Ventilator-Associated Pneumonia in Newborns: Distribution of Causative Agents and Antibiogram

Objectives: To characterize pathogen distribution and antibiograms in neonatal ventilator-associated pneumonia (VAP) and to examine clinical correlates of recurrent growth and colonization.
Methods: This was a single-center retrospective cohort study conducted between September 1, 2020, and September 1, 2025. Among 152 neonates with tracheal aspirate culture (TAC) growth, 61 met the VAP criteria; 48 with complete clinical and antibiogram data were analyzed. Recurrent growth was defined as a second positive TAC with a different species obtained at another time point, and colonization was defined as the same organism in ≥3 consecutive TACs. Demographics, inflammatory biomarkers, blood cultures, and EUCAST susceptibilities were recorded. Group comparisons were performed using the Mann–Whitney U test and Fisher’s exact test; temporal susceptibility trends were assessed using Spearman’s rho.
Results: Gram-negative organisms predominated. The most frequent first TAC isolates were Klebsiella pneumoniae (33.3%) and Escherichia coli (18.8%); K. pneumoniae also predominated among second isolates (45.0%). Blood cultures were positive in 33.3% of cases, with 37.5% TAC–blood species concordance. Compared with non-gram-negative cases, gram-negative infections had higher C-reactive protein levels (7.9 vs. 1.1 mg/L; p=0.029) and procalcitonin levels (3.13 vs. 0.22 ng/mL; p=0.045) but a lower neutrophil-to-lymphocyte ratio (0.93 vs. 2.37; p=0.017). NICU length of stay was longer in patients with gram-negative growth (63.0 [29.0–111.5] vs. 17.5 [10.25–45.75] days; p=0.023); the Hodges–Lehmann median difference was +39.5 days (95% CI +13.0 to +69.0), with a moderate effect size (Cliff’s δ=0.36). Recurrent growth occurred in 41.7% of cases and was associated with a longer intubation-to-growth interval (12.0 [5.0–15.75] vs. 4.5 [3.0–8.25] days; p=0.002) and colonization (p=0.002). Susceptibility to amikacin, colistin, and tigecycline was relatively preserved, whereas resistance to third- and fourth-generation cephalosporins, piperacillin–tazobactam, carbapenems, and fluoroquinolones was common. Overall susceptibility declined over the years (ρ=−0.95; p=0.001). In multivariable logistic regression, no variable independently predicted adverse prognosis.
Conclusion: In our tertiary NICU, neonatal VAP is predominantly caused by multidrug-resistant gram-negative organisms, particularly Klebsiella pneumoniae and Escherichia coli. These infections are associated with higher inflammatory markers and prolonged hospitalization. Recurrent growth, defined as the isolation of a different species at another time point, highlights the role of airway hygiene and adherence to ventilator bundle practices. Given the decreasing susceptibility trends, maintaining the efficacy of agents such as amikacin, colistin, and tigecycline through rational antibiotic use is crucial.

Keywords: Antibiogram, antimicrobial resistance, neonate, tracheal aspirate, ventilator-associated pneumonia