Molecular investigation of bacterial communities on the inner and outer surfaces of peripheral venous catheters

Peripheral venous catheters (PVCs) are some of the most widely used medical devices in hospitals worldwide. PVC-related infections increase morbidity and treatment costs. The inner surfaces of PVCs are rarely examined for the population structure of bacteria, as it is generally believed that bacteria at this niche are similar to those on the external surface of PVCs. We primarily test this hypothesis and also study the effect of antibiotic treatment on bacterial communities from PVC surfaces. The inner and outer surfaces of PVCs from 15 patients were examined by 454 GS FLX Titanium 16S rRNA sequencing and the culture method. None of the PVCs were colonised according to the culture method and none of the patients had a bacteraemia. From a total of 127,536 high-quality sequence reads, 14 bacterial phyla and 268 diverse bacterial genera were detected. The number of operational taxonomic units for each sample was in the range of 86–157, even though 60 % of patients had received antibiotic treatment. Stenotrophomonas maltophilia was the predominant bacterial species in all the examined PVC samples. There were noticeable but not statistically significant differences between the inner and outer surfaces of PVCs in terms of the distribution of the taxonomic groups. In addition, the bacterial communities on PVCs from antibiotic-treated patients were significantly different from untreated patients. In conclusion, the surfaces of PVCs display complex bacterial communities. Although their significance has yet to be determined, these findings alter our perception of PVC-related infections.     

Trisomy 22: no longer an enigma

We describe a live-born male with 47,XY,+22. He had multiple congenital anomalies, severe growth retardation and psychomotor delay. Physical manifestations included broad nasal bridge, epicanthic folds, micrognathia, long philtrum, cleft palate, microcephaly with prominent occiput, apparently low-set malformed ears, heart murmur, genital anomaly, clinodactyly of the fifth fingers, and a low total finger ridge count. He died just before his 3rd birthday. Chromosome analysis by multiple banding techniques based on lymphocyte and fibroblast cultures confirm that the boy had complete trisomy 22.     

Adherence of staphylococci to intravascular catheters

Adherence of seven strains of Staphylococcus epidermidis and three strains of S. aureus to three types of intravascular catheters was assessed by ATP bioluminescence, by culture after ultrasonication and by scanning electronmicroscopy. The catheter materials studied were silicone elastomer, thermoplastic polyurethane and polyurethane coated with Hydromer, a coating which absorbs water and provides a hydrophilic sheath around the catheter. The adherence assays were performed in phosphate-buffered saline on a rotary shaker at 37 degrees C, with the catheters precoated with serum and uncoated, and the results were correlated with bacterial hydrophobicity. There was wide strain-to-strain variation in bacterial adherence; S. aureus and slime-producing S. epidermidis strains adhered better than did non-slime-producing strains. Overall, there was less bacterial adherence to Hydromer-coated catheters than to polyurethane and silicone catheters but it was unrelated to bacterial hydrophobicity. Serum coating of catheters resulted in marked reduction of bacterial adherence.     

Microbiology of indwelling central intravascular catheters.

Indwelling central-line catheters (n = 502) from 362 patients in intensive care units were analyzed prospectively. The skin site, 6-cm-distal and -proximal subcutaneous segments of the catheter, exudates, and blood were cultured. Semiqualitative roll plate cultures of the catheter segments were followed by broth cultures and examined for 72 h. All isolates were identified, and susceptibilities were determined. Line infections, defined clinically, yielded 22 different microbial species; 10 different species were recovered from colonized lines. Of the Staphylococcus epidermidis isolates recovered, 39% occurred singly and 21% occurred in combination with other microorganisms; Enterococcus faecalis, S. hominis, and Pseudomonas aeruginosa were next in frequency of isolation. Line infections also yielded other staphylococci, viridans group streptococci, several members of the family Enterobacteriaceae, acinetobacters, anaerobic bacteria, Candida spp., and Aspergillus fumigatus. While S. epidermidis was also the most frequent isolate among the line colonizers, different species and different frequencies of isolation were found among this group. The study showed that the distal catheter segment broth culture was the best predictor of clinical line infections; in addition, gram-negative bacteria were isolated only from the catheters of patients with overt infections.     

