Neisseria Case File

Neisseria Case File

Eugene C.Toy, MD, Cynthia Debord, PHD, Audrey Wanger, PHD, Gilbert Castro, PHD, James D. Kettering, PHD, Donald Briscoe, MD

CASE 16

A 19-year-old woman presents to the physician’s office for the evaluation of a swollen knee. She states that for the past 1–2 week she has had some achiness in several of her joints and a low-grade fever, but it seemed to localize to her left knee approximately 3 days ago. It has been red, hot, and swollen. She has had no injury to the area and has never had anything like this before. Her past medical history is significant for having been treated for Chlamydia at the age of 17. She takes oral contraceptive pills regularly. She is sexually active, has been with her most recent boyfriend for about a month, and has had 5 partners in her lifetime. On examination, her vital signs are normal, but you notice that she walks with a limp. Her general examination is normal, and her skin is without rash. Her left knee is erythematous and warm to the touch. There is a visible effusion. Movement is limited because of pain and stiffness from the swelling. She refuses a pelvic examination because she doesn’t see what that has to do with her sore knee. However, she does allow you to perform a joint aspiration.

◆ What are the most likely Gram stain findings of the aspirated joint fluid?

◆ What cell surface factors facilitate attachment and penetration of this organism into the host cell?

ANSWERS TO CASE 16: Neisseria

Summary: A 19-year-old woman presents with septic arthritis. She has had an infection previously with Chlamydia.

◆ Likely findings on Gram stain of the joint fluid aspirate: Multiple polymorphonuclear leukocytes with intracellular gram-negative diplococci.

◆ Cell surface factors facilitating attachment and penetration into the host cell: Pili, which attach to epithelial cells, and Opa protein, which promotes firm attachment and cell penetration.

CLINICAL CORRELATION

Humans are the only known reservoir of Neisseria species. Neisseria gonorrhoeae is transferred from person to person by sexual contact. Approximately half of infected women have an asymptomatic carrier state. This is much less common in men. Neisseria gonorrhoeae causes urethritis in men and cervicitis in women. Complications of genital infections include pelvic inflammatory disease. The organism can also infect the rectum and oropharynx. Newborns passing through an infected birth canal may develop conjunctivitis by direct contact, a disease called ophthalmia neonatorum. Disseminated disease, including bacteremia with resultant joint and/or skin infections is more common in patients with complement deficiencies. Septic arthritis as a complication of disseminated disease may present in two forms, either as a systemic disease with fever, chills, and polyarticular syndrome, or as a monoarticular suppurative infection of a single joint without skin lesions or systemic symptoms. Most cases of disseminated gonococcal disease occur in persons with an asymptomatic genital infection.

Neisseria meningitidis is carried as normal upper respiratory flora in approximately 10 percent of the population. The polysaccharide capsule allows the organism to avoid phagocytosis and under unknown circumstances enter the blood and in some cases the central nervous system. The subsequent inflammatory response induced by the organism causes shock and disseminated intravascular coagulation. This is evidenced by skin lesions, which can mimic those seen in disseminated gonococcal infection. Bacteremia with or without meningitis usually occurs in teenage children. If untreated, the disease has a high mortality rate.

APPROACH TO SUSPECTED GONORRHOEAE PATIENT

Objectives

1. Know the structure and characteristics of Neisseria species.
2. Know the factors associated with the development on Neisseria infections and diseases.

Definitions

Disseminated intravascular coagulation (DIC): A complication of septic shock usually caused by endotoxin produced by the affecting organism.

Ophthalmia neonatorum: Conjunctivitis in the first month of life usually as a result of N. gonorrhoeae or Chlamydia trachomatis.

