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Table 1 Comparison of various identification methods for 4 ATCC reference strains of Lactobacillus, Pediococcus, Leuconostoc, and 26 catalase-negative, gram-positive clinical isolates from 1997–2004 (numbers 1–26) initially identified as Leuconostoc by API 20 STREP or 7 isolates from 2005–2006 expressing high levels of vancomycin resistance (numbers 31–33 and 35–38).

From: Accuracies of Leuconostocphenotypic identification: a comparison of API systems and conventional phenotypic assays

Isolate #-specimen type API 20 STREP (% identity) API 50 CHL (% identity) Gram's staining results ADH LAP MRS PYR Van PCR for Lactobacillus and Leuconostoc Sequencing of 16S rDNA gene (% identity)
Lactobacillus plantarum ATCC 14917* Enterococcus avium (63.2) Lactobacillus plantarum (99.9) B -/- +/+ - -/- R +ve Lactobacillus Lactobacillus plantarum (100)
Lactobacillus pentosus ATCC 8041* Leuconostoc (81.1) Lactococcus lactis ssp lactis 1 (82.5) B -/- +/+ + -/- R +ve Lactobacillus N/A
Pediococcus pentosaceus ATCC 33316* Leuconostoc (39.3) Lactobacillus pentosus (84.3) C +/+ +/+ - -/- R Neg Pediococcus pentosaceus (99.4)
Leuconostoc mesenteroides ATCC 8293 Leuconostoc (96.8) Leuconostoc mesenteroides ssp mesenteroides/dextranicum 1 (95.7) Cb -/- -/- + -/- R +ve Leuconostoc Leuconostoc mesenteroides (99.3)
1-pus* Streptococcus suis biotype I (85.6) Lactobacillus acidophilus (97.4) C-Ch -/+# +/-# - -/- S Neg Streptococcus suis (100)
2-blood* Leuconostoc (99.8) Lactococcus lactis ssp lactis 1 (90.5) Cb +/+ -/- + -/- R Neg N/A
3-corneal discharge Leuconostoc (97.9) Lactobacillus brevis 3 (98.8) C-Ch -/- -/- + -/- R +ve Leuconostoc N/A
4-ascitic fluid Leuconostoc (99.9) Leuconostoc mesenteroides spp mesenteroides/dextranicum 2 (99.9) C -/- -/- + -/- R +ve Leuconostoc Leuconostoc lactis or garlicum (99.5)
5-ascitic fluid* Leuconostoc (93.6) Lactobacillus acidophilus 1 (85.1) Cb +/+ -/- + -/- R Neg N/A
6-blood Leuconostoc (95.4) Leuconostoc lactis (96.0) Cb -/- -/- + -/- R +ve Leuconostoc Leuconostoc lactis or garlicum (99.6)
7-blood Leuconostoc (68.5) Leuconostoc lactis (92.0) Cb -/- -/- + -/- R Neg N/A
8-blood* Streptococcus mitis 1 (81.1) Lactobacillus acidophilus (92.1) Cb -/- +/-# - -/- S Neg N/A
9-blood* Leuconostoc (97.2) Leuconostoc mesenteroides spp cremoris (99.9) Cb +/+ -/- + -/- R Neg Weissella cibaria (100)
10-blood* Abiotrophia adiacens (46.9) Aerococcus viridans 2 (27.5) Lactobacillus delbrueckii spp delbrueckii (78.1) Cb -/- -/- - -/- S Neg N/A
11-blood* Leuconostoc (92.2) Lactobacillus acidophilus (72.5) C-Ch -/- -/+# - -/- S Neg N/A
12-ascitic fluid* Lactococcus lactis spp cremoris (47.2) Leuconostoc (45.1) Lactobacillus salivarius (99.9) C-Ch -/- -/- - -/- R +ve Lactobacillus N/A
13-blood* Streptococcus sanguis (49.2) other streptococci (48.5) Leuconostoc mesenteroides spp cremoris (98.7) Cb -/- +/-# - -/- S Neg N/A
14-blood* Leuconostoc (39.0) Lactococcus lactis ssp cremoris (37.9) Lactobacillus acidophilus 1 (88.2) C -/- -/+# - -/- S Neg Streptococcus pasteurianus (99.9)
15-blood* Streptococcus bovis (64.8) Leuconostoc lactis (87.9) Cb -/- +/-# - -/- R Neg Weissella confusa (99.9)
