Evaluation of the in vitro activity of six broad-spectrum beta-lactam antimicrobial agents tested against recent clinical isolates from India: a survey of ten medical center laboratories.

The widespread use of beta-lactam antimicrobial agents as first-line therapy for the treatment of serious infections has led to the development of various resistances that have compromised the use of some agents. In certain countries, the lack of local or national surveillance programs limits the ability to detect these resistant strains and prevent their dissemination. A 10 medical center study in India was initiated to benchmark prevailing resistance rates for a range of bacterial pathogens to beta-lactams, and it found high rates of beta-lactamase-mediated resistance in Escherichia coli and Klebsiella spp. These rates included: cephalosporins (55.6-61.3% resistance), with extended-spectrum beta-lactamase (ESBL) phenotypes noted in over 60% of E. coli isolates and in Salmonella spp. (3.2-8.1%). Imipenem, a carbapenem, was the only antimicrobial agent tested with 100% activity against Enterobacteriaceae. Cefpirome was the most active of the tested cephalosporins, and all were fully active against methicillin-susceptible staphylococci with the exception of ceftazidime. Molecular and susceptibility characterization of 52 selected ESBL-producing strains showed a high level of co-resistance with aminoglycosides and fluoroquinolones, and clonal dissemination of resistant strains within medical centers. Collaborative studies, such as those presented here, can accurately detect changes in resistance patterns, and their continued use may help limit the further development and spread of bacterial resistances in India.