Meatal Swabs Contain Less Cellular Material and Are Associated with a Decrease in Gram Stain Smear Quality Compared to Urethral Swabs in Men

Abstract

Urethral swabs are the samples of choice for point-of-care Gram stain testing to diagnose Neisseria gonorrhoeae infection and nongonococcal urethritis (NGU) in men. As an alternative to urethral swabs, meatal swabs have been recommended for the collection of urethral discharge to diagnose N. gonorrhoeae and Chlamydia trachomatis infection in certain populations by nucleic acid amplification testing (NAAT), as they involve a less invasive collection method. However, as meatal swabs could be sampling a reduced surface area and result in fewer collected epithelial cells compared to urethral swabs, the adequacy of meatal swab specimens to collect sufficient cellular material for Gram stain testing remains unknown. We enrolled 66 men who underwent either urethral or meatal swabbing and compared the cellular content and Gram stain failure rate. We measured the difference in swab cellular content using the Cepheid Xpert CT/NG sample adequacy control crossing threshold (SAC CT ) and determined the failure rate of Gram stain smears (GSS) due to insufficient cellular material. In the absence of discharge, meatal smears were associated with a significant reduction in cellular content (P ϭ 0.0118), which corresponded with a GSS failure rate significantly higher than that for urethral swabs (45% versus 3%, respectively; P Ͻ 0.0001). When discharge was present, there was no difference among results from urethral and meatal swabs. Therefore, if GSS testing is being considered for point-of-care diagnosis of N. gonorrhoeae infection or NGU in men, meatal swabs should be avoided in the absence of a visible discharge.KEYWORDS Chlamydia trachomatis, Gram stain, meatal swabs, Neisseria gonorrhoeae, urethral swabs C hlamydia trachomatis and Neisseria gonorrhoeae infections continue to rise, with 1.4 million and Ͼ350,000 cases reported, respectively, in the United States in 2015 (1); nongonococcal urethritis (NGU) remains the most common form of urethritis in men (2). For screening at-risk individuals, the Centers for Disease Control and Prevention (CDC) recommends highly sensitive nucleic acid amplification testing (NAAT) of urine or a urethral swab of urethral secretions (3). Meatal swabs have been suggested as a less invasive alternative to urethral swabs for specimen collection for NAAT and are amenable to self-obtained patient collection because they elicit less discomfort (4). Although not yet FDA approved or CDC recommended for NAAT in men, meatal swabs are recommended for NAAT in prepubertal boys with discharge, given concerns about urethral trauma from swabs (3,5). In men, self-obtained meatal swabs appear to be equivalent to clinician-collected urethral swabs for diagnosing C. trachomatis/N. gonorrhoeae infection by NAAT, although there have been mixed reports of the sensitivity of this sample type (6, 7). Currently, no rapid (Ͻ30-min) point-of-care NAAT is available to diagnose N. gonorrhoeae infection or NGU, and Gram stain smear (GSS) testing of

Neisseria gonorrhoeae host adaptation and pathogenesis

“…In addition, the prevailing dogma in the field is that female genital infections are mostly asymptomatic and male infections are mostly symptomatic 18-20 . However, there are many studies that show asymptomatic infections are common in both genders 21-25 . The long-held, highly-repeated supposition that female infections are mostly asymptomatic and males are symptomatic is mainly based on the fact that overt symptoms (that is, inducing immune cell influx and inflammation) in males are easier to diagnose, due to the purulent exudate from the penis and resultant painful urination.…”

Atypical, Yet Not Infrequent, Infections with Neisseria Species

“…However, clinical symptoms in women are more likely to go unnoticed because neutrophil infiltration does not affect the same niche as urination and pain is often absent. Although ecto/endo-cervicitis in women is commonly asymptomatic, several studies report that asymptomatic infections are indeed common in both genders [6][7][8][9]. In approximately 10-25% of untreated women, gonococci can ascend into the upper reproductive tract (through the endometrium, uterus, Fallopian tubes to ovaries and peritoneum).…”