Reporter-Phage-Based Detection and Antibiotic Susceptibility Testing of for a Rapid Plague Outbreak Response.

Pneumonic plague is a lethal infectious disease caused by , a Tier-1 biothreat agent. Antibiotic treatment can save infected patients; however, therapy should begin within 24 h of symptom onset. As some strains showed an antibiotic resistance phenotype, an antibiotic susceptibility test (AST) must be performed. Performing the Clinical and Laboratory Standards Institute (CLSI)-recommended standard process, which includes bacterial isolation, enumeration and microdilution testing, lasts several days. Thus, rapid AST must be developed. As previously published, the -specific reporter phage ϕA1122:: can serve for rapid identification and AST (ID-AST). Herein, we demonstrate the ability to use ϕA1122:: to determine minimal inhibitory concentration (MIC) values and antibiotic susceptibility categories for various therapeutic antibiotics. We confirmed the assay by testing several nonvirulent isolates with reduced susceptibility to doxycycline or ciprofloxacin. Moreover, the assay can be performed directly on positive human blood cultures. Furthermore, as may naturally or deliberately be spread in the environment, we demonstrate the compatibility of this direct method for this scenario. This direct phage-based ID-AST shortens the time needed for standard AST to less than a day, enabling rapid and correct treatment, which may also prevent the spread of the disease.