Influence of growth in biofilm in the formation of new biofilm by clinical isolates of Acinetobacter baumannii

The influence of growth in biofilm in formation of new biofilm by clinical isolates of Acinetobacter baumannii was investigated in this study. Sequential passage of A.baumannii isolates in biofilm culture in trypticase soy broth (TSB) resulted in gradually increased amount of biofilm production the by the isolates. On the other hand, passage of the same isolates in planktonic culture did not result in enhanced biofilm production. Passage induced enhanced biofilm production reached maximum level at passage 3 (P-3) for the strains A.baumannii strains AB-1 and AB-3 and passage 4 (P-4) for the strain AB-2. These values were 47 %, 40.4% and 71.8 % increased biofilm production, respectively by the biofilm passaged strains in comparison to their planktonic counterparts. Normal human serum (NHS), which enhances biofilm production by A.baumannii isolates was investigated to determine its effect on passage induced biofilm formation. NHS was found to further increase biofilm production by A.baumannii strains grown in biofilm mode, in comparison to their counterparts grown in planktonic state. Taken together, the results of this study indicate that growth of A. baumannii in biofilm enhances its potential to form new biofilm and biofilm formation is further increased by the presence of NHS in the growth medium.