The effect of systemic antibiotics on the microbiological diagnosis of experimental foreign body infections caused by S taphylococcus epidermidis

A state of the art review on optimal practices to prevent, recognize, and manage complications associated with intravascular devices in the critically ill

Intravascular catheters are inserted into almost all critically ill patients. This review provides up-to-date insight into available knowledge on epidemiology and diagnosis of complications of central vein and arterial catheters in ICU. It discusses the optimal therapy of catheter-related infections and thrombosis. Prevention of complications is a multidisciplinary task that combines both improvement of the process of care and introduction of new technologies. We emphasize the main component of the prevention strategies that should be used in critical care and propose areas of future investigation in this field.

Inhibition of Staphylococcus Epidermidis Colonization with Fusidic Acid-Impregnated Catheters

The aim of this study was the preparation and characterization of fusidic acid-impregnated peripheral catheters. In the first part of the study, in vitro drug release studies were performed, and the effect of fusidic acid impregnation on adherence of slime positive Staphylococcus epidermidis to catheters was evaluated as in vitro studies. Fusidic acid-impregnated and naïve catheters were incubated with 108 colony forming unit/mL (cfu/mL) slime positive S. epidermidis during the in vitro experiment. After incubation for 2, 4, 6, 8, 12, 24, 48, and 72 h, the number of colonies were determined in an aliquot and adhered to the catheter. During the in vivo experiment, contaminated naïve and fusidic acid-impregnated catheters ( n = 10 rats in both groups) were implanted subcutaneously in the back of the rats. Rats were killed at the end of the seventh day and catheters were removed. Microbiologic assessments from the explanted catheter segments were performed. Fusidic acid impregnation decreased the number of adherent bacteria to the catheters and the number of free bacteria within the liquid medium significantly. There were 3 positive catheter cultures out of 10 in rats implanted with fusidic acid-impregnated catheters, whereas all explanted catheters from naïve group yielded bacterial growth. The mean cfu counts were significantly less in the fusidic acid-impregnated catheter group. In vitro release studies and antibacterial activity studies correlated well. Additionally, morphological evaluations by scanning electron microscopy showed that fewer bacteria were evident on the fusidic acid-impregnated catheters compared with naïve catheters. As a conclusion, catheter impregnation with fusidic acid is effective in preventing colonization in these in vitro and in vivo sets of experiments, with slime-producing S. epidermidis.

Bench-to-bedside review: Challenges of diagnosis, care and prevention of central catheter-related bloodstream infections in children

Central venous catheters (CVCs) are indispensable in modern pediatric medicine. CVCs provide secure vascular access, but are associated with a risk of severe complications, in particular bloodstream infection. We provide a review of the recent literature about the diagnostic and therapeutic challenges of catheter-related bloodstream infection (CRBSI) in children and its prevention. Variations in blood sampling and limitations in blood culturing interfere with accurate and timely diagnosis of CRBSI. Although novel molecular testing methods appear promising in overcoming some of the present diagnostic limitations of conventional blood sampling in children, they still need to solidly prove their accuracy and reliability in clinical practice. Standardized practices of catheter insertion and care remain the cornerstone of CRBSI prevention although their implementation in daily practice may be difficult. Technology such as CVC impregnation or catheter locking with antimicrobial substances has been shown less effective than anticipated. Despite encouraging results in CRBSI prevention among adults, the goal of zero infection in children is still not in range. More high-quality research is needed in the field of prevention, accurate and reliable diagnostic measures and effective treatment of CRBSI in children.

