Influence of surface morphology on in vitro bacterial adherence to central venous catheters

The detailed surface topography of five poly-urethane centralvenous catheters (CVC) (Hydrocath, Deltacath, Certofix trio,Arrow-Howes and Multicath three) was examined by scanning electronmicroscopy and laser profilometry. The results were correlatedwith the ability of Staphylococcus epidermidis to adhere toeach CVC. Hydrocath CVC had the smoothest surface, as determinedby profile peak values of 0.17 µm (Ra) and 0.94 µm(Rz). These CVC also had the lowest number ofstaphylo-cocciadhering to the surface. In contrast, Certofix trio CVC hadan irregular surface (Ra 1.29µm and Rz 6.35 µm)which was confirmed by scanning electron microscopy. These latterCVC had significantly more bacteria colonizing their surfacecompared with Hydrocath and Arrow-Howes CVC (P < 0.01). Theresults suggest that a CVC with a smooth surface, absent ofsurface defects, may reduce the risk of colonization with bacteriaand therefore subsequent sepsis. (Br. J. Anaesth. 1994; 72:587–591)     

Further characterization of bacterial adherence to urinary bladder mucosa: comparison with adherence to anion exchange resin

Bacterial adherence to anion exchange resin has recently been reported to provide a useful, rapid, in vitro screening assay for identifying putative antiadherence agents. The studies presented in this report provide additional evidence that adherence to anion exchange resin is similar to urinary bladder mucosa adherence. Results are as follows. 1) Heparin inhibits the adherence of Escherichia coli, Klebsiella ozaenae, Proteus mirabilis, Streptococcus fecalis and Pseudomonas aeruginosa to both the mucin deficient bladder and anion exchange resin. 2) Drugs which inhibit E. coli adherence to the bladder also inhibit E. coli adherence to the resin and conversely, drugs which do not effect E. coli adherence to the resin do not affect attachment to the bladder. 3) Extracts from mammalian urinary bladder mucosa prevent E. coli adherence to both the bladder and resin. 4) The ability of heparin to displace preattached bacteria from anion exchange resin is inversely proportional to the time the bacteria are in contact with resin. Similar results were obtained for the ability of heparin to displace bacteria from the bladder. These studies indicate that bacterial adherence to anion exchange resin responds to heparin and other chemical agents in a manner similar to the mucin deficient rabbit urinary bladder. Because of the ease and rapid nature of this in vitro assay, it serves as a useful screen for potential bacterial antiadherence agents and could be used to help elucidate mechanisms of bacterial attachment.     

Impact of postantibiotic effect on bacterial adherence to vascular prostheses

The brief exposure of bacteria to high antibiotic concentrations can result in prolonged suppression of bacterial growth termed postantibiotic effect (PAE). A pathogenic Staphylococcus epidermidis strain (RP-62) was exposed to 2X and 6X minimum inhibitory concentrations (MIC) of cefazolin, vancomycin, or rifampin for 1 hr and incubated for 2 to 24 hr in inhibitory-free broth. PAE was defined as the difference in time required for a 1.0 log increase in test (T) vs control (C) cultures (PAE = T-C). PAE was observed only for rifampin: 6 hr at 2X MIC and 8 hr at 6X MIC. Bacterial adherence to Dacron grafts was calculated in PAE vs control cultures by a quantitative culture technique for graft specimens incubated 2 to 24 hr. A demonstrable PAE and its impact on adherence were found to be both antimicrobial and concentration dependent. A significant decrease in staphylococcal adherence to velour-knitted Dacron was demonstrated by rifampin at 2X MIC (P less than 0.05) and 6X MIC (P less than 0.01). This phenomena may be useful in reducing bacterial adherence and colonization of bioprosthetics in the perioperative period. Preoperative suppression of staphylococcal skin flora by high dose antimicrobials can alter the capacity of these organisms to adhere to vascular prosthetic grafts and, if incorporated into antibiotic prophylaxis regimens, may reduce graft colonization.     

