Effect of Delayed Entry on Time to Detection for the Lactose Nonfermentative Gram-Negative Rods / 대한임상미생물학회지

BACKGROUND: Prolonged transport or poor accessibility of blood culture equipment during night time may cause delayed entry of blood culture bottles. The effect of prestorage conditions on time to detection (TTD) for the blood culture was evaluated for the important gram-negative lactose nonfermentative bacteria. METHODS: Three different clinical isolates of Pseudomonas aeruginosa, Acinetobacter baumannii, Stenotrophomonas maltophilia, and Burkholdera cepacia were diluted to 150 CFU/mL and 15 CFU/mL and inoculated into standard aerobic bottles. These were stored at 25℃ and at 37℃ for 0, 6, 12, 18, and 24 h. They were entered to BacT/Alert 3D Systems (bio-Mérieux Inc.) and TTD was monitored for each condition. RESULTS: At the 150 CFU/mL concentration, P. aeruginosa and A. baumannii showed false-negative for the bottles prestored at 37℃ for 18 h and 24 h, respectively. However, there was no false-negative for S. maltophilia or B. cepacia at any prestorage conditions. There was a significant decrease of TTD for all experimental microorganisms except P. aeruginosa prestored for 24 h either at 25℃ or at 37℃ (P< 0.05). CONCLUSION: Delayed entry may cause false-negative, especially for the high level of bacteremia of P. aeruginosa or A. baumannii when the bottles are stored at 37℃ for ≥18 h. TTD could be reduced by prestorage of the bottles at 37℃ until 12 h without false-negative for nonfermentative bacteria.

Comprehensive Analysis of Blood Cultures Using BacT/Alert 3D FA Plus and FN Plus Media

BACKGROUND: We prospectively evaluated the performance of blood culture resin media, FA Plus and FN Plus, of the BacT/Alert 3D System (bioMérieux Inc., USA) in a tertiary university-affiliated hospital. METHODS: We obtained 2,994 blood culture sets. The positivity and time to detection (TTD) were compared between FA Plus and FN Plus for clinically significant microorganisms. We then categorized patients into two groups based on antibiotic treatment before blood culture to observe the difference of positivity between two groups. RESULTS: Among 2,994 sets received, 371 (12.4%) yielded 385 clinically significant pathogens. Comparing FA Plus to FN Plus media, lactose non-fermenters (18 vs. 1; P0.05). CONCLUSIONS: Complementary detection of microorganisms was observed between FA Plus and FN Plus. Gram-positive cocci including S. aureus grew faster in FA Plus. In addition, the rate of positivity was not affected by prior antibiotic therapy in BacT/Alert 3D resin media.