# A colorimetric amplification-based method for identification of Moraxella catarrhalis, a human respiratory tract pathogen

## TL;DR

This paper introduces a new color-based test to quickly and accurately detect Moraxella catarrhalis, a bacteria that causes respiratory infections.

## Contribution

The study presents the first use of the ompCD gene in a colorimetric PCR method for identifying Moraxella catarrhalis.

## Key findings

- The colorimetric PCR method detected M. catarrhalis with a sensitivity of 0.05 ng/μL and 100% specificity.
- The method produced a light red color and a 273 base pair band for positive samples.
- Negative samples showed a deep red color and no amplicon band with an A450/A570 ratio of 1.15 or less.

## Abstract

Moraxella catarrhalis is a significant pathogen associated with both upper and lower respiratory tract infections. This study aims to identify M. catarrhalis using the ompCD gene, which encodes a major outer membrane protein. Spectrophotometry was used to evaluate the accuracy of the colorimetric method by measuring the A450/A570. The colorimetric measurements and PCR method specificity were assessed utilizing twenty bacterial samples. The results of M. catarrhalis detection confirmed the presence of a specific band at 273 base pairs and a light red color, with an A450/A570 ratio of 1.5. However, 100% specificity was observed in negative samples with an A450/A570 ratio of 1.15 or less, lacking an amplicon band and showing a deep red color. Furthermore, the selectivity of the techniques was confirmed. The methods revealed a detection limit of 0.05 ng/μL. The colorimetric PCR approach is a suitable point-of-care test for rapidly and accurately identifying M. catarrhalis.

Image 1

•First-time detection of Moraxella catarrhalis using the ompCD gene colorimetric approach.•A colorimetric PCR technique was optimized to detect M. catarrhalis both by the naked eye and quantitatively.•To examine the diagnosis, endpoint spectrophotometry at 450 and 570 nm was carried out.•The specificity and selectivity of the method were investigated using several bacterial and mixed samples.•A sensitivity of 0.05 ng/μL and 100% specificity was achieved.

First-time detection of Moraxella catarrhalis using the ompCD gene colorimetric approach.

A colorimetric PCR technique was optimized to detect M. catarrhalis both by the naked eye and quantitatively.

To examine the diagnosis, endpoint spectrophotometry at 450 and 570 nm was carried out.

The specificity and selectivity of the method were investigated using several bacterial and mixed samples.

A sensitivity of 0.05 ng/μL and 100% specificity was achieved.