255 Aerobic Gram-negative micro-organisms Acinetobacter baumannii+ Burkholderia cepacia +* Campylobacter spp.+* Citrobacter freundii* Enterobacter aerogenes Enterobacter cloacae * Escherichia coli* Klebsiella oxytoca Klebsiella pneumoniae* Morganella morganii* Neisseria gonorrhoeae* Proteus mirabilis* Proteus vulgaris* Providencia spp.