Evaluation of SDS‐polyacrylamide gel systems for the study of outer membrane protein profiles of clinical strains of Acinetobacter baumannii

The outer membrane protein (OMP) profiles of 23 blood isolates of Acinetobacter baumannii representing all the different antimicrobial susceptibility patterns observed during a 3-year period in a Spanish hospital were studied. OMPs extracted from envelopes of sonicated cells after solubilisation with 2% of N-lauryl-sarcosinate were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) using the Laemmli's buffers. Eight running gel systems differing in the concentration of polyacrylamide (8%, 10% and 12%) and in the absence or presence of urea (4 M and 6 M) were used in a preliminary study analysing the OMP profiles of four clonally unrelated strains of A. baumannii. When this study was completed, the OMPs of the 23 A. baumannii were analysed in 10% SDS-polyacrylamide gels with 6 M urea and in 12% SDS-polyacrylamide gels. Ten OMP profiles were observed in 10% SDS-polyacrylamide gels with 6 M urea, whereas only 5 OMP profiles were visualised using 12% SDS-polyacrylamide gels. The OMP profiles obtained in 10% SDS-polyacrylamide gels with 6 M urea only partially correlated with those observed in 12% SDS-polyacrylamide gels. In conclusion, the use of 10% SDS-polyacrylamide gels with 6 M urea is recommended for the study of OMP profiles of A. baumannii.