Capsule formation around breast implants.

All implants are rapidly coated by the host with glycoproteins forming a thin capsule, and this is a normal response. Where an inflammatory stimulus such as infection is present, the capsule can thicken and become microvascularised and sometimes calcified. This inflammatory stimulus can take the form of leachable chemicals from the implant, or bacteria live or dead. The presence of live bacteria can lead to biofilm development, which is part of the chronic infective, inflammatory process. Staphylococcus epidermidis and Cutibacterium acnes have been implicated in chronic infection around breast implants, and some animal models suggest their involvement in capsule contracture. Molecular methods have revealed an array of microorganisms from samples of removed capsular material, though they are extremely sensitive to contamination. The relevance of the results to capsular contracture remains poorly understood. Bacteria of low virulence are shown associated with capsular contracture and calcification, and measures beyond those conventionally applied need to be investigated to limit perioperative contamination.

Surveillance of infection associated with external ventricular drains: proposed methodology and results from a pilot study.

BACKGROUND: The insertion of external ventricular drains (EVDs) is necessary in some neurosurgical patients, but increases the risk of meningitis/ventriculitis. While there are well-recognized risk factors, the proportion of patients who develop meningitis/ventriculitis varies partly due to differences in definitions. A multi-disciplinary working group was established to agree definitions for EVD-associated meningitis/ventriculitis, and a surveillance system was piloted in four centres in the UK and Ireland. METHODS: Definitions were agreed based on those published previously and on clinical and microbiological criteria. An agreed dataset was developed to monitor patients after the insertion of an EVD and until the EVD was removed and the microbial aetiology was recorded. FINDINGS: Four neurosurgical centres participated, with 61-564 patients surveyed in each unit. The vast majority of drains were cranial. Intracranial haemorrhage was the most common indication for the EVD insertion. Between 6% and 35% of EVDs were inserted by consultants rather than junior doctors. The proportion of patients who developed meningitis/ventriculitis varied from 3% to 18% and from 4.8 to 12.7/1000 EVD-days. Coagulase-negative staphylococci were the most common microbial causes. CONCLUSIONS: Routine and ongoing monitoring of patients with an EVD in situ to detect meningitis/ventriculitis presents logistical difficulties, and few units do so. This pilot study suggests that a national system of surveillance with agreed definitions and a methodology to enable unit-to-unit comparisons of EVD meningitis/ventriculitis is both necessary and feasible. This will, in turn, inform quality improvement processes leading to the minimization of infection.

A biodegradable antibiotic-impregnated scaffold to prevent osteomyelitis in a contaminated in vivo bone defect model.

Open fractures are at risk of serious infection and, if infected, require several surgical interventions and courses of systemic antibiotics. We investigated a new injectable formulation that simultaneously hardens in vivo to form a porous scaffold for bone repair and delivers antibiotics at high concentrations to the local site of infection. Duration of antimicrobial activity against Staphylococcus aureus was determined using the serial plate transfer test. Ultimate compressive strength and porosity of the material was measured with and without antibiotics. The material was evaluated in vivo in an ovine medial femoral condyle defect model contaminated with S. aureus. Sheep were sacrificed at either 2 or 13 weeks and the defect and surrounding bone assessed using micro-computed tomography and histology. Antimicrobial activity in vitro persisted for 19-21 days. Sheep with antibiotic-free material and bacteria became infected, while those with antibiotic-containing material and bacteria did not. Similarly, new bone growth was seen in uninoculated animals with plain polymer, and in those with antibiotic polymer with bacteria, but not in sheep with plain polymer and bacteria. The antibiotic-impregnated scaffolds were effective in preventing S. aureus infections whilst supporting bone growth and repair. If translated into clinical practice, this approach might reduce the need for systemic antibiotics.

Drug delivery to the ear.

Drug delivery to the ear is used to treat conditions of the middle and inner ear such as acute and chronic otitis media, Ménière's disease, sensorineural hearing loss and tinnitus. Drugs used include antibiotics, antifungals, steroids, local anesthetics and neuroprotective agents. A literature review was conducted searching Medline (1966-2012), Embase (1988-2012), the Cochrane Library and Ovid (1966-2012), using search terms 'drug delivery', 'middle ear', 'inner ear' and 'transtympanic'. There are numerous methods of drug delivery to the middle ear, which can be categorized as topical, systemic (intravenous), transtympanic and via the Eustachian tube. Localized treatments to the ear have the advantages of targeted drug delivery allowing higher therapeutic doses and minimizing systemic side effects. The ideal scenario would be a carrier system that could cross the intact tympanic membrane loaded with drugs or biochemical agents for the treatment of middle and inner ear conditions.

