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Journal of Clinical Microbiology, June 2009, p. 1923-1926, Vol. 47, No. 6
0095-1137/09/$08.00+0     doi:10.1128/JCM.01778-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Evaluation of the New Vitek 2 ANC Card for Identification of Medically Relevant Anaerobic Bacteria

Francine Mory,¹ Corentine Alauzet,¹ Céline Matuszeswski,¹ Philippe Riegel,² and Alain Lozniewski^1*

Laboratoire de Bactériologie, Centre Hospitalier Universitaire, Nancy,¹ Laboratoire de Bactériologie, Hôpitaux Universitaires, Strasbourg, France²

Received 15 September 2008/ Returned for modification 25 November 2008/ Accepted 14 April 2009

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Of 261 anaerobic clinical isolates tested with the new Vitek 2 ANC card, 257 (98.5%) were correctly identified at the genus level. Among the 251 strains for which identification at the species level is possible with regard to the ANC database, 217 (86.5%) were correctly identified at the species level. Two strains (0.8%) were not identified, and eight were misidentified (3.1%). Of the 21 strains (8.1%) with low-level discrimination results, 14 were correctly identified at the species level by using the recommended additional tests. This system is a satisfactory new automated tool for the rapid identification of most anaerobic bacteria isolated in clinical laboratories.

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Accurate identification of numerous bacterial species is nowadays possible with highly automated systems that are increasingly used in clinical laboratories because of their cost effectiveness, practicability, and ability to provide rapid turnaround time. It is now well established that anaerobes may be involved in numerous infections, including severe infections (8, 12). Until recently, however, identification of anaerobes in clinical laboratories relied mainly on the use of time-consuming and labor-intensive conventional methods or of manual commercial systems, the performances of which are quite variable at the species level (3, 5, 7, 10, 13, 14).

bioMérieux (Marcy, France) has recently developed a new colorimetric identification card (ANC card) which, in conjunction with the Vitek 2 system, permits this automated and widely distributed identification system to identify 63 taxa, including 49 taxa of anaerobic bacteria belonging to the genera Actinomyces, Bacteroides, Bifidobacterium, Clostridium, Collinsella, Eggerthella, Eubacterium, Finegoldia, Fusobacterium, Parabacteroides, Parvimonas, Peptoniphilus, Peptostreptococcus, Prevotella, Propionibacterium, and Veillonella. It is noteworthy that this system identifies Bifidobacterium spp. and Veillonella spp. only at the genus level. In the present study, the ANC card was evaluated for the identification of anaerobes in a routine clinical laboratory.

A total of 261 nonconsecutive clinical isolates belonging to 43 medically relevant taxa included in the ANC database and collected over a 1-year period in our laboratory were used. Strains were selected to represent the distribution of anaerobic isolates recovered annually in our laboratory. These organisms have been previously identified using conventional reference identification methods (6). The sources of the isolates included blood (n = 102), central nervous system samples (n = 9), pleuropulmonary samples (n = 11), intra-abdominal samples (n = 54), soft tissue samples (n = 29), osteoarticular samples (n = 14), urogenital samples (n = 11), stool samples (n = 20), and various other samples (n = 11). Actinomyces israelii ATCC 12102, Propionibacterium acnes ATCC 6919, and Clostridium difficile ATCC 9689 were also investigated. Bacteroides ovatus ATCC BAA-1296, Bacteroides vulgatus ATCC 8482, Parabacteroides distasonis ATCC BAA-1295, Clostridium septicum ATCC 12464, and Clostridium sordellii ATCC 9714 were used as quality controls and checked every month during the evaluation. Isolates were stored frozen, except for the available clinical isolates that were recovered directly from clinical specimens. Prior to testing, strains were subcultured twice onto Columbia sheep blood agar (bioMérieux) in an anaerobic atmosphere at 35°C. Inoculum preparation, incubation (approximately 6 h), and reading of the test panels were performed according to the manufacturer's instructions. Data were analyzed using the Vitek 2 ANC system software, which permits categorization of the results into four groups: correct identification (i.e., unambiguous identification [given as excellent, very good, good, or acceptable] to the species level or to the genus level for Bifidobacterium spp. and Veillonella spp. strains), low level of discrimination (low level of discrimination between two or more species, including the correct species, requiring additional tests), misidentification (the genus or the species identified with the ANC card was different from that identified using the reference methods), and no identification (strains without results). In the case of discrepancy between the identification obtained with the routine method and that obtained with the Vitek 2 system, 16S rRNA gene sequencing was used for genetic identification (1).

