Abstract
Escherichia coli isolates were recovered from the National Antimicrobial Resistance Monitoring System retail meat program and examined for antimicrobial susceptibility. Retail meat samples (n = 11,921) from four U.S. states collected during 2002 to 2008, consisting of 2,988 chicken breast, 2,942 ground turkey, 2,991 ground beef, and 3,000 pork chop samples, were analyzed. A total of 8,286 E. coli isolates were recovered. The greatest numbers of samples contaminated with the organism were chicken (83.5%) and turkey (82.0%), followed by beef (68.9%) and pork (44.0%). Resistance was most common to tetracycline (50.3%), followed by streptomycin (34.6%), sulfamethoxazole-sulfisoxazole (31.6%), ampicillin (22.5%), gentamicin (18.6%), kanamycin (8.4%), amoxicillin-clavulanic acid (6.4%), and cefoxitin (5.2%). Less than 5% of the isolates had resistance to trimethoprim, ceftriaxone, ceftiofur, nalidixic acid, chloramphenicol, and ciprofloxacin. All isolates were susceptible to amikacin. Compared to beef and pork isolates, the poultry meat isolates had a greater percentage of resistance to all tested drugs, with the exception of chloramphenicol, to which pork isolates had the most resistance. More than half of the turkey isolates (56%) were resistant to multidrugs (≥3 classes) compared to 38.9% of chicken, 17.3% of pork, and 9.3% of beef isolates. The bla(CMY) gene was present in all ceftriaxone- and ceftiofur-resistant isolates. The cmlA, flo, and catl genes were present in 45%, 43%, and 40% of chloramphenicol-resistant isolates, respectively. Most nalidixic acid-resistant isolates (98.5%) had a gyrA mutation in S83 or D87 or both, whereas only 6.7% had a parC mutation in either S80 or E84. The results showed that E. coli was commonly present in the retail meats, and antimicrobial resistance profiles differed according to the animal origin of the isolates.
Generated Summary
This research, published in the journal *Applied and Environmental Microbiology*, examined the prevalence of and antimicrobial resistance in *Escherichia coli* isolates recovered from retail meat samples in the United States. The study analyzed samples collected between 2002 and 2008 from four states, encompassing chicken breast, ground turkey, ground beef, and pork chop samples. The primary goal was to assess the antimicrobial susceptibility of *E. coli* and to identify resistance patterns across different meat types. The methodology involved isolating *E. coli* from meat samples and testing their susceptibility to various antimicrobial agents. This study provides insights into the prevalence of antimicrobial resistance in *E. coli* associated with retail meats, which is significant due to the potential public health implications of antibiotic-resistant bacteria in the food supply. The research highlights the differences in resistance profiles among isolates from different animal sources, which could inform targeted interventions to mitigate the spread of antimicrobial resistance.
Key Findings & Statistics
- A total of 11,921 retail meat samples were analyzed from four U.S. states.
- The samples included 2,988 chicken breast, 2,942 ground turkey, 2,991 ground beef, and 3,000 pork chop samples.
- A total of 8,286 *E. coli* isolates were recovered from these samples.
- The highest recovery rates of *E. coli* were from chicken (83.5%) and turkey (82.0%) samples.
- Beef samples had a recovery rate of 68.9%, while pork samples had a recovery rate of 44.0%.
- Resistance to tetracycline was most common (50.3%) followed by streptomycin (34.6%).
- Resistance to sulfamethoxazole-sulfisoxazole was observed in 31.6% of the isolates.
- Ampicillin resistance was present in 22.5% of the isolates.
- Gentamicin resistance was found in 18.6% of the isolates.
- Kanamycin resistance was observed in 8.4% of the isolates.
- Resistance to amoxicillin-clavulanic acid was present in 6.4% of the isolates.
- Cefoxitin resistance was seen in 5.2% of the isolates.
- Less than 5% of the isolates showed resistance to trimethoprim, ceftriaxone, ceftiofur, nalidixic acid, chloramphenicol, and ciprofloxacin.
- All isolates were susceptible to amikacin.
- Poultry meat isolates showed a greater percentage of resistance to tested drugs, excluding chloramphenicol.
- Pork isolates exhibited the highest resistance to chloramphenicol.
- 56% of turkey isolates were resistant to multiple drugs (≥3 classes).
- 38.9% of chicken isolates showed multidrug resistance.
- 17.3% of pork isolates showed multidrug resistance.
- 9.3% of beef isolates showed multidrug resistance.
- The *bla*(CMY) gene was found in all ceftriaxone- and ceftiofur-resistant isolates.
- The *cmlA*, *flo*, and *catl* genes were present in 45%, 43%, and 40% of chloramphenicol-resistant isolates, respectively.
- Most nalidixic acid-resistant isolates (98.5%) had a *gyrA* mutation in S83 or D87.
- Only 6.7% of nalidixic acid-resistant isolates had a *parC* mutation in either S80 or E84.
Other Important Findings
- The study demonstrated that *E. coli* was commonly present in the retail meats.
- Antimicrobial resistance profiles varied depending on the animal origin of the isolates.
- Compared to beef and pork, poultry meat isolates showed higher resistance to most tested drugs, with chloramphenicol being the exception.
- The presence of multidrug resistance was notably higher in turkey isolates compared to chicken, pork, and beef isolates.
- Specific genes (*bla*(CMY), *cmlA*, *flo*, and *catl*) were associated with resistance to certain antibiotics.
- Mutations in the *gyrA* and *parC* genes were linked to nalidixic acid resistance.
Limitations Noted in the Document
- The study’s data is limited to samples collected from four U.S. states, which may not fully represent the national prevalence of antimicrobial resistance in retail meats.
- The study period (2002 to 2008) may not reflect current resistance patterns, as antimicrobial resistance can evolve over time.
- The study focuses on *E. coli* isolates; it does not provide information on other bacterial species that may also be present in retail meats and exhibit antimicrobial resistance.
- The study does not explore the specific factors that contribute to the observed differences in resistance profiles between meat types, such as variations in animal husbandry practices, antibiotic use, or other environmental factors.
- The study is limited to phenotypic resistance data. It doesn’t provide information about the genetic mechanisms and the spread of resistance genes, which would give a better understanding of how resistance is spread.
Conclusion
The study’s findings underscore the significant presence of *E. coli* in retail meats and highlight the prevalence of antimicrobial resistance. The variations in resistance profiles across different meat types emphasize the complexity of the issue and suggest the need for targeted interventions. The high levels of resistance to tetracycline, streptomycin, and other antibiotics, along with the presence of multidrug resistance, are concerning from a public health perspective, potentially diminishing the effectiveness of antibiotic treatments for human infections. The identification of resistance genes provides crucial insights into the mechanisms of resistance. These results underscore the significance of the problem of antibiotic resistance and how it relates to food production. The findings emphasize that, since it differs by meat type, this could mean different farming practices are to blame. Interventions such as reducing antibiotic use in livestock and improving hygiene practices in meat processing can help to slow down the spread of antibiotic resistance. This study reinforces the need for continuous monitoring of antimicrobial resistance in the food supply chain to guide public health strategies and preserve the efficacy of antibiotics for both human and animal health. The differences in resistance profiles according to the animal of origin underline the need to consider these factors in targeted efforts to mitigate antimicrobial resistance. This highlights the broader implications for public health, the need for a holistic approach, and the continuous need for monitoring and interventions to protect public health.