A genital culture tests for bacteria, yeast, and sometimes viruses that may be causing an infection in the genital or reproductive tract. A healthcare provider collects a swab sample from the affected area, then sends it to a lab where microorganisms are grown on a special plate over two to three days. The culture identifies exactly which organism is responsible for symptoms like unusual discharge, itching, sores, or pain, and it can also reveal which medications will be most effective against that specific organism.
Bacteria and Yeast Commonly Identified
The most common reason for a genital culture is to identify the specific strain of bacteria or yeast behind an infection. For yeast infections, cultures can distinguish between several Candida species, including Candida albicans (the most common cause of vaginal yeast infections), Candida glabrata, Candida tropicalis, Candida parapsilosis, and Candida krusei. This matters because some of these species respond poorly to standard antifungal treatments, so knowing exactly which one you have changes how your infection is treated.
Bacterial cultures can identify organisms like E. coli, Group B Streptococcus, gonorrhea (Neisseria gonorrhoeae), and other bacteria that cause urinary or genital infections. The lab grows colonies from your sample, examines them under a microscope, and runs biochemical tests to pin down the exact species. Healthy bacteria like Lactobacillus may also show up in results, which is normal and expected in vaginal samples.
How Antibiotic Sensitivity Testing Works
One of the most valuable things a culture provides is antibiotic sensitivity testing. Once the lab identifies the organism causing your infection, they expose it to a panel of different antibiotics or antifungals to see which ones kill it effectively and which ones it resists. This is especially important for infections that haven’t responded to a first round of treatment, or in cases where antibiotic resistance is a concern.
Gonorrhea is a prime example. The bacteria that cause it have a well-documented ability to develop resistance to common antibiotics, making culture with sensitivity testing a critical tool when standard treatment fails. Similarly, roughly 4% to 10% of vaginal trichomoniasis cases involve resistance to the most commonly prescribed medication. For persistent infections like these, cultures provide the information needed to choose a drug that will actually work.
Cultures for gonorrhea and chlamydia are now most commonly ordered specifically to assess treatment failure and to provide a living sample of the organism for susceptibility testing, rather than as a first-line diagnostic tool.
Group B Strep Screening in Pregnancy
If you’re pregnant, you’ll likely have a genital culture between 36 and 38 weeks of pregnancy as part of routine prenatal care. This screens for Group B Streptococcus (GBS), a type of bacteria that can live in the vagina or rectum without causing you any symptoms but can be dangerous to a baby during delivery. The American College of Obstetricians and Gynecologists recommends this screening for all pregnant people. A positive result means you’ll receive antibiotics during labor to protect the baby.
What a Culture Cannot Reliably Detect
Genital cultures have real limitations when it comes to viruses, particularly herpes simplex virus (HSV). A viral culture requires active, replicating virus in the sample, so timing is everything. If a sore is small, already healing, or has been present for more than 48 hours, the culture may not pick up enough virus to produce a positive result. During recurrent herpes outbreaks, viral culture is positive only about 30% of the time.
For herpes and several other infections, nucleic acid amplification tests (NAATs), especially PCR, have largely replaced cultures as the preferred diagnostic method. NAATs detect genetic material from the organism rather than requiring it to grow in a lab, which makes them significantly more sensitive. For yeast infections, NAATs detect about 92% of cases compared to 83% for culture. For trichomoniasis, NAATs catch 100% of cases versus about 94% for culture. Both culture and NAATs can identify the specific type of herpes virus (HSV-1 versus HSV-2), but NAATs are far less likely to give a false negative.
One situation where viral culture still plays a specific role is when a provider suspects antiviral resistance. If herpes lesions persist or keep coming back despite treatment, a viral culture can be used for phenotypic sensitivity testing to determine whether the virus has become resistant to standard antiviral medications.
How the Sample Is Collected
For women and people with vaginas, the swab is typically collected from the vaginal sidewall, roughly halfway between the vaginal opening and the cervix. If a speculum exam is being performed, the provider may also take cervical samples first, then swab the vaginal walls as the speculum is withdrawn. In some cases, a provider can collect the sample through a blind vaginal insertion without a speculum. For men and people with penises, the swab is usually taken from the urethra or from any visible sores or lesions.
The process takes only a few seconds and involves a sterile swab similar to a long cotton-tipped stick. It can feel uncomfortable but is rarely painful.
What Can Affect Your Results
Because a culture depends on growing live organisms, anything that reduces the number of viable bacteria or yeast in your sample can lead to a false negative. The biggest factor is antibiotic or antifungal use. If you’re currently taking or recently finished antimicrobial therapy, surviving organisms may not grow well enough in the lab to be detected. Your provider needs to know about any recent medications so they can interpret the results correctly or adjust the timing of the test.
Douching, vaginal creams, and other topical products can also interfere by washing away or suppressing the organisms the lab is trying to grow. For the most accurate results, avoid inserting anything into the vagina before your appointment unless your provider says otherwise.
How Long Results Take
Most genital cultures take two to three days for results. The lab needs time to incubate the sample under controlled conditions, allowing any organisms present to multiply into visible colonies. If antibiotic sensitivity testing is ordered, the process can take an additional day or two because the lab must then expose the grown organisms to various drugs and observe which ones are effective. Your provider will typically contact you once results are finalized, though some clinics post results to an online patient portal as they become available.