Pathogenic Neisseria Species: Diseases, Symptoms & Treatment

Neisseria is a genus of Gram-negative bacteria, characterized by their spherical shape and tendency to appear in kidney-bean-like pairs under a microscope. While many Neisseria species exist, some are particularly relevant to human health, ranging from harmless colonization to severe disease.

Understanding Pathogenic Neisseria

The Neisseria genus includes many species that naturally inhabit human mucous membranes without causing harm. However, two species are uniquely adapted to humans and cause disease: Neisseria gonorrhoeae and Neisseria meningitidis. Neisseria gonorrhoeae primarily colonizes the mucosal lining of the reproductive and urinary tracts, but can also be found in the mouth, throat, rectum, and eyes. Neisseria meningitidis typically resides in the upper respiratory tract. Both are exclusively human pathogens.

Gonorrhea: Symptoms and Complications

Gonorrhea is a sexually transmitted infection (STI) caused by Neisseria gonorrhoeae. Symptoms vary by infection site, and many individuals, especially women, may experience no symptoms. In men, urethral infection often causes painful urination and a yellow, white, or green discharge from the penis. Women with genital infections may notice increased vaginal discharge, painful urination, or bleeding between menstrual periods.

Infections can also occur in the rectum, causing itching, soreness, bleeding, or painful bowel movements. Pharyngeal (throat) infections are often asymptomatic but can cause a sore throat. Ocular infections, such as gonococcal conjunctivitis, are possible, particularly in newborns exposed during childbirth, and can lead to blindness if untreated.

Untreated gonorrhea can result in serious health issues. Women may develop pelvic inflammatory disease (PID), leading to ectopic pregnancy and infertility. Men can experience epididymitis, an inflammation of the testicle, and urethral strictures, which can also contribute to infertility. The infection can spread to the bloodstream, causing disseminated gonococcal infection (DGI), which may manifest as skin lesions or septic arthritis, often affecting the knees, ankles, and wrists.

Meningococcal Disease: Symptoms and Complications

Neisseria meningitidis causes meningococcal disease, which commonly presents as two severe forms: meningitis and meningococcemia. Meningitis involves inflammation of the protective membranes surrounding the brain and spinal cord, while meningococcemia is a life-threatening bloodstream infection. The bacteria spread through respiratory droplets, such as those from coughing, sneezing, or close contact.

Symptoms typically appear rapidly and can be severe. Meningitis often begins with a sudden high fever, intense headache, and a stiff neck. Other signs may include nausea, vomiting, confusion, sensitivity to light, and sometimes seizures or loss of consciousness. A characteristic rash, appearing as small red or purple spots (petechiae) or larger bruises (purpura), can also develop.

Meningococcemia can cause fever, extreme tiredness, vomiting, cold hands and feet, severe body aches, rapid breathing, diarrhea, and a non-blanching rash. This form can quickly progress to septic shock, a dangerous condition that can damage organs. Long-term complications for survivors can include hearing loss, brain damage, loss of limbs, seizure disorders, and cognitive impairments. Infants, teenagers, and young adults face a higher risk.

Detection, Treatment, and Prevention

Detection

Detecting Neisseria infections involves several laboratory methods. For Neisseria gonorrhoeae, nucleic acid amplification tests (NAATs) are frequently used due to their high sensitivity in detecting bacterial DNA or RNA from samples like urogenital, rectal, or pharyngeal swabs, or first-catch urine. While microscopy (Gram stain) can provide rapid results for symptomatic urethral infections in men, it is less sensitive for other sites. Bacterial culture, though sometimes less sensitive and more time-consuming, allows for comprehensive antibiotic susceptibility testing, important for guiding treatment. Diagnosis of meningococcal disease often relies on isolating Neisseria meningitidis from sterile body sites, such as cerebrospinal fluid or blood, typically through culture or NAATs.

Treatment

Treatment for Neisseria infections primarily involves antibiotics. For gonorrhea, the increasing problem of antibiotic resistance, including to penicillin, fluoroquinolones, and certain cephalosporins and azithromycin, has led to evolving treatment guidelines. Current recommendations often suggest a dual therapy approach, such as an intramuscular injection of ceftriaxone, frequently paired with oral azithromycin or doxycycline. The dosage of ceftriaxone has been increased in recent years due to concerns about azithromycin resistance. New antibiotic agents are under investigation to address drug-resistant strains.

For meningococcal disease, prompt initiation of antibiotics is important due to the rapid progression of the illness. Empirical therapy commonly includes extended-spectrum cephalosporins like cefotaxime or ceftriaxone. Once the specific susceptibility of the bacterium is confirmed, treatment may be switched to other antibiotics such as penicillin G or ampicillin.

Prevention

Preventive measures differ for each type of Neisseria infection. Preventing gonorrhea involves practicing safer sexual behaviors, including the consistent and correct use of condoms or dental dams during vaginal, anal, and oral sex. Limiting the number of sexual partners and open communication about sexual health also reduce risk. Regular STI testing is also advised for sexually active individuals, particularly women under 25 and men who have sex with men. If diagnosed, partners should be notified and treated to prevent reinfection and further spread.

For meningococcal disease, vaccination is a primary prevention strategy. Meningococcal conjugate vaccines (MenACWY) protect against serogroups A, C, W, and Y, and are routinely recommended for adolescents, with a booster dose at age 16. Serogroup B meningococcal vaccines (MenB) are available for protection against serogroup B, often recommended for adolescents and individuals at increased risk. In addition to vaccination, prophylactic antibiotics are recommended for close contacts of individuals with meningococcal disease to eliminate the bacteria from the nose and throat. Common prophylactic antibiotics include rifampin, ciprofloxacin, or ceftriaxone, with ceftriaxone being an option for pregnant women.

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