DISCUSSION

Characteristics of Neisseria Species

Neisseria species are aerobic, nonmotile, nonspore-forming, gram-negative cocci. They usually are arranged in pairs (diplococci) with adjacent sides flattened, resembling kidney beans. Neisseria are fastidious organisms that require a complex medium and an atmosphere supplemented with carbon dioxide for optimal growth. Neisseria gonorrhoeae has specific cell surface components related to its adherence, cellular penetration, toxicity, and evasion of host defenses. Cellular adherence is conferred by the presence of pili, which attach to host epithelial cells and also provide resistance to killing by host neutrophils. The outer membrane also contains the Opa proteins (opacity proteins), which promote tight attachment and migration of the bacteria into the host. Then Por proteins (porin), which form channels (pores) in the outer membrane, prevent phagolysosome fusion, allowing intracellular survival. Rmp proteins (reduction-modifiable proteins) stimulate antibodies, which inhibit host bactericidal antibodies, protecting the other surface antigens from host attack.

Plasmid acquisition and transfer appear to play significant roles in the

development of antibiotic resistance by N. gonorrhoeae. Multiple plasmids,

which confer β-lactamase, have been identified. A conjugative plasmid that

causes high-level tetracycline resistance has also been identified. These plasmids

are becoming more common, resulting in more antibiotic-resistant gonococcal

disease. LOS (lipooligosaccharide), also present in the cell wall,

produces the inflammatory response responsible for most of the symptoms

associated with gonococcal disease by its release of tumor necrosis factor-α.

Neisseria meningitidis appear the same as N. gonorrhoeae on Gram stain. They also produce a polysaccharide capsule that prevents phagocytosis. Neisseria meningitidis is divided into 13 serogroups, the most common of which are A,C,Y, W135, and B.

Diagnosis

Septic arthritis must be differentiated from other noninfectious forms of arthritis such as rheumatoid arthritis and gout. Definitive diagnosis is made by analysis of cells and Gram stain from an aspirate of the joint. Gram stain would reveal intracellular gram-negative diplococci. A presumptive diagnosis of gonorrhea can be made from a smear from a male urethra; otherwise, culture

is required for diagnosis.

Neisseria species are fastidious organisms in that they require carbon dixide atmosphere, and N. gonorrhoeae also require chocolate agar. Neisseria gonorrhoeae also may require at least 48 hours for production of small grey colonies. Selective media such as Thayer Martin or Martin Lewis is usually needed to isolate N. gonorrhoeae from nonsterile sites such as the cervix or urethra. Neisseria gonorrhoeae are quite sensitive to drying, so plates must be placed in a warm environment quickly to maintain viability. If a delay in transit to the laboratory is expected to be longer than several hours, a transport media such as Jembec is required. Rapid identification can be made from gramnegative diplococci, growing on selective media that are oxidase positive. Isolates are specifically identified by acid production from select sugars. Neisseria gonorrhoeae ferments glucose only, and N. meningitidis ferments both glucose and maltose. Because of the fastidious nature of N. gonorrhoeae, genital infections are identified using DNA probes, which detect both N. gonorrhoeae and C. trachomatis, which commonly occur together and don’t require live organisms for detection.

Treatment and Prevention

Penicillin is the treatment of choice for meningococcemia. Approximately 30 percent of N. gonorrhoeae produce β-lactamase and are therefore resistant to penicillin. Treatment with ceftriaxone or a quinolones is usually recommended, although increase in resistance to quinolones has been demonstrated in some geographic locations. Prevention of meningococcal disease is by vaccination. A recent CDC recommendation advises vaccinating all adolescents for meningococcus at the age of 11–12 years. Other susceptible persons, such as military personnel, college students who will be living in dormitories and asplenic patients, should be vaccinated as well. Prophylaxis of close contacts is also recommended to prevent spread of the disease. Prevention of N. gonorrhoeae includes practicing safe sex and use of a condom, as well as screening sexually active persons. Screening of pregnant women for congenitally transmitted infections with appropriate treatment would prevent infection of the neonate with N. gonorrhoeae, as well as other congenitally transmitted infections.

COMPREHENSION QUESTIONS

[16.1] The source of N. meningitidis is the nasopharynx of human carriers who exhibit no symptoms. The ability of this bacterium to colonize the respiratory mucosa is associated with its ability to synthesize which of the following?

A. Coagulase

B. Collagenase

C. Hyaluronidase

D. Lipases

E. Pili

[16.2] Several Neisseria species are a part of the normal flora (commensals) of the human upper respiratory tract. Which of the following statements accurately describes the significance of these bacteria?

