Niall T. Stevens

Biofilm and the role of the ica operon and aap in Staphylococcus epidermidis isolates causing neurosurgical meningitis

Fifty-five Staphylococcus epidermidis isolates, classified as contaminants or causing device-related meningitis, from external ventricular drain (EVD) and non-EVD cerebrospinal fluid specimens were characterized. Thirty-three of 42 (78.6%) meningitis isolates were PCR-positive for ica and aap, known determinants of polysaccharide- and protein-mediated biofilm production, whereas five of 13 (38.5%) contaminants were ica- and aap-negative; 71.4% of meningitis isolates and 84.6% of contaminants produced biofilm. ica+aap+ meningitis isolates produced more biofilm than ica+aap- isolates (p 0.0020). ica+aap- isolates did not produce more biofilm than ica-aap+ isolates (p 0.4368). Apparently, ica and aap are associated with biofilm production in S. epidermidis device-related meningitis isolates.

Staphylococcus epidermidis polysaccharide intercellular adhesin induces IL‐8 expression in human astrocytes via a mechanism involving TLR2

Staphylococcus epidermidis is an opportunistic biofilm‐forming pathogen associated with neurosurgical device‐related meningitis. Expression of the polysaccharide intercellular adhesin (PIA) on its surface promotes S. epidermidis biofilm formation. Here we investigated the pro‐inflammatory properties of PIA against primary and transformed human astrocytes. PIA induced IL‐8 expression in a dose‐ and/or time‐dependent manner from U373 MG cells and primary normal human astrocytes. This effect was inhibited by depletion of N‐acetyl‐β‐d‐glucosamine polymer from the PIA preparation with Lycopersicon esculentum lectin or sodium meta‐periodate. Expression of dominant‐negative versions of the TLR2 and TLR4 adaptor proteins MyD88 and Mal in U373 MG cells inhibited PIA‐induced IL‐8 production. Blocking IL‐1 had no effect. PIA failed to induce IL‐8 production from HEK293 cells stably expressing TLR4. However, in U373 MG cells which express TLR2, neutralization of TLR2 impaired PIA‐induced IL‐8 production. In addition to IL‐8, PIA also induced expression of other cytokines from U373 MG cells including IL‐6 and MCP‐1. These data implicate PIA as an important immunogenic component of the S. epidermidis biofilm that can regulate pro‐inflammatory cytokine production from human astrocytes, in part, via TLR2.

Current and Future Approaches to the Prevention and Treatment of Staphylococcal Medical Device-Related Infections

Staphylococci, in particular Staphylococcus aureus and Staphylococcus epidermidis, are a leading cause of healthcare-associated infections. Patients who have a medical device inserted are at particular risk of an infection with these organisms as staphylococci possess a wide range of immune evasion mechanisms, one of which being their ability to form biofilm. Once embedded in a biofilm, bacteria are inherently more resistant to treatment with antibiotics. Despite advances in our understanding of the pathogenesis of staphylococcal biofilm formation, medical devices colonised with biofilms frequently require removal. New and novel approaches to prevent and treat biofilm infections are urgently required. In recent years, progress has been made on approaches that include antiadhesive strategies to prevent surface adhesion or production of bacterial adhesins, dissolution of already established biofilm, targeting of biofilm matrix for degradation and interference with biofilm regulation. Several obstacles need to be overcome in the further development of these and other novel anti-biofilm agents. Most notably, although in vitro investigation has progressed over recent years, the need for biofilm models to closely mimic the in vivo situation is of paramount importance followed by controlled clinical trials. In this review we highlight the issues associated with staphylococcal colonisation of medical devices and potential new treatment options for the prevention and control of these significant infections.

