Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1359 page)

   Genital cultures should be collected from patients with signs and symptoms of localized genital tract infection or sexually transmitted disease, including discharge, dysuria, or lower abdominal pain.

   Use

   This culture is used to detect common bacterial pathogens from genital specimens. Target pathogens typically include
N
.
gonorrhoeae
, yeast, group A and B β-hemolytic streptococci,
Staphylococcus aureus
, and
Listeria monocytogenes
.
Gardnerella vaginalis
should be reported if predominant and isolated in moderate to heavy growth. Invasively collected specimens should be cultured for isolation of these, as well as a broad range of other bacterial pathogens.

   
Method:

   A Gram stain should be prepared from specimens submitted for genital culture. In male patients, the presence of many intracellular gram-negative diplococci is consistent with a diagnosis of gonorrhea. In female patients, a vaginal Gram stain may be used to identify “clue cells”; the absence of lactobacilli may be a marker of disruption of the normal vaginal flora, as with bacterial vaginosis.

   Specimens are plated onto selective and nonselective media that support growth of fastidious pathogens. Examples include

   Blood and chocolate agar

   CNA and MacConkey agar, or comparable selective agar for gram-positive and gram-negative isolation

   Selective agar for
N
.
gonorrhoeae
, such as Thayer-Martin, Martin- Lewis, NYC, or comparable media

   
Turnaround time:
Routine genital cultures are incubated for up to 72 hours. Additional time is required in positive cultures for isolation, final identification, and further testing.

   Special Collection and Transport Instructions

   
Male:
An urethral swab should be collected. It may be possible to collect discharge expressed from the penile urethra. Collection of urethral discharge after prostatic massage may improve detection in patients with symptoms of prostatitis.