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Journal of Clinical Microbiology, March 2003, p. 1289-1294, Vol. 41, No. 3
0095-1137/03/$08.00+0 DOI: 10.1128/JCM.41.3.1289-1294.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Jean G. Jordan,1 Leonard W. Mayer,1 Shadi M. Rassouli,1 Winfred Barchet,1 Cindy Munro,2 L. Shuttleworth,2 and Kathryn Bernard2
Meningitis and Special Pathogens Branch, Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333,1 Special Bacteriology Laboratory, National Microbiology Laboratory, Health Canada, Winnipeg, Manitoba, Canada R3E 3R22
Received 29 August 2002/ Returned for modification 12 November 2002/ Accepted 9 December 2002
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Bacterial strains. The EO-2 strains studied, along with their sources and geographical origins, are presented in Table 1. The type strains of Psychrobacter immobilis (ATCC 43116), Paracoccus alcaliphilus (ATCC 51199), P. aminophilus (ATCC 49673), P. denitrificans (ATCC 17741), P. solventivorans (ATCC 700252), and P. versutus (ATCC 25364) were obtained from the American Type Culture Collection. The strains studied were cultured by using the methods of the SBRL of the CDC (15).
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TABLE 1. Sources of P. yeeii isolates and demographics of and clinical information on patients from whom they were isolated
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CFA analysis. Cells were saponified, and the liberated fatty acids were methylated and analyzed by capillary gas-liquid chromatography (GLC) (15). CFA profiles were identified by using a commercially available system (MIDI, Newark, Del.). The identification of fatty acids and the determination of double-bond positions in monounsaturated acids were accomplished by GLC and GLC-mass spectrometry.
DNA relatedness and determination of percent G+C. Cells were harvested and lysed, and the DNA was isolated and purified according to the method of Brenner et al. (2). DNA from strain G1212 was labeled with [32P]dCTP by using a commercial nick translation kit (Invitrogen Life Technologies, Carlsbad, Calif.) and tested for reassociation to unlabeled DNA from the same strain (homologous reaction) as well as to DNAs from other EO-2 strains and the type strains (heterologous reactions). The G+C content of G1212 was determined to be 62%; therefore, 65°C was chosen as the optimal reassociation temperature. Relative binding ratios (percent heterologous DNAs bound to hydroxyapatite to percent homologous DNA bound to hydroxyapatite, multiplied by 100) and percent divergence (percentage of unpaired bases in related DNA sequences) were calculated as described by Brenner et al. (2). Divergence was calculated to the nearest 0.5%, with each decrease of 1°C in the thermal stability of a heterologous DNA duplex due to an increase of approximately 1% in the percentage of unpaired bases within related DNAs (1). All reactions were done in duplicate at the optimal temperature of 65°C. The percent G+C was determined for strains G1212, G9205, and H1430 by the thermal denaturation method of Mandel et al. (7).
16S rRNA gene sequencing.
Purified genomic DNA was diluted to 1 µg ml-1 in sterile water. Diluted DNA (10 µl) was used in a 100-µl PCR mixture containing 200 µM deoxynucleoside triphosphates, 1 mM MgCl2, 1X PCR buffer II (Perkin-Elmer, Foster City, Calif.), 0.1 µM FD1 primer, 0.1 µM RD1 primer, and 2.5 U of Expand High-Fidelity PCR System Taq DNA polymerase mixture (Perkin-Elmer). The primers FD1 and RD1 were originally described by Weisburg et al. as suitable for amplifying the 16S rRNA genes of many eubacteria (14). The parameters for amplification were 94°C for 5 min, 35 cycles of 15 s at 94°C, 15 s at 50°C, 1.5 min at 72°C, and an extension for 5 min at 72°C before cooling to 4°C. The results of the PCR were checked by running 10 µl of each reaction mixture on a 1.2% (wt/vol) agarose gel. The amplicon was then purified and concentrated by using a Qia Quick PCR purification kit from Qiagen (Valencia, Calif.). Approximately 60 ng (
4 µl) of PCR product was used for each sequencing reaction. The sequencing reaction mixture consisted of DNA, 8 µl of ABI PRISM dye terminator cycle sequencing ready reaction kit (Perkin-Elmer), and 3.2 pmol of primer; sterile water was added to a final volume of 20 µl. The primer set used for sequencing was derived from primers designed by Stackebrandt and Charfreitag (10). The thermocycler conditions were according to the manufacturer's instructions for the cycle sequencing kit. Amplifications were performed on a Perkin-Elmer 9700 thermocycler. The extension products from each reaction were purified through a Centrisep column (Princeton Separations, Adelphia, N.J.) and dried in a vacuum centrifuge for 20 min. The sequencing reaction products were resolved on a 4.2% (wt/vol) acrylamide-8 M urea gel electrophoresed on an ABI 377 automated sequencer (Perkin-Elmer). The sequence data were edited and compiled with the Wisconsin Sequence Analysis Package (Genetics Computer Group, Madison, Wis.). The 16S rRNA gene sequences were aligned by using the PILEUP program. The multiple sequence alignments were edited manually. The edited alignments were used with TREECON (Version 1.3b; Yves Van de Peer) to derive a phylogenetic dendrogram by using the nucleotide substitution model of Jukes and Cantor (5) and the neighbor-joining method of Saitou and Nei (9).
The CDC group EO-2 includes 13 similar human clinical isolates received from seven different states in the United States and from three different provinces in Canada. Two of the isolates were from ears, two were from ankles, and one each was from blood, cerebrospinal fluid, eye, neck incision drainage, bile, abdominal dialysate, leg lesion, toe, and skin (Table 1). The source of these organisms and their route of entry into the body are not known. Since all of the EO-2 isolates known to date were submitted from clinical sources, the natural habitat (or habitats) of this species has not yet been identified. The geographic information available indicates that these strains may be isolated from patients in a wide variety of locations, ranging from Hawaii to Canada. Limited clinical information was available on patients, and no common underlying syndrome was indicated; however, wounds were the most frequent condition. The ages of the patients ranged from 6 weeks to 77 years; 8 of 13 patients were female and the remaining patients were male.
