSA may cause a relevant burden of disease in urban areas. Surprisingly, most infections in the present study occurred in the absence of a livestock link, suggesting inter-human transmission. These findings and the presence of PVL and other immune evasive complex virulence genes warrant future surveillance and preventative measures. Show less
Objectives: While Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA), defined as CC398, is a well-known pathogen among those working with livestock, there are indications... Show moreObjectives: While Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA), defined as CC398, is a well-known pathogen among those working with livestock, there are indications that LA-MRSA prevalence among the general population is increasing. However, the clinical impact in urban areas remains unknown. The aim of this study was to assess the genetic epidemiology and clinical characteristics of LA-MRSA in an urban area with a limited livestock population.Methods: In this retrospective study, we evaluated LA-MRSA strains that were collected between 2014 and 2018 from patients who received clinical care in a single urban area in Netherlands. Patient files were assessed for livestock exposure data, clinical findings, and contact tracing information. Next-generation sequencing (NGS) analysis in combination with wgMLST was conducted to assess genetic diversity and relatedness and to detect virulence and resistance genes.Results: LA-MRSA strains were cultured from 81 patients, comprising 12% of all the MRSA strains found in seven study laboratories between 2014 and 2018. No livestock link was found in 76% of patients (n = 61), and 28% of patients (n = 23) had an infection, mostly of the skin or soft tissue. Contact tracing had been initiated in 14 cases, leading to the identification of two hospital transmissions: a cluster of 9 cases and one of 2 cases. NGS data were available for 91% (n = 75) of the patients. wgMLST confirmed the clusters detected via contact tracing (n = 2) and identified 5 additional clusters without a known epidemiological link. Relevant resistance and virulence findings included the PVL virulence gene (3 isolates) and tetracycline resistance (79 isolates).Conclusion: LA-MRSA may cause a relevant burden of disease in urban areas. Surprisingly, most infections in the present study occurred in the absence of a livestock link, suggesting inter-human transmission. These findings and the presence of PVL and other immune evasive complex virulence genes warrant future surveillance and preventative measures. 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: Increased nasopharyngeal carriage of pathogenic bacteria is found in low socioeconomic status (SES) settings. How SES affects local immune responses, important for controlling... Show moreBackground: Increased nasopharyngeal carriage of pathogenic bacteria is found in low socioeconomic status (SES) settings. How SES affects local immune responses, important for controlling colonization, is currently unknown. Objective: Examining bacterial colonization and cytokine response in the nasal mucosa of children from high and low SES. Methods: Nasosorption samples were collected in October 2019 from 48 high SES and 50 low SES schoolchildren, in a cross-sectional study in Makassar, Indonesia. Twenty-five cytokines were measured in nasal fluid. Quantitative polymerase chain reaction was performed to determine carriage and density of Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis and Staphylococcus aureus. Data were analyzed using multivariate regression. Results: H. influenzae and S. pneumoniae densities were increased in low SES settings compared to the high SES settings (P = 0.006, P = 0.026), with 6 and 67 times higher median densities, respectively. Densities of H. influenzae and S. pneumoniae were positively associated with levels of IL-1beta and IL-6. After correcting for bacterial density, IL-6 levels were higher in colonized children from high SES than low SES for H. influenzae and S. pneumoniae (both P = 0.039). Conclusion: Increased densities of H. influenzae and S. pneumoniae were observed in low SES children, whereas IL-6 levels associated with colonization were reduced in these children, indicating that immune responses to bacterial colonization were altered by SES. Show less
