Table 1.
Bacterial strains used and results of phage propagation as detected by a standard lysis procedure and by the described qPCR assay.
Table 2.
Primers used for qPCR in this study.
Figure 1.
Lytic properties of bacteriophages φA1122, L-413C, and P2 vir1 towards Y. pestis CO92 pgm−.
The dynamics of lysis was determined in BHI broth at multiplicity of infection of 0.1. Optical density was normalized to the start of infection (1 on the Y axis corresponds to the initial OD600 = 0.2).
Figure 2.
Determination of lysis speed and burst sizes for bacteriophages φA1122, L-413C, and P2 vir1 on Y. pestis CO92 pgm−.
Phage burst sizes (an average phage progeny produced by one bacterial cell) correspond to plateaus on the curves.
Figure 3.
Parameters of φA1122- and L-413C-based qPCR tests for phage DNA and live phage particles determined by linear regression method.
A and B, standard curves plotted for DNA concentrations of φA1122 and L-413C, respectively. C and D, standard curves plotted for live phage particles of φA1122 and L-413C, respectively.
Figure 4.
Dynamics of growth of phages φA1122 and L-413C on different concentrations of Y. pestis cells detected by qPCR.
The starting points of phage infection correspond to 100 PFU per 1 µl sample and are normalized to 1. A. The titer rise of φA1122. B. L-413C amplification.
Figure 5.
qPCR tests on simulated clinical human blood samples.
A. Linear regression of φA1122 DNA concentration in blood diluted 1∶20 in comparison with SM buffer data. B. φA1122-based detection of Y. pestis in artificially contaminated blood diluted 10-fold with BHI broth. To calculate the actual bacterial loads in the undiluted blood samples, the CFU numbers shown should be multiplied by 10. The starting points of phage infection correspond to 100 PFU per 1 µl sample and are normalized to 100 = 1.