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Background <p>With the growing challenge of antibiotic resistance, evaluating the effectiveness of existing antimicrobials is crucial. This work aimed to compare the antimicrobial activity of colistin versus ceftazidime/avibactam (CAZ/AVI) against MDR <i>P. aeruginosa</i>. It also aimed to estimate the prevalence of <i>P. aeruginosa</i> as a causative agent for VAP and the rate of its multi-drug resistance.</p> Methods <p>This observational cross-sectional study was conducted from January to June 2025 on ICU patients with VAP at Kasr Alainy Hospitals. A total of 120 endotracheal aspirates were collected from patients and cultured. <i>P. aeruginosa</i> was identified, tested for antibiotic susceptibility by the Kirby-Bauer disc diffusion method, and underwent colistin minimal inhibitory concentration (MIC) testing via broth microdilution and CAZ/AVI MIC determination using E-test, following the Clinical and Laboratory Standards Institute 2025 guidelines.</p> Results <p>Of 120 ICU patients diagnosed with VAP, <i>P. aeruginosa</i> was isolated from 47 (39.2%). Among these, 40 isolates (85.1%) were identified as MDR. Of 40 MDR <i>P. aeruginosa</i> isolates, 32 (80%) were susceptible to colistin, with MIC₅₀ and MIC₉₀ values of 2&#xa0;µg/mL and 4&#xa0;µg/mL, respectively. In contrast, only 5 (12.5%) isolates were susceptible to CAZ/AVI, with both MIC₅₀ and MIC₉₀ exceeding 16&#xa0;µg/ml, indicating widespread resistance. The difference in susceptibility between the two antibiotics was statistically significant (<i>p</i> <b>&lt;</b> 0.01).</p> Conclusions <p>Colistin showed significantly greater in vitro effectiveness than CAZ/AVI against MDR <i>P. aeruginosa</i> from VAP patients in the ICU, supporting its continued use despite nephrotoxicity concerns. The limited activity of CAZ/AVI underscores the need for ongoing local antimicrobial surveillance and strict stewardship practices.</p>

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Comparison between the antimicrobial activity of colistin and ceftazidime-avibactam against multidrug-resistant Pseudomonas aeruginosa isolated from patients with ventilator-associated pneumonia in intensive care units of Kasr Al-Ainy hospitals

  • 期刊论文

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  • 发表日期：

    2026年3月24日

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  • Nahla Yassin Sahloul,
  • Somaia Sayed Helmy,
  • Alaa Reda Awad,
  • Ahmed Ibrahim Elsayed,
  • Mai A. Sahbal,
  • Alaa Mohamed Ibrahim Aboutaleb

摘要

Background

With the growing challenge of antibiotic resistance, evaluating the effectiveness of existing antimicrobials is crucial. This work aimed to compare the antimicrobial activity of colistin versus ceftazidime/avibactam (CAZ/AVI) against MDR P. aeruginosa. It also aimed to estimate the prevalence of P. aeruginosa as a causative agent for VAP and the rate of its multi-drug resistance.

Methods

This observational cross-sectional study was conducted from January to June 2025 on ICU patients with VAP at Kasr Alainy Hospitals. A total of 120 endotracheal aspirates were collected from patients and cultured. P. aeruginosa was identified, tested for antibiotic susceptibility by the Kirby-Bauer disc diffusion method, and underwent colistin minimal inhibitory concentration (MIC) testing via broth microdilution and CAZ/AVI MIC determination using E-test, following the Clinical and Laboratory Standards Institute 2025 guidelines.

Results

Of 120 ICU patients diagnosed with VAP, P. aeruginosa was isolated from 47 (39.2%). Among these, 40 isolates (85.1%) were identified as MDR. Of 40 MDR P. aeruginosa isolates, 32 (80%) were susceptible to colistin, with MIC₅₀ and MIC₉₀ values of 2 µg/mL and 4 µg/mL, respectively. In contrast, only 5 (12.5%) isolates were susceptible to CAZ/AVI, with both MIC₅₀ and MIC₉₀ exceeding 16 µg/ml, indicating widespread resistance. The difference in susceptibility between the two antibiotics was statistically significant (p < 0.01).

Conclusions

Colistin showed significantly greater in vitro effectiveness than CAZ/AVI against MDR P. aeruginosa from VAP patients in the ICU, supporting its continued use despite nephrotoxicity concerns. The limited activity of CAZ/AVI underscores the need for ongoing local antimicrobial surveillance and strict stewardship practices.