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New York: Marcel Dekker; 1993. Competing interests The authors declare that they have no competing interests. Authors’ contributions DW contributed to the study design, data collection, most experiments, writing of the initial draft, and revising the manuscript. WB, YW, WG, and RL collected the preliminary data, and helped to perform some experiments. ZY and NZ participated in the study design, interpretation of the data, the study coordination, technical issues, and revision of Cell Cycle inhibitor the manuscript. All authors read and approved the final manuscript.”
“Background Due to the resistance against a wide range of antimicrobials including important ones such as penicillins and all cephalosporins [1], Blasticidin S Extended Spectrum Beta-Lactamase (ESBL) producing bacteria are considered a vast threat to public health. Carriership of bacteria

producing ESBLs in humans is increasing in the community and health care. In Enterobacteriaceae ESBL-genes are mostly plasmid mediated and may be located on various plasmid types. In Dutch poultry bla CTX-M-1 is the predominant ESBL-gene, located on IncI1 plasmids [2] and these ESBL-genes seem to play an important Epoxomicin purchase role in humans as well [3]. The prevalence of ESBLs in poultry in the Netherlands is very high, 100% of investigated farms were positive for ESBL-producing Escherichia coli and on 85% of these farms, 80% (95% CI: 71-99%) or more of the animals carried ESBL-producers see more in their faeces [4]. Surveillance data show that among all broiler E. coli in the Netherlands, 15% carry plasmids with ESBL-genes [2]. The occurrence of the IncI1/CTX-M-1 combination in broilers as well as in humans indicates that the bacterium populations in poultry may play a role as a reservoir for ESBL-genes found in human

bacteria [5]. Although in general a high selective pressure by use of antimicrobials exists in broiler chickens, the reservoir role is unexpected in this particular case. Mass treatment of broiler chickens with cephalosporins is forbidden in the Netherlands. Cephalosporins are, however, used in one-day old reproduction animals in the poultry sector [6], selecting for bacteria producing ESBLs that can then successfully colonize broilers. To explain the widespread occurrence of the IncI1 and CTX-M-1 positive isolates, we wish to understand under what circumstances this gene-plasmid combination can be successful. The IncI1 plasmid is conjugative, and conjugation could explain the high abundance of bacteria carrying this plasmid in the microbiota of broilers. Within the microbiota, plasmids might act as infectious agents, which are able to persist by transfer to new bacterial hosts.