Effect of Acinetobacter baumannii secretions on Pseudomonas aeruginosa cell growth and biofilm formation / 临床检验杂志

ABSTRACT

Objective To investigate the effects of Acinetobacter baumannii culture supernatants on planktonic cell growth and biofilm formation of Pseudomonas aeruginosa.Methods The standard isolates (ATCC 19606,ATCC 1195) and clinical isolates (AB23,AB39,AB53) of Acinetobacter baumannii were collected and the 6,12,16,24 and 48 hour-cultured supernatants were extracted.The effects of the culture supernatants on the biofilm formation of Pseudomonas aeruginosa PAO1 were detected on the 96-well plate combined with crystal violet staining.Two-fold concentration of LB medium was prepared to eliminate the effects of nutrition consumption of Acinetobacter baumannii during culture on Pseudomonas aeruginosa growth.The active ingredients in the supernatant of Acinetobacter baumannii culture medium were investigated by using the concentrated tube containing protein with relative molecular mass 3 000.Results The most suitable period for Acinetobacter baumannii culture supernatant extraction was between 12 to 24 hours,so the 16 hourcultured supernatant was chosen for next experiments.The 50％ culture supernatant of Acinetobacter baumannii ATCC 1195 and ATCC 19606 significantly inhibited the planktonic cell growth of Pseudomonas aeruginosa PAO1,in which the absorbance at 630 nm reduced from(0.688 ± 0.014) and(0.692 ± 0.014) to (0.431 ± 0.023) and (0.428 ± 0.020) respectively (t =16.780,P ＜ 0.05;t =18.500,P ＜ 0.05).The 50％ culture supernatant of Acinetobacter baumannii ATCC 1195 and ATCC 19606 also significantly inhibited the biofilm formation of Pseudomonas aeruginosa PAO1 with decreased absorbance at 570 nm from (2.071 ± 0.068) and (1.986 ±0.023) to (1.639 ± 0.042) and (1.525 ± 0.202) respectively (t =9.358,P ＜ 0.05;t =3.924,P ＜ 0.05).The biofilm inhibitory effect of the protein with relative molecular mass less than 3 000 was obviously observed by reducing amount of biofilm formation from (1.177 ± 0.040) to(1.056 ± 0.030) (t =4.192,P ＜ 0.05),while there was no inhibitory effect of the proteins with relative molecular mass more than 3 000 in the composition.Conclusion Acinetobacter baumannii culture supernatant could effectively inhibit the planktonic cell growth and biofilm formation of Pseudomonas aeruginosa and the relative molecular mass of active ingredients in the culture supernatant may be less than 3 000.