A HAZARD of suboptimal antimicrobial therapy is the potential of creating an environment conducive to the growth of resistant organisms. This risk is potentially present in infants with meningitis caused by enteric gram-negative bacteria because of the poor accumulation of aminoglycoside antibiotics in the cerebrospinal fluid.1 Enteric gram-negative bacteria have previously been reported to acquire resistance to gentamicin during therapy of neonatal meningitis,2,3 but the phenomenon was incompletely documented and mechanism of acquisition not characterized.4 We have observed an Escherichia coli causing meningitis in a newborn infant that appeared to acquire resistance to several aminoglycoside antibiotics during therapy.Case Report . . .