Antibiotic resistance, caused by widespread use of antibiotics, leads to bacterial infections that are difficult, if not impossible, to treat and is a major worldwide health concern. Currently... Show moreAntibiotic resistance, caused by widespread use of antibiotics, leads to bacterial infections that are difficult, if not impossible, to treat and is a major worldwide health concern. Currently Methicillin-resistant Staphylococcus aureus (MRSA) is the most commonly identified antibiotic-resistant pathogen in clinical medicine worldwide. The spread of MRSA highlights the urgent need for alternative therapies, such as vaccination.Wall teichoic acids (WTAs), prime constituents of the Gram-positive cell wall, can function as effective antigenic epitopes and are therefore promising candidates for the development of a conjugate vaccine against S. aureus infections. WTAs are anionic poly-ribitol phosphate (RboP) chains attached to the peptidoglycan and they have a fundamentol role in the physiology in the bacteria.Since isolation from the bacteria of WTAs leads to heterogenous mixtures of fragments and bacterial contaminations, organic synthesis is the method of choice to generate WTA-fragments with pre-defined substitution patterns in higher purity and in larger amounts, allowing detailed immunological studies that can aid in future vaccine development.This Thesis presents methods to synthesize various WTA-fragments from Staphylococcus aureus and Enterococcus faecalis and their applications. Show less
Acute kidney injury (AKI) is a frequent complication in patients with Staphylococcus aureus bacteremia (SAB), with a significant impact on patient management and outcome. This study aimed to... Show moreAcute kidney injury (AKI) is a frequent complication in patients with Staphylococcus aureus bacteremia (SAB), with a significant impact on patient management and outcome. This study aimed to provide insight in the proportion of patients with SAB that develop AKI, the risk factors for developing AKI in this population, and its reversibility. In this retrospective, multicenter cohort study, adult patients with SAB were eligible for inclusion. Patient characteristics, clinical variables, and laboratory results were retrieved from the electronic patient files. Primary outcome was development of AKI, defined as 1.5 times baseline creatinine. Secondary outcomes were reversibility of AKI and risk factors for AKI. A total of 315 patients with SAB were included, of whom 115/315 (37%) developed acute kidney injury. In 68/115 (59%), the AKI was reversible. If kidney function recovered, this occurred within 7 days in 56/68 (82%) of patients. In multivariable logistic regression analyses, independent risk factors for AKI were as follows: complicated SAB, use of diuretics, and hemodynamic instability. Development of AKI was associated with 30-day mortality (OR 3.9; CI 2.2-6.9; p < 0.01). Acute kidney injury is a frequent complication in patients with Staphylococcus aureus bacteremia. Considering the irreversibility in a relevant proportion of patients, future research into the underlying pathophysiology and potential interventions is warranted. Show less
Background: During a meticillin-resistant Staphylococcus aureus contact tracing and screening investigation, two borderline oxacillin-resistant Staphylococcus aureus (BORSA)positive screening... Show moreBackground: During a meticillin-resistant Staphylococcus aureus contact tracing and screening investigation, two borderline oxacillin-resistant Staphylococcus aureus (BORSA)positive screening cultures were encountered among neonatal intensive care unit (NICU) healthcare workers (HCWs). This finding led to further investigations. Aim: To assess the likelihood of an outbreak with direct transmission among HCWs. Methods: An infection control team was initiated after the discovery. The team initiated additional infection control measures and evaluated new findings. All NICUs and paediatric ward HCWs were screened for BORSA carriage, and a prospective BORSA seven-week monitoring period for patients was observed. To assess the likelihood of an outbreak with direct transmission among HCWs, the BORSA isolates were analysed using augmented fragment length polymorphism and whole-genome sequencing (WGS). Findings: Positive HCWs were prohibited from clinical work while awaiting the results from the screening programme. In all, 127 NICU and 77 general paediatric ward HCWs were screened for BORSA carriage; five HCWs were BORSA positive. Seventy-two patients were screened during the seven-week period