The quality control strains were always correctly identified, with the test results being reproducible and in accordance with those expected from the database previously established by bioMérieux. The other three reference strains tested were correctly identified at the species level. Among the 261 routine clinical isolates tested, 257 (including all Bifidobacterium spp. and Veillonella spp. strains [n = 10], which can only be identified at the genus level with the ANC card) of 261 (98.5%) were correctly identified at the genus level and 217 of 251 (86.5%) at the species level without performing additional tests (Table 1). Two strains (0.8%) were not identified, and eight (3.1%) were misidentified (Table 2). Of the 121 gram-negative strains, 114 (94.3%) were correctly identified without further testing and 3 (2.5%), which gave low-level discrimination results, were identified with additional tests (Table 3). Among the 140 gram-positive isolates, 80.7% (100% of the cocci, 95.7% of the nonsporeforming bacilli, and 64.3% of the clostridia) were correctly identified at the species level without further testing. Of the 21 Clostridium species that gave low-level-discrimination identifications, 14 were correctly identified by using recommended additional tests, while 7 (5 C. butyricum and 2 C. difficile) could be easily identified by using other supplementary tests (Table 3). Indeed, a simple Gram stain permitted us to differentiate C. butyricum (gram-positive straight rod with subterminal spore) from C. clostridioforme (cigar-shaped gram-negative rod), while C. difficile could be differentiated from C. subterminale by determining the fermentation of glucose and mannitol. Thus, the use of additional tests other than those recommended by the manufacturer permitted an increase in the rate of correct identification of clostridia from 84.3% to 94.3%.

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TABLE 1. Identification of 261 clinical anaerobic isolates with the Vitek 2 ANC card

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TABLE 2. Strains misidentified by the Vitek 2 ANC systema

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TABLE 3. Strains identified with a low level of discrimination by the Vitek 2 ANC systema

Identification systems should be able to correctly identify, overall, 90% of the organisms isolated in routine laboratories, while commonly isolated organisms should be identified with at least 95% accuracy (2). This cutoff was achieved at the genus level without the need for additional tests for all strains tested. With regard to the species level, an accuracy rate of at least 95% was achieved without the need for additional tests for gram-positive cocci, nonsporeforming bacilli, and species belonging to the genus Bacteroides. Satisfactory results were also achieved for the identification of Fusobacterium spp., considering that 94.7% of the strains tested were correctly identified at the species level without further testing and that the only strain which was identified with a low level of discrimination could be correctly identified after performing a simple Gram stain as recommended by the manufacturer. Slightly less satisfactory results were observed for the identification of Prevotella species. Indeed, for these latter, a correct identification rate of 91.7% was achieved after the application of additional tests. Overall, these results are comparable to those recently reported by other authors evaluating the Vitek 2 ANC system (11, 15). As in those studies, difficulties were encountered in the present study in identifying clostridia species, except for C. perfringens.

When taking into account taxa included in the databases of all identification systems, including that of the Vitek 2 ANC system, as well as taxonomic changes, the performance obtained with this system still compares favorably overall to those previously reported for other commercialized identification systems. Indeed, among these latter, the API 20 A system, which necessitates an anaerobic incubation of up to 48 h, is best suited for the identification of only saccharolytic, rapidly growing organisms, such as those belonging to the Bacteroides fragilis group (2, 6). Among rapid identification systems, accuracies as high as 95% were only reported, with regard to the species level and without the application of additional tests, with the Rapid ID 32A system for the identification of gram-positive cocci, with the Rapid ANA II system for the identification of these organisms and Prevotella spp., and with the BBL Crystal ANR system for the identification of Fusobacterium spp. (3, 4, 7). Moreover, even if the use of additional tests has been shown to increase the rates of correct identification with these systems, the performances achieved are variable, depending on the species tested and the study (5, 7, 9, 10).

Thus, our results indicate that the Vitek 2 ANC system is a simple, rapid, and satisfactory method for the identification of anaerobes in a clinical microbiology laboratory. This system is not yet perfect, particularly with regard to the identification of clostridia at the species level, but represents, overall, an improvement over other available systems used for the identification of the most frequently encountered anaerobes. In the present study, strains were subcultured twice prior to testing. Considering that this step is not performed routinely, further studies are needed to evaluate whether the Vitek 2 ANC system performs as well as in the present study when strains from primary isolation plates are analyzed.

 
bioMérieux provided the study materials.

We thank Monique Chaon, Céline Guichou and Laurence Genet for their technical assistance and Sonia Chatellier and Romuald Courtade for their support during the evaluation.

 
* Corresponding author. Mailing address: Laboratoire de Bactériologie, Hôpital Central, 29 Avenue du Maréchal de Lattre de Tassigny, 54035 Nancy Cedex, France. Phone: 33 3 83 85 18 14. Fax: 33 3 83 85 26 73. E-mail: a.lozniewski{at}chu-nancy.fr

Published ahead of print on 22 April 2009.

