Propionibacterium acnes is a common colonizer of intravascular catheters.

Propionibacterium spp. are common flora of human skin. Nevertheless, currently recommended culture procedures do not include anaerobic processing with the result that this organism may go undetected on a colonized catheter. To determine the rate of catheter colonization by Propionibacterium spp., a sample of 1000 vascular catheters was processed by the roll-plate technique and, after conventional aerobic processing, all primary culture plates were reincubated in an anaerobic atmosphere. Propionibacterium acnes was detected in significant counts in the vascular catheters of 39 patients. This represents 14.7% (95% CI, 12.5-16.9) of all positive catheters. Propionibacterium is the second most frequent genus-colonizing catheter tips after Staphylococcus spp. Methodological shortcomings impair the detection and proper adscription of P. acnes as a potential cause of catheter-related infections.

A randomized and prospective study of 3 procedures for the diagnosis of catheter-related bloodstream infection without catheter withdrawal.

BACKGROUND: Suspicion of catheter-related bloodstream infection (CR-BSI) leads frequently to unnecessary catheter withdrawals, and many catheter-tip cultures yield negative results. The objective of this study was to compare the yield of 3 microbiological procedures to assess CR-BSI without catheter withdrawal. METHODS: The study was prospectively performed in a group of patients without neutropenia or blood disorders who were admitted to the intensive care unit during a 37-month period with sepsis suspected on clinical grounds and who had central venous catheters inserted for >48 h. The microbiological procedures compared were semiquantitative cultures from hub and skin (superficial), differential quantitative blood cultures, and differential time to positivity between cultures of blood obtained from catheter hubs and peripheral blood. RESULTS: Of the 204 episodes of suspected CR-BSI included in the study, 28 were confirmed to be CR-BSI. We obtained the following results for sensitivity, specificity, positive and negative predictive values, and accuracy: superficial cultures, 78.6%, 92.0%, 61.1%, 96.4%, and 90.2%, respectively; differential quantitative blood cultures, 71.4%, 97.7%, 83.3%, 95.6%, and 94.1%, respectively; and differential time to positivity, 96.4%, 90.3%, 61.4%, 99.4%, and 91.2%, respectively. CONCLUSIONS: CR-BSI can be assessed without catheter withdrawal in patients without neutropenia or blood disorders who have catheters inserted for a short time and are hospitalized in the intensive care unit. Convenience, use of resources, and expertise should determine the technique of choice in different medical contexts. Because of ease of performance, low cost, and wide availability, we recommend combining semiquantitative superficial cultures and peripheral vein blood cultures to screen for CR-BSI, leaving differential quantitative blood cultures as a confirmatory and more specific technique.

An instant procedure to demonstrate catheter-tip colonization may help clinicians.

This study compared the acridine orange and Gram stains of an external smear of intravascular catheter-tip segments with the culture results obtained 24 to 48 h later. Both staining techniques were randomly assigned to be performed either before (group A) or after (group B) rolling on the agar plate. Of the 425 catheter tips processed, 25.7% were significantly colonized and 6.1% were from patients with catheter-related bloodstream infections (CRBSIs). The yield of group A was superior to that of group B for the prediction of colonization (sensitivity, 94.3%/69.6%; specificity, 92.4%/96.2%; positive predictive value (PPV), 80.6%/86.7%; negative predictive value (NPV), 98.0%/90.0%; and full concordance, 91.9%/89.3%). The values for the prediction of CRBSIs were as follows for group A and group B: sensitivity, 100%/69.2%; specificity, 96.3%/100%; PPV, 86.7%/100.0%; NPV, 100%/93.9%; and full concordance, 97.0%/94.7%. Catheter-tip staining before culture is an easy-to-perform, cheap, and effective procedure to anticipate catheter colonization and rule out CRBSIs.

A prospective, randomized, and comparative study of 3 different methods for the diagnosis of intravascular catheter colonization.

BACKGROUND: Demonstration of catheter tip colonization is usually performed by use of Maki's semiquantitative technique, although the superiority of quantitative techniques has been claimed on the basis of their purported ability to detect both endoluminal and exoluminal microorganisms. METHODS: We prospectively compared Maki's semiquantitative technique and the quantitative methods of sonication and vortexing for the detection of colonization of intravascular catheter tips and catheter-related bloodstream infections. All 3 techniques were performed on the tip of each catheter, and the order in which each technique was performed was randomly assigned. RESULTS: Of the 1000 catheter tips that were processed, 329 (32.9%) had positive results for at least 1 of the 3 techniques when a breakpoint of >or=100 colony-forming units (cfu)/catheter segment was used for the quantitative techniques and a breakpoint of >or=15 cfu was used for Maki's technique. Eighty-two of the catheter tips for which results were positive were from patients with catheter-related bloodstream infections. For each technique, the likelihood of detection decreased progressively depending on the order in which the technique was performed (i.e., second vs. first and third vs. second). The likelihood of detection of catheter colonization for each technique, when the technique was performed first and when 2 breakpoints (>or=100 cfu/catheter segment [criterion B] and >or=1000 cfu/catheter segment [criterion A]) were used for the quantitative techniques and a breakpoint of >or=15 cfu was used for Maki's technique, was as follows: 99.1% and 100% for Maki's technique, 95.1% and 92.9% for sonication, and 93.1% and 72.8% for vortexing (for criteria B and A, respectively). No inferiority of Maki's technique could be demonstrated when results were compared according to whether catheter placement was short term (i.e., <7 days) or long term (i.e., >or=7 days), either for the detection of colonization or for the detection of catheter-related bloodstream infections. CONCLUSIONS: According to data from the present study, the quantitative techniques of sonication and vortexing were not superior to Maki's technique under the test conditions used. The greater simplicity of Maki's semiquantitative technique makes it the procedure of choice for routine work in the microbiology laboratory.