Silicone neonatal peripherally inserted central catheters (SN-PICCs) are widely used in neonatal intensive care units. Catheter-related bloodstream infection (C-RBSI) is the most common associated complication.1,2
The microbiological diagnosis of catheter colonization can be made either by rolling the catheter tip on the agar surface (Maki’s roll-plate technique) or by sonicating the distal 4–5 cm of the catheter.3,4 The roll-plate technique is sufficiently reliable for the diagnosis of colonization in adult catheters, as shown by several authors.5–7 However, the yield of both techniques in demonstrating colonization in SN-PICCs has not been assessed. In a previous study performed in our institution,8 the roll-plate technique frequently failed to detect colonization of SN-PICCs. Its yield improved when the catheter was cut open and the slices were rubbed on the surface of a blood agar plate.8
Our objective was to compare the yield of roll-plate, sonication, and catheter slicing for the detection of colonization and C-RBSI in SN-PICCs.
MATERIALS AND METHODS
The study was carried out in the laboratory of the Clinical Microbiology and Infectious Disease Department, Hospital General Universitario Gregorio Marañón, Madrid, Spain. For 6 months, we prospectively cultured tips from SN-PICCs withdrawn from pediatric patients admitted to our institution with suspicion of infection. We first cultured the catheter tip using the roll-plate technique on blood agar plates. We then divided the catheter into 2 segments and performed 2 procedures in a random order. One segment was longitudinally sliced (2–3 fragments), and the fragments were rubbed forth and across of a blood agar plate. Another segment was sonicated (1 minute + vortex) in 0.5-mL brain-heart infusion, and 100 µL of the sonicate was cultured on blood agar plates (see Figure, Supplemental Digital Content 1, http://links.lww.com/INF/C366).
Catheter Tip Colonization
Isolation of ≥15 cfu/plate by roll-plate, ≥15 cfu/plate in slicing and/or ≥100 cfu/catheter in sonication.
Catheter-related Bloodstream Infection
Presence of ≥1 positive peripheral blood culture from a patient with an intravascular catheter and clinical manifestations of infection (fever, chills and/or hypotension) and no apparent source of infection other than the catheter. C-RBSI requires microbiological confirmation with the isolation of the same microorganism both in the SN-PICC tip and in the peripheral vein.
The diagnostic standard for the confirmation of catheter colonization was positivity of the tip culture by roll-plate (≥15 cfu/plate), slicing (≥15 cfu/plate) or sonication (≥100 cfu/catheter).
We calculated the validity values of each technique individually by comparing it with the diagnostic standard of colonization and C-RBSI. The sensitivity, specificity and positive and negative predictive values, with their 95% confidence intervals, were calculated using EPIDAT 3.1. Accuracy was defined as the sum of true-positive and true-negative results. All statistical tests were 2-tailed. Statistical significance was set at P < 0.05 for all the tests. The statistical analysis was performed using IBM SPSS Statistics for Windows version 21.0 (IBM Corp, Armonk, NY).
This study was approved by the local ethics committee.
We included a total of 90 SN-PICCs sent with suspicion of infection. The prevalence of colonization and C-RBSI was 32.2% (29/90) and 23.3% (21/90), respectively.
All 3 techniques were positive in 15 of the 29 colonized catheters (51.7%). Two of the 3 techniques were positive in 8 colonized catheters (27.6%). In the remaining 6 catheters, colonization was detected in 1 (3.4%), 2 (6.9%) and 3 (10.3%) by roll-plate, sonication and slicing, respectively. In colonized catheters from patients with concomitant bacteremia, 12 of the 21 C-RBSI episodes (57.1%) were detected by all 3 techniques. In 6 episodes, 2 of the 3 techniques were positive. In the remaining 3 C-RBSI episodes, 1 (4.8%), 1 (4.8%) and 1 (4.8%) were detected by the roll-plate, sonication and slicing, respectively (see Table, Supplemental Digital Content 2, http://links.lww.com/INF/C367).
The distribution of microorganisms in the colonized catheters (detected by any of the 3 techniques) was as follows: Gram-positive, 79.4%; Gram-negative, 14.7% and yeasts, 5.9% (see Figures, Supplemental Digital Content 3–5, http://links.lww.com/INF/C368, http://links.lww.com/INF/C369, and http://links.lww.com/INF/C370). Overall, colonization was polymicrobial in 5 (17.2%) of the 29 colonized catheters. The etiology of the C-RBSI episodes was as follows: Staphylococcus epidermidis, 57.7%; Enterococcus faecalis, 7.7%; coagulase-negative staphylococci, 3.8%; Enterobacter cloacae, 7.7%; Staphylococcus aureus, 3.8%; Klebsiella oxytoca, 3.8%; Klebsiella pneumoniae, 3.8%; Escherichia coli, 3.8% and Candida parapsilosis, 7.7%. Overall, 23.8% (5/21) of the C-RBSI episodes were polymicrobial.
The sensitivity of roll-plate, sonication and slicing for the prediction of colonization was 58.6%, 82.7% and 89.6%, respectively. The negative predictive value for colonization based on roll-plate, sonication and slicing was 86.7%, 94.4% and 96.6%, respectively (Table 1). The sensitivity of roll-plate, sonication and slicing for the prediction of C-RBSI was 66.7%, 85.7% and 90.5%, respectively. The negative value for the prediction of catheter colonization based on roll-plate, sonication and slicing was 92.2%, 96.7% and 97.8%, respectively (Table 1).
