Key Takeaways
Surveillance of bacterial pathogens provides a platform to detect any emergence of antimicrobial resistance.Ongoing antimicrobial susceptibility surveillance for swine respiratory disease (SRD) from Zoetis helps inform responsible antibiotic use.The most recent data set shows that antimicrobial resistance among swine pathogens remains very low against almost all antibiotics that are tested in the program.
Since 1998, Zoetis has been conducting antimicrobial resistance surveillance for swine respiratory disease (SRD) and bovine respiratory disease. More than 28 years of susceptibility data continues to successfully help guide veterinarians on which antibiotics are best suited to treat specific respiratory pathogens in swine.
The most recent data set for 2025 continues to show that antimicrobial resistance among swine respiratory pathogens remains very low.
Why antimicrobial resistance surveillance matters for swine herds
“Antimicrobials are critical to treat and control infections in food animals,” said Mike Sweeney, Senior Principal Scientist and Swine Respiratory Disease Susceptibility Surveillance Program Lead at Zoetis. “The right antibiotic intervention is vital to not only control bacterial diseases, but to minimize development of antimicrobial resistance. Surveillance of bacterial pathogens obtained from clinical specimens we receive from diagnostic laboratories provides a platform we can use to detect any emergence of antimicrobial resistance. That’s the key strength of our surveillance program.”
How Zoetis conducts SRD susceptibility surveillance
The SRD surveillance program has generated data for more than 28 years from clinical isolates collected from more than 25 veterinary diagnostic laboratories across the United States and Canada.
Zoetis receives about 800 to 1,000 isolates each year, which are individually processed and identified at the species level using the Maldi-Tof instrument (a specialized mass spectrometer), providing a robust dataset.
Susceptibility is determined based on minimum inhibitory concentration (MIC) — the lowest concentration of each antimicrobial that prevents visible growth of a bacterium. Testing is conducted with strict adherence to the Clinical and Laboratory Standards Institute (CLSI) standardized methods.
“We crunch the data down to MIC50 and MIC90 values, and then to susceptible, intermediate or resistant, based on available CLSI-endorsed breakpoints,” Sweeney said. “Surveillance helps identify resistance trends and fosters an improved understanding of antimicrobial resistance. It also supports responsible antimicrobial use.”
2025 data: Swine respiratory pathogens show very low antimicrobial resistance
Sweeney said the most recent results continued to show the same trends as previous datasets. Antimicrobial resistance among swine respiratory pathogens remains very low against almost all the antibiotics tested in the program.1
“The exception is tetracycline; we see higher levels of resistance for tetracycline with some of the key SRD pathogens,” he said. “For organisms such as Actinobacillus pleuropneumoniae, we saw that isolates were 100% susceptible to ceftiofur, enrofloxacin, florfenicol, tilmicosin and tulathromycin. Pasteurella multocida were 100% susceptible to ceftiofur, enrofloxacin, florfenicol and tulathromycin (Table).”
The 2025 study showed very high rates of susceptibility, meaning anywhere from 95% to greater than 99%, for A. pleuropneumoniae to ampicillin and tilmicosin, and for P. multocida to ampicillin and penicillin.
Streptococcus suis resistance was also very low to ceftiofur, ampicillin and florfenicol. Bordetella bronchiseptica susceptibility to tulathromycin remains exceptionally good with susceptibility at 100%.
Summary of surveillance results, 2025 – % resistance1
“For producers and the industry, this means that the management practices being used in swine facilities are working. If we compare our surveillance data for swine to cattle, there's a big difference among the cattle pathogens. In some cases, we see considerable resistance among cattle pathogens, but we don't see that among swine pathogens,” Sweeney said. “Bottom line, these results are really good news for the swine industry. It shows that judicious use is being followed for antibiotic products.”
Veterinarians are doing a good job taking susceptibility or resistance data from diagnostic labs, interpreting it correctly and then prescribing the antibiotics according to the susceptibility profiles and expected efficacy, he said.
Surveillance also contributes to a sustainable industry. If a drug shows high resistance to an organism, veterinarians wouldn’t want to prescribe that drug because it would not be effective in treating the bacterial infection.
“At Zoetis, we strongly believe in the judicious use of antibiotics; they are precious commodities. That’s why Zoetis wants to continue sharing this data with veterinarians in North American and globally. We want to protect the antimicrobial products veterinarians have available to them so when respiratory disease hits the herd, using the right treatment will get the herd back to a healthy, productive status faster,” Sweeney said.
Responsible antimicrobial use: Key reminders for swine producers
Use antimicrobial products correctly. Follow label directions for storage, handling and dosing.Work with a veterinarian on antimicrobial use protocols, including surveillance and withdrawals.Control diseases quickly and humanely so fewer animals are affected.Avoid unnecessary treatment when antimicrobials are not indicated.
