Beta-Lactam Antibiotic Resistance among Enterobacter spp. Isolated from Infection in Animals

Nosocomial infections are frequent complications of hospitalization, caused by opportunistic pathogens that gain access to hosts undergoing invasive procedures, such as surgery, intubation, and placement of deep vein lines. Nosocomial infections in animal hospitals can infect other animals, as well as be transmitted to human personnel. Enterobacter is a genus of common gram-negative bacteria, which can be associated with antibiotic resistant hospital infections. Because of an outbreak in antibiotic resistance in the genus, we decided to investigate five years of Enterobacter infections in the Large Animal Services of the Lois Bates Acheson Veterinary Teaching Hospital (LBAVTH) at Oregon State University. The demographics from 37 Enterobacter-infected patients of the LBAVTH were obtained from charts and analyzed. The identified clusters of infections suggested possible patient-environment sources of infection. The environment of the hospital was sampled in an attempt to determine the source of infection. Although Enterobacter was not isolated, three of the collected samples contained bacteria with resistance to third-generation cephalosporins. Enterobacter isolates from six of the 37 patients were further analyzed for presence of specific ESBL resistance genes. All six of the isolates harbored multiple extended-spectrum beta-lactamase genes, i.e., CTX-M-15, TEM-80, SHV-2 and AmpC. In summary, Enterobacter infection in the veterinary hospital was caused by beta-lactam-resistant strains, carrying ESBL-resistant genes. Veterinary hospital personnel should be aware of the potential for transmission, to both humans and animals, of ESBL-gene-containing bacteria.