Mary Anne Giannini

Diagnosis of catheter-related bloodstream infections among pediatric oncology patients lacking a peripheral culture, using differential time to detection.

Background: Current methods for in situ diagnosis of catheter-related bloodstream infections require concurrent collection of central venous catheter (CVC) and peripheral vein (PV) blood cultures. Both the pain and inconvenience of PV cultures are undesirable. Methods: A prospective study was conducted (August 2002 to March 2004) to assess the accuracy of diagnosing catheter-related bloodstream infections based on the difference in time to detection of blood cultures drawn concurrently from 2 lumens of a multilumen CVC. This difference in time to detection between 2 lumens was compared with results of the standard criterion with paired CVC and PV blood cultures. Results: Twenty-one infectious episodes were categorized as catheter-related bloodstream infections and 38 as non-catheter-related bloodstream infections. With a cutoff in difference in time to detection between 2 lumens of ≥180 minutes, the sensitivity of this test to diagnose a catheter-related bloodstream infection was 61% (95% confidence interval, 39–80%) and the specificity was 94% (95% confidence interval, 82–99%). In 4 of 7 episodes with false-negative results, the colony counts in cultures from both lumens were >400 colony-forming units/mL (maximal value reported), indicating the limitation of this method when both lumens of the catheter are colonized. With the pretest probability of catheter-related bloodstream infections ranging from 28% to 54%, the positive predictive value of a difference in time to detection between 2 lumens of ≥180 minutes for diagnosis of catheter-related bloodstream infections ranged from 81% to 93% and the negative predictive value ranged from 67% to 86%. Conclusion: Within the context of its limitations, this novel method provides an alternative for diagnosing catheter-related bloodstream infections among patients with a CVC, without PV cultures.

Optimizing blood culture practices in pediatric immunocompromised patients: evaluation of media types and blood culture volume

Background. The optimal use of blood cultures to determine the etiology of febrile episodes in neutropenic children has not been well-defined. Methods. Single volume blood cultures using the Pediatric ISOLATOR System (ISO), were compared with variable, weight-based culture volumes using the BACTEC 9240 Culture System (BAC). Additionally the value of routinely inoculating the BACTEC MYCO/F LYTIC culture vial (MFL) as well as the BACTEC AEROBIC/F culture vial (AF) was examined Results. A total of 2620 cultures had both ISO and BAC inoculated; 182 cultures were positive (7.0% of cultures); 97.8% of positive cultures were detected by the BAC (AF and/or MFL) vs. 46.2% detected by the ISO. The advantage of the BAC over the ISO was statistically significant for overall recovery of isolates and bloodstream infections, including most individual organism categories. There were only two instances (one each of histoplasmosis and candidemia) in which a blood stream infection was detected by ISO only. All the isolates judged to be contaminants were recovered by BAC only. AF detected significantly more coagulase-negative Staphylococcus spp. than the MFL. Of the isolates 16%, representing 14% of the bloodstream infections (including Gram-negative infections), were detected by the MFL only. Infections were detected more quickly by BAC than by ISO (P < 0.0001). Among the BAC media types, AF was faster than MFL (P < 0.0001). Conclusions. Optimal yield of blood cultures in immunocompromised pediatric patients included the use of BAC with a weight-based, graduated volume of culture inoculation and routine use of both AF and MFL.

Are toilet seats a vector for transmission of methicillin-resistant Staphylococcus aureus?

We studied the bacterial burden on toilet seats in a childrens cancer hospital to validate a policy requesting that immunocompromised children use alcohol wipes on the seats prior to use of the toilets. Methicillin-resistant Staphylococcus aureus (MRSA) was recovered from 3.3% of hospital toilets when wipes were not in use. Use of wipes resulted in a 50-fold reduction in mean daily bacterial counts and eliminated MRSA.