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Comparison of three methods for identification of pathogenic Neisseria species
Abstract:
A radiometric procedure was compared with the Minitek and Cystine Trypticase Agar sugar degradation methods for identification of 113 Neisseria species (58 Neisseria meningitidis, 51 Neisseria gonorrhoeae, 2 Neisseria lactamica, 2 Neisseria sicca). Identification of meningococci and gonococci was confirmed by agglutination and fluorescent antibody techniques, respectively. The Minitek method identified 97% of meningococci, 92% of gonococci, and 100% of other Neisseria after 4 h of incubation. The radiometric (Bactec) procedure identified 100% of gonococci and 100% of miscellaneous Neisseria after 3 h, but problems were encountered with meningococci: 45% of the later strains yielded index values for fructose between 20 and 28 (recommended negative cut-off point, less than 20), with strongly positive (greater than 100) glucose and maltose and negative o-nitrophenyl-beta-D-galactopyranoside reactions in all 58 strains. The Cystine Trypticase Agar method identified 91% of meningococci, 90% of gonococci, and 100% of other Neisseria after 24 to 48 h. Prolongation of the Cystine Trypticase Agar incubation period led to abnormal lactose/sucrose reactions in some meningococci and gonococci. Radiometric and Minitek systems are more accurate and convenient than Cystine Trypticase Agar techniques, but, on the basis of these results, radiometric fructose sensitivity levels for meningococci need reevaluation.
Insights
Comparing diagnostic methods for Neisseria species, the radiometric (Bactec) and Minitek systems offer faster and more accurate identification than Cystine Trypticase Agar. However, radiometric fructose sensitivity requires reevaluation for meningococci identification.
Area of Science:
- Microbiology
- Clinical Diagnostics
- Bacteriology
Background:
- Accurate identification of Neisseria species, including Neisseria meningitidis and Neisseria gonorrhoeae, is crucial for effective clinical management and public health.
- Traditional sugar degradation methods like Cystine Trypticase Agar (CTA) can be time-consuming and may present challenges in interpretation.
- The development of more rapid and accurate diagnostic tools is essential for timely patient care.
Purpose of the Study:
- To compare the accuracy and efficiency of a radiometric (Bactec) procedure against the Minitek system and Cystine Trypticase Agar (CTA) for the identification of Neisseria species.
- To evaluate the performance of these methods specifically for differentiating Neisseria meningitidis and Neisseria gonorrhoeae.
Main Methods:
- A total of 113 Neisseria isolates were tested, including Neisseria meningitidis (n=58), Neisseria gonorrhoeae (n=51), Neisseria lactamica (n=2), and Neisseria sicca (n=2).
- Identification was performed using a radiometric (Bactec) method, the Minitek system, and Cystine Trypticase Agar (CTA) sugar degradation.
- Confirmation of Neisseria meningitidis and Neisseria gonorrhoeae was achieved through agglutination and fluorescent antibody techniques, respectively.
Main Results:
- The Minitek method achieved 97% accuracy for meningococci and 92% for gonococci within 4 hours.
- The radiometric (Bactec) procedure identified 100% of gonococci and other Neisseria within 3 hours, but showed ambiguous fructose results for 45% of meningococci strains.
- Cystine Trypticase Agar (CTA) required 24-48 hours for identification, with 91% accuracy for meningococci and 90% for gonococci, and noted potential issues with prolonged incubation.
Conclusions:
- Radiometric and Minitek systems demonstrate superior speed and accuracy compared to traditional CTA methods for Neisseria species identification.
- The radiometric method's performance with Neisseria meningitidis warrants further investigation, particularly regarding fructose substrate sensitivity levels.
- Optimized protocols for radiometric and Minitek systems could significantly improve the efficiency of Neisseria diagnostics in clinical laboratories.