Staphylococcus aureus dominates ventilator-associated pneumonia after brain injury
Ventilator-associated pneumonia in patients with neurological injury carried a distinctly different microbiological profile than in other ICU patients, with Staphylococcus aureus emerging as the dominant pathogen. In this multicenter retrospective cohort, 407 patients with ventilator-associated pneumonia were ultimately included from a much larger pool of 15,702 ICU admissions, a reminder of how selectively this complication concentrates in critically ill populations. Among those with brain injury, S. aureus was involved in 122 cases, or 61.6%, compared with 63 cases, or 30.1%, in patients without brain injury. The gap is large enough to matter at the bedside because empiric antibiotic choices in neurocritical care often hinge on whether the respiratory infection is likely to be driven by a skin-flora organism, gram-negative pathogens, or a mixed flora dominated by aspiration-related organisms.
The microbiology fits the physiology. Patients with acute neurological injury frequently have impaired airway protection, prolonged intubation, depressed consciousness, and repeated airway manipulation, all of which can alter colonization patterns in the trachea and lower respiratory tract. When cough and swallow reflexes are blunted, the upper airway becomes a more permissive reservoir for organisms such as S. aureus, especially in the context of intensive care exposures. The study’s results suggest that ventilator-associated pneumonia in this population is not simply a generic ICU infection wearing a neurologic label; it is a syndrome with its own microbial tendencies.
Risk factors separated brain-injured from non-brain-injured patients
Multivariate modeling in the brain-injured cohort identified several factors associated with the likelihood of S. aureus in ventilator-associated pneumonia. Age was associated with lower odds, with an estimate of 0.97 [0.95; 0.98]. Antibioprophylaxis was associated with a marked reduction in risk, with an estimate of 0.31 [0.18; 0.53], and the association reached strong statistical significance with p < 0.0001. Subarachnoid hemorrhage carried increased odds at 2.18 [1.01; 4.68], while lower Glasgow coma score and higher SAPS II were also associated with the pathogen profile, with estimates of 0.92 [0.87; 0.97] and 0.98 [0.97; 1], respectively.
The pattern is clinically coherent. Severe neurologic compromise likely increases vulnerability to respiratory colonization and early infection with S. aureus, while a lower Glasgow coma score marks reduced spontaneous airway clearance and more prolonged dependence on mechanical ventilation. Subarachnoid hemorrhage may represent a subgroup with a particularly high burden of autonomic disturbance, immobility, and neurocritical care interventions, all of which can intensify infection risk. SAPS II captures global illness severity, which likely reflects both physiologic fragility and the intensity of invasive support.
A separate signal emerged outside the brain-injured cohort. Among patients without neurological injury, antibioprophylaxis again lowered the likelihood of S. aureus involvement, with an estimate of 0.38 [0.22; 0.65] and p=0.0006. Age and SAPS II retained associations similar to the brain-injured cohort, with estimates of 0.96 [0.95; 0.98] and 0.98 [0.97; 1]. Thoracic surgery was associated with reduced odds at 0.21 [0.09; 0.48], while peripheral neurosurgery increased odds at 1.95 [1.2; 3.19]. Those findings point to the way surgical exposure, device use, and perioperative contamination patterns can shape ICU respiratory microbiology even when the primary admission diagnosis is not neurologic.
Empiric coverage may need to account for neurocritical care microbiology
The practical value of the study lies in its signal about early empiric therapy. In ventilated patients with brain injury, a pathogen profile dominated by S. aureus suggests that early antibiotic selection should not rely on assumptions built from mixed ICU populations alone. Neurocritical care units see patients with prolonged ventilation, depressed consciousness, and frequent airway interventions, so the threshold for anti-staphylococcal coverage may need to be lower when pneumonia is suspected. The findings do not establish a new treatment algorithm, but they do make the microbiology harder to ignore when a patient with intracranial pathology deteriorates after several days on the ventilator.
This cohort also raises a larger stewardship question. If antibioprophylaxis was associated with lower odds of S. aureus across both populations, then prior antibiotic exposure may be suppressing staphylococcal overgrowth or shifting the airway flora in ways that alter the eventual pneumonia pathogen. The data do not prove causation, and prophylaxis can also carry the well-known cost of selection pressure and resistance, but the association is strong enough to prompt closer scrutiny of antibiotic timing, spectrum, and indication in critically ill patients. The pathogen distribution suggests that infectious risk in neuro-ICU patients may reflect both the neurologic lesion and the microbial ecology created by care itself.
Mortality stayed high regardless of the causative organism
The cohort had substantial mortality. A total of 172 patients died during the ICU stay, representing 42.3%, and 90-day mortality reached 47.7% with 194 deaths. No difference in mortality was observed according to the pathogen responsible for ventilator-associated pneumonia. In other words, the microbiology shaped who got sick, but it did not separate survivors from non-survivors in this dataset.
That finding should be read carefully. In severe neurocritical illness, death is often driven by the underlying brain injury, multisystem organ failure, or the cumulative burden of prolonged intensive care rather than by the bacterial species alone. Once ventilator-associated pneumonia develops in a fragile patient with major neurologic injury, the pathogen may matter less for outcome than the severity of neurologic damage, overall illness burden, and the speed with which infection is recognized and treated. The absence of a mortality difference by pathogen does not diminish the importance of microbiologic stratification; it simply means that identifying S. aureus is more useful for initial management than for prognostication.
What the cohort can and cannot support
The study has the strengths of a multicenter design and a focused clinical question, but it remains retrospective and preprint status means the findings have not yet undergone peer review. The inclusion of 407 patients from 15,702 ICU admissions also signals that the analyzed cohort reflects a selected subset rather than the full universe of ventilated neurocritical care patients. The abstract does not provide enough detail here to judge antibiotic protocols, local resistance patterns, timing of pneumonia onset, or diagnostic thresholds, all of which could influence pathogen distribution.
Even with those limits, the signal is hard to dismiss. Ventilator-associated pneumonia after neurological injury was frequently a S. aureus infection, and the factors associated with that pattern were clinically recognizable at the bedside: coma depth, subarachnoid hemorrhage, illness severity, and prior antibiotic exposure. For intensive care teams, the immediate consequence is a more disciplined approach to empiric coverage in the neuro-ICU, coupled with a recognition that the path from brain injury to pneumonia may carry its own microbial signature.