yielding a total of 138 cultures, ranging from one to nine cultures per patient. No spread from HCWs to patients occurred, and the BORSA screening programme was discontinued. WGS analysis with core genome multi-locus sequence typing of all five BORSA strains showed relatedness between two NICU strains. Conclusion: During a seven-week period, no transmission from BORSA-positive HCWs to neonates was observed in either screening or clinical cultures. More vigilance and experience is needed to design adequate evidence-based interventions in the future for this vulnerable population. (c) 2020 Published by Elsevier Ltd on behalf of The Healthcare Infection Society. Show less
Introduction. The course of both the bacterial species and load and the incidence of infection during negative pressure wound therapy (NPWT) are unclear, with published studies presenting... Show moreIntroduction. The course of both the bacterial species and load and the incidence of infection during negative pressure wound therapy (NPWT) are unclear, with published studies presenting contradicting results. Objective. The aim of the study is to assess the changes in both bacterial species and load, as well as the incidence of infection, before and after NPWT in a patient population with a variety of wounds. Methods. Surgical patients 18 years of age or older who needed NPWT were included in this multicenter, prospective cohort study. A wound swab culture was taken before NPWT and either immediately following NPWT or 6 weeks of follow-up. The change of bacterial species, bacterial load, and rate of infection were determined before and after the start of NPWT. Results. In total, 104 patients were analyzed. The number of positive cultures increased from pre- to post-NPWT. The most cultured pathogenic bacterium was Staphylococcus aureus. The bacterial load was moderately higher at the end of NPWT than at the start (P < .0001). It was noted that 2 swabs contained multidrug-resistant bacteria, 1 pre-NPWT and 1 post-NPWT. Prior to NPWT, 26 patients had a wound infection, 5 of which had a persisting infection at the end of the study. Post-NPWT, 14 patients developed a wound infection. Conclusions. The number of S aureus strains and overall bacterial load increased during NPWT, and the incidence of infection remained the same. Further studies should be conducted to determine whether the increase in bacterial load influences other wound outcome parameters. Show less
Background: We investigated the efficacy of a synthetic antimicrobial peptide SAAP-148, which was shown to be effective against Methicillin-resistant Staphylococcus aureus (MRSA) on tape-stripped... Show moreBackground: We investigated the efficacy of a synthetic antimicrobial peptide SAAP-148, which was shown to be effective against Methicillin-resistant Staphylococcus aureus (MRSA) on tape-stripped mice skin. Unexpectedly, SAAP-148 was not effective against MRSA in our pilot study using rats with excision wounds. Therefore, we investigated factors that might have contributed to the poor efficacy of SAAP-148. Subsequently, we optimised the protocol and assessed the efficacy of SAAP-148 in an adapted rat study.Methods: We incubated 100 mu L of SAAP-148 with 1 cm(2) of a wound dressing for 1 h and determined the unabsorbed volume of peptide solution. Furthermore, 10(5) colony forming units (CFU)/mL MRSA were exposed to increasing dosages of SAAP-148 in 50% (v/v) human plasma, eschar- or skin extract or PBS. After 30 min incubation, the number of viable bacteria was determined. Next, ex vivo skin models were inoculated with MRSA for 1 h and exposed to SAAP-148. Finally, excision wounds on the back of rats were inoculated with 10(7) CFU MRSA overnight and treated with SAAP-148 for 4 h or 24 h. Subsequently, the number of viable bacteria was determined.Results: Contrary to Cuticell, Parafilm and Tegaderm film, < 20% of peptide solution was recovered after incubation with gauze, Mepilex border and Opsite Post-op. Furthermore, in plasma, eschar- or skin extract > 20-fold higher dosages of SAAP-148 were required to achieve a 2-log reduction (LR) of MRSA versus SAAP-148 in PBS. Exposure of ex vivo models to SAAP-148 for 24 h resulted in a 4-fold lower LR than a 1 h or 4 h exposure period. Additionally, SAAP-148 caused a 1.3-fold lower mean LR at a load of 10(7) CFU compared to 10(5) CFU MRSA. Moreover, exposure of ex vivo excision wound models to SAAP-148 resulted in a 1.5-fold lower LR than for tape-stripped skin. Finally, SAAP-148 failed to reduce the bacterial counts in an adapted rat study.Conclusions: Several factors, such as absorption of SAAP-148 by wound dressings, components within wound exudates, re-colonisation during the exposure of SAAP-148, and a high bacterial load may contribute to the poor antimicrobial effect of SAAP-148 against MRSA in the rat model. Show less
