Increasing prevalence of multidrug-resistant non-typhoidal salmonellae, Kenya, 1994-2003

Over the last decade there has been a steady increase in the proportion of multidrug resistance among non-typhoidal salmonellae (NTS) isolated from adult patients with bacteraemia in Kenya. The prevalence of NTS multiply resistant to all commonly available drugs including ampicillin, streptomycin, co-trimoxazole, chloramphenicol and tetracycline rose from 31% in 1994 to 42% at present, with concomitantly higher MICs of each drug. Resistance is encoded on large self-transferable 100-110 kb plasmids. Pulsed field gel electrophoresis of XbaI and SpeI digested chromosomal DNA revealed three main digest patterns for Salmonella enterica serotype Typhimurium and two main patterns for Salmonella enterica serotype Enteritidis. Although the genotypes of NTS remained fairly stable over the last decade, the large increase in MICs of all commonly used drugs and increased MICs of ciprofloxacin, poses a major challenge for treatment of invasive NTS infection.