# Comparison of in vitro antimicrobial susceptibility between mucoid and non-mucoid Pseudomonas aeruginosa and its guiding value for antibiotic therapy

## TL;DR

This study compares antibiotic susceptibility in mucoid and non-mucoid Pseudomonas aeruginosa to guide better treatment choices.

## Contribution

The study provides large-scale evidence on the differing antimicrobial susceptibility and treatment outcomes between mucoid and non-mucoid P. aeruginosa.

## Key findings

- Mucoid P. aeruginosa showed lower resistance to most antibiotics compared to non-mucoid strains.
- In vitro susceptibility tests aligned well with treatment outcomes for both mucoid and non-mucoid infections.
- Mucoid infections were more common in females and primarily from respiratory tract specimens.

## Abstract

The aim of the study was to compare in vitro antimicrobial susceptibility between mucoid and non-mucoid Pseudomonas aeruginosa and its guiding value for antibiotic therapy. A retrospective review was conducted on the sources of isolates, patient information, in vitro antimicrobial susceptibility results, and antimicrobial usage records for mucoid and non-mucoid P. aeruginosa isolates spanning from 2021 to 2023, comparing the differences between the two types. Additionally, infection cases of mucoid and non-mucoid P. aeruginosa were selected for in-depth analysis of their treatment courses, evaluating the guiding value of antimicrobial susceptibility results for antimicrobial therapy. We collected 1,443 non-mucoid P. aeruginosa and 342 mucoid P. aeruginosa. Our findings revealed that mucoid P. aeruginosa was predominantly found in respiratory tract specimens, while non-mucoid P. aeruginosa was primarily isolated from a broader range of specimen sources. Regarding antimicrobial susceptibility, mucoid P. aeruginosa exhibited notably lower levels of resistance compared to their non-mucoid counterparts, except for ciprofloxacin, levofloxacin, and cefepime. The most frequently prescribed drugs for mucoid P. aeruginosa were levofloxacin and ceftazidime, whereas for non-mucoid P. aeruginosa, ceftazidime and meropenem were more frequently used. A total of 42 non-mucoid P. aeruginosa cases and 36 mucoid P. aeruginosa cases were further analyzed, which were isolated from hospitalized patients with a confirmed diagnosis of monomicrobial P. aeruginosa infection. The analysis of case information revealed that 90.2% of non-mucoid P. aeruginosa infections and 94.4% of mucoid P. aeruginosa infections showed consistency between in vitro antimicrobial susceptibility and outcomes. Our results revealed differences in demographic and clinical characteristics, antimicrobial susceptibility, and selection of antimicrobial agents between mucoid and non-mucoid P. aeruginosa. The findings will help optimize prognosis and combat the challenges posed by P. aeruginosa infections.

This study represents a large-scale comparative research conducted over two years at a tertiary hospital in China, involving 1,443 non-mucoid and 342 mucoid strains. We found significant differences between mucoid and non-mucoid P. aeruginosa infections in terms of gender, antimicrobial susceptibility test, and the selection of antimicrobial agents. Specifically, mucoid P. aeruginosa infections were predominantly observed in females and were mainly associated with respiratory tract infections. Moreover, the isolates with mucoid phenotype exhibited higher susceptibility to most antimicrobial agents compared to non-mucoid isolates. According to the data of the pharmacy department, we found the most frequently prescribed drugs for mucoid P. aeruginosa were levofloxacin and ceftazidime, whereas for non-mucoid P. aeruginosa, ceftazidime and meropenem were more frequently used. The analysis of case information revealed that no matter whether in mucoid or non-mucoid P. aeruginosa, the in vitro antimicrobial susceptibility test results were in good agreement with the therapeutic outcomes.