Comparison of Bact/ALERT Microbial Detection System and the Isolator Blood Culture System for the Recovery of Filamentous Fungi

B. Gandhi, T. Mazzulli

Author address: 

Dept. of Microbiol., Mt. Sinai Hosp., Toronto, ON, CANADA, Dept. of Microbiol., Mt. Sinai Hosp. and Univ. Hlth.Network, and Univ. of Toronto, Toronto, ON, CANADA.

Abstract: 

Background: The aim of this study was to compare the BacT/ALERT microbial detection (MB) automated system (bioMerieux) to the Isolator lysis centrifugation system (Wampole) for the recovery and time of detection of seeded cultures of emerging filamentous fungi. Method: 47 characterized species of Scedosporium, Fusarium, Aspergillus, Acremonium, Paecilomyces and Trichoderma clinical isolates were tested after sporulating on Potato Dextrose agar for 7-10 days. Heavy suspensions of each organism were prepared in 5.0 ml of Tryptic Soy broth and allowed to stand for 30 minutes to allow hyphal material to settle. and then sampled from the top. Fungal suspensions were standardized to 0.5 McFarland using a DensiCHEKâ„¢ turbidity meter (bioMerieux) and then serially diluted to 102 CFU/mL.One ml of adjusted inoculum was transferred to each BacT/ALERT MB plastic bottle and Isolator tube containing sterile sheep blood performed in triplicate. Purity plates were also set up in triplicate. The inoculated BacT/ALERT MB bottles were incubated at 35ºC for up to 21 days while the isolator tubes were centrifuged at 3000rpm for 30 minutes and the suspension inoculated onto 3 SAB plates and incubated for 8 days at room temperature. Suspected positive bottles were removed and tested for viability and purity. Results: All 9 Scedosporium species were detected by the BacT/ALERT MB bottles whereas only 33% were detected by the Isolator system. 50% of the 22 Fusarium species were detected by the BacT/ALERT MB bottles and 100% by the Isolator system. All 6 Aspergillus fumigatus and 2 Aspergillus terreus were detected by both methods with earlier detection by the BacT/ALERT MB bottles. Two Acremonium species were also detected by both systems. Paecilomyces and Trichoderma species were only detected by the Isolator system as most species do not grow at 35ºC. Conclusions: The BacT/ALERT MB appears better for the isolation of Scedosporium species while the Isolator appears better for Fusarium species. Otherwise they appear similar. However because only certain organisms will grow at 35ºC-37ºC, recovery by the BacT/ALERT MB system may be improved if the incubation temperature was lowered to 30oC.
2010

abstract No: 

F-2137

Full conference title: 

110th General Meeting American Society for Microbiology
    • ASM 110th (2010)