16-blood* Enterococcus faecium (98.7) Lactobacillus plantarum 1 (98.6) Cb +/+ +/-# - +/-# S Neg Enterococcus faecium (99.9)
17-blood* Aerococcus viridans (62.6) Lactobacillus delbrueckii spp delbruekii (95.5) Cb -/- -/- - -/- S Neg Actinomyces odontolyticus (98.9)
18-brain abscess* Streptococcus constellatus (99.9) Lactobacillus acidophilus (82.1) C-Ch +/+ +/-# + -/- S Neg Streptococcus anginosus or constellatus (99.7)
19-blood* Streptococcus bovis biotype II (64.8) Lactobacillus acidophilus 1 (98.1) C-Ch -/- +/-# + -/- S Neg Streptococcus constellatus (99.7)
20-blood* Leuconostoc (92.2) Weissella viridescens (99.8) C -/+# -/+# - -/- R Neg Weissella viridescens (99.9)
21-lung swab* Leuconostoc (99.9) Lactobacillus acidophilus (78.4) Cb +/+ -/- + -/- R Neg Weissella cibaria (100)
22-bone* Leuconostoc (99.6) Lactobacillus coprophilus (96.9) Cb +/+ -/- + -/- R Neg Weissella confusa (99.61)
23-NR* Leuconostoc (98.8) Lactobacillus coprophilus (96.9) Cb +/+ -/+# - -/+# R Neg Weissella confusa (100)
24-NR* Aerococcus viridans (48.5) Lactococcus lactis ssp cremoris (41.6) Leuconostoc mesenteroides spp cremoris (94.7) C-Ch -/+# +/-# - -/- S Neg Streptococcus anginosus (99.9)
25-pus* Streptococcus constellatus (99.9) Lactobacillus delbrueckii (80.4) C-Ch +/+ +/-# - -/- S Neg Streptococcus constellatus (99.7)
26-duodenal* content Leuconostoc (89.9) Lactobacillus salivarius (99.9) Cb -/- +/-# - -/- R +ve Lactobacillus Lactobacillus salivarius (100)
31-urine* Leuconostoc (99.7) Lactobacillus acidophilus 1 (49.5) Cb +/+ -/- + -/- R Neg Weissella cibaria (99.5)
32-gastric content Leuconostoc (99.4) Leuconostoc lactis (95.3) C-Ch -/- -/- + -/- R +ve Leuconostoc Leuconostoc garlicum or lactis (99.2)
33-tissue biopsy Leuconostoc (99.9) Leuconostoc mesenteroides spp mesenteroides/dextranicum2 (99.9) C-Ch -/- -/- + -/- R +ve Leuconostoc Leuconostoc garlicum or lactis (99.6)
35-ascitic fluid* Leuconostoc (65.8) Pediococcus pentosaceus 1 (63.6) C -/- +/+ - -/- R neg Pediococcus stilesii (91.5)
36-blood Leuconostoc (92.8) Lactobacillus collinoides or fermentum 1 (98.3) Cb -/- -/- + -/- R neg Weissella confusa (99.9)
37-pleural fluid* Leuconostoc (69.2) Lactobacillus salivarius (99.9) Cb -/- +/+ - -/- R neg N/A
38-tissue biopsy* Leuconostoc (82.7) Pediococcus pentosaceus (99.9) C +/+ +/+ - -/- R neg Pediococcus pentosaceus (98.2)
  1. ADH = arginine dihydrolase, LAP = leucine arylamidase, MRS = gas production in MRS broth, PYR = pyrrolidonyl arylamidase test, Van = vancomycin MIC; S = MIC in the range of 0.5–1.0 μg/ml; R = MIC ≥ 256 μg/ml NR = no record available, N/A = result not available. ADH, LAP, and PYR test results listed are from API 20 STREP and from conventional phenotypic assays, respectively. Discordant results between the two methods are marked with #. In Gram's staining results column, C = cocci, Cb = coccobacillary form, C-Ch = cocci in chain, B = bacilli. * = phenotype(s) opposite to what is (are) expected for Leuconostoc in our criteria above. API 20 STREP identifies Leuconostoc at the genus level only. PCR results are indicated as positive for Leuconostoc or Lactobacillus or negative for both protocols. 16S rDNA sequencing results are indicated together with % similarity to the closest GenBank sequences.