Commentary on genetic mechanisms of antimicrobial resistance in bacteria from u.s. food animals: esbls are here

A commentary on
Genetic mechanisms of antimicrobial resistance identified in Salmonella enterica, Escherichia coli , and Enteroccocus spp. isolated from U. S. food animals

by Frye, J. G., and Jackson, C. R. (2013). Front. Microbiol. 4: 135. doi: 10. 3389/fmicb. 2013. 00135

While Frye and Jackson do a good job describing the common mechanisms of resistance found in food animals in the U. S., they err in stating that in the U. S. extended spectrum β-lactamases (ESBLs) “ thus far have only been found in human and not food animal isolates.”

In fact, Wittum et al., in 2010 first reported the collection of Escherichia coli expressing CTX-M-type ESBLs in fecal isolates from healthy cattle at a livestock market and from a diagnostic isolate submitted to the Ohio Animal Disease Diagnostic Laboratory. Since then, CTX-M-type ESBLs have been found in E. coli collected from healthy dairy calves in the western U. S. ( Davis et al., 2011 ) and from 5 of 20 dairy farms in Ohio ( Mollenkopf et al., 2012 ); in clinical Salmonella enterica isolates from swine in Minnesota and from turkeys in 4 states ( Wittum et al., 2012 ); in E. coli from swine finishing barns in Michigan and Ohio and in Klebsiella pneumoniae from swine in Illinois ( Mollenkopf et al., 2013 ).

We are not aware of studies finding CTX-M-type ESBLs in isolates from broiler chickens, but a retail chicken meat E. coli isolate expressing CTX-M-type ESBLs from Pennsylvania has been reported ( Doi et al., 2010 ). Given the situation in other livestock species and in other countries, we expect the lack of detection of CTX-M-type ESBLs in U. S. chicken isolates is more the result of lack of appropriate studies than a real absence of these on chicken farms. In addition to CTX-M-type ESBLs, the study of dairy calves in the western U. S. also found E. coli expressing OXA-type ESBLs ( Davis et al., 2011 ).

References

Davis, M. A., Besser, T. E., Orfe, L. H., Baker, K. N., Lanier, A. S., Broschat, S. L., et al. (2011). Genotypic-phenotypic discrepancies between antibiotic resistance characteristics of Escherichia coli isolates from calves in management settings with high and low antibiotic use. Appl. Environ. Microbiol . 77, 3293–3299. doi: 10. 1128/AEM. 02588-10

Doi, Y., Paterson, D. L., Egea, P., Pascual, A., López-Cerero, L., Navarro, M. D., et al. (2010). Extended-spectrum and CMY-type beta-lactamase-producing Escherichia coli in clinical samples and retail meat from Pittsburgh, USA and Seville, Spain. Clin. Microbiol. Infect . 16, 33–38. doi: 10. 1111/j. 1469-0691. 2009. 03001. x

Mollenkopf, D. F., Mirecki, J. M., Daniels, J. B., Funk, J. A., Henry, S. C., Hansen, G. E., et al. (2013). Escherichia coli and Klebsiella pneumoniae producing CTX-M cephalosporinase from swine finishing barns and their association with antimicrobial use. Appl. Environ. Microbiol . 79, 1052–1054. doi: 10. 1128/AEM. 03169-12

Mollenkopf, D. F., Weeman, M. F., Daniels, J. B., Abley, M. J., Mathews, J. L., Gebreyes, W. A., et al. (2012). Variable within- and between-herd diversity of CTX-M cephalosporinase-bearing Escherichia coli isolates from dairy cattle. Appl. Environ. Microbiol . 78, 4552–4560. doi: 10. 1128/AEM. 00373-12

Wittum, T. E., Mollenkopf, D. F., and Erdman, M. M. (2012). Detection of Salmonella enterica isolates producing CTX-M Cephalosporinase in U. S. livestock populations. Appl. Environ. Microbiol . 78, 7487–7491. doi: 10. 1128/AEM. 01682-12

Wittum, T. E., Mollenkopf, D. F., Daniels, J. B., Parkinson, A. E., Mathews, J. L., Fry, P. R., et al. (2010). CTX-M-type extended-spectrum β-lactamases present in Escherichia coli from the feces of cattle in Ohio, United States. Foodborne Pathog. Dis . 7, 1575–1579. doi: 10. 1089/fpd. 2010. 0615