Diversity of Antimicrobial Resistance Phenotypes in Salmonella Isolated from Commercial Poultry Farms

Abstract

Salmonella remains the leading cause of foodborne illness in the United States, and the dissemination of drug-resistant Salmonellae through the food chain has important implications for treatment failure of salmonellosis. We investigated the ecology of Salmonella in integrated broiler production in order to understand the flow of antibiotic susceptible and resistant strains within this system. Data were analyzed from a retrospective study focused on antimicrobial resistant Salmonella recovered from commercial broiler chicken farms conducted during the initial years of the US FDA’s foray into retail meat surveillance by the National Antimicrobial Resistance Monitoring System (NARMS). Sixty-three percentage of Salmonella were pan-susceptible to a panel of 19 antimicrobials used by the NARMS program. Twenty-five antimicrobial resistance phenotypes were observed in Salmonella isolated from two broiler chicken farms. However, Salmonella displaying resistance to streptomycin, alone, and in combination with other antibiotics was the most prevalent (36.3%) antimicrobial resistance phenotype observed. Resistance to streptomycin and sulfadimethoxine appeared to be linked to the transposon, Tn21. Combinations of resistance against streptomycin, gentamicin, sulfadimethoxine, trimethoprim, and tetracycline were observed for a variety of Salmonella enterica serovars and genetic types as defined by pulsed-field gel electrophoresis. There were within and between farm differences in the antibiotic susceptibilities of Salmonella and some of these differences were linked to specific serovars. However, farm differences were not linked to antibiotic usage. Analysis of the temporal and spatial distribution of the endemic Salmonella serovars on these farms suggests that preventing vertical transmission of antibiotic-resistant Salmonella would reduce carcass contamination with antibiotic-resistant Salmonella and subsequently human risk exposure.

Zoonotic Escherichia coli is a potential Driver of Antimicrobial Resistance among Pastoralist Communities in Uganda: A Laboratory based Cross sectional Study

“…Highest resistance was observed to; Trimethoprim-sulphurmethoxazole, Tetracycline, Ampicillin and Nitrofurantoin: these have been documented as the most commonly used antimicrobial agents in the agricultural sector in Uganda [21]. These finding are consistent with studies done elsewhere on similar isolates whose source was animals [22]. In addition, these studies also reported a possible transmission of the resistance in these isolates to humans.…”

Frequent human‐poultry interactions and low prevalence of Salmonella in backyard chicken flocks in Massachusetts

“…In nontyphoidal Salmonella serotypes as a whole, NARMS found 11.2% of isolates resistant to streptomycin and 10.4% resistant to tetracyclines (CDC, ). Streptomycin resistance is thought to be linked with numerous resistance genes, which may explain why our isolates demonstrated phenotypic resistance to streptomycin yet a known gene encoding this resistance was not identified (Liljebjelke et al, ).…”

Antimicrobial Resistant Salmonella enterica Typhimurium Colonizing Chickens: The Impact of Plasmids, Genotype, Bacterial Communities, and Antibiotic Administration on Resistance

“…As most Salmonella infections are associated with consumption of meats, milk, and eggs, the veterinary use of antimicrobials, especially those important for treatment of humans, has long been a contentious issue (Cox and Ricci, 1969). While there is epidemiological data to support the link between antimicrobial use and resistance (Bortolaia et al, 2015;Noyes et al, 2016;Andersen et al, 2017;Caffrey et al, 2017;Shigemura et al, 2018), it is generally difficult to ascertain causal effect depending on the antimicrobial (Fairchild et al, 2005;Smith et al, 2007;Agga et al, 2016), food animal (Agga et al, 2016), level or scope of food animal production system (Idris et al, 2006;Andersen et al, 2017;Liljebjelke et al, 2017), or method of quantifying resistance (Fairchild et al, 2005;Smith et al, 2007;Agga et al, 2016). In poultry production, the antimicrobials available for use in the US are limited to 15 drugs (Singer and Hofacre, 2006).…”

“…The likelihood that any of these antimicrobials are used are mostly dependent on economics, weighing the cost of the drug against the level of disease (Singer and Hofacre, 2006). A commercial poultry farm may go a full year without any therapeutic antimicrobial use (Liljebjelke et al, 2017).…”

“…In addition, the poultry environment also has a diverse array of tetracycline resistance genes with evidence of horizontal gene transfer among evolutionarily disparate genera, as evident in the presence of tetO in Campylobacter and Enterococcus (Fairchild et al, 2005). It is therefore not surprising that Salmonella isolated from the poultry environment can possess a diverse array of antimicrobial resistances, even on farms where there has been no therapeutic use of antimicrobials (Liljebjelke et al, 2017). However, it is not clear what factors have the highest impact on resistance in Salmonella.…”