Cold Air Plasma To Decontaminate Inanimate Surfaces of the Hospital Environment

ABSTRACT The hospital environment harbors bacteria that may cause health care-associated infections. Microorganisms, such as multiresistant bacteria, can spread around the patients inanimate environment. Some recently introduced biodecontamination approaches in hospitals have significant limitations due to the toxic nature of the gases and the length of time required for aeration. This study evaluated the in vitro use of cold air plasma as an efficient alternative to traditional methods of biodecontamination of hospital surfaces. Cultures of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), extended-spectrum-β-lactamase (ESBL)-producing Escherichia coli, and Acinetobacter baumannii were applied to different materials similar to those found in the hospital environment. Artificially contaminated sections of marmoleum, mattress, polypropylene, powder-coated mild steel, and stainless steel were then exposed to a cold air pressure plasma single jet for 30 s, 60 s, and 90 s, operating at approximately 25 W and 12 liters/min flow rate. Direct plasma exposure successfully reduced the bacterial load by log 3 for MRSA, log 2.7 for VRE, log 2 for ESBL-producing E. coli, and log 1.7 for A. baumannii. The present report confirms the efficient antibacterial activity of a cold air plasma single-jet plume on nosocomial bacterially contaminated surfaces over a short period of time and highlights its potential for routine biodecontamination in the clinical environment.

Candida infection of the central nervous system following neurosurgery: a 12-year review

BackgroundCandida infection of the central nervous system (CNS) following neurosurgery is relatively unusual but is associated with significant morbidity and mortality. We present our experience with this infection in adults and discuss clinical characteristics, treatment options, and outcome.MethodsAll episodes of Candida isolated from the central nervous system were identified by searching our laboratory database. Review of the cases was performed by means of a retrospective chart review.ResultsEleven episodes of Candida CSF infection following neurosurgery were identified over a 12-year period. Candida albicans was the predominant species isolated (n = 8, 73%). All infections were associated with foreign intracranial material, nine with external ventricular drains (82%), one with a ventriculoperitoneal shunt, one with a lumbar drain, and one with Gliadel wafers (1,3-bis [2-chloroethyl]-1-nitrosurea). Fluconazole or liposomal amphotericin B were the most common anti-fungal agents used. The mortality rate identified in our series was 27%.ConclusionsCandida infection following neurosurgery remains a relatively rare occurrence but one that causes significant mortality. These are complex infections, the management of which benefits from a close liaison between the clinical microbiologist and neurosurgeon. Prompt initiation of antifungal agents and removal of infected devices offers the best hope of a cure.

Biofilm characteristics of Staphylococcus epidermidis isolates associated with device-related meningitis

Staphylococcus epidermidis biofilm causes device-related meningitis in neurosurgical patients. This study assessed the contribution of polysaccharide and protein to the development of a strong biofilm-positive phenotype in four S. epidermidis isolates associated with probable device-related meningitis, under varying environmental conditions. RT-PCR analysis of the intercellular adhesion operon (icaADBC) and assessment of polysaccharide intercellular adhesin (PIA) production indicated a correlation between increased icaA transcription and PIA production in ica(+) isolates grown in medium with 4 % ethanol and 4 % NaCl. Treatment of biofilm with sodium metaperiodate caused dispersion of adhered cells (P <0.0001), indicating involvement of PIA. Transcriptional levels of protein factors revealed that atlE transcription levels were similar in all isolates, whilst aap levels were variable, with induction being seen in two isolates following growth in the presence of alcohol or salt. Transcription of agr did not influence protein expression and RNAIII transcription varied among the strains. Although aap transcription was induced, the treatment of biofilm with proteinase K did not always disperse the biofilm. Our data suggest that, among the three ica(+) S. epidermidis isolates clinically associated with meningitis that were studied, PIA contributed to the strong biofilm-positive phenotype, whereas protein factors appeared to have a secondary role.

