Work

Rapid Phenotypic Antibiotic Susceptibility Testing Using Forward-Angle Laser Light Scattering

Year: 2016

Type: article

Abstract: Background. Rapid antimicrobial susceptibility testing (AST) enables clinicians to prescribe targeted therapies more quickly, thereby improving patient care and promoting antibiotic stewardship. Forward-angle laser light scattering (FLLS) is a sensitive technique for detection of microbial growth at lower limits of detection than most conventional methods. The objective of this study was to evaluate the effectiveness of FLLS to provide rapid phenotypic susceptibility information for clinical Gram-negative urine isolates. Methods. A BacterioScan 216Dx FLLS instrument was used to assess bacterial growth. Disposable multicuvettes were prefilled, up to 30 days before use, with breakpoint concentrations of ciprofloxacin (CIP), trimethoprim-sulfamethoxazole (SXT), nitrofurantoin (NIT), and ceftriaxone (CRO). Standardized inocula of urine isolates were prepared in Mueller-Hinton broth and dispensed into the multicuvettes. The inoculated multicuvettes were analyzed in the 216Dx for 20 hours at 37°C. Growth in the presence of antibiotics, as measured by FLLS, was compared with a no-antibiotic control to facilitate susceptible/intermediate/resistant interpretations by a blinded observer. Susceptibility profiles generated by FLLS were then compared with a standard agar dilution method. Results. A total of 20 pathogens were evaluated in this study, including strains of Escherichia coli, Klebsiella, Pseudomonas, Enterobacter, and Citrobacter species. Overall, the experimental and reference data were in agreement, with 6 minor errors and 4 major errors committed. Detection times ranged from 3 to 5 hours for both susceptible (Figure 1) and resistant (Figure 2) strains. This time frame was also suitable for pathogens known to require longer incubation times, such as Pseudomonas aeruginosa (Figure 3). Conclusion. Forward-angle laser light scattering can provide phenotypic AST information with a faster time-to-result than most current clinical AST methods (e.g. disc diffusion, broth microdilution, agar dilution). Further evaluation of additional clinical isolates and isolate-antibiotic combinations will be required for validation of this technique, and the development of a computational algorithm for susceptible/intermediate/resistant interpretation of FLLS growth curves. Disclosures. A. Tomaras, BacterioScan, Inc: Employee, Salary

Source: Open Forum Infectious Diseases

DOI: 10.1093/ofid/ofw172.43

Authors: Andrew Norgan, Andrew Tomaras

Institution: Mayo Clinic

Language: English

Topic: Bacterial Identification and Susceptibility Testing

Subfield: Clinical Biochemistry

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

SDG: Good health and well-being

Open Access status: gold

Estimated APC paid: $4,053