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Improving Human and Animal Health by Combating Antibiotic Resistance

May 2, 2016

Robert Chappell, a student at the UC Davis Graduate School of Management, battled a dangerous MRSA infection.

Robert Chappell, a student at the UC Davis Graduate School of Management, battled a dangerous MRSA infection.

In 2004 then University of California San Diego freshman Robert Chappell suffered a blister on his foot that became swollen and painful. Within one week, he found himself in the emergency room when the blister and pain worsened dramatically after not responding to two different antibiotics prescribed to him from his student health center.

“I had been through two fairly serious hospitalizations before in my life, but something about the growing pain in my foot really worried me,”  Chappell said, now 30 years old and attending the UC Davis Graduate School of Management.

He asked a friend to take him to the local hospital emergency room where a tissue sample extracted from his foot showed he had contracted MRSA (pronounced ‘mursa’ and stands for methicillin-resistant Staphylococcus aureus)  –an infection caused by a type of staph bacteria that's resistant to many antibiotics used to treat ordinary staph infections.  

Community-associated MRSA, found among healthy people like Chappell, can be contracted through crowded places or activities, such as athletics, that involve skin-to-skin contact or shared equipment.  Sometimes referred to as the "Super Bug”, the infection often begins as a painful skin boil and can be fatal.  According to the Centers for Disease Control (CDC), MRSA is carried by about two percent of the population. 

Human and veterinary medicine professionals at UC Davis are constantly faced with determining proper treatment for their patients- whether it’s an ear infection in a child or pneumonia in a calf - while working to minimize the misuse or overuse of antimicrobials (which include antibiotics) that could lead to antibiotic-resistance bacterial infections like MRSA. In fact, more than 150 human and animal health stakeholders, food companies and retailers have made commitments to implement changes in the coming years to slow the emergence of resistant bacteria and prevent the spread of resistant infections, as part of the White House’s National Action Plan for Combating Antibiotic-Resistant Bacteria.

A serious public health threat to both humans and animals

In spite of these efforts, antibiotic resistance continues to be one of the most serious health threats to both humans and animals.  The problem – arising at the intersection of the health of humans, animals and the environment -   is complex and often misunderstood. According to the CDC, each year in the United States at least two million people become infected with bacteria that are resistant to antibiotics; approximately 23,000 die annually as a direct result of these infections.

In human patients, some antibiotics aren’t used anymore due to ineffectiveness because of the widespread development of antibiotic resistance, according to Dean Blumberg, chief of pediatric infectious diseases at the UC Davis Children’s Hospital. Blumberg says that the number and severity of antibiotic-resistant infections occurring in people is alarming. 

Human patients may receive ineffective therapy, he explains, if the pathogen causing the infection is resistant to the prescribed antibiotic. When an antibiotic-resistant infection is identified, then therapy is often changed, sometimes to second-line agents that may result in greater toxicity, lesser effectiveness, decreased convenience or greater costs.  For example, if no oral antibiotic is effective, then long-term intravenous devices may need to be surgically inserted so that antibiotic therapy may be administered. 

“Some patients may have infections that are also resistant to second-line agents, leading to last-ditch treatment with combination or experimental antibiotics,” said Blumberg.

Physicians at the UC Davis Health System are involved in antimicrobial stewardship in several ways. They review and monitor human patients using antibiotics, and modify treatment when appropriate. Current guidelines help physicians more accurately diagnose infections, as well as recommend effective therapy before a cause is identified.  Some antibiotics have restricted use, requiring an infectious disease specialist approval or consultation. Blumberg says that antimicrobial resistance patterns are monitored so that they can respond to trends with changes to the antibiotic formulary and guidelines. In addition, its clinical laboratory is introducing faster and more accurate assays for infectious diseases that allow physicians to narrow antibiotic therapy sooner and improve treatment.

Humans aren’t the only ones that experience resistance to antibiotics - animals do too, making it difficult to treat illnesses like pneumonia or mastitis (a potentially fatal mammary gland infection in cattle).  With the recent passage of California Senate Bill (SB) 27, veterinarians at the UC Davis School of Veterinary Medicine are embracing a growing role in reducing antibiotic resistance. Veterinarians in California will soon have more oversight than ever before for the therapeutic use of antibiotics in livestock. The law supplements new FDA guidelines to phase out the use of antimicrobial drugs to promote growth in animals and places tough restrictions on all antibiotics used in livestock that are also medically important for humans.  Research and public service programs at the school are also in place to improve food safety and safeguard animal and public health.

“Our programs help prevent unwanted drugs from entering the food supply,” said Terry Lehenbauer, director of the UC Davis Veterinary Medicine Teaching and Research Center in Tulare County.  “And the training and education we offer is critical to helping the next generation of veterinarians properly use antibiotics in animals raised for food, like livestock and poultry.”  

For example, the school is conducting research to find ways to reduce the routine use of medically-important antibiotics in dry cow therapy –a common treatment of antibiotics at the end of lactation to treat existing infections and prevent new ones in cattle. Its research also supports vaccine development that eliminates or reduces the need for antibiotics. The school conducts international outreach on food safety and antibiotic resistance in countries like China, and in coming years will provide training to California dairy producers to help them comply with the new guidelines resulting from SB 27. In addition, the California Animal Health and Food Safety Laboratory System, a partnership between the school and the state Department of Food and Agriculture, provides surveillance and diagnostic testing on milk and dairy products for drug residues and antibiotics that may have been used to treat sick cows. 

“Antibiotic resistance calls for a shared responsibility in reducing its impact,” Lehenbauer said.  “We meet the challenge only by working together with our public health, physician and industry partners.”

For Robert Chappell who contracted MRSA as a student at UC San Diego, a surgical procedure was successful in removing the infected tissue from his foot and required he only take the winter quarter off to recuperate. Coincidentally, at the airport in route to his parents’ home to undergo a rigorous 30-day antibiotic treatment, he met a woman who had also contracted MRSA. While they waited in their wheelchairs to board the airplane, she explained to him that her infection was so serious that her foot needed to be amputated.  Fortunately, Chappell experienced a full recovery. 



Monique Garcia Gunther, Communications Officer