Global Spread of Multidrug-Resistant Gram-Negative Bacilli

Abstract

This chapter describes three emerging issues with multiply resistant gram-negative bacilli, each of which has worldwide importance. First, community-onset infections with CTX-M-15-producing Escherichia coli threaten to permanently alter empiric antibiotic choices for urinary tract infection (UTI). Second, Klebsiella pneumoniae producing the K. pneumoniae carbapenemase (KPC) are now spreading from their epicenter in New York City to multiple parts of the globe and are complicating management of infections in hospitals and nursing homes. Finally, global dissemination of carbapenem-resistant Acinetobacter baumannii underscores the epidemic potential of successful bacterial lineages. The antibiotic resistance phenotype of the ST131-positive E. coli is that the organisms are typically resistant to ceftriaxone, cefotaxime, fluoroquinolones, trimethoprim, trimethoprim-sulfamethoxazole, penicillin/beta-lactamase inhibitor combinations, and tetracyclines. Resistance to aminoglycosides is variable. The clone confers multidrug resistance by the presence of multiple antibiotic resistance genes. As can be expected by the resistance profile of ST131 E. coli, treatment options are limited. The isolates are often susceptible to nitrofurantoin, pivmecillinam, and fosfomycin. Interspecies spread of the KPC gene has been documented in a single patient with K. pneumoniae, E. coli, and Serratia marcescens. The most important mechanism of antibiotic resistance in A. baumannii is production of beta-lactamases. A. baumannii and K. pneumoniae isolates with resistance to polymyxins and sometimes all antibiotic options have now been detected. If these strains were to spread widely, it is likely that significant mortality would be observed.