The objective of the global study, which is part of the SENTRY antimicrobial surveillance program, was to compare the antimicrobial activity of colistin and polymyxin B against other antimicrobial agents for 40,625 strains of pathogens at Gram negative collected from patients around the world.

Sensitivity was determined and interpreted using CLSI criteria by the method of serial micro-dilutions, with the exception of the determination of the activity of colistin against microorganisms of the family. Enterobacteriaceae.

Polymyxins showed pronounced in vitro activity (MPC90 less than 0.5-1 mg / L) against a large collection of clinical isolates, and the frequency of resistance to polymyxin was very low (less than 0.1-1.5%) Resistance to polymyxins has remained stable among all microorganisms, with the exception of some Klebsiella spp. Strains obtained from patients from the Asia-Pacific region and Latin America, where there was a tendency to detect higher resistance levels (p less than 0.05)

In addition, a significant decrease in the sensitivity to imipenem of the Acinetobacter spp strains has been detected in most geographical regions. and Klebsiella spp.

Thus, although polymyxins exhibit remarkable in vitro activity against the vast majority of gram negative microorganisms tested, resistance to polymyxins has been observed in the Asia-Pacific region and in certain countries of the Latin America. Therefore, it is necessary to use polymyxins very carefully in clinical practice and to monitor the level of antibiotic resistance of Gram negative pathogens in each specific region and even in a separate hospital.