Bacterial involvement in otitis media with effusion.

OBJECTIVE: Otitis media with effusion (OME), a common chronic childhood condition affecting hearing, is thought to be a result of bacterial infection, with biofilms recently implicated. Although bacterial DNA can be detected by polymerase chain reaction in 80% of patients, typically fewer than half of effusions are positive using standard culture techniques. We adopted an alternative approach to demonstrating bacteria in OME, using a bacterial viability stain and confocal laser scanning microscopy (CLSM): staining allows detection of live bacteria without requiring growth on culture, while CLSM allows demonstration of the three-dimensional structure typical of biofilms. METHODS: Effusion samples were collected at the time of ventilation tube insertion, analysed with CLSM and bacterial viability stain, and extended culture techniques performed with the intention of capturing all possible organisms. RESULTS: Sixty-two effusions (42 patients) were analysed: 28 (45.2%) were culture-positive, but 51 (82.3%) were CLSM-positive. Combining the two techniques demonstrated live bacteria in 57 (91.8%) samples. Using CLSM, bacteria exhibited biofilm morphology in 25 effusions and were planktonic in 26; the proportion of samples exhibiting biofilm morphology was similar in the culture-positive and culture-negative groups (50.0% and 48.3%, respectively). Biofilm samples contained an average of 1.7 different bacterial isolates and planktonic samples 2.0, with the commonest bacteria identified being coagulase-negative staphylococci. CONCLUSION: Live bacteria are present in most effusions, strongly suggesting that bacteria and biofilms are important in the aetiopathogenesis of OME.

Ureteric stents: investigating flow and encrustation.

Blockages of the ureter, e.g. due to calculi (kidney stones), can result in an increase in renal pelvic pressure. This may be relieved by inserting a stent (essentially a permeable hollow tube). However, a number of complications are associated with stent use. Stents can result in reflux (backflow of urine along the ureter), which will promote recurrent urinary infection and possible renal parenchymal damage. Furthermore, long-term stent use is associated with infection and precipitation of salts from the urine, which can lead to a build-up of crystalline deposits on the stent surface, making stent removal difficult and painful. This paper examines factors governing urine flow in a stented ureter, the implications for reflux, and the processes by which the stent surface encrusts, in particular focusing on the influence of bacterial infection. An interdisciplinary approach is adopted, involving a combination of theoretical investigations and novel experiments.

Persistent and intractable ventriculitis due to retained ventricular catheters.

It is generally recommended that, in cases of difficulty in removing a ventricular catheter during a shunt revision, it is best left alone to avoid intraventricular haemorrhage. Retained ventricular catheters (RVCs) are usually safe, although in the presence of ventriculitis they may become colonized by organisms and become a source of persistent or recurrent infection. The authors present a case of persistent and intractable ventriculitis due to an old retained ventricular catheter. A 23-year-old female, who had a RVC and a functioning shunt, was admitted for a suspected blocked shunt. At surgery the shunt was found to be infected and external drainage was instituted. Over the next 4 months, she developed intractable and persistent staphylococcal ventriculitis, despite undergoing 10 further surgical procedures, and appropriate intravenous and intrathecal antibiotic therapy. She responded rapidly only after surgical removal of the old RVC via a craniotomy. The staphylococcus cultured from the RVC had an identical antibiogram to the organism responsible for the intractable ventriculitis. This case emphasizes the point that, although RVC are generally considered safe, removal becomes imperative in the presence of concurrent CSF infection that fails to respond quickly to intrathecal antibiotic therapy.

Is otitis media with effusion a biofilm infection?

Recent attention has focused on the possibility that otitis media with effusion (OME) may represent a chronic infective state such as those evidenced in conditions secondary to biofilms or small colony variants. This review discusses the evidence suggesting that this may indeed be the case and explains why this may prove to be important in the future management of this condition by discussing recent advances in understanding these bacterial phenotypic variants.

Electromagnetic augmentation of antibiotic efficacy in infection of orthopaedic implants.

Infection of orthopaedic implants is a significant problem, with increased antibiotic resistance of adherent 'biofilm' bacteria causing difficulties in treatment. We have investigated the in vitro effect of a pulsed electromagnetic field (PEMF) on the efficacy of antibiotics in the treatment of infection of implants. Five-day biofilms of Staphylococcus epidermidis were grown on the tips of stainless-steel pegs. They were exposed for 12 hours to varying concentrations of gentamicin or vancomycin in microtitre trays at 37 degrees C and 5% CO2. The test group were exposed to a PEMF. The control tray was not exposed to a PEMF. After exposure to antibiotic the pegs were incubated overnight, before standard plating onto blood agar for colony counting. Exposure to a PEMF increased the effectiveness of gentamicin against the five-day biofilms of Staphylococcus epidermidis. In three of five experiments there was reduction of at least 50% in the minimum biofilm inhibitory concentration. In a fourth experiment there was a two-log difference in colony count at 160 mg/l of gentamicin. Analysis of variance (ANOVA) confirmed an effect by a PEMF on the efficacy of gentamicin which was significant at p < 0.05. There was no significant effect with vancomycin.

