Clinical comparison of the BACTEC 9000 Standard Anaerobic/F and Lytic/F blood culture media

Ultra-fast direct method for identifying microorganisms from BACTEC lytic/10 anaerobic/F flasks

Background: Fast diagnosis of bloodstream infections remains the most important challenge for clinical microbiologists. The introduction of the mass-spectrometry represents a breakthrough, although several methods are already commonly used for the direct identification from positive blood cultures we present a faster method (ultra fast) for Lytic anaerobic flasks. Methods: We compare the ultra-fast (UF) method with the extensively employed differential centrifugation method (DC) and both to routine identification after 18-24 h of incubation. UF and DC method correlation rates to the gold standard were calculated, and statistical significance was proved with the Z test. Results: UF performed better overall than DC, with this difference being statistically significant. This tendency was observed in every subanalysis.

Prospective study of the clinical performance of three BACTEC media in a modern emergency department: Plus Aerobic/F, Plus Anaerobic/F, and Anaerobic Lytic/F

The performance of 3 blood culture bottles (BACTEC Plus Aerobic/F, Plus Anaerobic/F, and Anaerobic Lytic/F) were analyzed with clinical specimens collected from 688 Emergency Department patients. A total of 270 strains belonging to 33 species were identified, with E. coli and S. aureus as the most frequently detected. Overall recovery rate (RR) of bacteria and yeast was equivalent in the Plus Aerobic/F vials (208 of 270 isolates; 77.0%) and Anaerobic Lytic/F vials (206 isolates; 76.3%) and significantly better than in the Plus Anaerobic/F vials (189 isolates; 70.0%). Median time to detection (TTD) was earliest with the Anaerobic Lytic/F vials (12.0h) compared with the Plus Aerobic/F (14.6h) and Plus Anaerobic/F vials (15.4h). Positivity rate (PR) was similar for Anaerobic Lytic/F vials (76.9%) and Plus Aerobic/F vials (76.5%), but better if compared with Plus Anaerobic/F vials (69.4%). The PR and TTD for the combination of Plus Aerobic/F with Anaerobic Lytic/F (94.5% and 12.3h, respectively) was significantly better than with Plus Aerobic/F with Plus Anaerobic/F (87.8% and 14.1h).

Controlled clinical comparison of BACTEC plus anaerobic/F to standard anaerobic/F as the anaerobic companion bottle to plus aerobic/F medium for culturing blood from adults

To determine the optimal anaerobic companion bottle to pair with BACTEC Plus Aerobic/F medium for recovery of pathogenic microorganisms from adult patients with bacteremia and fungemia, we compared Plus Anaerobic/F bottles with Standard Anaerobic/F bottles, each of which was filled with 4 to 6 ml of blood. The two bottles were paired with a Plus Aerobic/F bottle filled with 8 to 12 ml of blood. A total of 14,011 blood culture sets were obtained. Of these, 11,583 sets were received with all three bottles filled adequately and 12,257 were received with both anaerobic bottles filled adequately. Of 818 clinically important isolates detected in one or both adequately filled anaerobic bottles, significantly more staphylococci (P < 0.001), streptococci (P < 0.005), Escherichia coli isolates (P < 0.02), Klebsiella pneumoniae isolates (P < 0.005), and all microorganisms combined (P < 0.001) were detected in Plus Anaerobic/F bottles. In contrast, significantly more anaerobic gram-negative bacilli were detected in Standard Anaerobic/F bottles (P < 0.05). Of 397 unimicrobial episodes of septicemia, 354 were detected with both pairs, 30 were detected with Plus Aerobic/F-Plus Anaerobic/F pairs only, and 13 were detected with Plus Aerobic/F-Standard Anaerobic/F pairs only (P < 0.05). Significantly more episodes of bacteremia caused by members of the family Enterobacteriaceae (P < 0.05) and aerobic and facultative gram-positive bacteria (P < 0.025) were detected with Plus Anaerobic/F bottles only. In a paired-bottle analysis, 810 of 950 isolates were recovered from both pairs, 90 were recovered from Plus Aerobic/F-Plus Anaerobic/F pairs only, and 50 were recovered from Plus Aerobic/F-Standard Anaerobic/F pairs only (P < 0.001). Paired Plus Aerobic/F-Plus Anaerobic/F bottles yielded significantly more staphylococci (P < 0.001), streptococci (P < 0.05), and members of the family Enterobacteriaceae (P <0.001). We conclude that Plus Anaerobic/F bottles detect more microorganisms and episodes of bacteremia and fungemia than Standard Anaerobic/F bottles as companion bottles to Plus Aerobic/F bottles in the BACTEC 9240 blood culture system.

