As expected, the isolates recovered from the foods studied, clustered with the type strains of C.
sakazakii and C. malonaticus. Antimicrobial susceptibility testing indicated that all isolates were susceptible to ampicillin, compound sulphonamides, furazolidone, gentamicin, spectinomycin and streptomycin. These findings are in agreement with the data obtained MK 8931 by Stock and Wiedemann [25]. In their study they identified Cronobacter as being more susceptible to β-lactam antibiotics, including ampicillin, when compared with the Enterobacter species, E. amnigenus, E. cancerogenus and E. gergoviae. Interestingly, the Cronobacter isolates screened in their study were naturally susceptible to neomycin. The isolates CFS-FSMP 1500, 1510 and 1512 were resistant to this antibiotic. Neomycin is an aminoglycoside antibiotic, the mode of action of which is to bind to the 30S ribosomal subunit of bacteria. A possible reason behind this observed resistance could be an alteration to the binding site protein of the 30S subunit. Such an occurrence
has previously led to streptomycin resistance, another aminoglycoside compound. In the Stock and Wiedemann study [25] all Cronobacter and Enterobacter Captisol strains tested were susceptible to antifolate compounds. However, in our study isolate CFS-FSMP 1510 was resistant trimethoprim. Trimethoprim is an antifolate compound and acts by inhibiting dihydrofolate reductase enzymes in susceptible bacteria. Resistance in Gram-negative bacteria has previously been reported and it is believed that Interleukin-3 receptor the mechanism of resistance lies within the expression of plasmid and/or transposon mediated dihydrofolate reductase genes. Conclusion This study identified and characterized Cronobacter isolates recovered from dried milk and related food products. Although the majority of the strains were susceptible to the panel of antibiotics tested, resistance patterns observed in three isolates may indicate increasing risks to selleck products public health associated with the presence of Cronobacter in foods. Phenotypic and genotypic analysis should
be applied to further monitor and characterize the presence of Cronobacter in food production environments and prevent its transmission thereby improving food safety and quality. Acknowledgements The authors acknowledge the financial support provided through the Irish governments Food Institutional Research Measure (FIRM) grant no. 05/R&D/D/363 and a research scholarship from the Irish Research Council for Science, Engineering and Technology (IRCSET). The authors would also like to acknowledge the Nestlé Research Centre, Lausanne, Switzerland for providing a strain used in this study. References 1. Iversen C, Lehner A, Mullane N, Bidlas E, Cleenwerck I, Marugg J, Fanning S, Stephan R, Joosten H: The taxonomy of Enterobacter sakazakii : proposal of a new genus Cronobacter gen. nov. and descriptions of Cronobacter sakazakii comb. nov. Cronobacter sakazakii subsp.