Reduction of heparin dose is not beneficial to platelet function

BACKGROUND: To clarify the effects of the reduction of heparin dose on platelets, we conducted a prospective trial on patients undergoing cardiopulmonary bypass. METHODS: Twenty-three patients undergoing coronary artery bypass grafting were studied. The systemic heparin dose was 300 IU/kg in the control group (n = 11) and 200 IU/kg in the low-dose group (n = 12). Heparin-coated cardiopulmonary bypass equipment was used for both the groups. Platelet counts, beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) concentrations were measured and the arterial filters in the circuits were observed by electron microscopy. RESULTS: Platelet counts were higher in the low-dose group than in the control group (p < 0.01). No significant differences were found in the platelet release reaction (beta-TG and PF4). Electron microscopy demonstrated that cell adhesion on the arterial filters in the control group was significantly more marked than in the low-dose group (p < 0.01) and that most of the cells on the filters were neutrophils. CONCLUSIONS: We conclude that the reduction of heparin dose with the use of heparin-coated equipment reduces platelet loss, but does not suppress the platelet release reaction. Furthermore, the reduction of heparin dose reduces adherence of leukocytes to the filter surface.     

Prevention of bacterial adherence to implant surfaces with a crosslinked albumin coating in vitro

Titanium surfaces were coated with bovine serum albumin using carbodiimide, a crosslinking agent. The durability of the coated surfaces and the inhibitory effect of the albumin coating on bacterial adherence were tested in vitro for 20 consecutive days at 37°C in phosphate buffered saline, with intermittent agitation. The results showed that only 10% of the coated bovine serum albumin decayed off the surface during the 20-day incubation period. The inhibition rate of the albumin coating on bacterial adherence remained high (greater than 85% ) throughout the experiment. The results suggested potential use of this crosslinked albumin coating to reduce bacterial adherence and thus the subsequent possibility of prosthetic or implant infection in vivo.     

Halothane decreases bacterial adherence in vitro

BACKGROUND: Adherence of pathogenic bacteria to host epithelial cells is thought to be the initial step in infection, while the presence of the commensal flora is an important host defence mechanism. Anything altering bacterial adherence to human epithelial cells may contribute to bacterial infections. The impact of anaesthesia on this first step to infection is not known. In this study the effect of halothane on bacterial adherence was investigated. METHODS: Human epithelial cells (HEp-2) and two strains of Escherichia coli were exposed to halothane 2% for 2 h. Then HEp-2 cells were coincubated with bacteria for 3 h. Bacteria attached to the epithelial cells were evaluated by light microscopy. RESULTS: Compared to the control, bacterial adherence was reduced by 37% to 56% with the different strains when HEp-2 cells were exposed to halothane. No significant difference was found when only bacteria were treated with halothane. CONCLUSION: Our results show that halothane reduces bacterial adherence to human epithelial cells in vitro. Reduced number or function of epithelial cell surface receptors may be responsible for the reduced adherence as no changes were observed when only the bacteria were exposed to halothane.     

Peritonitis in peritoneal dialysis: bacterial colonization by biofilm spread along the catheter surface

We have used modern techniques of direct microscopic examination and quantitative bacterial recovery to show the existence of a route of bacterial colonization along the external and internal surfaces of Tenckhoff catheters implanted in experimental animals. The external route of progressive bacterial colonization extends from the cutaneous exit site through the dacron cuff and into the peritoneum. Bacterial growth along this route consists primarily of glycocalyx enclosed bacterial biofilms adherent to catheter and tissue surfaces, and this surface colonization may or may not give rise to peritoneal infection in which free-living bacteria are found in the peritoneal fluid. The rate of this progressive bacterial colonization depends on the degree of bacterial contamination of the exit site at the time of implantation. Exit site sterilization (hibitane) delays the process while inoculation with rabbit skin strains of Staphylococcus epidermidis accelerates it. Even with optimal implantation techniques, bacterial colonization proceeds via this subcutaneous route so that most Tenckhoff catheter surfaces are covered with a bacterial biofilm, consisting predominantly of gram positive cocci, within three weeks after the implantation of these devices. The rate of bacterial biofilm development on both surfaces of these Tenckhoff catheters, the bacterial colonization of peritoneal tissues, and the dissemination of bacteria into the peritoneal fluid are all significantly accelerated by dialysis in this experimental animal model of continuous ambulatory peritoneal dialysis (CAPD).     

