Objectives: Implantable devices are major risk factors for hospital-acquired infection. Biomaterials coated with silver oxide or silver alloy have all been used in attempts to reduce infection, in most cases with controversial or disappointing clinical results. We have developed a completely new approach using supercritical carbon dioxide to impregnate silicone with nanoparticulate silver metal. This study aimed to evaluate the impregnated polymer for antimicrobial activity. Methods: After impregnation the nature of the impregnation was determined by transmission electron microscopy. Two series of polymer discs were then tested, one washed in deionized water and the other unwashed. In each series, half of the discs were coated with a plasma protein conditioning film. The serial plate transfer test was used as a screen for persisting activity. Bacterial adherence to the polymers and the rate of kill, and effect on planktonic bacteria were measured by chemiluminescence and viable counts. Release rates of silver ions from the polymers in the presence and absence of plasma was measured using inductively coupled plasma mass spectrometry (ICP-MS). Results: Tests for antimicrobial activity under various conditions showed mixed results, explained by the modes and rates of release of silver ions. While washing removed much of the initial activity there was continued release of silver ions. Unexpectedly, this was not blocked by conditioning film. Conclusions: The methodology allows for the first time silver impregnation (as opposed to coating) of medical polymers and promises to lead to an antimicrobial biomaterial whose activity is not restricted by increasing antibiotic resistance.

✓ The aim of this study was to find reasons for the high incidence of cerebrospinal fluid shunt infections seen in neonates. Four-hundred sixty-six consecutive shunt operations were analyzed retrospectively in 294 children, and 60 children were studied prospectively by quantitative sampling of skin bacteria before surgery and by sampling open wounds, shunt catheters, surgical gloves, and airborne bacteria. In total, 110 strains of coagulase-negativeStaphylococcusisolated from the skin of 53 children before surgery were then tested for bacterial adherence.Retrospectively, the infection rate for infants younger than 6 months old was 15.7% (28 of 178 procedures), compared with 5.6% (16 of 288 procedures) for older children (p = 0.0005). Of all infections, 67% were due to coagulase-negativeStaphylococcus.Age was the only major factor influencing the infection rate. Three of the 60 children studied prospectively developed postoperative shunt infections. All were younger than 6 months and all had high skin bacterial densities before surgery. Contamination during surgery was generally low, but correlated with the preoperative skin bacterial density. Strains of coagulase-negativeStaphylococcuswith high bacterial adherence were more commonly found in neonates than in older children.High skin bacterial density in neonates before surgery was a risk factor for infection in this study. These results also suggest that there is selection of more virulent strains of coagulase-negativeStaphylococcuson the skin of neonates. Prevention of shunt infections in this high-risk group could be facilitated by the reduction of skin bacterial density before surgery using chlorhexidine shampoos and by the elimination of contamination by skin bacteria during surgery using packs soaked in an antiseptic agent to isolate wound edges and glove-changing before handling the shunt.

Catheter-associated urinary tract infection (CAUTI) is the commonest hospital-acquired infection, accounting for over 100,000 hospital admissions within the USA annually. Biomaterials and processes intended to reduce the risk of bacterial colonization of the catheters for long-term users have not been successful, mainly because of the need for long duration of activity in flow conditions. Here we report the results of impregnation of urinary catheters with a combination of rifampicin, sparfloxacin and triclosan. In flow experiments, the antimicrobial catheters were able to prevent colonization by common uropathogens Proteus mirabilis, Staphylococcus aureus and Escherichia coli for 7 to 12weeks in vitro compared with 1-3days for other, commercially available antimicrobial catheters currently used clinically. Resistance development was minimized by careful choice of antimicrobial combinations. Drug release profiles and distribution in the polymer, and surface analysis were also carried out and the process had no deleterious effect on the mechanical performance of the catheter or its balloon. The antimicrobial catheter therefore offers for the first time a means of reducing infection and its complications in long-term urinary catheter users.

Objectives External ventricular drain (EVD) insertion is a common neurosurgical procedure. EVD-related infection (ERI) is a major complication that can lead to morbidity and mortality. In this study, we aimed to establish a national ERI rate in the UK and Ireland and determine key factors influencing the infection risk. Methods A prospective multicentre cohort study of EVD insertions in 21 neurosurgical units was performed over 6 months. The primary outcome measure was 30-day ERI. A Cox regression model was used for multivariate analysis to calculate HR. Results A total of 495 EVD catheters were inserted into 452 patients with EVDs remaining in situ for 4700 days (median 8 days; IQR 4–13). Of the catheters inserted, 188 (38%) were antibiotic-impregnated, 161 (32.5%) were plain and 146 (29.5%) were silver-bearing. A total of 46 ERIs occurred giving an infection risk of 9.3%. Cox regression analysis demonstrated that factors independently associated with increased infection risk included duration of EVD placement for ≥8 days (HR=2.47 (1.12–5.45); p=0.03), regular sampling (daily sampling (HR=4.73 (1.28–17.42), p=0.02) and alternate day sampling (HR=5.28 (2.25–12.38); p<0.01). There was no association between catheter type or tunnelling distance and ERI. Conclusions In the UK and Ireland, the ERI rate was 9.3% during the study period. The study demonstrated that EVDs left in situ for ≥8 days and those sampled more frequently were associated with a higher risk of infection. Importantly, the study showed no significant difference in ERI risk between different catheter types.