In Vitro Approach for Identification of the Most Effective Agents for Antimicrobial Lock Therapy in the Treatment of Intravascular Catheter-Related Infections Caused by Staphylococcus aureus

ABSTRACT Infection of intravascular catheters by Staphylococcus aureus is a significant risk factor within the health care setting. To treat these infections and attempt salvage of an intravascular catheter, antimicrobial lock solutions (ALSs) are being increasingly used. However, the most effective ALSs against these biofilm-mediated infections have yet to be determined, and clinical practice varies greatly. The purpose of this study was to evaluate and compare the efficacies of antibiotics and antiseptics in current clinical use against biofilms produced by reference and clinical isolates of S. aureus. Static and flow biofilm assays were developed using newly described in vivo-relevant conditions to examine the effect of each agent on S. aureus within the biofilm matrix. The antibiotics daptomycin, tigecycline, and rifampin and the antiseptics ethanol and Taurolock inactivated established S. aureus biofilms, while other commonly used antistaphylococcal antibiotics and antiseptic agents were less effective. These findings were confirmed by live/dead staining of S. aureus biofilms formed and treated within a flow cell model. The results from this study demonstrate the most effective clinically used agents and their concentrations which should be used within an ALS to treat S. aureus-mediated intravascular catheter-related infections.

Use of e-learning to enhance medical students’ understanding and knowledge of healthcare-associated infection prevention and control

An online infection prevention and control programme for medical students was developed and assessed. There was a statistically significant improvement (P<0.0001) in the knowledge base among 517 students after completing two modules. The majority of students who completed the evaluation were positive about the learning experience.

Ventriculoperitoneal shunt-related infections caused by Staphylococcus epidermidis: pathogenesis and implications for treatment.

The insertion of medical devices, such as intraventricular shunts, is often complicated by infection leading to ventriculitis. Frequently, such infections result from colonisation and subsequent biofilm formation on the surfaces of the shunts by Staphylococcus epidermidis. The pathogenesis of neurosurgical shunt-related infection is complex with interactions between the pathogen, the device and the unique local immunological environment of the central nervous system (CNS). An ability to form biofilm, the main virulence determinant of Staphylococcus epidermidis, facilitates protection of the organism from the host defences while still initiating an immunological response. The presence of the blood brain barrier (BBB) and the biofilm itself also complicates treatment, which presents many challenges when managing shunt infections. A greater understanding of the interplay between S. epidermidis and the CNS could potentially improve the diagnosis, treatment and management of such infections. This review describes the pathogenesis, treatment and implications of S. epidermidis ventriculoperitoneal shunt-related infections, concentrating on recent research and the implications for treatment.

Effectiveness of podcasts as an adjunct learning strategy in teaching clinical microbiology among medical students

The educational tool of podcasting is just one way in which new technologies are being integrated into medical education. The use of podcasts in the medical curriculum provides the potential for ‘anytime, anywhere’ learning experiences. To assess the impact of podcasts as an educational tool, the Clinical Microbiology Department in the RCSI carried out a pilot study of third year medical students studying microbiology in the RCSI. The study was carried out over eleven weeks and all 270 students in the year were asked to participate. A 5-8 minute podcast was developed on individual microbiology topics e.g. antibiotic treatment of selected infections. Topics selected were those which the department felt were important to emphasise and formed an adjunct to lectures and tutorials on the topic. A quiz incorporating ten questions in a multiple choice format were devised for each podcast. Over the eleven week period the podcasts and quizzes were released at various intervals following completion of lectures and tutorials on the topic. Initially students completed a quiz on the topic one day before the release of the podcast. The quiz was then closed and the podcast on the topic released. Following release of the podcast students performed the same quiz five days later. A quiz completion rate of between 45 and 58 percent was achieved for each quiz. Analysis of the quiz results showed that the average result (out of 10) for the pre-podcast quiz was 4.2, whilst the average result for the post-podcast quiz was 5.9. This demonstrated a statistically significant difference in the quiz results pre and post release of the podcast (p-value <0.05). These results establish the importance of podcasts in complementing lectures, tutorials and e-learning to further student knowledge. Podcasting has the potential to enhance medical education by complementing current and future teaching modalities.