TABLE 5.
Isolate identities furnished by direct MALDI-TOF MS analysis of BacT/Alert and Bactec BC brothsa
| Microorganism(s) | BacT/Alert bottles (n = 188) |
Bactec bottles (n = 175) |
P | ||
|---|---|---|---|---|---|
| No. of standard method IDsb | Correct IDs by direct broth analysisc | No. of standard method IDsb | Correct IDs by direct broth analysisc | ||
| Monomicrobial cultures | 178 | 167 (93.8) | 165 | 154 (93.3) | NS |
| Gram-negative | 81 | 79 (97.5) | 83 | 81 (97.6) | NS |
| Bacteroides fragilis | 5 | 5 | 5 | 5 | NA |
| Escherichia coli | 35 | 35 (100) | 34 | 34 (100) | NS |
| Klebsiella pneumoniae | 18 | 18 (100) | 20 | 20 (100) | NS |
| Morganella morganii | 4 | 3 | 3 | 3 | NA |
| Proteus mirabilis | 0 | 0 | 1 | 0 | NA |
| Pseudomonas aeruginosa | 19 | 18 (94.7) | 20 | 19 (95) | NS |
| Gram-positive | 90 | 83 (92.2) | 74 | 67 (90.5) | NS |
| Enterococcus faecalis | 9 | 8 (88.9) | 4 | 4 | NA |
| Enterococcus faecium | 1 | 1 | 1 | 0 | NA |
| Staphylococcus aureus | 35 | 35 (100) | 31 | 31 (100) | NS |
| Staphylococcus epidermidis | 32 | 28 (87.5) | 27 | 24 (88.9) | NS |
| Staphylococcus haemolyticus | 2 | 2 | 2 | 1 | NA |
| Staphylococcus hominis | 1 | 1 | 1 | 1 | NA |
| Streptococcus anginosus | 5 | 3 | 3 | 1 | NA |
| Streptococcus constellatus | 1 | 1 | 1 | 1 | NA |
| Streptococcus pneumoniae | 4 | 4 | 3 | 3 | NA |
| Yeasts | 7 | 5 (71.4) | 8 | 6 (75) | NS |
| Candida albicans | 4 | 3 | 6 | 5 | NA |
| Candida parapsilosis | 1 | 1 | 0 | 0 | NA |
| Candida tropicalis | 2 | 1 | 2 | 1 | NA |
| Polymicrobial cultures | 10/10 | 6/3 (60/30) | 10/10 | 6/3 (60/30) | NS |
| Staphylococcus haemolyticus/Proteus mirabilis | 1/1 | 0/1 | 1/1 | 0/1 | NA |
| Pseudomonas aeruginosa/Proteus mirabilis | 1/1 | 1/0 | 2/2 | 2/0 | NA |
| Escherichia coli/Klebsiella pneumoniae | 4/4 | 4/2 | 3/3 | 3/2 | NA |
| Pseudomonas aeruginosa/Stenotrophomonas maltophilia | 1/1 | 1/0 | 1/1 | 1/0 | NA |
| Parvimonas micra/Campylobacter rectus | 1/1 | 0/0 | 1/1 | 0/0 | NA |
| Bacteroides fragilis/Streptococcus constellatus | 1/1 | 0/0 | 1/1 | 0/0 | NA |
| Klebsiella pneumoniae/Candida albicans | 1/1 | 0/0 | 1/1 | 0/0 | NA |
| Total | 198 | 176 (88.9) | 185 | 163 (88.1) | NS |
BacT/Alert broths (FA Plus and FN Plus); Bactec broths (Aerobic/F and Anaerobic/FN). Abbreviations: BC, blood culture; ID, identification; MALDI-TOF MS, matrix-assisted laser desorption ionization–time of flight mass spectrometry; NS, not significant. NA, not applicable. Percentages were not calculated when ≤5 microorganisms were isolated.
Standard method, microscopic examination, routine subculture, and MALDI-TOF MS analysis of colony samples (supplemented when necessary with additional biochemical methods and/or 16S rRNA gene sequencing).
No. (%) of identifications (IDs) furnished by direct Bruker MALDI BioTyper analysis of BC broths that were concordant with standard IDs at the species level. (Percentages are not reported for individual species recovered from polymicrobial cultures.)