Appropriate Antimicrobial Therapy for A baumannii Lowers Mortality in Severely Ill Patients

In patients severely ill with Acinetobacter baumannii (A baumannii) bacteremic pneumonia and with an APACHE II score of 35 or greater, appropriate antimicrobial therapy significantly reduced 14-day mortality, according to study findings published in Antimicrobial Resistance and Infection Control.

High antimicrobial resistance of A baumannii leads to the administration of inappropriate empirical antimicrobial therapies and may contribute to a greater risk for mortality in patients with A baumannii bacteremic pneumonia. Studies reported that lower mortality rates of A baumannii bacteremic pneumonia was associated with appropriate therapy and the effects may be more pronounced in severely ill patients. This retrospective study evaluated the affect of appropriate antimicrobial therapy on 14-day mortality in A baumannii bacteremic pneumonia patients after adjusting for risk factors, demographics, and clinical characteristics.

In total, 336 patients with monomicrobial A baumannii bacteremic pneumonia collected from 5 medical centers in Taiwan from 2012 to 2016 were included in this study. Logistic regression was used to analyze risk factors for 14-day mortality, and to assess the interaction between the Acute Physiology and Chronic Health Evaluation (APACHE) II score and appropriate antimicrobial therapy.

Results suggested to the investigators that 14-day mortality is reduced primarily severely ill patients who received appropriate antimicrobial therapy (n=151) compared with those who did not receive appropriate antimicrobial therapy (n=185). The overall mortality rate was 47.3% (159/336). Administration of appropriate antimicrobial therapy was independently associated with lower mortality (odds ratio [OR], 0.57; 95% CI, 0.34-0.97; P =.04). Independent predictors of 14-day mortality include APACHE II score (P <.001) and extensive drug resistance (P <.001), defined as non-susceptibility to all drug classes except colistin and tigecycline. In addition, the severity of infection had a statistically significant effect of appropriate antimicrobial therapy on survival (OR, 0.0098; 95% CI, 0.0005-0.1885; P =.001).

Appropriate antimicrobial therapy was only associated with lower mortality in patients with an APACHE II score of greater than 35 (OR, 0.0098; 95% CI, 0.0005-0.1885; P =.002), even in subgroups of patients who were admitted to the ICU at the time of bacteremia and patients who were ventilator-assisted at the time of bacteremia. Multivariate analysis of demographic and clinical characteristics showed that patients with higher APACHE II scores (P =.001), extensive drug resistance (P =.029), and a history of myocardial infarction (P =.045) were more likely to receive inappropriate antimicrobial therapy. Patients who had a history of connective tissue disease (P =0.035) or received a central venous catheter at the time of bacteremia onset (P =.004) were more likely to receive appropriate antimicrobial therapy. In patients with APACHE II scores of 35 or less, appropriate antimicrobial therapy was not associated with lower mortality.

In patients who received appropriate antimicrobial therapy, tigecycline and colistin was associated with higher 14-day (P =.008; P =.012, respectively) and 28-day (P =.045; P =.030, respectively) mortality; these patients were also infected with carbapenem-resistant A baumannii more frequently than patients receiving other agents. (P <.001). In patients who received inappropriate antimicrobial therapy, antipseudomonal penicillins was associated with higher 28-day mortality compared with other agents.

Overall, the study authors conclude that, “appropriate antimicrobial therapy may be of crucial importance to the survival of the most severely ill patients (APACHE II score >35) is in line with the previous studies.”

Reference

Kang FY, How CK, Wang YC, et al. Influence of severity of infection on the effect of appropriate antimicrobial therapy for Acinetobacter baumannii bacteremic pneumonia. Antimicrob Resist Infect Control. 2020;9(1):160. doi:10.1186/s13756-020-00824-4

This article originally appeared on Infectious Disease Advisor