A. As a part of the normal flora, Neisseriae provide a natural immunity in local host defense.

B. As a part of the respiratory flora, they are the most common cause of acute bronchitis and pneumonia.

C. Commensal bacteria stimulate a cell-mediated immunity (CMI).

D. Commensal Neisseriae in the upper respiratory tract impede phagocytosis by means of lipoteichoic acid.

E. Normal flora such as nonpathogenic Neisseriae provide effective nonspecific B-cell–mediated humoral immunity.

[16.3] A 22-year-old man presents to the STD clinic with a 5-day history of burning on urination and a 3-day history of a nonpurulent urethral discharge. He is sexually active with many female partners and does not use condoms. There is no history of prior sexually transmitted diseases. Laboratory findings from endourethral exudate are most likely to show which of the following?

A. A negative gonorrhea culture

B. Abundant intracellular diplococci in neutrophils

C. Immunofluorescence using monoclonal antibodies to serotypes A–C

D. Intracellular elementary bodies

[16.4] The two pathogenic Neisseria species, N. meningitidis and N. gonorrhoeae, differ from the nonpathogenic Neisseria species in what way?

A. The former are less resistant to certain antibiotics than the nonpathogenic species.

B. The pathogenic species are oxidase positive.

C. The pathogenic species grow well in enriched chocolate agar.

D. The pathogenic species do not grow well at room temperature.

Answers

[16.1] E. Both N. gonorrhoeae and N. meningitidis adhere to the mucous membrane tissues by means of pili (short protein appendages from the membrane through the cell wall). Coagulase and lipase are products of streptococci, whereas collagenase and hyaluronidase are enzyme products of streptococci.

[16.2] A. The normal or usual flora seldom cause disease in humans, except the several species that may be opportunistic in the right circumstances. One mechanism that has been suggested as to how the normal flora help to protect humans from pathogenic strains of bacteria is to stimulate the immune system to produce antibodies (or CMI) that would recognize related pathogens and inhibit their growth. An unexplained component of this mechanism is how the normal flora continue to exist as part of the body flora in spite of these immune mechanisms.

[16.3] B. This presentation is classic for gonorrhea infection and symptoms. Abundant gram-negative diplococci will be found both intracellularly and outside of the phagocytic cells. Interestingly, gonococci may even divide within the phagocytic cell. This evidence (Gram stain of the exudate) is presumptive evidence of gonococcal infection, and treatment should be made immediately. Such a specimen should be positive for culture with the correct medium (e.g., Thayer-Martin) and incubation conditions (37°C [98.6°F], increased carbon dioxide atmosphere). Serotypes A–C refers to N. meningitidis, and elementary bodies would indicate Chlamydia microorganisms.

[16.4] D. Neisseria gonorrhoeae and N. meningitidis are true human pathogens, surviving best in the human host. They are more fastidious in their nutritional requirement, requiring an enriched selective medium for growth. All Neisseria are oxidase positive. Normal flora (nonpathogenic) Neisseria will grow at room temperature on simple medium. Because of β-lactamase production, sensitivities should be done to ensure proper antimicrobial selection for treatment.

MICROBIOLOGY PEARLS ❖ Neisseria meningitidis is a highly contagious organism, which can cause meningitis in otherwise healthy young people. ❖ Neisseria meningitidis can be successfully prevented with the use of the vaccine for high-risk individuals. ❖ Neisseria gonorrhoeae is a treatable sexually transmitted disease and should be ruled out in high-risk patients to prevent further complications including disseminated disease.

REFERENCES

Apicella, MA. Neisseria meningitidis. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases, 5th ed. Philadelphia, PA: Churchill Livingstone, 2000:2228–41. 

Murray PR, Rosenthal KS, Pfaller MA. Neisseria. In: Murray PR, Rosenthal KS, Pfaller MA. Medical Microbiology, 5th ed. St. Louis, MO: Mosby, 2005:311–21. 

Sparling, PF, Handsfield, HH. Neisseria gonorrhoeae. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases, 5th ed. Philadelphia, PA: Churchill Livingstone, 2000:2242–58.

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