Experimental study of bacterial adherence to biliary tract in rabbits]

Adherence to host tissues and cell surfaces is an early step in infections. However nothing has been reported about bacterial adherence in biliary infections. The following experiment was carried out in rabbits with Escherichia coli isolated from the bile of a patient with acute suppurative cholangitis. Adhesion was observed by scanning electron microscopy. First, with cholecystic mucosa of normal, jaundice, acid (mucosa was injured with 0.1 N hydrochloric acid) and stone groups (stones were inserted into the gallbladder), bacterial adhesion as a virulence factor was examined in vitro. Second, in a cholangitis model the role of bacterial adherence to the bile duct in the development of localized biliary infection was examined in vivo. Result: (1) As compared to the normal, jaundice and stone groups, the number of adhering bacteria was remarkably increased in the acid group. The mucosa of the former groups was relatively intact, but that of the latter was remarkably destroyed. (2) In the cholangitis model, the number of bacteria adhered to the bile duct was negatively correlated with that of bacteria isolated from blood. These results suggest that bacterial adherence to the biliary tract is an important virulence factor, but not in the development from localized cholangitis to sepsis.     

不同剂量肝素钠脐静脉导管封管效果比较

目的探讨肝素钠对新生儿的影响,以选择适合新生儿脐静脉导管的封管液。方法选择留置脐静脉导管的危重新生儿60例,按随机数字表法分为观察Ⅰ组和观察Ⅱ组各30例,观察Ⅰ组用25U肝素液,观察Ⅱ组用50U肝素液脉冲正压封管;封管前后分别经外周血管采血检测血小板参数(PLT、PCT、PDW)和凝血功能(PTA、PTR、PT、INR、APTT、FIB、TT);置管期间全程观察患儿有无出血倾向和导管通畅等情况。结果两组均未出现皮肤淤斑、注射穿刺处拔针后出血不止等现象,未发生堵管;封管前后PLT、PCT、PDW值和PTA、PTR、PT、INR、APTT、FIB、TT值比较,差异无统计学意义(均P0.05);观察Ⅰ组封管前后PT变化曲线与观察Ⅱ组相比,接近相交点较多,曲线较少分离。结论脐静脉导管使用小剂量(25U)肝素液脉冲式正压封管有效,安全。     

A quantitative in vivo assay for bacterial adherence to the urethra

Bacterial adherence to urinary tract mucosal surfaces is thought to be the initiating event in ascending urinary tract infection. To study this process, we have developed a physiologic, quantitative, in vivo assay for bacterial adherence to the urethra. The effect of local (vaginal mucosa) immunization on the adherence of E. coli to the urethra was studied. Local immunization with a formalinized E. coli vaccine significantly reduced the capacity of viable cells of the immunizing strain to adhere to the urethra. Immunization-induced decrease in bacterial adherence to urethral mucosa is in agreement with our previous observations that immunization of the vaginal mucosa decreases the adherence of E. coli to the rat bladder. These data provide further evidence of a protective effect from local immunization against ascending urinary tract infection. No obvious change in indigenous urethral flora occurred after mucosal immunization.     

Estimation of heparin leak into the systemic circulation after central venous catheter heparin lock.

