Colistin therapy and survival outcomes in neonatal carbapenem-resistant gram-negative sepsis

Carbapenem-resistant Gram-negative (CR-GN) sepsis is a growing cause of neonatal mortality, especially in low- and middle-income countries. Colistin remains one of the few effective therapeutic options.

This retrospective cohort study reviewed hospital files of inborn neonates admitted within six hours of birth to the neonatal intensive care unit (NICU) of Imam Khomeini Hospital, Ahvaz, Iran (March 2019-March 2023), with blood culture-proven CR-GN sepsis. Blood cultures were obtained from peripheral samples and processed in Trypticase Soy Broth; isolates were identified and antibiotic susceptibility determined using the Kirby-Bauer disk diffusion method per Clinical and Laboratory Standards Institute (CLSI) guidelines. Because colistin disks were unavailable, clinical and microbiological responses were used to evaluate efficacy. Neonates received either a colistin-containing regimen (colistin + meropenem) or a non-colistin regimen (amikacin + meropenem). Univariate logistic regression was performed, and a sensitivity analysis limited to survivors was conducted for length-of-stay comparison.

The hospital records of 108 neonates were analyzed (36 colistin-treated, 72 non-colistin-treated). Acinetobacter spp. were the most frequent isolate. Among infants who received colistin, the rate of late-onset sepsis was significantly higher than that of early-onset sepsis (69.4% vs. 25.0%, p < 0.001). The mortality rate was significantly lower in the colistin group (41.7% vs. 70.8%, p = 0.006).

A colistin-containing regimen was associated with significantly improved survival among neonates with CR-GN sepsis. Despite limitations in susceptibility testing, these findings underscore the clinical value of colistin in resource-limited NICUs, warranting prospective validation of dosing, safety, and antimicrobial stewardship strategies.