Skip to main content
PMC home page
Journal of Clinical Microbiology logoLink to Journal of Clinical Microbiology
. 1996 Jul;34(7):1788–1793. doi: 10.1128/jcm.34.7.1788-1793.1996

Evaluation of CHROMagar Orientation for differentiation and presumptive identification of gram-negative bacilli and Enterococcus species.

J Merlino 1, S Siarakas 1, G J Robertson 1, G R Funnell 1, T Gottlieb 1, R Bradbury 1
PMCID: PMC229116  PMID: 8784591

Abstract

A new chromogenic plate medium, CHROMagar Orientation, was evaluated for use in the differentiation and presumptive identification of gram-negative bacilli and Enterococcus species by a multipoint inoculation (replicator) technique. In this study, 1,404 gram-negative bacilli and 74 enterococcal isolates were tested on CHROMagar Orientation. Six control American Type Culture Collection strains were also included with the testing to ensure quality control of the media. Of the Escherichia coli isolates (n = 588) tested, 99.3% produced a pink-to-red color. Only in four isolates that were O-nitrophenyl-beta-D-galactopyranoside (ONPG) negative did this result differ. Proteus mirabilis and P. vulgaris were well differentiated on this medium. P. mirabilis (n = 184) produced a clear colony with diffusible brown pigment around the periphery. By contrast, 15 of 16 P. vulgaris isolates produced bluish-green colonies with a slight brown background. All Aeromonas hydrophila isolates (n = 26) tested produced clear to pink colonies at 35 to 37 degrees C. This colony color changed to blue after 2 to 3 h of incubation at room temperature. A. hydrophila exhibited stronger color and better growth at 30 degrees C. Serratia marcescens (n = 29) demonstrated an aqua blue color that deepened to a darker blue when exposed to room temperature. All enterococcal isolates (n = 74) resulted in a blue color and gave pinpoint colonies on purity subcultures at 35 to 37 degrees C after 18 h of incubation. Similarity in color resulted in failure to discriminate accurately between Klebsiella, Enterobacter, and Citrobacter species. However, these species could be readily differentiated from other members of the family Enterobacteriaceae. Pseudomonas aeruginosa (n = 151) was easily differentiated from members of the Enterobacteriaceae but was less easily distinguishable from other gram-negative nonmembers of the Enterobacteriaceae. The medium was found to facilitate easy visual detection of mixed bacterial isolates in culture. When used in a replicator system, it easily detected mixed growths of organisms which may have otherwise led to false antibiotic susceptibility results. These mixed growths were not obvious on the routine susceptibility testing medium (Isosensitest).

Full Text

The Full Text of this article is available as a PDF (535.1 KB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Allen J. R., Hightower A. W., Martin S. M., Dixon R. E. Secular trends in nosocomial infections: 1970-1979. Am J Med. 1981 Feb;70(2):389–392. doi: 10.1016/0002-9343(81)90777-4. [DOI] [PubMed] [Google Scholar]
  2. Bryan C. S., Reynolds K. L., Brenner E. R. Analysis of 1,186 episodes of gram-negative bacteremia in non-university hospitals: the effects of antimicrobial therapy. Rev Infect Dis. 1983 Jul-Aug;5(4):629–638. doi: 10.1093/clinids/5.4.629. [DOI] [PubMed] [Google Scholar]
  3. Damron D. J., Warren J. W., Chippendale G. R., Tenney J. H. Do clinical microbiology laboratories report complete bacteriology in urine from patients with long-term urinary catheters? J Clin Microbiol. 1986 Sep;24(3):400–404. doi: 10.1128/jcm.24.3.400-404.1986. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Donabedian S., Chow J. W., Shlaes D. M., Green M., Zervos M. J. DNA hybridization and contour-clamped homogeneous electric field electrophoresis for identification of enterococci to the species level. J Clin Microbiol. 1995 Jan;33(1):141–145. doi: 10.1128/jcm.33.1.141-145.1995. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Dusch H., Altwegg M. Comparison of Rambach agar, SM-ID medium, and Hektoen Enteric agar for primary isolation of non-typhi salmonellae from stool samples. J Clin Microbiol. 1993 Feb;31(2):410–412. doi: 10.1128/jcm.31.2.410-412.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Dutka-Malen S., Evers S., Courvalin P. Detection of glycopeptide resistance genotypes and identification to the species level of clinically relevant enterococci by PCR. J Clin Microbiol. 1995 Jan;33(1):24–27. doi: 10.1128/jcm.33.1.24-27.1995. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Edberg S. C., Kontnick C. M. Comparison of beta-glucuronidase-based substrate systems for identification of Escherichia coli. J Clin Microbiol. 1986 Sep;24(3):368–371. doi: 10.1128/jcm.24.3.368-371.1986. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Edberg S. C., Trepeta R. W. Rapid and economical identification and antimicrobial susceptibility test methodology for urinary tract pathogens. J Clin Microbiol. 1983 Dec;18(6):1287–1291. doi: 10.1128/jcm.18.6.1287-1291.1983. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Hawkey P. M., McCormick A., Simpson R. A. Selective and differential medium for the primary isolation of members of the Proteeae. J Clin Microbiol. 1986 Mar;23(3):600–603. doi: 10.1128/jcm.23.3.600-603.1986. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Macfarlane J. R., Browne M. K. Cholecystectomy wounds: source of infection. J Hosp Infect. 1982 Mar;3(1):49–54. doi: 10.1016/0195-6701(82)90030-5. [DOI] [PubMed] [Google Scholar]
  11. Murray B. E. The life and times of the Enterococcus. Clin Microbiol Rev. 1990 Jan;3(1):46–65. doi: 10.1128/cmr.3.1.46. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Odds F. C., Bernaerts R. CHROMagar Candida, a new differential isolation medium for presumptive identification of clinically important Candida species. J Clin Microbiol. 1994 Aug;32(8):1923–1929. doi: 10.1128/jcm.32.8.1923-1929.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Pitt H. A., Postier R. G., Cameron J. L. Biliary bacteria: significance and alterations after antibiotic therapy. Arch Surg. 1982 Apr;117(4):445–449. doi: 10.1001/archsurg.1982.01380280037008. [DOI] [PubMed] [Google Scholar]
  14. Rambach A. New plate medium for facilitated differentiation of Salmonella spp. from Proteus spp. and other enteric bacteria. Appl Environ Microbiol. 1990 Jan;56(1):301–303. doi: 10.1128/aem.56.1.301-303.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Schaberg D. R., Culver D. H., Gaynes R. P. Major trends in the microbial etiology of nosocomial infection. Am J Med. 1991 Sep 16;91(3B):72S–75S. doi: 10.1016/0002-9343(91)90346-y. [DOI] [PubMed] [Google Scholar]

Articles from Journal of Clinical Microbiology are provided here courtesy of American Society for Microbiology (ASM)

RESOURCES