Roll-plate showed lower sensitivity and negative predictive value for the detection of colonization and C-RBSI than sonication and slicing before culture of SN-PICCs tips.
SN-PICCs are widely used in neonates, probably because of the lack of alternative routes to administer fluids.1,2 C-RBSI is a major problem among neonates and infants admitted to the neonatal intensive care unit and is mainly associated with SN-PICCs. Frequency has been reported to range from 1.16 to even 15.2 episodes/1000 catheter days in recent years.2,9
Most C-RBSI episodes that occur early after catheter insertion originate in the skin and are responsible for extraluminal infection, whereas C-RBSI episodes occurring approximately ≥7 days after catheter insertion are caused by hub contamination resulting from catheter manipulation and represent intraluminal contamination.10,11 These differences could account for the poor correlation between the techniques tested, as roll-plate mainly detects extraluminal colonization, whereas sonication and slicing mainly detect intraluminal colonization. Studies recommending roll-plate for the diagnosis of colonization were performed in adults with central venous catheters.5,6,12 However, neonates are a specific population with a higher risk of infection because of age, placement of catheters of different materials and sizes, and frequent catheter manipulation.13 These factors could account for our poor findings with the roll-plate technique.
Of the techniques used to detect intraluminal colonization, catheter slicing before culture was better than sonication, as demonstrated previously by our group.8 However, the findings of both our previous and the present study were limited by the fact that the procedure of catheter slicing is risky for healthcare workers if a scalpel is used for the procedure.
Another limitation of the present study was that we did not randomly distribute the order in which the techniques were performed, as demonstrated in a previous study in our institution showing that the likelihood of detection with several techniques decreased progressively depending on the order in which the techniques were performed.5 Even so, performing sonication and slicing after roll-plate would have favored roll-plate, which was not the case in the present study. Besides, despite silicone catheters did not have clear distinct parts, we always used the catheter tip for the roll-plate method, which may bias the results. Regarding the coagulase-negative staphylococci isolates, as we did not use molecular typing, the concordance between strains isolated from the tip and from the blood may not be genetically the same.
We conclude that the roll-plate technique can be omitted from the diagnosis of colonization of SN-PICCs at the cost of missing confirmation of catheter origin in 4.8% of cases. We recommend that future updates of guidelines for the diagnosis of catheter-related infections should take our findings into account. Recommendations for the diagnosis of catheter colonization cannot be extrapolated to all kinds of catheters.
The authors thank Thomas O’Boyle for his help in the preparation of the manuscript.
1. Chitnis AS, Magill SS, Edwards JR, et al. Trends in Candida central line-associated bloodstream infections among NICUs, 1999-2009. Pediatrics. 2012;130:e46–e52
2. Milstone AM, Reich NG, Advani S, et al. Catheter dwell time and CLABSIs in neonates with PICCs: a multicenter cohort study. Pediatrics. 2013;132:e1609–e1615
3. Maki DG, Weise CE, Sarafin HW. A semiquantitative culture method for identifying intravenous-catheter-related infection. N Engl J Med. 1977;296:1305–1309
4. Sherertz RJ, Raad II, Belani A, et al. Three-year experience with sonicated vascular catheter cultures in a clinical microbiology laboratory. J Clin Microbiol. 1990;28:76–82
5. Bouza E, Alvarado N, Alcalá L, et al. A prospective, randomized, and comparative study of 3 different methods for the diagnosis of intravascular catheter colonization
. Clin Infect Dis. 2005;40:1096–1100
6. Erb S, Frei R, Schregenberger K, et al. Sonication
for diagnosis of catheter-related infection is not better than traditional roll-plate culture: a prospective cohort study with 975 central venous catheters. Clin Infect Dis. 2014;59:541–544
7. Sherertz RJ, Heard SO, Raad II. Diagnosis of triple-lumen catheter infection: comparison of roll plate, sonication
, and flushing methodologies. J Clin Microbiol. 1997;35:641–646
8. Martín-Rabadán P, Nisa HS, Guembe M, Bouza E. Neonatal percutaneously inserted silicone catheters must be sectioned to detect its colonization
. European Congress of Clinical Microbiology and Infectious Diseases, Oral Sesion. May 10–13, 2014 Barcelona
9. Sannoh S, Clones B, Munoz J, et al. A multimodal approach to central venous catheter hub care can decrease catheter-related bloodstream infection
. Am J Infect Control. 2010;38:424–429
10. Bouza E, Alvarado N, Alcalá L, et al. A randomized and prospective study of 3 procedures for the diagnosis of catheter-related bloodstream infection
without catheter withdrawal. Clin Infect Dis. 2007;44:820–826
11. Cercenado E, Ena J, Rodríguez-Créixems M, et al. A conservative procedure for the diagnosis of catheter-related infections. Arch Intern Med. 1990;150:1417–1420
12. Mermel LA, Allon M, Bouza E, et al. Clinical practice guidelines for the diagnosis and management of intravascular catheter-related infection: 2009 Update by the Infectious Diseases Society of America. Clin Infect Dis. 2009;49:1–45
13. López Sastre JL, Fernández Colomer B, Coto Cotallo GD, et al. [Prospective evaluation of percutaneous central venous catheters in newborn infants. Castrillo Hospital Group]. An Esp Pediatr. 2000;53:138–147