Using the rate of bacterial clearance determined by real-time polymerase chain reaction as a timely surrogate marker to evaluate the appropriateness of antibiotic usage in critical patients with Acinetobacter baumannii bacteremia.
OBJECTIVE
Bacteremia caused by Acinetobacter baumannii is becoming more frequent among critically ill patients, and has been associated with high mortality and prolonged hospital stay. Multidrug resistance and delay in blood culture have been shown to be significant barriers to appropriate antibiotic treatment. Quantitative polymerase chain reaction assays were recently used to monitor bacterial loads; we hypothesized that the rate of bacterial clearance determined by quantitative polymerase chain reaction can be used as a timely surrogate marker to evaluate the appropriateness of antibiotic usage.


METHODS
Prospective observational study.


METHODS
University hospital and research laboratory.


METHODS
Patients with culture-proven A. baumannii bacteremia in the intensive care units were prospectively enrolled from April 2008 to February 2009.


METHODS
Plasmid Oxa-51/pCRII-TOPO, which contained a 431-bp fragment of the A. baumannii-specific Oxa-51 gene in a pCRII-TOPO vector, was used as the standard. Sequential bacterial DNA loads in the blood were measured by a quantitative polymerase chain reaction assay.


RESULTS
We enrolled 51 patients with A. baumannii bacteremia, and examined 318 sequential whole blood samples. The initial mean bacterial load was 2.15 log copies/mL, and the rate of bacterial clearance was 0.088 log copies/mL/day. Multivariate linear regression using the generalized estimation equation approach revealed that the use of immunosuppressants was an independent predictor for slower bacterial clearance (coefficient, 1.116; p<.001), and appropriate antibiotic usage was an independent predictor for more rapid bacterial clearance (coefficient, -0.995; p<.001). Patients with a slower rate of bacterial clearance experienced higher in-hospital mortality (odds ratio, 2.323; p=.04)


CONCLUSIONS
Immunosuppression and appropriate antibiotic usage were independent factors affecting the rate of clearance of A. baumannii bacteremia in critical patients. These findings highlight the importance of appropriate antibiotic usage and development of effective antibiotics against A. baumannii in an era of emerging antibiotic resistance. The rate of bacterial clearance could serve as a timely surrogate marker for evaluating the appropriateness of antibiotics.
Department of Internal Medicine, Institute of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
Yu-Chung
YC
Chuang
Shan-Chwen
SC
Chang
Wei-Kung
WK
Wang
D000151:Acinetobacter Infections / Q000175:diagnosis / Q000188:drug therapy* / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000235:genetics; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D016470:Bacteremia / Q000175:diagnosis / Q000188:drug therapy* / Q000382:microbiology; D058491:Bacterial Load; D015415:Biomarkers / Q000097:blood; D016638:Critical Illness; D004269:DNA, Bacterial / Q000235:genetics; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods
D000900:Anti-Bacterial Agents; D015415:Biomarkers; D004269:DNA, Bacterial