Prognostication of Resistance Pattern of Colistin Resistant Gram-Negative Bacilli at Intensive Care Units Prognostication of Resistance Pattern of Colistin Resistant Gram-Negative Bacilli at Intensive Care Units

Abstract

Colistin, or polymyxin E, is an antibiotic effective against Gram-negative bacteria, especially Enterobacteriaceae. Due to its potential for horizontal transmission, it is used as a last resort for treating Enterobacteriaceae infections. This study evaluates colistin resistance in Gram-negative bacilli from clinical samples and analyzes their antibiotic resistance patterns. We identified 1175 colistin-resistant Gram-negative bacilli isolates from various ICU sources, with only 1.44% (n=17) classified as colistin-resistant. These included one isolate from the Neonatal ICU, three from the Pediatric ICU, seven from the ICU, three from Obstetrics and Gynecology, and one from the Male Medical Ward. The resistant isolates comprised 6 (35.2%) Escherichia coli, 3 (17.6%) Enterobacter cloacae, and 8 (47%) Klebsiella pneumoniae. Despite more Klebsiella spp. being present, E. coli showed greater sensitivity to colistin. Pseudomonas spp. did not show colistin resistance. The resistance levels indicated that 47% of the colistin-resistant isolates had MIC values of ≥16µg/ml. A related study found p-values for Pseudomonas ranging from 0.001 to 0.052, for E. coli from 0.001 to 1, for Klebsiella spp. from 0.001 to 0.8, for Acinetobacter spp. from 0.1 to 1, and for Enterobacter spp. from 0.177 to 1 when compared to colistin and other antibiotics. Pseudomonas spp shows reduced effectiveness against clinical isolates, especially with antibiotics like Ampicillin, Amoxyclav, Cefuroxime, Ceftriaxone, Etrapenem, and Nalidixic acid. In contrast, Enterobacter spp exhibited diminished efficacy against Piperacillin/Tazobactam, Etrapenem, Tigecycline, Amikacin, Ceftazidime, and Doripenem. Additionally, antibiotics such as triclocarban, ceftazidime, aztreonam, doripenem, levofloxacin, and minocycline had reduced bactericidal inhibition zones against Klebsiella spp. Resistance in E. coli and Klebsiella spp was particularly significant for Colistin, while other species showed less resistance. Further research should include additional pathogenic microorganisms to better understand colistin susceptibility.