A 20-year-old college student comes to his campus health center for treatment. His chief complaint is dysuria, especially at the beginning of urine flow, and urethral itching. He first noticed these symptoms four days ago and they have persisted since then. For the last two days, he has also been experiencing increasing production of a yellowish, mucoid urethral discharge. He is not experiencing urinary frequency or urgency. His vital signs are normal. A physical exam detects urethral tenderness to palpitation, but no other abnormalities. A history is taken and the student reveals that he attended a large party 10 days ago, at which he consumed a considerable amount of alcohol, and met an attractive young woman (for the first time) with whom he later had intercourse. Unfortunately, he cannot remember if any precautions were taken during their intimate interlude.

Question 2.1: What is your preliminary diagnosis and what tests would confirm it?

The symptoms are consistent with an acute urethritis. Given the lack of frequency and urgency, other complications such as cystitis are unlikely. The yellowish, mucoid urethral discharge is suggestive of gonorrhea, although chlamydial NGU is not out of the question. Given the high likelihood of gonorrhea, you should carry out a Gram stain and culture of a urethral smear.

Test Results

The Gram stain of the urethral smear reveals the presence of intracellular, kidney-shaped Gram-negative cocci that tend to occur in pairs. Small numbers of PMNs are also present.

Question 2.2: Do these findings confirm your diagnosis? What is the causative agent of this infection?

The finding of PMNs and intracellular Gram-negative diplococci in a urethral smear is generally considered sufficient to establish a diagnosis of gonorrhea in symptomatic males. The urethral smear culture can be identified by the lab to provide further confirmation. The causative agent is Neisseria gonorrhoeae.

Question 2.3: What measures should be observed when taking and handling a urethral smear for culturing and subsequent laboratory analysis?

Urethral smear samples should be collected with Dacron or rayon swabs, preferably from 2 to 4 hours after voiding to prevent bacterial washout with voiding. Cotton swabs should not be used for samples to be cultured because they are bactericidal. Part of the sample should be inoculated onto a plate of modified Thayer Martin ("chocolate agar") or other gonococcal-selective medium for culture. It should be noted that this is a fastidious organism that is difficult to grow. It is important to process all samples immediately because gonococci do not tolerate drying. If plates cannot be incubated immediately, they can be held safely for several hours at room temperature in candle extinction jars prior to incubation. If processing will occur within 6 hrs, transport of specimens may be facilitated by the use of nonnutritive swab transport systems such as Stuart or Ames medium. For longer holding periods (e.g., when specimens for culture must be mailed to a lab), culture media with self-contained CO2-generating systems (such as the JEMBEC or Gono-Pak systems) may be used.

Question 2.4: What biological characteristics of this causative agent are important with respect to its virulence and how it is transmitted?

Neisseria gonorrhoeae possesses pili that act as adhesins and enable the bacterium to attach very readily to the surface of columnar epithelial cells in the urethra and cervix (thereby initiating the infection process). Sophisticated genetic mechanisms enable this organism to rapidly modify its surface antigens, and this renders the antibody-mediated immune response largely useless as a defense mechanism. Another gonococcal surface protein, the opacity-associated protein (Opa) is responsible for the organism's adherence to a variety of eukaryotic cells, including polymorphonuclear leukocytes (PMNs). Several types of outer membrane proteins (e.g., transferrin binding proteins Tbp1 and Tbp2, and lactoferrin-binding protein) enable the bacterium to scavenge large amounts of iron from transferrin and lactoferrin in the human body.

Neisseria gonorrhoeae is extremely sensitive to drying and to low temperature (i.e., temperatures below human body temperature). It is almost always transmitted via direct contact between two individuals because it cannot survive in most outside environments for more than a few seconds.

Question 2.5: How can this causative agent be distinguished from other members of the same genus, some of which are nonpathogenic members of the human mouth flora?

All species of Neisseria are Gram-negative cocci that tend to occur in pairs (diplococci). The individual cells are shaped like a coffee bean, and the concave sides are adjacent to one another when they occur in pairs. (This can be seen in a Gram stain.) All species are oxidase positive, but N. gonorrhoeae can be distinguished from other Neisseria species by its ability to grow on selective media and to utilize glucose, but not maltose (such as N meningitidis), sucrose, or lactose, as a carbon source.

Question 2.6: How should this infection be treated?

Resistance to penicillins, sulphonamides, and tetracyclines is now widespread among strains of N. gonorrhoeae. In 1998, CDC published the following recommended first-line regimens for treatment of gonococcal infections: Cefixime (400 mg, PO, single dose), Ceftriaxone (125 mg, IM, single dose), Ciprofloxacin (500 mg, PO, single dose), or Ofloxacin (400 mg, PO, single dose). Any of these should be followed by azithromycin (1 g, PO, single dose) or doxycycline (100 mg, PO, bid, for 7 days).