The challenge of anticipating catheter tip colonization in major heart surgery patients in the intensive care unit: are surface cultures useful?
OBJECTIVE
Patients undergoing heart surgery show a high risk of catheter colonization and catheter-related bloodstream infections. We evaluated whether skin insertion site and catheter hub surveillance cultures ("surface cultures") could predict catheter colonization and help establish the origin of bloodstream infections.


METHODS
: Prospective cohort study.


METHODS
An 11-bed heart surgery intensive care unit in a tertiary university hospital.


METHODS
Heart surgery patients spending >4 days in intensive care over an 11-month period.


METHODS
All catheters were surveyed. Cultures were obtained from the skin insertion site and all hubs on day 5 after surgery, every 72 hrs thereafter, and on catheter removal. Swabs were processed semiquantitatively by streaking the surface of a Columbia agar plate. Catheters were processed using Maki's method. The observation of > or = 15 colonies/plate was taken to indicate a positive skin or catheter colonization culture result.


RESULTS
Over the study period, 561 catheters were inserted in 130 patients. The median time a catheter was in place was 6 days (interquartile range 3-11), and 3,712 surface cultures were obtained (median four per patient). Catheter colonization occurred in 133 catheters, and there were 15 episodes of catheter-related bloodstream infection (incidence density of colonization 29.3 and of catheter-related bloodstream infection 8.8 per 1,000 catheter-days). Validity indexes for the capacity of surface cultures to predict catheter colonization and catheter-related bloodstream infection, respectively, were as follows: accuracy, 71.4, 65.6; sensitivity, 83.5%, 100%; specificity, 67.1%, 64.7%; positive predictive value, 47.6%, 7.2%; negative predictive value, 91.9%, 100%; positive likelihood ratio, 2.5, 2.83; and negative likelihood ratio, 0.2, 0. Surface cultures correctly predicted 77.4% of all bacteremia episodes (catheter-related and non-catheter-related).


CONCLUSIONS
Systematic surveillance cultures of catheter hub and skin insertion sites in patients admitted to a heart surgery intensive care unit could help identify patients who would benefit from decontamination and preventive measures and establish whether catheters are the portal of entry of bloodstream infection.
Bouza
Emilio
E
Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Universidad Complutense, Madrid, Spain. ebouza@microb.net
Muñoz
Patricia
P
Burillo
Almudena
A
López-Rodríguez
Javier
J
Fernández-Pérez
Cristina
C
Pérez
María Jesús
MJ
Rincón
Cristina
C
D016470:Bacteremia / Q000175:diagnosis / Q000209:etiology* / Q000517:prevention & control; D006348:Cardiac Surgical Procedures; D002408:Catheters, Indwelling / Q000009:adverse effects*; D003666:Decontamination; D004866:Equipment Contamination; D006801:Humans; D007362:Intensive Care Units; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D012867:Skin / Q000382:microbiology; D013997:Time Factors