Prevalence of the colistin resistance gene in colistin-resistant in Egypt.

is a nosocomial pathogen with high morbidity and mortality rates in hospitalized patients. The emergence of multidrug-resistant has become more challenging to treat, with the prevalence of colistin-resistance. Therefore, reliable methods for detecting colistin resistance are required. Many plants' essential oils have antimicrobial activity and have been used to combat multiple antibiotic resistances. This study aimed to investigate the characterization and prevalence of the colistin resistance gene in in Egypt, evaluate rapid polymyxin NP test, determine the transferability of gene, and study the synergistic activity of eugenol combined with colistin against isolates. Eighty-two isolates were collected from different human samples, followed by antibiotic susceptibility testing, rapid polymyxin NP test, and detection of the gene and its transfer frequency. Determination of the MICs of colistin alone and in combination with eugenol was performed, then gene expression was determined in the presence of eugenol. Thirty-two isolates (39%) were colistin-resistant. Rapid polymyxin NP test failed to detect resistant isolates with MICs below 32 µg/mL. Detection of gene was made in 27 (84%) of colistin resistant isolates. The rest isolates possess alteration in the gene which probably causes colistin resistance. The gene was transferred by conjugation to other sensitive isolates. MIC of eugenol ranged from 416 to 1664 µg/mL, and FICI ranged from 0.265 to 0.75. Results also revealed suppression of gene expression in the presence of sub MIC of eugenol. Our results demonstrated a high prevalence of in Egypt and its ability to transfer to other strains. Difficult determination of colistin-resistant isolates with low values with rapid polymyxin NP test was apparent. Eugenol exerted a synergistic effect with colistin and improved its antimicrobial activity.