# Colorimetric Ready-to-Use Microfluidic Chips for Rapid Antibiotic Susceptibility Testing of Methicillin-Resistant Staphylococcus aureus by a Smartphone-Based Analysis

## TL;DR

A new microfluidic chip with smartphone analysis enables rapid antibiotic resistance testing for MRSA in a few hours.

## Contribution

A ready-to-use microfluidic chip with anthocyanin pH indicators and smartphone-based analysis for rapid MRSA antibiotic susceptibility testing.

## Key findings

- Colorimetric responses in microfluidic chip wells indicate MRSA antibiotic resistance profiles.
- The system demonstrated feasibility using standard S. aureus reference strains.
- Antibiotic susceptibility testing was achieved in a few hours with minimal device requirements.

## Abstract

Many phenotypic resistance tests have been developed
for Methicillin-resistant Staphylococcus aureus (MRSA), but they still have
disadvantages such as long incubation times, complicated procedure
and a lack of portability. Herein, we designed ready-to-use microfluidic
chips to use more advanced and new methods for analyzing antibiotic
resistance specifically for the rapid detection of MRSA. Anthocyanin
molecules, which change color depending on the pH value of the reaction
medium in the microfluidic chip wells, are utilized as pH indicator
in the test. The color change in the wells depends on the inhibition
of antibiotic-resistant or susceptible bacteria at varying cefoxitin
doses. The antibiotic resistance profiles of MRSA to multiple doses
were revealed on a single chip. The obtained colorimetric responses
were analyzed using a mobile application and color image processing
techniques. The feasibility of the system was demonstrated using standard
reference strains (S. aureus ATCC 43300
and ATCC 25923). Thus, this proof-of-concept study shows that antibiotic
resistance detection can be performed in a few hours with minimal
device requirements, warranting further validation with clinical isolates.