Inhibition of growth and biofilm of Pseudomonas aeruginosa by Streptococcus sanguinis cpnp culture supernatant
Objective To explore the role of Streptococcus sanguinis cpnp(hereinafter the cpnp)culture supernatant(CS)in inhibiting the growth and biofilm formation of Pseudomonas aeruginosa(P.aeruginosa)and destroying the ma-ture biofilm,as well as its inhibitory effect in combination with antibiotics,in order to provide a basis for the use of respir-atory commensal bacterial agents to intervene in the colonization of P.aeruginosa in respiratory tract and reduce the respir-atory tract infections.Methods The inhibitory effect of the cpnp on the growth of P.aeruginosa was determined using Oxford cup method.96-well plate method was used to determine the inhibitory effect of the cpnp CS combined with ceftazidime on the growth of P.aeruginosa.The biofilm model of P.aeruginosa was established in vitro,and the inhibit-ory effect of the cpnp CS on the formation of its biofilm was determined with crystal violet semiquantitative method,congo red staining method,and RT-qPCR method;the destructive effect of the cpnp CS on mature biofilm was measured by us-ing crystal violet semiquantitative method and MTT method;and the morphology of the biofilm wasobserved using light microscopy and electron microscopy.Results The cpnp CS inhibited the growth of P.aeruginosa,showed synergistic ef-fect when combined with ceftazidime(P＜0.001),and reduced the amount of P.aeruginosa biofilm formed(P＜0.001),the production of extracellular polysaccharides(P＜0.001),and the level of expression of extracellular polysaccharide genes(P＜0.050).The cpnp CS reduced the total amount of mature biofilm(P＜0.001)and decreased the metabolic activ-ity of biofilm(P＜0.001).Conclusion The cpnp CS and combined antibiotics antagonized the growth of P.aeruginosa,and the supernatant had a good inhibitory and destructive effect on its biofilm.
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