pseudomallei by genome reduction [11]. Previously sequenced B. mallei strains do not carry intact prophages but can be infected by many phages isolated from B. pseudomallei[8–10, 12]. In this study we isolated φX216 from spontaneous plaques formed by the Thai B. pseudomallei environmental isolate E0237 and determined its DNA sequence. φX216 is a member of the widely distributed Burkholderia P2-like phage family [8]. It has broad B. pseudomallei strain infectivity for members of the B. pseudomallei clade. Our data indicate that φX216

may serve as a good candidate for developing rapid phage-based diagnostic tools for B. pseudomallei and B. mallei. Results and discussion ϕX216 isolation and host range B. pseudomallei buy Crenigacestat environmental isolate E0237 was observed to spontaneously form clear phage plaques after plating of overnight liquid cultures on agar plates. The spontaneously released phage, φX216 (named for the E0237 laboratory stock number), was AZD1480 trial plaque purified on B. pseudomallei strain 2698a and used to create medium-titer [106 plaque

forming units (pfu)/mL] plate lysates with a variety of B. pseudomallei host strains and high-titer (108 pfu/mL) liquid lysates using B. mallei ATCC23344. This strain was also chosen for production of larger volume liquid lysates to prevent contamination with other phages as it is not predicted to contain a prophage [8]. One-step growth curves demonstrated that φX216 has an approximate 60-minute latent phase, an 80-minute life cycle, and a burst size of 120 pfu per infected cell (Figure 1). φX216 formed plaques on 56 of a panel of 72 B. pseudomallei strains composed of 30 Nutlin-3a chemical structure environmental and 30 clinical isolates from Thailand, Venetoclax as well as 12 well-characterized strains from various sources, some of which are commonly used laboratory strains (see Additional file 1). At 77.8%, φX216 has one of the broadest strain infectivity ranges reported for a B. pseudomallei phage, comparing favorably with the Thai soil phages ST2 (78%, 49/63) and ST96 (67%, 42/63) [13, 14]. φX216 plaques were

1–2 mm in diameter and mostly-clear on the majority of B. pseudomallei strains although there was some strain-dependent variation in plaque appearance with some forming pinpoint and/or turbid plaques. In addition, φX216 was also able to form plaques on all (9/9) B. mallei strains tested. In contrast, φX216 did not form plaques on closely related (B. thailandensis and B. oklahomensis) or other (B. ubonenesis, B. vietnamensis and B. gladioli pathovar cocovenenans) Burkholderia species (see Additional file 1). Although fewer isolates of these species were tested, φX216 does appear to have specificity for B. pseudomallei and B. mallei as compared with ST2 and ST96, which formed plaques on five of seven tested B. thailandensis strains. Because of the close relatedness of B. pseudomallei and B. thailandensis it will be prudent to assess more B.