A Gram stain is routinely performed as part of aerobic cultures on all specimens (except urine, blood, and stool) provided that an adequate quantity of specimen is submitted. See
Aerobic culture and Susceptibilities (AERS) for details.
A Gram stain is included in an aerobic culture when adequate specimen is received, with the exception of blood, urine, and feces. Only order this test if:
- an aerobic culture is NOT also being ordered at the same time.
- A Gram stain is desired with an accompanying urine culture.
For feces Gram stain, order
WBC-Stool (STWBC). Consult microbiology laboratory if a Gram stain of blood or bone marrow is desired.
Swabs:
- ESwab: collect one swab for Gram stain, aerobic and anaerobic cultures, and an additional swab for each additional culture type or stain (e.g. fungus or mycobacteria).
- Other Amies medium swab types: collect one swab for every culture and stain (including Gram) to be ordered.
‘ESwab’ is a trademark of Copan Diagnostics.
A definitive diagnosis of gonorrhea depends on the detection of its causative agent, Neisseria gonorrhoeae, by culture or PCR. However, Gram-negative diplococci contained within leukocytes in a urethral exudate from a male patient may be considered presumptive evidence of gonorrhea. Gram stain of other sources including cervical, throat, or rectal specimens should not be performed for gonorrhea since morphologically similar intracellular organisms are often found in these types of specimens. Urethral swabs from a male patient are used to prepare a smear at bedside. The slide should be labeled, allowed to air-dry and sent to the lab along with a swab specimen for gonorrhea culture. Alternately, two swabs can be submitted in bacterial transport medium and sent to the lab, where the smear will be prepared by laboratory personnel. Gram stain and gonorrhea culture should be ordered.
Vincent’s Angina (Trench mouth)
A swab-collected specimen is applied to the surface of a microscope slide, allowed to air-dry, and then sent to the microbiology laboratory. A swab can also be placed into the transport medium and sent to the laboratory where the smear is then prepared by lab personnel, stained, and examined. The requisition form must specify “Rule out Vincent’s Angina”.