From the Guidelines
Neisseria and Moraxella can be differentiated in the laboratory through several key tests, with oxidase testing being a primary method, where Neisseria species are oxidase-positive with a rapid reaction, as noted in various studies, including those on molecular typing of meningococci 1. To differentiate between Neisseria and Moraxella in the laboratory, several tests can be employed, focusing on their biochemical and morphological characteristics.
- Oxidase testing is a key differentiator, with Neisseria species showing a rapid positive reaction, whereas Moraxella species also test positive but with a slower reaction.
- Glucose utilization is another distinguishing factor, as Neisseria gonorrhoeae and N. meningitidis are capable of fermenting glucose, in contrast to Moraxella species, which are non-fermenters.
- Colony morphology provides visual cues for differentiation: Neisseria colonies are typically small, round, and grayish with a "hockey puck" appearance when pushed, while Moraxella colonies are larger and more opaque.
- Catalase testing, though positive for both, can be further differentiated with superoxol testing, which shows an explosive reaction for N. gonorrhoeae.
- Gram stain morphology is also informative, with Neisseria appearing as gram-negative diplococci with adjacent sides flattened (coffee bean appearance), and Moraxella as short gram-negative coccobacilli often in pairs. These methods, particularly the rapid oxidase test as a first-line differentiation tool, as discussed in the context of molecular typing for meningococci 1, allow for reliable differentiation between these clinically significant genera.
From the Research
Differentiation Methods
To differentiate between Neisseria and Moraxella in a laboratory setting, several methods can be employed:
- Gram stain, oxidase, and either indoxyl acetate, spot MUB, or tributyrin hydrolysis test can be used as a combination for reliable identification 2
- Erythromycin susceptibility testing can also distinguish between M. catarrhalis and commensal Neisseria 2
- 16S or 23S ribosomal DNA (rDNA) sequencing can be used for accurate speciation of isolates, with the 16S rDNA region being more suitable for molecular diagnosis of Neisseriaceae and Moraxellaceae 3
- DNA hydrolysis test can be included in the routine procedure for identification of M. catarrhalis in sputum samples to improve accuracy 4
Limitations of Conventional Methods
Conventional biochemical identification methods may not always be specific and can lead to diagnostic errors:
- The API Campy and Vitek 2 Neisseria-Haemophilus card systems have limitations in identifying Campylobacter and related organisms, with poor sensitivity in identifying related organisms 5
- Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has shown promise as a reliable method for the routine identification of Campylobacter and other Epsilobacteria, with high sensitivity and short response time 5