Epidemiology, diagnosis, treatment, and prevention of cerebrospinal fluid shunt infections.

Soon after cerebrospinal fluid (CSF) shunts became available in the late 1950s, infection was recognized as a serious complication of their use, although the bacterial cause of the infections and the way in which they arose was not clarified for a number of years. Subsequent research has since revealed their etiology and provided data that have improved the understanding of aspects of diagnosis, treatment, and prevention.

Use of antibiotics in penetrating craniocerebral injuries. "Infection in Neurosurgery" Working Party of British Society for Antimicrobial Chemotherapy.

The Working Party was instituted to investigate the rationale of prophylactic and therapeutic antibiotic use in penetrating craniocerebral injuries (PCCI), and to make recommendations for current practice. A systematic review of papers on civilian and military PCCI over the past 25 and 50 years, respectively, was done via electronic databases and secondary sources, and data were evaluated. Guidelines on the removal of indriven bone or metal fragments only if further neural damage can be avoided were supported. However, no publications were identified where the data on infection or its treatment and prevention were complete or satisfactorily derived, and no controlled trials have been published. All studies were retrospective or anecdotal. Working Party recommendations are based on the data available and the professional experience and knowledge of the members. Broad-spectrum antibiotic prophylaxis is recommended for both military and civilian PCCI, Including those due to sports or recreational injuries.

Recurrent infection and catheter loss in patients on continuous ambulatory peritoneal dialysis.

OBJECTIVE: To elucidate the factors leading to catheter loss from recurrent infection in patients on continuous ambulatory peritoneal dialysis (CAPD). DESIGN: All catheters removed from patients were prospectively examined for infection. SETTING: CAPD unit in large tertiary-care general hospital. PATIENTS: Sixty-five consecutive patients undergoing catheter removal for whatever cause; 20 catheters rejected because of desiccation or contamination in transit. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Micro-organisms linked to catheter removal; their locations on removed catheters. RESULTS: Of 45 catheters removed between January 1994 and August 1995, 26 were infected: 13/26 infections were caused by Staphylococcus aureus and 7/26 by Pseudomonas aeruginosa. In only one case was S. epidermidis associated with catheter removal. The most striking finding was that the inner cuff harbored large numbers of the infecting organisms, even when antibiotics had eradicated them from the peritoneal cavity and exit site, where present, and the catheter lumen. CONCLUSION: The importance of S. aureus and Ps. aeruginosa rather than S. epidermidis in catheter loss due to relapsing infection is confirmed. Persistence of the causative organisms in the inner cuff is a likely explanation for relapse after treatment, and might be due to the predominantly intraperitoneal administration of antibiotics. A clinical trial of the effect on catheter retention of empirical use of systemic or oral agents that give high tissue levels and are active against intracellular micro-organisms, along with recommended intraperitoneal regimens, is indicated.

Bacterial surface properties of clinically isolated Staphylococcus epidermidis strains determine adhesion on polyethylene.

The role of surface physiochemical properties of Staphylococcus epidermidis strains in adhesion to polyethylene (PE) was investigated under physiological flow conditions in phosphate buffered saline (PBS) and 1% platelet poor plasma (PPP). Four clinically isolated strains were divided into two groups: low and high relative hydrophobicity, and the F1198 and RP62A strains showing significantly greater hydrophobicity than the F21 and F1018 strains. In PBS, adhesion of all S. epidermidis strains was shear dependent from 0 to 15 dyn/cm2, after which adhesion becomes shear independent. Strains with higher surface hydrophobicity showed higher adhesion to PE, demonstrating the influence of bacterial surface hydrophobicity in nonspecific adhesion. Bacterial adhesion correlated well with bacterial surface hydrophobicity at low shear stresses (0-8 dyn/cm2). In 1% PPP, adhesion of all strains dramatically decreased and we found no correlation between bacterial surface hydrophobicity and adhesion. The presence of plasma proteins reduced nonspecific adhesion. S. epidermidis surface charge did not correlate with bacterial adhesion in either test media. The results suggested that S. epidermidis surface hydrophobicity may mediate nonspecific adhesion to PE at low shear stresses in protein-free media.