A seven year survey of antibiotic susceptibility and its relationship with usage.

Bacterial susceptibilities to 14 antibiotics of 7385 clinical isolates, belonging to six species of Gram-negative bacilli, were analysed during seven years (1980-86). The recovery of Serratia marcescens, Acinetobacter calcoaceticus and Pseudomonas aeruginosa increased while their sensitivity to antibiotics decreased significantly, especially to aminoglycosides and tetracycline. There were significant correlations between increase in antibiotic use and decrease in susceptibility. There was a striking relationship between third-generation cephalosporin use and increasing number of isolates of the species mentioned above.