Simulated Pediatric Blood Cultures to Assess the Inactivation of Clinically Relevant Antimicrobial Drug Concentrations in Resin-Containing Bottles

The bacteremia level as well as the administration of antibiotics before blood collection may significantly affect the recovery of bacterial pathogens from pediatric blood cultures in BacT/Alert Virtuo or Bactec FX BC systems, which remain the common techniques to diagnose bacteremia in pediatric patients. We simulated pediatric blood cultures with low or intermediate bacteremia level to evaluate BacT/Alert PF Plus and Bactec Peds Plus blood culture bottles for resin-based inactivation of 16 antibiotic–bacterium combinations. Overall, 105/192 (54.7%) of BacT/Alert PF Plus bottles and 69/192 (36.0%) of Bactec Peds Plus bottles allowed organisms to grow when exposed to antibiotics. In particular, both BacT/Alert PF Plus and Bactec Peds Plus bottles proved to be effective with piperacillin/tazobactam and Pseudomonas aeruginosa or with oxacillin and methicillin-susceptible Staphylococcus aureus (100% growth), whereas no effectiveness was apparent with ceftriaxone and Escherichia coli, Streptococcus agalactiae, or Streptococcus pneumoniae or with cefepime and E. coli (0% growth). In some relevant instances (e.g., with vancomycin and methicillin-resistant S. aureus or Streptococcus pneumoniae), BacT/Alert PF Plus bottles were superior to Bactec Peds Plus bottles. Together, these findings underscore the potentiality of resin-containing bottles to enhance diagnosis of bacteremia in pediatric patients on antimicrobial therapy. This is particularly true with one of the evaluated BC systems and with simulated intermediate bacteremia level only.

Comprehensive Evaluation of Compendial USP, BacT/Alert Dual-T, and Bactec FX for Detection of Product Sterility Testing Contaminants

ABSTRACT The emergence of cell therapy programs in large academic centers has led to an increasing demand for clinical laboratories to assist with product sterility testing. Automated blood culture systems have shown promise as alternatives to the manual USP<71> compendial method, but current published data are limited by small organism test sets, particularly for molds. In 2015, failure of the Bactec FX system to detect mold contamination in two products prompted us to evaluate three test systems (compendial USP<71>, Bactec FX, and BacT/Alert Dual-T) over seven different culture combinations, using 118 challenge organisms representative of the NIH current good manufacturing practice (cGMP) environment. At <96 h and <144 h for bacterial and fungal detection, respectively, the compendial USP<71> method significantly outperformed the Bactec FX system (84.7% versus 64.4%; P = 0.0006) but not the BacT/Alert system at 32.5°C (78.8%; P = 0.3116). Extended incubation to 360 h with terminal visual inspection improved sensitivity, without a significant difference between compendial USP<71> and BacT/Alert testing (95.7% versus 89.0%; P = 0.0860); both systems were better than the Bactec FX system (71.2%; P < 0.0001 and P = 0.0003, respectively). The Bactec FX and BacT/Alert systems performed equivalently for 30 isolates derived from clinical bloodstream infections, confirming system optimization for clinical organisms rather than environmental contaminants. Paired Sabouraud dextrose agar (SDA) plates were always positive for fungi within the acceptable time frame. This study shows that the Bactec FX system is suboptimal for product sterility testing, and it provides strong data to support the use of BacT/Alert testing at 32.5°C paired with a supplemental SDA plate as an acceptable alternative to the compendial USP<71> method for product sterility testing.

Resistance to Echinocandins inCandidaCan Be Detected by Performing the Etest Directly on Blood Culture Samples

ABSTRACTWe examined the rapid evaluation of susceptibility to echinocandins inCandidaspp. using the Etest performed directly on positive blood cultures and anidulafungin-containing agar plates. We prospectively collected 80 positive blood cultures (Bactec-FX system, Becton-Dickinson, Cockeysville, MD, USA) with echinocandin-susceptibleCandidaspp. (n= 60) and echinocandin-intermediateCandida parapsilosis(n= 20) from patients with candidemia. Additionally, blood culture bottles of nonfungemic/bacteremic patients were spiked with 35 echinocandin-resistantCandidaspecies isolates. A total of 2 to 4 drops of medium from each bottle were stroked directly onto both RPMI 1640 agar plates with micafungin and anidulafungin Etest strips (ETDIR) and Sabouraud agar plates containing 2 mg/liter of anidulafungin. The isolates were tested according to the EUCAST method and Etest standard (ETSD). Essential and categorical agreement between the methods was calculated. The essential agreement and categorical agreement between the EUCAST method and ETDIRand ETSDwere both >97.4%. The essential agreement between ETDIRand the EUCAST method for both echinocandins was >97%. The categorical agreement between theFKSsequence and ETDIRwas 97.4%. The ETDIRMICs of anidulafungin and micafungin (≥0.19 mg/liter and ≥0.064 mg/liter, respectively) effectively separated all susceptibleFKSwild-type isolates from the resistantFKSmutant isolates. The categorical agreement (62.6%) between the EUCAST method and growth on anidulafungin-containing plates was poor, with the best agreement observed forCandida glabrata(94.2%). When performed directly on positive blood cultures from patients with candidemia, the Etest with micafungin and anidulafungin is a reliable procedure for the rapid testing of susceptibility to echinocandins inCandidaspecies isolates.

The Bactec FX Blood Culture System Detects Brucella melitensis Bacteremia in Adult Patients within the Routine 1-Week Incubation Period

ABSTRACTThe performance of the Bactec FX blood culture system for detectingBrucellabacteremia within the routine 1-week incubation period was assessed in a prospective study conducted in an area in southern Israel in whichBrucella melitensisis endemic. Aerobic vials (BD Bactec Plus Aerobic/F medium) inoculated with blood specimens obtained from adult patients with positive Rose-Bengal screening test results were monitored for 4 consecutive weeks, and blind subcultures of negative vials were performed on solid media on days 7 and 28. During a 16-month period, a total of 31 (35.2%) of 88 cultures, obtained from 19 (38.0%) of 50 patients, were positive forBrucella melitensis. The blood culture instrument identified 30 (96.8%) of 31 positive vials within 7 days of incubation; the single positive vial that was missed by the automated readings was detected only by the blind subculture performed on day 28. It is concluded that the Bactec FX system is able to detect the vast majority of episodes ofBrucellabacteremia within the 1-week incubation protocol instituted in most clinical microbiology laboratories and without the need to perform blind subcultures of negative vials, enabling early diagnosis and saving labor and incubation time and space.

Blood Volume Required for Detection of Low Levels and Ultralow Levels of Organisms Responsible for Neonatal Bacteremia by Use of Bactec Peds Plus/F, Plus Aerobic/F Medium, and the BD Bactec FX System: anIn VitroStudy

We used anin vitrotechnique to investigate blood volumes required to detect bacteremia and fungemia with low concentrations of an organism. At 1 to 10 CFU/ml,Escherichia coli,Staphylococcus epidermidis,Staphylococcus aureus,Listeria monocytogenes,Candida albicans, andCandida parapsilosisisolates were detected in volumes as low as 0.5 ml. Detection ofStreptococcus agalactiaeand detection of bacteremia at <1 CFU/ml were unreliable.