An annual surveillance report from federal health officials that provides a snapshot of antibiotic resistance in foodborne pathogens gives a mixed picture, showing that levels are still low overall, with some notable increases, especially in multidrug-resistant Salmonella.
The findings from today's National Antimicrobial Resistance Monitoring System (NARMS) Integrated Report combines 2015 data from the US Food and Drug Administration (FDA), the Centers for Disease Control and Prevention, and the US Department of Agriculture Food Safety and Inspection Service. Agencies use the information to help make decisions about preserving the effectiveness of antibiotics for human and animal health and for investigating foodborne illness outbreaks.
Yearly NARMS reports spotlight resistance patterns in bacteria samples from humans, raw retail meat, and animals at slaughter. They include information from whole-genome sequencing on resistance genes for all Salmonella and some Campylobacter isolates.
In its statement unveiling the report, the FDA said this latest edition covers a time period before full implementation of FDA guidance to curb the use of medically important antibiotics in food-producing animals.
Certain types of resistance are on the rise
Though overall resistance levels stayed low for most human infections, with measurable improvement in some key areas, NARMS is closely monitoring a few concerning trends.
Of Salmonella isolates from humans, 76% showed no resistance to any of the 14 antimicrobial drugs tested. However, among isolates showing resistance, multidrug resistance rose from 9% to 12%, fueled mostly by an increase in combined resistance to ampicillin, streptomycin, sulfonamides, and tetracycline among Salmonella serotype I 4,,12:i:-.
Ceftriaxone resistance fell or remained low in nontyphoidal Salmonella from all sources except turkey samples, in which the 15.7% resistance level was the same as in 2010. Meanwhile, azithromycin resistance in Salmonella is still rare, but in some strains, it was seen alongside resistance to other antibiotics.
In Campylobacter isolates from humans and chicken carcasses, erythromycin resistance rose three- to five-fold between 2011 and 2015.
Another area of concern were signs that quinolone resistance in Salmonella may be increasing. "The underlying resistance traits reside on mobile genetic elements and therefore have the potential to be shared, either alone or together with other resistance genes, with susceptible strains of Salmonella," the FDA said.
Ground turkey resistance levels continue decline
On a positive note, from 2014 to 2015 the proportion of retail ground turkey Salmonella isolates that were resistant to at least one antimicrobial declined from 73% to 57%. In the past, the majority of isolates from turkey sources have been resistant to at least one antimicrobial.
Oct 23 FDA press release
FDA 2015 NARMS integrated report
Aug 30, 2016, CIDRAP News story "NARMS report shows resistance low in Salmonella but up in 1 strain"