ERIC-PCR has been widely used as genomic fingerprinting technology for classification and identification of bacterial isolates. Recently, it has been used by some labs to characterize bacterial mixtures. However, there are still disputes regarding the mechanism of product formation in ERIC-PCR. We cloned and sequenced the 1. 1kb major band of the ERIC-PCR fingerprint of E. coli K-12 strain MG1655, the strain used for whole genome sequencing, and found that the band consisted of 3 different DNA fragments with one fragment the most abundant (93 out of 95 clones, i. e. 97. 89%). Sequence analysis showed that two of the three fragments amplified from a chromosomal region where one ERIC element exist either upstream or downstream, while one fragment amplified from a region where no ERIC element was found. It was thus postulated that ERIC-PCR is not an absolutely random amplified PCR technique, especially when it is applied to those genomes containing ERIC elements.

Objective To evaluate antibacterial activities of Cefoperazone-Sulbactam upon gram negative bacilli,and compare the differences in susceptibility between two different concentrations of Cefoperazone-Sulbactam combination disc.Method A total of 381 strains of commonly occurred gram negative bacilli were found from 2nd Affiliated Hospital of Zhejiang University School of Medicine,Zhejiang Provincial People's Hospital,The Third Hospital of Hangzhou and Hangzhou Hospital of Traditional Chinese Medicine respectively.Susceptibility test was conducted by K-B method using 75 μg/disc Cefoperazone plus with 75 μg/disc Sulbactam(150 disc)and 75 μg/disc Cefoperazone with 30 μg/disc Sulbactam(105 disc),respectively.Meanwhile the minimal inhibitory concentration(MIC)of Cefoperazone-Sulbactam was determined by standard agar dilution.The data were analyzed by using WHONET 5.4 and SPSS.Results Disc diffusion method was carried out to detect the antibacterial activities upon Escherichia coli,Klebsiella pneumonia,Pseudomonas aeruginosa and Acinetobacter baumannii,using 105 disc and 150 disc,respectively.The data indicated that consistency rates between these two different discs were 26.3%,79.2%,83.7%and 33%,respectively.The k-related sample test was performed by using SPSS version 10.0 and shown that the P value was less than 0.05.Upon those organisms mentioned above,the consistency rates between the antibacterial activities of 105 disc and those of agar dilution were 77.8%,89.6%,70.9%and 77%,respectively.When it was going to compare agar dilution vs.150 disc upon the susceptibility of those organisms the consistency rates were 27.3%,79.2%,61.6%and 30%,respectively.Compared with agar dilution,the error rates of those two different concentration discs revealed that the false susceptibility and false intermediate of 105 disc were higher than those of 105 disc.ConclusionsThe results of susceptibility test showed that 105 disc was more close to agar dilution than that of 150 disc.However,the 150 disc used in clinic led to increase in sensitivity of susceptibility test to organisms.