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Objective To explore the effects of aspirin on formation and dispersion of Pseudomonas aeruginosa (P.aeruginosa) biofilm.Methods The broth microdilution method was used to detect the minimal inhibitory concentration(MIC) of aspirin for P.aeruginosa.The anti-biofilm effects of aspirin on P.aeruginosa were determined on the microtiter plates combined with crystal violet staining.The serial dilution method for counting colony number on microtiter plate was used to explore the effects of aspirin on initial adherence of P.aeruginosa.Results The MIC values of aspirin against PAO1,PA18,PA53 and PA67 strains of Pseudomonas aeruginosa were 5,2.5,5 and 5 mg/mL respectively.Aspirin significantly inhibited the formation and dispersion of the biofilm of PAO1 and PA18 strains (t =5.65,P ＜ 0.05 and t =5.06,P ＜ 0.05 for inhibition;t =6.45,P ＜ 0.05 and t =6.26,P ＜ 0.05 for dispersion) at the concentration of 2.5 mg/mL.Similar effects were also found in the determination for PA67 and PA53 strains(t =6.45,P ＜0.05 and t =6.26,P ＜ 0.05 for inhibition;t =7.82,P ＜ 0.05;t =9.18,P ＜ 0.05 for dispersion) at aspirin concentration of 1.25 and 0.313 mg/mL respectively.Aspirin inhibited the initial adherence of P.aeruginosa at the concentration of 2.5 mg/mL(P ＜0.05).Conclusion Aspirin could significantly inhibit the initial adherence and biofilm formation of P.aeruginosa and disperse the 24 hour-formed mature bioiflm.
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Objective To investigate the biofilm (BF)formation rule of nontypeable Haemophilus influenzae (NTHi)in vitro, and to observe the internal structure of BF by scanning electron microscope (SEM). Methods NTHi ATCC49247 was investigated in the present study,Pseudomonas aeruginosa (PA)PAO1 was cultured as positive control,at the same time blank control group was set up.The BF of the bacteria were cultured and then collected on day 1,2,3,4,5,6,and 7.The BF formation was detected by crystal violet staining and plate counting and the structure of BF formed by ATCC49247 was observed under SEM on day 3.Results The plate colony counting of biofilm BF by ATCC49247 and PAO1 raised during first 3 d, and then declined to (0.823 6±0.007 5)×107 cfu·mL-1 and (0.942 6±0.019 9)×107cfu·mL-1 respectively on day 7. The differences between two groups were statistically significant on day 3,4,5,and 6 (P<0.05).The differences between different time points in the same bacteria group were statistically significant (P<0.05).The densities of BF formed by ATCC49247 and PAO1 raised during the first 3 d.The absorbances on 570 nm wavelength (A570 )in two groups were 2.717 4±0.017 2 and 2.885 3±0.039 0 ,respectively;and then the A570 values in two groups declined to 0.151 7±0.074 5 and 1.196 9±1.108 5,respectively on day 7;the differences between bacteria groups and blank control were statistically significant (P<0.05 );the differences between two bacteria groups were statistically significant on day 3,4,5,and 6 (P<0.05);the differences between different time points in the same bacteria group were statistically significant (P<0.05).On day 3,the obvious BF formed by ATCC49247 were observed under SEM.Conclusion BF could be formed by NTHi in vitro;crystal violet staining,plate colony counting and SEM could be taken as conventional methods to detect BF.