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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
Article

Abstract

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.

Keywords

Sensitivity Rate Conventional Technique Rapid Method Bacteriuria Screen Method 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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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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