IMIPENEM RESISTANCE IN AEROBIC GRAM-NEGATIVE BACTERIA

A prospective study was undertaken to observe the emergence of resista nce to imipenem, if any, among aerobic Gram-negative bacteria. A total of 736 isolates were tested during 1994-95 and less than 1% of them w ere resistant to imipenem, whereas the next year ('95-'96) the rate in creased to 11 of the 903 isolates tested. The resistant isolates durin g '94-'95 were all Stenotrophomonas maltophilia whereas the spectrum o f resistant bacterial species increased in '95-'96 to include Pseudomo nas aeruginosa, Burkholderia cepacia, Acinetobacter calcoaceticus, Ent erobacter cloacae, Proteus mirabilis and Morganella morganii with a te ndency to an increase in the minimum inhibitory concentration (MIC) in the later part of the year. A majority (72%) of the resistant isolate s were from patients with burns, and burn wounds were most frequently infected with such organisms. These data suggest that over a period of time aerobic Gram-negative bacteria may develop resistance to imipene m and the pool of such bacteria increases with extensive use of the dr ug. Non-fermentative aerobic bacteria tend to develop resistance faste r with widespread dissemination than Enterobacteriaceae. Hospital Burn Units are a potential source of development of such resistance.