Background: The preferred treatment for severe methicillin-sensitive Staphylococcus aureus infections is flucloxacillin, a small-spectrum antibiotic administered intravenously (IV) and orally.... Show moreBackground: The preferred treatment for severe methicillin-sensitive Staphylococcus aureus infections is flucloxacillin, a small-spectrum antibiotic administered intravenously (IV) and orally. However, clinicians switch to the less preferred broad-spectrum antibiotics because of the variable absorption after oral administration of flucloxacillin. A classical oral absorption test (OAT) requires overnight fasting and interruption of IV therapy, and is laborious. In the current study, we investigated whether a simplified OAT can be utilized in a clinical setting to guide antibiotic treatment in patients with severe S. aureus infections. For this, OAT IV therapy is continued and oral dosing is performed after a one-hour fast and implemented after a small study.Methods: In 196 patients receiving IV flucloxacillin by continuous infusion, a classical OAT (test A) or simplified version of the OAT (test B) was performed. In both tests, 1 g oral flucloxacillin was given and serum samples were taken prior to intake and at one and two hours after administration. Flucloxacillin concentrations were determined by high-performance liquid chromatography. Adequate absorption was defined as an increase of flucloxacillin concentration of at least 10 mg/l after one or two hours compared to baseline.Results: In a sample of 196 patients (85 F/111 M), test A was performed in 28 patients, and test B in 168 patients. Age, gender, and baseline values of creatinine and albumin were similar in both groups. The maximal increase of flucloxacillin absorption was highly variable between patients. In 26 (13%) of the 196 patients, the flucloxacillin increase did not reach the value of 10 mg/l. The median (interquartile range, IQR) maximal increase of flucloxacillin absorption was 22.0 (15-31.25) mg/l for test A and 21.5 (13-32.25) mg/l for test B. There was no significant difference in maximal increase of flucloxacillin absorption between test A and B (p = 0.74), nor between males and females (p = 0.95). Age, creatinine, and albumin were not correlated with flucloxacillin levels.Conclusions: The simplified version of the OAT is useful to identify patients with adequate oral flucloxacillin absorption, and to ensure the effective continuation of an oral small-spectrum treatment. Show less
Koppen, B.C.; Mulder, P.P.G.; Boer, L. de; Riool, M.; Drijfhout, J.W.; Zaat, S.A.J. 2019
Infection of burn wounds remains the leading cause of death in burn patients. Topical treatment of such infections with conventional antibiotics is often unsuccessful due to the presence of... Show moreInfection of burn wounds remains the leading cause of death in burn patients. Topical treatment of such infections with conventional antibiotics is often unsuccessful due to the presence of drug-resistant bacteria and/or to the formation of bacterial biofilms. Taken together there is a clear need for novel antimicrobial agents with modes of action different that of current antibiotics. Identification of new synthetic peptide antibiotics for topical use holds a promising approach. In vitro skin models pose many similar properties as normal human skin, and are often used in laboratory settings. In this thesis in vitro models were used to study the effect of colonization and infection of healthy skin, (thermally) wounded skin (chapter 2), mucosal membranes (chapter 3) and skin with characteristics of atopic dermatitis (chapter 6). In addition, the difference in bacterial biofilm formation on biotic (in vitro skin models) versus a-biotic surfaces (polystyrene) was investigated (chapter 7). Finally, skin models were used to identify potent synthetic antimicrobial peptides against drug-resistant bacteria such as Staphylococcus aureus (chapter 3,4). These peptides proved to be effective when applied topically in saline, but also in a hydrogel (chapter 5). Show less
