Neisseriaceae includes the pathogenic bacteria Neisseria meningitidis (meningococci) and Neisseria gonorrhoeae (gonococci). Meningococci are Gram-negative cocci typically found in the nasopharynx that can cause meningitis. They have multiple serogroups defined by capsular antigens. Gonococci are Gram-negative diplococci and the exclusive cause of the sexually transmitted infection gonorrhea. Both are fastidious organisms that require special growth conditions. They possess virulence factors like pili and can develop antibiotic resistance.

1. Neisseriaceae
(meningococci, gonococci)
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2. NEISSERIA MENINGITIDIS
(MENINGOCOCCI)
• family Neisseriaceae, genus Neisseria, and
species Neisseria meningitidis
• Meningococci are Gram-negative, oval or
spherical cocci, 0.6 – 0.8 μm in size
• typically arranged in pairs
• non-sporeforming non-motile organisms
• multiple pili and fimbriae
• pathogenic meningococci are enveloped
by a polysaccharide capsule
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3. Cultivation
• fastidious bacteria!
• can’t grow on basic nutrient media
• they should be cultured on media with
blood, serum or ascitic fluid
• better in atmosphere with 5-10% CO2
(capnophilic bacteria).
• optimum temperature for growth is 36-
37°С. Bacteria can’t grow at 22°C.
• Meningococci are aerobic or facultatively
anaerobic bacteria
• They are catalase and oxidase positive
• poor biochemical activity
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4. Antigenic properties
• Based on their capsular polysaccharide antigens, meningococci are classified into at least 13
serogroups, (A, B, C, D, Y, W-135, etc.)
• Groups A,B and C are most important.
• Group A is usually associated with epidemics
• Group C mostly with localized outbreaks
• Group B caused both epidemics and outbreaks
Virulence factors
• Pili
• outer membrane proteins
• polysaccharide capsule
• IgA proteases
• Hyaluronidase and neuraminidase
• endotoxin
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5. Resistance
• Meningococci are very delicate organisms being highly susceptible to
heat, dessication, alterations in pH and to disinfectants.
• They are sensitive to penicillin and other antibiotics, but resistance
strains have emerged and become common in many areas.
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6. Pathogenesis and Clinical Findings
in Meningococcal Infections
• anthroponotic disease
• occurs worldwide
• Meningococcal carriers are the predominant source of
infection
• Meningococcus is localized primarily in their
nasopharynx
• The infection is transmitted by the air droplet route
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7. Several forms of
meningococcal
infection:
• meningococcal carriage,
• meningococcal nasopharyngitis,
• meningitis,
• and meningococcemia (including
fulminant meningococcal sepsis).
• If meningococcal sepsis (meningococcemia)
has abnormally high fatality rate (20-50%
and even more), meningococcal meningitis
develops lower rate of lethality (about 1-5%)
and post-infectious neurological sequelae (in
10-20% of patients).
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8. Laboratory Diagnosis
• Nasopharyngeal swabs and blood samples are taken for culture.
• Specimens of cerebrospinal fluid (CSF) and skin petechiac biopsy are taken for microscopy,
culture, and microbial antigen detection.
• Microscopy of gram-stained slides with the samples of centrifuged CSF detects typical gram-
negative bean-shaped diplococci
• Cultivation of clinical specimens is performed in serum, ascitic or blood agar, supplemented with
antibiotics, suppressing gram-positive microflora (vancomycin, amphotericin or ristomycin). After
incubation for 48 h in aerobic atmosphere pure cultures of meningococci can be recovered from
CSF or blood.
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9. Treatment and Prophylaxis
• antibiotics are the cornerstone of treatment
• Beta-lactam antibiotics (penicillin G or third-generation
cephalosporins) are the drugs of choice
• Azalides or chloramphenicol can be used in allergic persons
• specific prophylaxis - polysaccharide chemical vaccines
Vaccination is highly effecient in the control of outbreaks and
epidemics of meningococcal infection conferring the protective
immunity at least for 2-3 years. However, vaccination doesn’t affect
carriers.
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10. NEISSERIA
GONORRHOEAE
• causative agents of gonorrhoea
• family Neisseriaceae, genus Neisseria, and species
Neisseria gonorrhoeae
• Gonococci are similar with meningococci (about 70% of
genetic similarity).
• gram-negative, bean-shaped diplococci
• non-sporeforming, non-motile. Unlike meningococci,
Neisseria gonorrhoeae is lack of capsule.
• multiple pili and fimbriae
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11. Cultivation
• Gonococci are more difficult to grow than
meningococci.
• They are aerobic but may grow
anaerobically also.
• Growth occurs best at a temperature of
35-36c with 5-10% CO2.
• They grow well on chocolate agar.
• Colonies are small, round, translucent,
convex and slightly umbonate, with a finely
granular surface and lobate margins.
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12. Antigenic structure, virulence factors
• gonococci are regarded as the bacteria with highest genetic variability
and genetic exchange with other bacterial species
• Bacterial adhesins, including pili
• Opa and Por proteins
• Endotoxin (LOS)
• beta-lactamases
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13. Resistance
• The gonococcus is a very delicate organism, readily killed by heat,
drying and antiseptics.
• In cultures, the coccus dies in 3-4 days but survives in slant cultures at
35oC.
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14. Pathogenesis and
Clinical Findings in
Gonorrhoea
• Gonococcus is the strictly human
pathogen.
• Gonorrhoea is a typical sexually
transmitted disease
• Unprotected sexual intercourse
results in 50% likelihood of
disease contraction in women
and 30-50% in men.
• Also gonococci produce
gonorrhoeal conjunctivitis in
adults and ophthalmia
neonatorum (or blennorrhoea)
in newborn infants transmitted
by contact route.
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15. Laboratory Diagnosis of Gonorrhoea
• Specimens are collected from the discharge of urethra, vagina, vulva,
cervix, rectum or conjunctiva
• Gram-stained smears of secretions show typical gram-negative bean-
shaped cocci within leukocytes
• microbial culture - the collected specimens are inoculated
immediately into serum or ascitic agar. For men the culture is not
necessary in case of positive microscopic examination, but cultures
for women are indispensable.
• immunofluorescent test
• PCR
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16. Treatment and Prophylaxis of Gonorrhoea
• cephalosporins (e.g., ceftriaxone) and macrolides/azalides
(azithromycin)
• combination of azithromycin and gentamycin - against multiresistant
gonococcal strains
• For protection of newborns - eye instillations of sulfacetamide
(sulfacyl-sodium) administered immediately after birth
• protected intercourse - for adults
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