Scanning electron microscopy of bacteria adherent to intravascular catheters

Scanning electron microscopy was used to assess the morphological features of coagulase-negative staphylococci adherent to polyvinylchloride intravascular catheter specimens. Clinical specimens were obtained by using patient catheters from which coagulase-negative staphylococci (greater than or equal to 15 colonies per catheter) grew on semiquantitative blood agar roll cultures. In vitro specimens were prepared by a previously published technique in which sterile polyvinylchloride catheters were immersed in 10(6) CFU of coagulase-negative staphylococci per ml suspended in phosphate-buffered saline. Unused sterile polyvinylchloride catheters were also examined. Scanning electron microscopy of unused sterile polyvinylchloride catheters demonstrated multiple linear surface irregularities. Scanning electron microscopy of infected patient catheters showed a diffuse amorphous material covering the entire surface and the presence of bacteria which appeared anchored to that surface by several different means. These included a slime layer, "foot" processes, and lodgement in surface irregularities. Scanning electron microscopy of in vitro specimens demonstrated no background surface coating, but it did show attachment of cocci to the surface by the same mechanisms as described for clinical specimens. These observations of similar means of attachment in clinical and in vitro specimens suggest that intrinsic catheter surface properties, bacterial surface features, and perhaps coating with host substances may all play a role in bacterial attachment to intravascular catheters. More sophisticated analysis of these interactions may clarify mechanisms of pathogenesis.     

Relevance of culturing Candida species from intravascular catheters.

The significance of isolating Candida species from intravascular catheters was examined retrospectively. Our findings demonstrate that these organisms are encountered among patients with proven invasive candidiasis or as an isolated finding. Febrile patients with yeasts in two or more additional sites may be at risk for invasive cadidiasis and may benefit from treatment.     

Collaboration between nurses and physicians: no longer a choice.

Collaboration, a relationship of interdependence, requires the recognition of complementary roles. Traditionally, physicians generally have not demonstrated collaboration in their work with nurses; nurses, on the other hand, have more often sought a collaborative relationship. But the rapidly changing, increasingly complex and constraining world of health care requires that doctors, nurses, and the institutions that educate and employ them reevaluate the doctor-nurse relationship and assess the value of making it a more collaborative one. This essay deals with the phenomenon of collaboration, why there are compelling reasons to promote it, the barriers that exist between nurses and physicians in achieving collaborative relationships, and strategies to promote change. Comments of experienced observers and summaries of the pertinent research literature are presented.     

Vancomycin-resistant Staphylococcus aureus: no apocalypse now

The number of reports concerning vancomycin-resistant Staphylococcus aureus is much higher than the number of true resistant strains or unexpected clinical failures. Many confounding factors, including inadequate serum levels, severely ill patients, foreign devices or undrained abscesses, are more likely to be responsible for the clinical failures than resistance to vancomycin.     

Role of catheter surface morphology on intravascular thrombosis of plastic catheters.

The role of catheter surface roughness in initiation and propagation of intravascular catheter thrombosis was studied in dogs, utilizing the scanning electron microscope. Catheters were inserted in major arteries and veins for 200 min and the animals then sacrificed. Catheter segments, both with and without associated thrombi, were scrutinized with the scanning electron microscope. No correlation was found between catheter surface roughness and thrombus formation, suggesting that the inherent chemical characteristics of the catheter is most important in the initiation of intravascular catheter thrombus formation.     

Roughness and thrombogenicity of the outer surfaces of intravascular catheters

Thirty-seven types of catheters made from plastics including silicone rubber, polyvinylchloride, polyethylene, and polyurethane were tested for thrombogenesis in the cephalic vein of sheep. The range in the mass of thrombus on the catheters at autopsy 9 days after insertion was 20-fold. There was considerable variation when catheters made from the same types of plastic were compared, but polyethylene catheters tended to be more thrombogenic than other types. Scanning electron microscopy (SEM) revealed a variety of surfaces ranging from very smooth to very rough. Roughness was frequently associated with the presence of radioopaque particles which in several catheters were concentrated into radio-opaque tracer strips. Within types of plastics, catheters with rougher surfaces were usually more thrombogenic than those with smooth surfaces.     

Scanning electron microscopy of bacterial biofilms on indwelling bladder catheters

Fifty Foley bladder catheters that had been indwelling for periods ranging from 3 to 83 days (mean 35 days) were examined for the presence of bacterial biofilm. Scanning electron microscopy on freeze-dried cross-sections and fixed, critical point-dried longitudinal sections revealed biofilm formation on the luminal surfaces of 44 of the catheters. Culture of urine samples and sonicates from catheters revealed that the prevalence of bacteriuria was less than that of catheter colonization. A wide range of nosocomial species were found colonizing the catheters,Escherichia coli being most often isolated. The bacterial composition of the biofilms ranged from single species to mixed communities containing up to four species. There was no relationship between the length of time that the catheter had been in situ and the extent of biofilm formation. The biofilms varied in thickness from 3 to 490 µm and were visible as layers of bacterial cells up to about 400 cells deep, embedded in a matrix.