Cells grown on heart infusion agar at 35°C had forms ranging from coccoid or diplococcoid to coccobacillary, often appearing vacuolated or peripherally stained (O shape), and stained gram negative, sometimes appearing gram variable (15). All grew well on blood agar that was incubated aerobically or in a candle jar under CO2 atmosphere for 18 to 24 h at 35°C, and the growth was frequently mucoid to extremely mucoid. No growth was obtained under anaerobic conditions. Isolated colonies were usually punctate. No distinct hemolytic reaction was observed after overnight incubation. The phenotypic characteristics of the CDC group EO-2 are given in Table 2. All strains were positive for oxidase, urease, citrate utilization (sometimes delayed 3 to 7 days), acid production from xylose and lactose (often delayed), growth on MacConkey agar, and growth at 35°C. All except one strain produced acid from glucose and reduced nitrate. All strains were negative for motility, indole, lysine decarboxylase, H2S (triple sugar iron [TSI] butt), insoluble pigment, production of gas from glucose, hydrolysis of esculin and gelatin, and acid production from sucrose and TSI.
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TABLE 2. Phenotypic characteristics of P. yeeiia
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TABLE 3. DNA relatedness and percent 16S similarity between P. yeeii, Psychrobacter immobilis, P. alcaliphilus, P. aminophilus, P. denitrificans, P. solventivorans, and P. versutus
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7c (71%) and small amounts of 3-OH-10:0 and 3-OH-14:0. It also contains moderate amounts of 16:0 (13%) and small amounts of 12:1
7c, 17:0, 18:2, 18:1
9c, and 18:0. The overall CFA profile of EO-2 is similar to that of Paracoccus species (Table 4). Furthermore, the overall CFA profile of the EO-2 group is most like that of the CFA group including Methylobacterium species, Roseomonas fauriae, and Roseomonas genomospecies 6 except for the presence of 3-OH-10:0 (3% versus 0%) (8, 12, 15). EO-2 has about 3% of 12:1
7, which is absent in all Methylobacterium species and all Roseomonas species and three genomospecies (8, 12, 15). In addition, EO-2 contains ubiquinone with eight isoprene units (Q-8) as the major isoprenolog (8). All the Paracoccus species examined to date contain ubiquinone-10 (Q-10) as the respiratory quinone (6). This difference indicates that CDC group EO-2 can be distinguished from related organisms on the basis of its isoprenoid quinone content. |
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TABLE 4. CFA compositions of P. yeeii, P. alcaliphilus, P. aminophilius, P. denitrificans, P. solventivorans, and P. versutusa
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FIG. 1. Phylogenetic tree based on 1,450-bp 16S rRNA gene sequences and showing the position of P. yeeii strains. The tree was rooted by using Psychrobacter immobilis as the outgroup. Bootstrap analysis was done with 100 resamplings; bootstrap values are indicated at some branch points. The scale bar represents 2% difference in DNA sequences. The accession numbers for the sequences used in the study are shown.
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The assignment of the CDC group EO-2 to the genus Paracoccus as a new species, P. yeeii, is supported by phenotypic and phylogenetic considerations. The cellular morphology and basic biochemical profile of these organisms are consistent with the reference description of this genus. The CFA profile of the EO-2 group is also similar to CFA profiles of other Paracoccus type strains studied. Comparative analysis of 16S rRNA gene sequences of eight members of EO-2 strains places all strains analyzed in a highly related cluster within the Paracoccus region of the phylogenetic tree. Whole chromosomal DNA-DNA hybridization analysis with Paracoccus type strains indicates all EO-2 strains studied to be related at the species level (>70% relatedness under stringent conditions). No other type strains of Paracoccus species studied produced DNA relatedness values of greater than 54% when compared with the proposed type strain of the new species (G1212, ATCC BAA-599, CCUG 46822). The description of this group as a new species of the genus Paracoccus is as follows:
P. yeeii sp. nov. (yeeii'. N.L. gen. m. yeeii, in recognition of the contributions of Robert B. Yee, University of Pittsburgh Graduate School of Public Health, to the characterization of pathogenic bacteria [11, 16, 17]). Gram negative (sometimes appearing gram variable), non-spore forming, nonmotile, with coccoid or diplococcoid to coccobacillary forms, often appearing vacuolated or peripherally stained (O shape). Frequently mucoid to extremely mucoid, nonpigmented colonies on heart infusion agar with 5% rabbit blood at 35°C. All strains were positive for oxidase, urease, citrate utilization, lactose, growth on MacConkey agar, and acid production from xylose. All except one strain produced acid from glucose and reduced nitrate. All strains were negative for motility, indole, lysine decarboxylase, acid production from sucrose, and hydrolysis of esculin and gelatin. All strains shared similar CFA profiles characterized by major amounts of 18:1
7c, moderate amounts of 16:0, and minor amounts of 3-OH-10, 12:1
7c, 3-OH-14, 17:0, 18:2, 18:1
9c, and 18:0. Strain G1212, isolated in Pennsylvania from abdominal dialysate, is the type strain of the species and has been designated in the American Type Culture Collection as ATCC BAA-599 and in the Culture Collection University of Goteborg as CCUG 46822. The percent G+C content of the DNA for G1212 was 62%.
Nucleotide sequence accession number. The newly determined 16S rRNA gene sequence of G1212 has been submitted to GenBank and assigned the accession number AY014173.
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