BACKGROUND: Although most catheter problems in haemodialysis are related to infection or clotting, bleeding associated with the heparin lock is of clinical importance especially during peri-operative conditions. The objective of this in vitro study is to estimate the volume of heparin that may leak into the circulation immediately after performing a catheter lock. METHODS: Different volumes (ml) of a dextrose solution were used to perform a catheter lock on haemodialysis catheters. The tip of the catheter was placed in a test tube containing water for a pre-specified period. The final concentrations of dextrose in the test tube were used to determine the volume of solution that leaked from the catheter. RESULTS: When the total lumen volume was filled, the catheter leak was estimated to be 0.59+/-0.03 and 0.71+/-0.04 ml after 15 and 25 s, respectively. There was a continuous leak of 1.23+/-0.41, 2.20+/-0.34 and 3.38+/-0.23 ml at 5, 15 and 30 min, respectively, after performing a catheter lock on a catheter with a total lumen volume of 4.5 ml. The catheter leak was significantly reduced when only 3.7 ml of solution was used to fill the total lumen volume of 4.5 ml. CONCLUSION: The present study demonstrates a significant early and late leakage from the catheter that occurs after performing a catheter lock. When applied to heparin, the volume of the unwanted catheter leak may result in adverse clinical events, especially following haemodialysis sessions and during peri-operative periods. However, these results are hypothesis-generating, and clinical studies are necessary to evaluate the efficacy of underfilling.     

Comparison of catheter surface morphologies

The surface morphologies of different generic types of Foley catheter have been investigated using scanning electron microscopy (SEM). The characteristic features of each material are illustrated and it is shown that distinct differences exist between the inner and outer surfaces of latex-based catheters; these differences are attributed to the methods of manufacture. The possible relations between morphology and performance in situ are discussed.     

Inhibition of sodium urate crystal adherence to bladder surface by polysaccharide

Bladder surface glycosaminoglycan (polysaccharide) has been shown to act in a nonspecific manner as an antiadherence factor and may potentially be important in the pathogenesis (and prevention) of renal calculi. It has been shown that when present, bladder surface GAG will reduce the adherence of both calcium and calcium oxalate crystals. This study was conducted to see if a similar effect would be found with uric acid crystals, in that the presence of the normal bladder mucus with its contained GAG and exogenously supplied polysaccharide, pentosanpolysulfate, would be inhibitory to crystal adherence. Radioactively labeled uric acid crystals were made by dissolving 14C labeled sodium urate to a point of saturation at pH 7.5 and then rapidly lowering the pH to 5.5. These crystals were placed into four groups of bladders: 1) normal bladders, 2) bladders rendered mucus deficient with hydrochloric acid, 3) mucus deficient bladders which were pre-treated with sodium pentosanpolysulfate prior to crystal addition and 4) mucus deficient bladders to which were added crystals pretreated with pentosanpolysulfate. There was a significant rise in crystal adherence after acid treatment of the bladder, a 2.3-fold increase, which was blocked with prior treatment of the crystals with pentosanpolysulfate and to a lesser degree by pretreating mucus deficient bladders with pentosanpolysulfate.     

An experimental study exploring the relationship between the size of bacterial inoculum and bacterial adherence to prosthetic mesh

Background

Infection is a major concern with medical implants. Surgical meshes used for the repair of abdominal wall hernias are associated with wound infection rates ranging from 7 to 18 %. Although mesh infection is relatively rare, once a patient shows clinical signs of mesh infection, the surgeon may be required to remove the mesh, resulting in additional surgery, morbidity, and cost. The usual causative organisms associated with cases of mesh infection are Staphylococcus species. The first stage of implant infection is bacterial adherence to the biomaterial. An accurate assessment of adherent bacteria to medical prosthetics is therefore important in order to determine the infection risk associated with surgical implants.

Methods

This experimental study evaluated the relationship between the size of the bacterial inoculum and bacterial adherence to three commonly used hernia prosthetics (polypropylene, polyester, and ePTFE). Tenfold dilutions of S. epidermidis (Evans-ATCC 12228) and S. aureus (Rosenbach-ATCC 25923), created with phosphate-buffered saline, were used to inoculate each of the meshes in 3 ml of tryptone soya broth for 18 h at 37 °C, 95 % air/5 % CO₂. The number of viable bacteria in each dilution was calculated using a spot plate technique. The number of adherent bacteria to the meshes was counted using direct imaging analysis with scanning electron microscopy and expressed as a mean.