Controlled comparative evaluation of BacT/Alert FAN and ESP 80A aerobic media as means for detecting bacteremia and fungemia

During a one-year period, a total of 6,305 blood cultures were processed in a tertiary-care teaching hospital; 6 to 12 ml of blood was inoculated into both a BacT/Alert Fan aerobic bottle and an ESP 80A aerobic bottle. The FAN aerobic bottle contains an antimicrobial-absorbing material; the 80A aerobic bottle does not. Bottles were processed on their respective continuous-monitoring blood culture instruments for up to five days of incubation. Four hundred thirty-three cultures (6.9%) representing 301 septic episodes in 235 different patients yielded 490 bacteria or yeasts thought to be clinically significant. Two hundred seventy-five of the 433 presumed clinically significant positive cultures (63.5%) representing 195 septic episodes and yielding 301 isolates were positive in both FAN and 80A bottles. One hundred nine significant positive cultures (25.2%) (i.e., cultures positive with an organism judged to be of probable clinical significance) from 70 septic episodes yielded 126 isolates only in FAN bottles. Conversely, the 80A bottle was exclusively positive in 49 instances (11.3%), representing 36 septic episodes and yielding 63 isolates. The higher rates of significant positive blood cultures, numbers of septic episodes documented, and numbers of isolates recovered in FAN bottles versus 80A bottles were all statistically significant (P < 0.05). Enhanced rates of detection of presumed clinically significant isolates in FAN bottles were largely accounted for by Staphylococcus aureus, members of the Enterobacteriaceae, and non-Pseudomonas aeruginosa miscellaneous gram-negative bacilli from patients receiving antimicrobial therapy at the time blood cultures were obtained. Enhanced recovery of one organism group, the beta-hemolytic streptococci, occurred in 80A. With one exception, detection times were essentially equivalent in the two systems. The single exception pertained to streptococci and enterococci, which were recovered significantly faster in 80A bottles. Three hundred thirty-eight of the 6,305 blood cultures evaluated in this study (5.4%) were judged likely to be contaminated. The percentages of probable contaminated cultures were as follows: 26.6% FAN and 80A; 42.3% FAN only; 31.1% 80A only (P < 0.05). Finally, the instrument false-positive rates for the two systems were 0.7% with FAN and 3.0% with 80A (P < 0.05). We conclude that while contamination rates were slightly higher with FAN than with 80A, use of FAN aerobic bottles in conjunction with the BacT/Alert system will yield significantly higher numbers of clinically significant blood culture isolates than 80A bottles and the ESP system. Furthermore, this enhanced detection is most conspicuous in patients receiving antimicrobial therapy at the time blood cultures are performed, probably due to the presence of an antimicrobial-absorbing material in FAN aerobic bottles.

Improved recovery of antibiotic-stressed microorganisms on inclusion of saponin in aerobic blood culture media

The recovery rates and times to detection of microorganisms isolated from two similar blood culture media, one containing saponin, were compared. A total of 2117 blood cultures were analysed in a prototype automated blood culture system. Significantly more gram-positive organisms (P<0.05) and gram-negative organisms (P<0.05), including Enterobacteriaceae (P<0.05) were recovered from the lytic medium. Average time to detection in the lytic medium was 15.8 h, compared to 22.7 h in the other medium (P<0.001). The improved recovery of microorganisms was most pronounced in blood samples obtained from patients being treated with antibiotics at the time of venesection. In vitro experiments on antibiotic affected bacteria confirmed the protective effect of saponin.