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​​Gradient Strip (GC ETest) Neisseria gonorrhoeae, Antimicrobial Susceptibility Testing Services Frequently Asked Questions (FAQ)

June 26, ​​​2023

  1. Wha​t types of samples should we s​end?​​​​

  1. The following Neisseria gonorrhoeae pure isolates may be submitted to the California Department of Public Health (CDPH), Microbial Diseases Laboratory (MDL) for Gradient Strip (Etest) Antimicrobial Susceptibility Testing (AST).

  1. ​​​​N. gonorrhoeae isolates with decreased susceptibility to cefixime (MIC ≥0.25 µg/mL), ceftriaxone (MIC ≥0.125 µg/mL), and azithromycin (MIC >16 µg/mL). ​​
  2. N. gonorrhoeae isolates from suspected treatment failures (Clinical Guidelines for Gonorrhea Treatment and Management of Suspected Treatment Failure ​PDF​) and isolated from sites, including but not limited to urethra, endocervix/vagina, rectum, pharynx, blood, synovial fluid and eye.

  3. N. gonorrhoeae isolates from disseminated gonococcal infections (DGI).​

  4. N. gonorrhoeae isolates from ocular infections.

  1. Pre-approval for other N. gonorrhoeae isolates not meeting the listed criteria will be determined on a case-by-case basis after consultation with STD program at ​

  1. Primary clinical specimens for culture isolation are not accepted by MDL at this time. Primary clinical specimens from suspected treatment failures may be tested via the Antimicribal Resistance Laboratory Network regional laboratory in Washington state. Contact or​​ for submission instructions. ​

  1. ​How should samples be sent in for the laboratory testing?​​
  1. ​​​Instructions for submission of isolates to the MDL Bacterial Diseases Section (BDS): 
  1. ​​Submitters can use one of the following submittal methods:  ​​​ 
    1. ​​​​​MDL Lab Web Portal (LWP) (Prefe​rred)​​. If your  laboratory is already enrolled on the MDL LWP please go to ​MDL Lab Web Portal (LWP)​​​. ​Submitters interested in using MDL LWP please contact the CDPH LWP team at​
    2. MDL barcode submittal form. If you don’t have access to MDL LWP please use the MDL barcode submittal form: MDL Submission Instructions and Forms. ​

  2. ​​​​Under the Select Test Requisition field, select the Antimicrobial Susceptibility Testing-AST form.

  3. Please ​t​ype in patient, submitter and test requistion information into electronic submission form. ​

  4. Type in the genus and species identification on the submittal form in the “Submitter’s Identification of Organism” box. ​​

  5. Follow the directions to select the test requested as ‘N. gonorrhoeae Etest‘ in the “Test(s) Requested” box on the Page 2.

  6. Provide a copy of isolate AST results or/and other patient records that would indicate suspected treatment failure. ​​

  7. The reason for requesting testing (e.g., suspected treatment failure) should be entered in the ‘Other Tests or Comments Field’ on Page 2. Additionally, if applicable, the name and contact information of the provider/entity requesting the isolate be sent for testing can also be entered here.

  8. ​​Enter Travel history on Page 1. Please include most recent international or interstate travel within one month prior to specimen collection (if available).
  1. ​Prepare culture for submission.

  1. ​​Isolates must be identified as N. gonorrhoeae by the submitter.​
  2. Mixed cultures received by MDL will not be tested. 

  3. Refer to Disseminated Gonococcal Infection (DGI) Guidance for Laboratories for detailed procedures. The ‘Specimen preparation for transport’ instructions can be used for preparing any N. gonorrhoeae isolate for shipment to CDPH. The instruction is briefly described as following. ​​​​

    1. First, grow a pure N. gonorrhoeae isolate at 35°C in 5% CO2 on suitable media for gonorrhea (such as chocolate agar or modified Thayer-Martin) for 24-48 hours, until obtain visible growth. 
    2. ​Then, prepare for shipment with three options. Make sure to submit the culture fresh (24-72 hr) at time of shipping to ensure it is viable when it arrives at MDL.​​
    1. To ship using an agar slant: Heavily inoculate a chocolate (or other suitable media for GC) slant with fresh growth. Incubate at 35°C with 5% CO2 until you see visible growth (18 – 24 hours is ideal). Then close cap tightly, pack, and ship at ambient temperature.
    2. ​To ship using an agar plate: Heavily inoculate a chocolate (or other suitable media for GC) plate with fresh growth. Incubate at 35°C with 5% CO2 until you see visible growth (18 – 24 hours is ideal). Then seal the plate lid tightly with parafilm and place the plate in zip lock biohazard bag, pack and ship at ambient temperature.
    3. ​​To ship using a frozen cryotube with TSB and 15% glycerol: Heavily inoculate a cryotube with fresh growth. Immediately place in a -60°C or lower freezer. Once the isolate is fully frozen, ship the isolate on dry ice.
  1. What is the shipping address?

​California Deparment of Public Health
Microbial Diseases Laboratory
ATTN: Bacterial Diseases Section
850 Marina Bay Parkway​
Specimen Receiving, Room B-106
Richmond, CA 94804​

  1. Who ​can submit isolates for testing?​​​​

Isolates are accepted from California Local Public Health Laboratories ​o​​nly. Isolates ​will not be ​​accepted directly from hospitals or other healthcare facilities unless prior arrangements have been made by MDL and the applicable Local Public Health Laboratory.  ​​​

  1. What is the turn-around-time?​​​​

Results of GC Etest will be available within 12 calendar days of isolate receipt. Expedited testing may be available with pre-approval from MDL. ​

  1. How do I get more informartion?

For more information on the GC Etest and submission criteria or instructions, please email , or call the MDL Bacterial Diseases Section at (510) 412-3903.​​

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