Characteristics of ventilator-associated pneumonia due to Gram-negative bacteria in the intensive care unit: A single-center experience

Abstract

Ventilator-associated pneumonia (VAP) is one of the most common and serious infections in hospitalized patients. VAP is associated with worse outcomes and significant morbidity and mortality worldwide. Our primary goal in this study was to identify the VAP pathogen with its distribution characteristics, clarify risk factors, prognosis, and outcomes, and help reduce associated morbidity and mortality. This retrospective observational study was conducted between June 2019 and June 2022 in 3 general intensive care units of a training and research hospital. Data on demographic, clinical and laboratory parameters were collected retrospectively from medical cards and electronic records. A total of 204 patients were diagnosed with VAP caused by Gram-negative microorganisms. Chronic renal failure (RF) and neurological diseases were significantly associated with mortality (P = .01, P = .023). The duration of mechanical ventilation before VAP and the duration of mechanical ventilation were significantly longer in survivors compared to non-survivors. The number of patients with early VAP was significantly higher, and the days of VAP were shorter in the non-survivors compared to the survivors (P = .006, P = .016). The number of VAP episodes (P = .0001), the presence of RF, acute respiratory distress syndrome, bacteremia, and sepsis before VAP (<48 hours) were associated with mortality. Intensive care unit and the length of hospital stay were significantly shorter in non-survivors than in survivors (P = .0003, P = .0001). Administration of monotherapy, inadequate empirical antibiotic therapy, inadequate antibiotic therapy (P = .004, P = .002, and P = .0006), persistence of the pathogen (P = .0001), C-reactive protein and procalcitonin levels (P = .002, P = .041) were associated with mortality. The presence of neurological diseases and RF was associated with a greater likelihood of mortality in patients with VAP. As risk factors, early-onset VAP, presence of RF-acute respiratory distress syndrome-bacteremia-sepsis 48 hours before VAP, organ failure, need for hemodialysis, shock and the persistence of the pathogen increased the risk of mortality.

Keywords: Gram-negative microorganisms; mortality; multidrug-resistant pathogens; prognosis; ventilator-associated pneumonia.

Figure 1.

Flow chart of the study. CNS = coagulase-negative staphylococcus, MRSA = methicillin-resistant Staphylococcus aureus, VAP = ventilator-associated pneumonia.

Figure 2.

Percentage of drug susceptibility patterns for each organism. Numbers represent the number of patients; susceptible means susceptible to all antimicrobial agents in 4 patients infected with Serratia (2), Proteus mirabilis (1), Enterobacter (1); multidrug-resistant in 4 patient infected with Serratia (2), Proteus mirabilis (1), Enterobacter (1), Aeromanas (1) and extensively drug-resistant in 1 patients infected with Pantoea. (1). MDR = multidrug-resistant; XDR = extensively drug-resistant.