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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