Results

One hundred eight mesh samples were analysed. The size of the bacterial inoculum of S. epidermidis significantly influenced the number of adherent bacteria to the mesh, and lower rates of adhesion were observed with smaller inoculums for all three meshes (polypropylene, p = 0.02; ePTFE p = 0.03; polyester p = 0.02). A similar, albeit less profound, pattern of results was observed with S. aureus. Bacterial adherence was observed with inoculum sizes as small as <10 bacteria.

Conclusions

The results demonstrate that even a very low number of bacterial inoculums can result in adherence to hernia biomaterials and that the level of adherence is directly related to the size of the inoculum. These in vitro results provide evidence that the size of the inoculum is important in the colonization of hernia biomaterials and demonstrate the importance of minimising the bacterial inoculum in the clinical setting.     

The effect of pentosanpolysulphate and carbenoxolone on bacterial adherence to the injured urothelium

The effect of the glycosaminoglycan (GAG) layer on the adherence of Escherichia coli to the bladder urothelium of rats has been studied. The study was performed by destroying the GAG layer and the changes were observed using the electron microscope. Bacterial adherence to the bladder with a destroyed GAG layer was much higher than to the normal bladder. Following the destruction of the GAG layer, the instillation of sodium pentosanpolysulphate significantly reduced the adhesion of bacteria. Prophylactic intramuscular administration of carbenoxolone increased the speed of regeneration of the destroyed GAG layer.     

The life-threatening hemodialysis catheter heparin lock caused bleeding in a child after peritoneal catheter removal

Hemodialysis catheter patency is regularly maintained by high-concentration heparin filling, according to manufacturer's recommendation. Surprisingly, there are only few reports on serious bleeding complications in children on dialysis. A case of serious, life-threatening hemorrhage in a child after tunneled peritoneal catheter removal because of hemodialysis catheter heparin lock flushing is described. Discussion of the literature data is presented. Further investigations are needed to develop the guidelines for pediatric dialysis catheter care, including the optimal concentration for heparin lock as the possible heparin alternatives, but until that moment, previously suggested guidelines to prevent hemorrhagic complications in dialyzed children should be emphasized.     

Concentrated heparin lock is associated with major bleeding complications after tunneled hemodialysis catheter placement

Vascular access complications, including thrombosis, are associated with significant patient morbidity and mortality. Currently, up to 60% of new patients and 30% of prevalent patients are using a catheter for dialysis. To prevent interdialytic catheter thrombosis, these devices are routinely locked with concentrated heparin solutions. Several recent studies have elucidated the potential for abnormal coagulation markers (aPTT) that may arise from this practice. This abnormal elevation in aPTT may be explained by significant early and late leakage from the catheter that occurs after performing a catheter lock. To date no study has evaluated the impact of this practice, or the elevation in aPTT that may result from it, on bleeding complication rates. We conducted a retrospective analysis comparing bleeding rates in subjects who received concentrated heparin catheter lock (5000 u/cc) [group 1, n = 52] to those who received citrate or dilute heparin catheter lock (1000 u/cc) [group 2, n = 91] immediately after tunneled hemodialysis catheter insertion. Baseline characteristics did not differ between the groups except for the preprocedure INR, which was higher in the postpolicy group compared with the prepolicy group (1.29 vs. 1.21, p = 0.04). Results from logistic regression analyses revealed that the likelihood of a composite bleeding event in group 1 was 11.9 times that of a composite bleeding event in group 2, p = 0.04. Concentrated heparin (5000 u/ml) is associated with increased major bleeding complications posttunneled catheter placement compared with low-dose heparin (1000 u/ml) or citrate catheter lock solution, p = 0.02. Given the findings of this study, a randomized controlled trial comparing the safety and efficacy of common anticoagulation lock solutions is warranted.