Read the Zoetis commitment on responsible use of antibiotics in animals
Surveillance of bacterial pathogens provides a platform to detect any emergence of antimicrobial resistance.Ongoing antimicrobial susceptibility surveillance for swine respiratory disease (SRD) from Zoetis helps inform responsible antibiotic use.The most recent data set shows that antimicrobial resistance among swine pathogens remains very low against almost all antibiotics that are tested in the program.
Since 1998, Zoetis has been conducting antimicrobial resistance surveillance for swine respiratory disease (SRD) and bovine respiratory disease. More than 28 years of susceptibility data continues to successfully help guide veterinarians on which antibiotics are best suited to treat specific respiratory pathogens in swine.
The most recent data set for 2025 continues to show that antimicrobial resistance among swine respiratory pathogens remains very low.
Why antimicrobial resistance surveillance matters for swine herds
“Antimicrobials are critical to treat and control infections in food animals,” said Mike Sweeney, Senior Principal Scientist and Swine Respiratory Disease Susceptibility Surveillance Program Lead at Zoetis. “The right antibiotic intervention is vital to not only control bacterial diseases, but to minimize development of antimicrobial resistance. Surveillance of bacterial pathogens obtained from clinical specimens we receive from diagnostic laboratories provides a platform we can use to detect any emergence of antimicrobial resistance. That’s the key strength of our surveillance program.”
How Zoetis conducts SRD susceptibility surveillance
The SRD surveillance program has generated data for more than 28 years from clinical isolates collected from more than 25 veterinary diagnostic laboratories across the United States and Canada.
Zoetis receives about 800 to 1,000 isolates each year, which are individually processed and identified at the species level using the Maldi-Tof instrument (a specialized mass spectrometer), providing a robust dataset.
Susceptibility is determined based on minimum inhibitory concentration (MIC) — the lowest concentration of each antimicrobial that prevents visible growth of a bacterium. Testing is conducted with strict adherence to the Clinical and Laboratory Standards Institute (CLSI) standardized methods.
“We crunch the data down to MIC50 and MIC90 values, and then to susceptible, intermediate or resistant, based on available CLSI-endorsed breakpoints,” Sweeney said. “Surveillance helps identify resistance trends and fosters an improved understanding of antimicrobial resistance. It also supports responsible antimicrobial use.”
2025 data: Swine respiratory pathogens show very low antimicrobial resistance
Sweeney said the most recent results continued to show the same trends as previous datasets. Antimicrobial resistance among swine respiratory pathogens remains very low against almost all the antibiotics tested in the program.1
“The exception is tetracycline; we see higher levels of resistance for tetracycline with some of the key SRD pathogens,” he said. “For organisms such as Actinobacillus pleuropneumoniae, we saw that isolates were 100% susceptible to ceftiofur, enrofloxacin, florfenicol, tilmicosin and tulathromycin. Pasteurella multocida were 100% susceptible to ceftiofur, enrofloxacin, florfenicol and tulathromycin (Table).”
The 2025 study showed very high rates of susceptibility, meaning anywhere from 95% to greater than 99%, for A. pleuropneumoniae to ampicillin and tilmicosin, and for P. multocida to ampicillin and penicillin.
Streptococcus suis resistance was also very low to ceftiofur, ampicillin and florfenicol. Bordetella bronchiseptica susceptibility to tulathromycin remains exceptionally good with susceptibility at 100%.
Summary of surveillance results, 2025 – % resistance1
“For producers and the industry, this means that the management practices being used in swine facilities are working. If we compare our surveillance data for swine to cattle, there's a big difference among the cattle pathogens. In some cases, we see considerable resistance among cattle pathogens, but we don't see that among swine pathogens,” Sweeney said. “Bottom line, these results are really good news for the swine industry. It shows that judicious use is being followed for antibiotic products.”
Veterinarians are doing a good job taking susceptibility or resistance data from diagnostic labs, interpreting it correctly and then prescribing the antibiotics according to the susceptibility profiles and expected efficacy, he said.
Surveillance also contributes to a sustainable industry. If a drug shows high resistance to an organism, veterinarians wouldn’t want to prescribe that drug because it would not be effective in treating the bacterial infection.
“At Zoetis, we strongly believe in the judicious use of antibiotics; they are precious commodities. That’s why Zoetis wants to continue sharing this data with veterinarians in North American and globally. We want to protect the antimicrobial products veterinarians have available to them so when respiratory disease hits the herd, using the right treatment will get the herd back to a healthy, productive status faster,” Sweeney said.
Responsible antimicrobial use: Key reminders for swine producers
Use antimicrobial products correctly. Follow label directions for storage, handling and dosing.Work with a veterinarian on antimicrobial use protocols, including surveillance and withdrawals.Control diseases quickly and humanely so fewer animals are affected.Avoid unnecessary treatment when antimicrobials are not indicated.
Read the Zoetis commitment on responsible use of antibiotics in animals