Medical Microbiology and Immunology

, Volume 170, Issue 3, pp 173–184 | Cite as

Evaluation of Gram-stain screen and Micro-ID methods for direct identification ofEnterobacteriaceae from urines

  • Peter C. Appelbaum
  • C. C. Olmstead


A rapid method of urine screening and enterobacterial identification was evaluated. Results indicated that an average of 13.5 bacteria/oil immersion field (threshold value ⩾ 1) was observed in unsedimented urine of patients with significant bacteriuria, with an average of < 1 bacterium/field in urines of patients without significant bacteriuria. In centrifuged urines, numbers of bacteria divided by amount of urine sedimented yielded similar results. Of 1758 urines studied, 136 yielded ⩾ 105 bacteria/ml, and 58 > 104 but < 105 bacteria/ml, by conventional techniques. Gram-screening of unsedimented specimens gave sensitivity rates of 94.1%, specificity of 97.7%, and predictive positive and negative values of 78.5%, 99.5%, respectively; similar values were obtained with sedimented urines. Sensitivity rates of both screening methods for the 58 urines with > 104 but < 105 bacteria/ml were 9.0%, 10.0%, respectively. Total correct enteric identification in 113 urines with positive screens and significant bacteriuria (⩾ 105/ml) was 82.3% and 90.3% with direct saline and broth Micro-ID methods, respectively. In 99 urines yielding pure or predominantly pure growth of 1 species ofEnterobacteriaceae identification by direct saline and broth Micro-ID corresponded with isolated colony identification in 85.9%, 94.9% of cases, respectively. Gram-stain screening (together with back-up conventional plating in certain patient categories) and enterobacterial identification by direct broth Micro-ID, of urines with pure stains suggestive of ⩾ 105 Gram-negative rods/ml has been shown to be useful in laboratories without automated equipment for urine screening.


Sensitivity Rate Conventional Technique Rapid Method Bacteriuria Screen Method 
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  1. 1.
    Aldridge KE, Gardner BB, Clark SJ, Matsen JM (1978) Comparison of Micro-ID, API 20E, and conventional media systems in identification ofEnterobacteriaceae. J Clin Microbiol 7:507–513PubMedGoogle Scholar
  2. 2.
    Appelbaum PC, Schick SF, Kellogg JA (1980) Evaluation of the four-hour Micro-ID technique for direct identification of oxidase-negative, gram-negative rods from blood cultures. J Clin Microbiol 12:533–537PubMedGoogle Scholar
  3. 3.
    Barry AL, Smith PB, Turck M (1975) Cumitech 2: Laboratory diagnosis of urinary tract infections. Coordinating ed, TL Gavan. American Society for Microbiology, Washington, DCGoogle Scholar
  4. 4.
    Bartlett RC (1974) Medical microbiology. Quality, cost, and clinical relevance. John Wiley, New YorkGoogle Scholar
  5. 5.
    Blazevic DJ, Mackay AL, Warwood NM (1979) Comparison of Micro-ID and API 20E systems for identification ofEnterobacteriaceae. J Clin Microbiol 9:605–608PubMedGoogle Scholar
  6. 6.
    Buesching WJ, Rhoden DL, Esaias AO, Smith PB, Washington JA II (1979) Evaluation of the modified Micro-ID system for identification ofEnterobacteriaceae. J Clin Microbiol 10:454–458PubMedGoogle Scholar
  7. 7.
    Dornfest FD (1979) The rapid diagnosis of urinary tract infection. A side-room method. S Afr Med J 56:841–843PubMedGoogle Scholar
  8. 8.
    Edberg SC, Atkinson B, Chambers C, Moore MH, Palumbo L, Zorzon CF, Singer JM (1979) Clinical evaluation of the Micro-ID, API 20E, and conventional media systems for identification ofEnterobacteriaceae. J Clin Microbiol 10:161–167PubMedGoogle Scholar
  9. 9.
    Heinze PA, Thrupp LD, Anselmo CA (1979) A rapid (4–6 hour) urine-culture system for direct identification and direct antimicrobial susceptibility testing. Am J Clin Pathol 71:177–183PubMedGoogle Scholar
  10. 10.
    Jenkins RD, Hale DC, Matsen JM (1980) Rapid semiautomated screening and processing of urine specimens. J Clin Microbiol 11:220–225PubMedGoogle Scholar
  11. 11.
    Johnston HH, Newsom SWB (1976) Second international symposium on rapid methods and automation in microbiology. Research Studies Press, Inc., Forest Grove, OregonGoogle Scholar
  12. 12.
    Kunin CM (1972) Detection, prevention, and management of urinary tract infections. Lea and Febiger, PhiladelphiaGoogle Scholar
  13. 13.
    Paik G (1980) Reagents, stains and miscellaneous test procedures, p 1000–1024. In: Lennette EH, Balows A, Hausler WJ Jr, Truant JP (eds), Manual of clinical Microbiology, 3rd ed. American Society for Microbiology, Washington, DCGoogle Scholar
  14. 14.
    Schersten B, Fritz H, Kohler L, Westlung L (1968) Screening for bacteriuria with a test paper for glucose. J Am Med Assoc 204:113–116CrossRefGoogle Scholar
  15. 15.
    Simmonds NA, Williams JD (1962) A simple test for significant bacteriuria. Lancet 1:1377–1378Google Scholar
  16. 16.
    Smith PB, Tomfohrde KM, Rhoden DL, Balows A (1972) API system: a multiple micromethod for identification ofEnterobacteriaceae. Appl Microbiol 24:449–452PubMedGoogle Scholar
  17. 17.
    Thornsberry C, Gavan TL, Sherris JC, Balows A, Matsen JM, Sabath LD, Schoenknecht F, Thrupp LD, Washington JA II (1975) Laboratory evaluation of a rapid, automated susceptibility testing system: report of a collaborative study. Antimicrob Agents Chemother 7:466–480PubMedGoogle Scholar
  18. 18.
    Thrupp LD, Heinze PD, Pezzlo MA (1976) Direct rapid urine cultures: same day reporting of quantitation, speciation and antimicrobial susceptibility tests. In: Balows A (ed), ASM symposium of automation in clinical microbiology. Pfizer Diagnostics, New YorkGoogle Scholar
  19. 19.
    Tilton RE, Tilton RC (1980) Automated direct antimicrobial susceptibility testing of microscopically screened urine cultures. J Clin Microbiol 11:157–161PubMedGoogle Scholar

Copyright information

© Springer-Verlag 1982

Authors and Affiliations

  • Peter C. Appelbaum
    • 1
  • C. C. Olmstead
    • 1
  1. 1.Department of Pathology, Division of Clinical Microbiology, Room H504A, The Milton S. Hershey Medical CenterThe Pennsylvania State UniversityHersheyUSA

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