Assessment of Gentamicin and Ertapenem Susceptibilities of Canadian Neisseria Gonorrhoeae Isolates

Sawatzky, Pam

Tuesday, June 10, 2014

International Ballroom

Pam Sawatzky, BSc¹, Irene Martin, BSc¹, Angela Yuen, Student¹, Vanessa Allen, MD², Linda Hoang, MD³, Brigitte Lefebvre, PhD⁴, Marguerite Lovgren, BSC⁵, Greg Horsman, MD⁶, Paul Vancaeseele, MD⁷, Richard Garceau, MD⁸, Tom Wong, MD, MPH, FRCPC⁹, Chris Archibald, MDCM, MHSc, FRCPC¹⁰ and Michael Mulvey, PHD¹¹, 1Streptococcus and STI Unit, National Microbiology Laboratory, Winnipeg, MB, Canada, 2Public Health Ontario, Canada, 3British Columbia Centre for Disease Control, Canada, 4Laboratoire de santé publique du Québec, Canada, 5Alberta Provincial Laboratory for Public Health, Canada, 6Saskatchewan Disease Control Laboratory, Canada, 7Cadham Provincial Laboratory, Canada, 8George L Dumont Hospital, Canada, 9Professional Guidelines and Public Health Practice Division, Centre for Communicable Diseases and Infection Control, Public Health Agency of Canada, Ottawa, ON, Canada, 10Centre for Communicable Diseases and Infection Control, Public Health Agency of Canada, Ottawa, ON, Canada, 11National Microbiology Laboratory, Canada

Background: The emergence of isolates with decreased susceptibilities to the cephalosporins and reports of treatment failures in Canada and around the world has made the concept of untreatable gonorrhea infections a future possibility. Alternative therapies such as gentamicin and ertapenem need to be evaluated for future therapeutic use.

Methods: Neisseria gonorrhoeae were collected by Canadian provincial public health laboratories in 2012 and submitted to the National Microbiology Laboratory for testing. Neisseria gonorrhoeae multi-antigen sequence types (NG-MAST or STs) and minimum inhibitory concentrations (MICs) were determined using the Etest for gentamicin (n=334) and ertapenem (n=378). Five reference cultures were also tested and their results were compared to established MICs. Currently there are no ertapenem or gentamicin interpretation criteria for N. gonorrhoeae.

Results: The MICs of gentamicin ranged from 1 mg/L to 6 mg/L with a modal MIC of 4 mg/L. The MICs of ertapenem ranged from <0.002 mg/L to 0.064 mg/L with a modal MIC of 0.008 mg/L. Isolates with decreased susceptibilities to ceftriaxone and cefixime had a modal MIC for ertapenem of 0.047 mg/L. The gentamicin modal MIC for these isolates remained the same. There were 139 different STs identified among the 378 isolates tested. ST-1407 was found to have the highest prevalence [10.% (n=39)] with ST-3158, ST-3307, ST-4709 and ST-7986 following at 5.3% (n=18) each. The modal MICs for the ST-1407 isolates were 0.032 mg/L for ertapenem and 3 mg/L for gentamicin.

Conclusions: Modal MICs to gentamicin and ertapenem in a collection of diverse Canadian N. gonorrhoeae isolates are similar to that reported in other countries. Gentamicin is already used for gonorrhea treatment in other countries and may be a future option for treatment in combination with azithromycin in Canada. Ertapenem MICs remained low but are slightly elevated in the isolates with decreased susceptibilities to ceftriaxone and cefixime.

WP 148 Assessment of Gentamicin and Ertapenem Susceptibilities of Canadian Neisseria Gonorrhoeae Isolates