Pathogenesis Of Catheter-associated Infections Research Articles

Tissue around catheters is a niche for bacteria associated with medical device infection

To investigate whether pericatheter tissue is an additional niche for bacteria potentially causing catheter-associated infections in humans. Postmortem patient study. Intensive care unit, autopsy room, and microbiological laboratory in a university hospital. Eighteen deceased patients from whom 35 catheters plus surrounding tissues were collected. Under axenic conditions catheters and surrounding tissue were excised from deceased intensive care unit patients. The excised parts of the catheters and samples of surrounding tissue were quantitatively cultured and bacteria identified, and tissue histology/immunohistochemistry was performed. Nine of the 35 (26%) pericatheter tissue samples tested were highly culture positive. The corresponding catheter segments were culture negative or yielded only low numbers of bacteria. Bacteria cultured from different sites of the catheter and surrounding tissues almost all were coagulase-negative staphylococci (predominantly Staphylococcus epidermidis) and Enterococcus faecalis. In histology, bacteria were seen in tissue, intercellularly and associated with host phagocytes. Tissue surrounding biomedical devices forms a niche for bacteria. This is an as yet nonrecognized element in the pathogenesis of catheter-associated infections, with possible consequences for strategies of prevention and treatment of these infections.

Pathogenic Implication of a Fibrinogen-Binding Protein of Staphylococcus epidermidis in a Rat Model of Intravascular-Catheter-Associated Infection

The involvement of Fbe, a fibrinogen-binding protein of Staphylococcus epidermidis, in the pathogenesis of catheter-associated infection was investigated. An fbe (gene encoding Fbe protein) mutant was constructed by allelic replacement, wherein an erythromycin resistance gene replaced a portion of the A region of fbe. Meanwhile, a rat central venous catheter (CVC) infection model was established to assess the importance of Fbe in the pathogenesis of CVC-associated infection due to S. epidermidis. Fbe-positive S. epidermidis strain HB was significantly more likely to cause a CVC-associated infection resulting in bacteremia and metastatic disease than its isogenic Fbe-deficient mutant (100% versus 20%, P < 0.01). These results confirm the importance of adherence associated with Fbe in the pathogenesis of CVC-associated infection caused by S. epidermidis.

Prevention of infections caused by central venous catheters--established and novel measures.

Intravascular catheters play an important role in infections in intensive care and hemodialysis patients. This becomes evident only if full microbiological diagnoses are made. Difficulties in the diagnosis and treatment of microbially colonized catheters make the prevention of infection particularly important. The most important preventive measures are a strict evaluation of the indications for the use of the catheter and strict hygienic precautions during insertion and maintenance of the central venous catheter. Other measures, some of which are controversial, may be considered, such as the specific decontamination of Staphylococcus carriers using mupirocin. A new approach in the prevention of catheter-related infections is the use of catheter materials impregnated with antibiotics, antiseptics or metals. Slow-delivery systems release the antimicrobially active substance from the catheter material and thus reduce the proliferation of adherent bacteria. Some of these slow-delivery systems have been used in clinical trials, with varied results. Current research is directed towards the prevention of the first stage in the pathogenesis of catheter-associated infections, namely the adherence of bacteria to the catheter polymer, e.g. by impregnation of the polymer with silver. Laboratory studies, animal experiments and initial clinical trials suggest that it will soon be possible to reduce the frequency of catheter-associated infections to below the levels attainable with current general and specific preventive measures, through the use of coated catheters.

Antimicrobial activity and biocompatibility of polyurethane and silicone catheters containing low concentrations of Silver: A new perspective in prevention of polymer-associated foreign-body-infections

In modern medicine, infection is one of the most serious complications of implanted plastic devices. The host is not able to overcome this special type of opportunistic infection despite having a normal immune response and a low virulence of most of the bacteria involved. Antimicrobial therapy alone generally cannot cure the infection and the removal of catheters often remains the only choice of therapy. Bacterial adhesion to the polymer surface of the catheter, be it luminal or external, is an important step in the pathogenesis of catheter-associated infections. In this report, we describe new approaches to the prevention of infections by impregnation of polyurethane and silicone with silver by two different methods. The antimicrobial activity of these silver-impregnated catheters is more than 10 fold higher for coagulase-negative staphylococci (CNS) compared to catheters without silver. Similar results are obtained with other microbial organisms like Staphylococcus aureus, Enterococcus faecalis, Escbericbia coli, Pseudomonas aeruginosa and Candida albicans. The new polymers show no cytotoxic or thrombogenic side effects in vitro.

Movement of pseudomonas aeruginosa along catheter surfaces A mechanism in pathogenesis of catheter-associated infection

The etiologic mechanism involved in the establishment of catheter-associated bacteriuria is suggested in this in vitro study of the movement of Pseudomonas aeruginosa along a catheter surface against a flowing artificial urine milieu in the presence and absence of antibiotics. Following a lag phase, during which a bacterial biofilm becomes firmly established at a site of contamination, the bacteria ascend the surface of the Foley catheters in a rapidly expanding coherent biofilm. The speed of the bacterial ascent is increased as a result of turbulence-associated planktonic saltatory bacterial movement within the urine column. Bacteriocidal concentrations of antibiotics in the urine can slow down the bacterial ascent, but they do not preclude it.

Coagulase-negative staphylococci as nosocomial pathogens in neonates: The role of host defense, artificial devices, and bacterial hydrophobicity

In contrast to the well-established pathogen Staphylococcus aureus, the coagulase-negative staphylococci-formerly collectively called Staphylococcus epidermidis-were until recently regarded as harmless commensals. During the last two decades, however, the coagulase-negative staphylococci have clearly emerged as pathogens in patients who have artificial devices implanted, such as prosthetic heart valves, hip prostheses, and cerebrospinal fluid shunts, and in those with compromised host defenses such as premature neonates, cancer patients, and transplant recipients. Recently, an increasing incidence of septicemia due to coagulasenegative staphylococci was detected in our neonatal intensive care unit. More than 90 percent of cases occurred in premature infants of low birth weight (less than 2,500 g). All septicemic infants were receiving intravenous therapy, and total parenteral nutrition solutions had been administered to nearly 80 percent just before or during the septic episode. This led us to examine the role of host defense factors in neonates and the possible significance of bacterial surface characteristics in the pathogenesis of catheter-associated infections.

In vitro quantitative adherence of bacteria to intravascular catheters

Adapting standard techniques, a simple in vitro system was devised to compare quantitative bacterial adherence to iv catheters of different compositions. Upon brief immersion of catheters in suspensions of Staphylococcus aureus, coagulase-negative staphylococci, and Escherichia coli, organisms adhered to catheter surfaces. After overnight growth in broth, organisms remained adherent and formed colonies, as shown by light and scanning electron microscopy. In addition, quantitative adherence using a blood agar roll technique, expressed as bacteria per square centimeter of catheter surface area per 10 6 colonies per milliliter inoculum, was calculated. Adherence was greater on polyvinylchloride (PVC) catheters (geometric mean 342) than on Teflon catheters (geometric mean 49.6) for coagulase-negative staphylococci ( P < 0.005). Also, the number of coagulase-negative staphylococci adherent to PVC catheters was significantly greater than for E. coli (geometric mean 70.6) at analogous inocula ( P < 0.02). Differences in bacterial adherence to the surface of iv devices may be important in the pathogenesis of catheter-associated infections. This in vitro method could prove useful in testing bacterial adherence properties of newly developed catheter materials, and allow development of catheters less prone to be associated with bacterial adherence and catheter-related infections.