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1
1. Alauzet, C., F. Mory, J. P. Carlier, H. Marchandin, E. Jumas-Bilak, and A. Lozniewski. 2007. Prevotella nanceiensis sp. nov., isolated from human clinical samples. Int. J. Syst. Evol. Microbiol. 57:2216-2220.[Abstract/Free Full Text]
2
2. Carroll, K. C., and M. P. Weinstein. 2007. Manual and automated systems for detection and identification of microorganisms, p. 192-217. In P. R. Murray, E. J. Baron, J. H. Jorgensen, M. L. Landry, and M. A. Pfaller (ed.), Manual of clinical microbiology, 9th ed. ASM Press, Washington, DC.
3
3. Cavallaro, J. J., L. S. Wiggs, and J. M. Miller. 1997. Evaluation of the BBL Crystal Anaerobe identification system. J. Clin. Microbiol. 35:3186-3191.[Abstract/Free Full Text]
4
4. Celig, D. M., and P. C. Schreckenberger. 1991. Clinical evaluation of the RapID-ANA II panel for identification of anaerobic bacteria. J. Clin. Microbiol. 29:457-462.[Abstract/Free Full Text]
5
5. Downes, J., A. King, J. Hardy, and I. Phillips. 1999. Evaluation of the Rapid ID 32A system for the identification of anaerobic gram-negative bacilli, excluding Bacteroides fragilis group. Clin. Microbiol. Infect. 5:319-326.[Medline]
6
6. Jousimies-Somer, H. R., P. Summanen, E. J. Baron, D. M. Citron, H. M. Wexler, and S. M. Finegold (ed.). 2002. Wadsworth-KTL anaerobic bacteriology manual, 6th ed. Star Publishing Company, Belmont, CA.
7
7. Kitch, T. T., and P. C. Appelbaum. 1989. Accuracy and reproducibility of the 4-hour ATB 32A method for anaerobe identification. J. Clin. Microbiol. 27:2509-2513.[Abstract/Free Full Text]
8
8. Lassmann, B., D. R. Gustafson, C. M. Wood, and J. E. Rosenblatt. 2007. Reemergence of anaerobic bacteremia. Clin. Infect. Dis. 44:895-900.[CrossRef][Medline]
9
9. Looney, W. J., A. J. C. Gallusser, and H. K. Modde. 1990. Evaluation of the ATB 32 A system for identification of anaerobic bacteria isolated from clinical specimens. J. Clin. Microbiol. 28:1519-1524.[Abstract/Free Full Text]
10
10. Marler, L. M., J. A. Siders, L. C. Wolters, Y. Petttigrew, B. L. Skitt, and S. D. Allen. 1991. Evaluation of the new RapID-ANA II system for the identification of clinical anaerobic isolates. J. Clin. Microbiol. 29:874-878.[Abstract/Free Full Text]
11
11. Rennie, R. P., C. Brosnikoff, L. A. Turnbull, L. B. Reller, S. Mirrett, W. Janda, K. Ristow, and A. Krilcich. 2008. Multicenter evaluation of the Vitek 2 anaerobe and Corynebacterium identification card. J. Clin. Microbiol. 46:2646-2651.[Abstract/Free Full Text]
12
12. Rosenblatt, J. E. 1997. Can we afford to do anaerobic cultures and identification? A positive point of view. Clin. Infect. Dis. 25(Suppl. 2):S127-S131.[CrossRef][Medline]
13
13. Schreckenberger, P. C., D. M. Celig, and W. M. Janda. 1988. Clinical evaluation of the Vitek ANI card for identification of anaerobic bacteria. J. Clin. Microbiol. 26:225-230.[Abstract/Free Full Text]
14
14. Summanen, P., and H. Jousimies-Somer. 1988. Comparative evaluation of Rapid ANA and API-20A for identification of anaerobic bacteria. Eur. J. Clin. Microbiol. Infect. Dis. 7:771-775.[CrossRef][Medline]
15
15. Wilkey, K., J. Brinkmeyer, J. Colon-Reveles, N. Moss, J. Mills, E. Mathias, E. Fossman, D. Pincus, J. Clarridge III, C. Jitjai, A. McLaughlin, and S. Chatellier. 2006. Rapid automated identification of anaerobic and coryneform species with the new Vitek 2 ANC card, abstr. C-013. Abstr. 106th Gen. Meet. Am. Soc. Microbiol. American Society for Microbiology, Washington, DC.

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Journal of Clinical Microbiology, June 2009, p. 1923-1926, Vol. 47, No. 6
0095-1137/09/$08.00+0     doi:10.1128/JCM.01778-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services E-mail this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Mory, F. Articles by Lozniewski, A. Search for Related Content PubMed PubMed Citation Articles by Mory, F. Articles by Lozniewski, A.