beta-Lactam resistance in gram-negative bacteria: global trends and clinical impact

Microbial drug resistance is an inescapable consequence of the utilization of antimicrobial agents in a given environment. Nowhere is the importance of resistance more evident than among agents of the beta-lactam family. Trends toward increased resistance can be seen among fastidious gram-negative bacteria like Haemophilus influenzae, where ampicillin resistance varies from 1% to 64% globally. For Escherichia coli, ampicillin resistance has risen to > or = 50% in high-risk populations, and resistance to third-generation cephalosporins is now being seen in certain areas. Inducible beta-lactamases have been responsible for increasing multiple beta-lactam resistance among certain Enterobacteriaceae and Pseudomonas aeruginosa, and this has been associated with increased use of newer cephalosporins. Xanthomonas maltophilia with its two inducible beta-lactamases is becoming an increasingly important nosocomial pathogen, especially in areas of heavy imipenem utilization. Only through the recognition of factors associated with increasing resistance and the mechanisms responsible can strategies be designed for minimizing beta-lactam resistance.