SAN DIEGO – Canadian hospitals are making progress in reducing the rates of methicillin-resistant Staphylococcus aureus, but the rates of antimicrobial resistance in Canadian hospitals increased significantly for extended-spectrum beta-lactamase–producing Escherichia coli and Klebsiella pneumoniae, as well as vancomycin-resistant enterococci.
Those are among the key findings from a large national analysis known as CANWARD that were presented at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy. “What it’s telling us is that some of the things that we’re doing on the antimicrobial resistance side are working,” lead study author George G. Zhanel, Pharm.D., professor of microbiology and infectious diseases at the University of Manitoba, Winnipeg, said in an interview. “But it also tells us that some of these pathogens like [vancomycin-resistant enterococci] and [extended-spectrum beta-lactamase]–producing E. coli continue to go up. So there is some good news and some bad news, but it tells us that it’s not all just doom and gloom. Some progress has been made, but there’s still a long way to go.”
Frontline Medical News
Dr. George G. Zhanel
Conducted annually, CANWARD is a national health surveillance study that assesses pathogens causing infections in Canadian hospitals and their patterns of antimicrobial resistance. For the current analysis, Dr. Zhanel and his associates collected 36,607 isolates from patients in tertiary care hospitals in Canada from January 2007 to December 2014. They used Clinical and Laboratory Standards Institute broth microdilution methods to perform antimicrobial susceptibility testing on more than 45 marketed and investigational agents.
Slightly more than half of the patients (55%) were male, and 87% were over age 18. The most common pathogens were E. coli (19.7%), methicillin-susceptible Staphylococcus aureus (MSSA; 16.4%), Pseudomonas aeruginosa (8.7%), S. pneumoniae (6.5%), K. pneumoniae (6.1%), methicillin-resistant S. aureus (MRSA; 4.7%), Enterococcus species (4.0%), and Hemophilus influenzae (4.0%). Susceptibility rates for E. coli were 99.9% for meropenem and tigecycline, 99.7% for ertapenem, 97.7% for piperacillin/tazobactam, 92.5% for ceftriaxone, 90.4% for gentamicin, 77.2% for ciprofloxacin, and 73.0% for trimethoprim and sulfamethoxazole. Susceptibility rates for P. aeruginosa were 94.2% for colistin, 84.3% for piperacillin/tazobactam, 83.3% for ceftazidime, 81.2% for meropenem, 77.6% for gentamicin, and 74.1% for ciprofloxacin. Susceptibility rates for MRSA were 100% for linezolid and telavancin, 99.9% for daptomycin, 99.4% for tigecycline, 99.1% for vancomycin, and 93.3% for trimethoprim and sulfamethoxazole. The rates of resistant organisms between 2007 and 2014 increased significantly for extended-spectrum beta-lactamase–producing E. coli (from 3.4% to 11.6%) and K. pneumoniae (from 1.5% to 6.5%), as well as vancomycin-resistant enterococci (from 1.8% to 7.0%), while rates of MRSA significantly declined (from 26.1% to 20.2%).
“The biggest surprise to me is that the hospital-acquired genotype of MRSA is going down,” Dr. Zhanel commented. “The community-acquired genotype is still going up, but the hospital-acquired [genotype] has plummeted in hospitals.”
He noted that CANWARD data suggest that antimicrobial resistance “is not confined to one part of the hospital. We have resistance happening in medical wards, ICUs, and hospital emergency rooms. We consistently find that resistance is highest in the ICU and by far the lowest in the ER. With clinics we find that it’s a variable scenario.”
The study was supported in part by Abbott, Achaogen, Affinium, Astellas, Astra Zeneca, Bayer, Cerexa/Forest, Cubist, Galderma Laboratories, Merck, Paladin Labs, Pfizer/Wyeth, Sunovion, and the Medicines Co. The researchers reported having no relevant financial disclosures.