Clinical Features and Outcomes of Monobacterial and Polybacterial Episodes of Ventilator-Associated Pneumonia Due to Multidrug-Resistant Acinetobacter baumannii

Abstract

Multidrug-resistant A. baumannii (MDRAB) VAP has high morbidity and mortality, and the rates are constantly increasing globally. Mono- and polybacterial MDRAB VAP might differ, including outcomes. We conducted a single-center, retrospective (January 2014–December 2016) study in the four ICUs (12–18–24 beds each) of a reference Lithuanian university hospital, aiming to compare the clinical features and the 30-day mortality of monobacterial and polybacterial MDRAB VAP episodes. A total of 156 MDRAB VAP episodes were analyzed: 105 (67.5%) were monomicrobial. The 30-day mortality was higher (p < 0.05) in monobacterial episodes: overall (57.1 vs. 37.3%), subgroup with appropriate antibiotic therapy (50.7 vs. 23.5%), and subgroup of XDR A. baumannii (57.3 vs. 36.4%). Monobacterial MDRAB VAP was associated (p < 0.05) with Charlson comorbidity index ≥3 (67.6 vs. 47.1%), respiratory comorbidities (19.0 vs. 5.9%), obesity (27.6 vs. 9.8%), prior hospitalization (58.1 vs. 31.4%), prior antibiotic therapy (99.0 vs. 92.2%), sepsis (88.6 vs. 76.5%), septic shock (51.9 vs. 34.6%), severe hypoxemia (23.8 vs. 7.8%), higher leukocyte count on VAP onset (median [IQR] 11.6 [8.4–16.6] vs. 10.9 [7.3–13.4]), and RRT need during ICU stay (37.1 vs. 17.6%). Patients with polybacterial VAP had a higher frequency of decreased level of consciousness (p < 0.05) on ICU admission (29.4 vs. 14.3%) and on VAP onset (29.4 vs. 11.4%). We concluded that monobacterial MDRAB VAP had different demographic/clinical characteristics compared to polybacterial and carried worse outcomes. These important findings need to be validated in a larger, prospective study, and the management implications to be further investigated.

Risk factors for mortality in intensive care unit patients with <i>Stenotrophomonas maltophilia</i> pneumonia in South Korea

“…Given the heterogeneity in the type and distribution of coisolates in those studies [ 9 , 11 , 12 ] and the potential interactions between S. maltophilia and certain strains [ 23 , 24 ], clearly elucidating the significance of polymicrobial infection as a prognostic factor in critically ill patients with S. maltophilia based on the current small-scale study is difficult. Conversely, a recent study on multidrug-resistant Acinetobacter baumannii VAP reported a similar result to ours, which showed a lower mortality rate in the case of polymicrobial infection than that in monomicrobial, and the attenuation of virulence due to competition with coexisting pathogens in a polymicrobial setting was suggested as a possible explanation [ 25 ].…”

Clinical Features and Outcomes of VAP Due to Multidrug-Resistant Klebsiella spp.: A Retrospective Study Comparing Monobacterial and Polybacterial Episodes

“…During recent decades, progress in diagnostic techniques has aided in detecting the rising prevalence of polybacterial pneumonia [ 28 , 29 ]. Notwithstanding this, the studies examining the discrepancies in outcomes among patients with mono- vs. polybacterial VAP caused by the same pathogen are very limited [ 30 , 31 ]. Despite the increasing knowledge about the composition of the normal microbiome of the lower respiratory tract, previously thought to be sterile, it is still difficult to clarify the precise role of each microorganism in polybacterial lung infections: are they true etiological pathogens or merely colonizers/commensals?…”

Treatment and Management of Acinetobacter Pneumonia: Lessons Learned from Recent World Event

“…It was observed that the majority of MDRAB VAP episodes were monomicrobial (67.5%), and the study concluded that monobacterial MDRAB VAP exhibited different demographic and clinical characteristics compared to polybacterial infections and was associated with worse outcomes. 94 …”