Rapid Microbiological Identification And Major Drug Resistance Phenotyping With Novel Multiplexed Automated Digital Microscopy (MADM) For Ventilator-Associated Pneumonia (VAP) Surveillance

Abstract

Background Methods Results Conclusions Introduction. Clinical diagnosis of VAP is imprecise. Cumbersome microbiological identification and antimicrobial sensitivity testing techniques delay treatment and are associated with increased morbidity, mortality and antimicrobial resistance. W e hypothesized that rapid microbiological detection and sensitivity reporting from mini-BAL samples obtained during surveillance of at-risk mechanically ventilated (MV) adults would reduce time to initiation of targeted treatment for VAP compared with a clinical and quantitative-culture guided approach. Methods. Adult MICU patients with identified surrogate were included within 72 hours of intubation and if anticipated to require MV for >48h. Moribund state or pregnancy were exclusions. Surveillance mini-BAL (Combicath, Plastimed) was performed on Day 1, 3, 5, 7 and 10 of MV. Samples were processed for both a) routine respiratory quantitative microbiological culture (QCx) and sensitivity assays (> 48h result availability) and b) rapid (<8 hour) flowcell/surface-capture and automated microscopy (MADM). Viable bacteria were identified using growth analysis enhanced by a focused VAP antibody panel (S. aureus, P. aeruginosa, A. baumannii). Untypable organisms were also reported. Sensitivity was assessed using growth analysis. Attending physicians were blinded to MADM results. Results. 77 miniBALs (median 2; Range 1-7 per patient) were performed on 33 MV patients (Median age 55, range 26-84 years; 30% Female; 52% active smokers, Median APACHE II 21 (IQR 16-24). 20 (61%) patients had diffuse or patchy CXR infiltrates and 3 patients had no infiltrates on enrollment. 70 BAL samples were tested using MADM. 12 samples grew ≥ 1 bacterial type at >104 CFU/mL by QCx. 8 samples contained mixed respiratory bacteria. 7 samples contained VAP associated bacteria (4 S. aureus (incl 1 auxotroph and 3 MRSA), 2 S. maltophilia, 1 K. pneumoniae). MADM identified 3 of 4 target organisms accurately and antimicrobial response enabled identification of 2 of 2 S. maltophilia. A K. pneumoniae sample was reported untypable. Auxtrophic growth precluded testing for 1 S. aureus sample. Antimicrobial response matched in 5 samples (3 MRSA, 2 S. maltophilia). 14 samples grew ≥ 1 bacterial type at < 104 CFU/mL by QCx. 10 samples contained mixed respiratory bacteria, 3 samples yeast, 2 samples lactose fermenting GNB, 1 sample non lactose fermenting GNB, 1 sample H. influenzae, beta lactamase positive, 1 sample H. species, not influenzae, 1 sample Beta hemolytic Streptococcus. None of the patients having bacteria detected by QCx at <104 CFU/mL developed clinical VAP. In 98% of samples MADM was concordant with QCx-negative samples. MADM detected a enteric organism (10 5)) in one sample negative by QCx. One VAP was diagnosed by clinical criteria. MADM based ID would have resulted in important and earlier antibiotic change/addition in 63% of mini-BAL samples with above threshold target organisms by QCx. Conclusions. MADM is 100% specific and had 85% identification consisten...

Rapid Automated Microscopy for Microbiological Surveillance of Ventilator-associated Pneumonia

“…Some of the data in this study were presented at the American Thoracic Society 2011 International Conference (22).…”

Next-Generation Antimicrobial Susceptibility Testing

“…This technology has been extended for use with microcolonies and serial photography in the presence or absence of antibiotics. Such technologies can generate a "1-day AST" for bacteria from positive blood culture bottles (48). This demonstrates that simple, seemingly old-fashioned test formats can still be adapted into systems that better serve the patient's needs.…”