Salmonella Heidelberg resistant to ceftiofur and disinfectants routinely used in poultry

Bacteria of the genus Salmonella may infect humans and domestic animals, causing a serious public health problem worldwide. Nowadays, Salmonella enterica serovar Heidelberg (SH) is among the top three serovars isolated from people with salmonellosis and it is present in the poultry production chain. Moreover, it seems to be more invasive than other serotypes that cause enteritis. The overall status of the antimicrobial resistant of Brazilian strains of SH is still unknow. The bacterium may use similar mechanisms of resistance to antibotics, as well as disinfectants such as the efflux system and enzymatic degradation of chemical compounds. Thus, the objective of this study was to identify the Minimal Inhibitory Concentration (MIC) for ceftiofur of SH isolated from different materials of poultry origin, as well as to verify the relation between antibiotic resistance and disinfectant resistance. In addition, the screening efflux system was performed, using ethidium bromide to determine the presence of this mechanism of resistance. MIC results indicated high levels of SH resistance to ceftiofur, indicating the need for alternative drugs to treat salmonellosis. The concentration of ceftiofur needed to eliminate SH resistant isolates were 32 times higher than the therapeutic dose. Regarding disinfectants, most of the disinfectants tested were efficient to eliminate SH, however one isolate was resistant to glutaraldehyde-quaternary ammonia. All isolates were negatives in the screening efflux system, which suggest a different mechanism of resistance. It is possible to conclude that SH shows a real threat to poultry production, and caution should be taken when choosing the right antibiotic and disinfectant against this serovar.