O serotype-independent susceptibility of Pseudomonas aeruginosa to lectin-like pyocins.
Bottom Line: The recombinant proteins exhibit species-specific antagonistic activities down to nanomolar concentrations against clinical and environmental P. aeruginosa strains, including several multidrug-resistant isolates.No correlation was found between L pyocin susceptibility and phylogenetic relatedness of P. aeruginosa isolates.Sensitive strains were retrieved in 13 out of 15 O serotypes tested, excluding the possibility that the highly variable and immunogenic O serotype antigen of the LPS coating would represent a dominant susceptibility-discriminating factor.
Affiliation: Centre of Microbial and Plant Genetics, University of Leuven, 3001, Heverlee, Belgium.Show MeSH
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Mentions: Antibacterial activity of the purified proteins was assessed against a panel of clinical and environmental P. aeruginosa isolates and several strains of other Pseudomonas species. For this purpose, drops of recombinant protein were spotted onto Pseudomonas cell lawns, grown overnight at 30°C or 37°C, and scored the following day for growth inhibition halos (Fig. 3B, C, and D). A major number of the P. aeruginosa isolates proved pyocin L susceptible, while no activity was observed against other Pseudomonas species (Table 1, Table S1). More than 65% of the tested P. aeruginosa strains were susceptible to at least one pyocin, with 20% being killed by PyoL1, 24.7% by PyoL2, and 47.3% by PyoL3 (Fig. 4). These values are higher than those of LlpAs in other species, typically targeting only 10–15% of the respective test panels (Ghequire et al. 2012b, 2013b). Interestingly, several susceptible strains targeted by these pyocins are known to be multidrug-resistant (Table S1). MICs of the most sensitive strains are within the lower nanomolar range (Table 2). These values are of the same order of magnitude as the MIC of P. putida BW11M1 LlpA against P. syringae GR12-2R3 (2.08 nmol/L) (Ghequire et al. 2013a). The MICs of L pyocins are comparable to inhibitory concentrations reported for modular pyocins, such as pyocin S5 from strain PAO1 (Ling et al. 2010) and the M-type pyocins PaeM (Barreteau et al. 2009) and syringacin M (Grinter et al. 2012).
Affiliation: Centre of Microbial and Plant Genetics, University of Leuven, 3001, Heverlee, Belgium.