Foreign body infections due to Staphylococcus epidermidis

Staphylococcal infections are one of the main causes of complications in patients with implanted foreign prosthetic material. Implants are associated with a significant reduction of the threshold at which contaminating Gram-positive bacteria, particularly Staphylococcus epidermidis, become infectious and develop a biofilm with phenotypic resistance to almost all antibiotics. A 1000-fold increase in minimal bactericidal levels against most antibiotics except rifampin has been repeatedly observed. Since only removal of the foreign material reverses these phenomena, the clinical challenge consists in finding approaches to cure the infection without removal of the implanted device. Rifampin combinations with other antibiotics, administration of exceedingly high antibiotic concentrations in situ, and early therapy before biofilm development are efficacious. Although these strategies have dramatically improved the outcome of foreign body infections, an improved understanding of biofilm-grown S. epidermidis is necessary to develop new antibacterial agents. Here, we review the pathogenesis, prevention, and treatment of implant infections due to S. epidermidis and highlight some new compounds with already promising in vitro results.

Diagnosis and prevention of catheter-related infections

PURPOSE OF REVIEW

To highlight the major advances in diagnosing and preventing catheter-related infections published in research articles published between March 2004 and May 2007.

RECENT FINDINGS

The challenge remains to make the diagnosis of catheter-related infection with good accuracy without catheter removal. The differential time to obtain positive qualitative blood culture appeared to be the most accurate available technique. Many catheter-related bloodstream infections are preventable. Simple interventions are often useful and multimodal programs are very efficacious, particularly in the intensive care setting. For long-term catheter-related bloodstream infection prevention, patient education appeared promising. Interesting evidence suggested that anticoagulant, by decreasing the biofilm formation, could decrease the risk of infection. For short-term central venous catheter-related infections research is ongoing on antiseptic dressings. Antiseptic lock appeared promising for preventing long-term central venous catheter bloodstream infections.

SUMMARY

Nowadays, multimodal programs of catheter infection prevention are efficacious. Levels of catheter-related bloodstream infection of more than one or two per 1000 catheter-days are usually only found in the intensive care unit. It is a prerequisite to evaluate the cost-effectiveness of new techniques of prevention. As catheter-related bloodstream infections become rarer, strategies limiting unnecessary removal of catheters need to be developed and tested.

A RAT MODEL OF POLYPROPYLENE GRAFT INFECTION CAUSED BY STAPHYLOCOCCUS EPIDERMIDIS

BACKGROUND

The aim of this study was to constitute a valid graft infection model with Staphylococcus epidermidis in rats.

METHODS

Rats were divided into seven groups. In groups 1 and 2, 2 cm x 2 cm polypropylene grafts were incubated with 10(8) c.f.u./mL slime-positive S. epidermidis at 37 degrees C for 2 and 24 h and were then placed subfascially to the groins of rats. In the third group, naive grafts were placed and 0.5 mL of 3 x 10(7) c.f.u. slime-positive S. epidermidis were injected on the inside of the wounds. Rifampicin (30 mg/kg) in group 4 and teicoplanin (20 mg/kg) in group 5 were applied i.p. to rats with 2-h incubated grafts for prophylaxis. The same prophylactic regimens were given to groups 6 and 7 in which rats were incubated for 24 h. At eighth day, rats were killed and wounds were assessed with macroscopic evaluation and cultures.

RESULTS

No death occurred in any of the groups. In groups 1 and 2, 100% infection rates were achieved. However, graft infection was detected in only two (20%) of the rats in group 3 (P = 0.001). Prophylactic application of teicoplanin or rifampicin decreased the infection rates significantly in the short-incubation groups.

CONCLUSION

Incubation of polypropylene grafts with slime-producing S. epidermidis for 2 and 24 h in the pre-application period achieved the occurrence of a standardized graft infection. Prophylactic use of teicoplanin and rifampicin decreased the infection rates. We propose to use this reproducible and reliable animal model of graft infection in future studies.

Improving the treatment of musculoskeletal infections with molecular diagnostics

Molecular diagnostic strategies have been implemented to enhance the treatment of musculoskeletal infections. Once primarily a research tool, molecular-based assays, have become accepted clinical tests for the genomic detection of certain pathogens involved in bone and joint infections. Currently, culture remains the gold standard for identifying most organisms causing infection. However, molecular assays are beneficial in clinical cases in which standard culture-based tests are unreliable or untimely. We will review current clinical utility of this emerging technology and roles for assays in the future.