Dynamics of microbial colonization in various biotopes of preterm neonates with extremely low and very low birth weight: a pilot study

Introduction. Preterm neonates with extremely low birth weight (ELBW) and very low birth weight (VLBW) are at a high risk of infectious complications. Their microbiota may harbor microorganisms facilitating nosocomial infections («scout microbes»), yet the dynamics of colonization remain poorly understood. Objective. To assess microbial colonization dynamics in various biotopes of ELBW and VLBW neonates and determine optimal decontamination strategies. Material and methods. This pilot prospective study analyzed biological samples (blood, gastric aspirate, oropharyngeal and tracheobronchial secretions, urine, and cerebrospinal fluid) from 15 preterm neonates with ELBW and VLBW admitted to the neonatal intensive care unit (NICU). Microbial colonization was assessed using culture-based methods with species identification via MALDI-TOF mass spectrometry. Statistical analysis included the Shapiro-Wilk test, Pearson’s correlation, and linear regression. Results. Cultures remained sterile for the first 3—4 weeks. By weeks 5—6, the predominant flora consisted of coagulase-negative staphylococci (CoNS) and non-fermenting Gram-negative opportunistic bacteria (NFGNOB). Klebsiella pneumoniae (ESBL+) was the primary colonizing pathogen in ELBW neonates (22—23 weeks of gestation), while Staphylococcus haemolyticus predominated in VLBW neonates. K. pneumoniae colonization correlated with more severe infections (p<0.05). Conclusion. Preterm neonates initially exhibit sterile biotopes during the early postnatal period; however, a predictable sequence of microbial colonization occurs, with Gram-positive bacteria predominating in the early phase, followed by Gram-negative flora by week 6. The primary colonizing microorganisms are influenced by gestational age and birth weight, necessitating an individualized approach to antimicrobial therapy. Further studies are warranted.