Neisseriaceae
The Gram-Negative Cocci of
Clinical Importance
Neisseriaceae Genera
• Gram (-) cocci & rods:
– Neisseria – aerobic
cocci
– Kingella - coccobacilli;
fac. anaerobes
• Former members:
Moraxellaceae
– Moraxella (Branhamella)
- cocci; asacchrolytic
– Acinetobacter - rods
Neisseria
• Found as NF of naso- and oropharynx
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–
–
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N. lactamica
N. sicca
N. subflava
N. mucosa
• Human pathogens - encapsulated
– N. gonorrhoeae (GC) – strict pathogen
– N. meningitidis (MGC) – NF in 3-30%, pathogen
Gram Stain
• Gram (-) diplococci,
adjacent sides
flattened (coffee-bean)
• In a direct smear GC
found extracellular,
intracellularly in PMN
Culture Media: TSA
• Non-pathogenic Neisseria ssp., M.
catarrhalis grow on TSA
• Colonies of may be dry, wrinkled,
opaque, yellow, tend to be selfadherent
Enriched Media: CBA, CHOC
• MGC & GC fastidious,
require serum or
blood
• MGC grows on CBA
and Chocolate agar
• GC grows only on
CHOC
• Colonies small,
translucent to
grayish-white
Selective Media: MTM
• Specimen with heavy NF
• Modified Thayer Martin
(MTM): CHOC + antibiotics
–
–
–
–
Vancomycin - inhibits G(+)
Colistin - inhibits Gram (-)
Nystatin - inhibits fungi
Trimethoprim - inhibits swarming
Proteus
– Occasional strains of GC sensitive
to Vancomycin, so both CHOC and
MTM always used
– May require 48-72 hours for
growth
Lab Culture: CO2
• Neisseria and Moraxella
aerobic, no growth
under anaerobic
conditions
• MGC & GC require CO2
(3-10%) for growth,
particularly primary
isolation plates
Lab Culture: Temperature
• GC & MGC sensitive to temperature
extremes, drying:
– At 25°C produce autolytic enzymes and
alkaline pH, lead to cell lysis
– Optimal culture – specimen from patient
plated directly onto culture media,
incubated immediately
Neisseria Lab ID
• Colony morphology on agar plate:
size, shape, texture
• Gram stain: G(-) diplococci
• Catalase (+) and Oxidase (+):
– Oxidase test – agar plate or filter paper
add chromogenic reducing reagent to
test for cytochrome oxidase
Biochemical ID: CHO Utilization
• Use CHO oxidatively (not fermentatively)
• Cystine-tryptic-agar (CTA) sugars - glucose,
maltose, lactose, sucrose
• Incubate 24-72 hours; check for acid product
• Some fastidious GC grow poorly on CTA
• Differential ID of isolates:
– GC = (+)glucose only
– MGC = (+)glucose & maltose
– M. catarrhalis = (-) all four CHO
Biochemical ID Test
• CarboFerm™Neisseria Kit: rapid test
– Chromogenic substrate for specific enzymes
– ID MOs by enzyme profile
– Isolated colony subcultured overnight and then
tested for specific enzymes
– Preformed enzymes (heavy inoculation MO used
with small volume of CHO (glucose, maltose,
lactose, sucrose)
– Results read in ≤4 hours
• DNAse test: M. catarrhalis = (+)
all Neisseria = (-).
• Nitrate reduction: M. catarrhalis = (+)
GC & MGC = (-)
ID: Other Methods
• Many kits available for serologic ID:
– Agglutination (rapid, inexpensive)
– Fluorescent antibody staining (sensitive,
specific)
• Auxotyping: distinguishes GC by
nutritional requirements; strains
associated with disseminated disease
have multiple requirement for arginine,
hypoxanthine and uracil (AHU strains)
• Nucleic acid current test of choice
– Probe based (chemiluminescent label)
– PCR based (DNA amplification) for ID of
GC directly from clinical samples
– Highly sensitive, specific
Pathogenicity: N. gonorrhoeae
• Capsule – antiphagocytic
• Pili- attach to epithelial
cells, also antiphagocytic
• Cell wall proteins:
– Protein I- porin; inhibit
PMN phagocytosis, prevents
phagolysosome fusion
– Protein II – attachment,
invasion
– Protein III – elicits Ab that
protects surface Ags from
host bactericidal Ab lysis
Pathogenicity: N. gonorrhoeae
• Lipooligosaccharide (LOS) –
endotoxin; mediates mucous
membrane damage, fever, toxcity
• IgA protease – cleaves mucosal Ab
• Both pili, protein I, II subject to
antigenic variation; evade host
immune defense
• Diseminated gonococcal infection
(DGI) strains, resistant to
phagocytosis, serum bactericidal
activity; multiply in presence of
PMNs
• Acquire iron from host - outer
membrane proteins; enhanced
capacity occurs in DGI strains
Clinical Significance: N.
gonorrhoeae
• Transmitted by direct sexual contact
• Formerly, most common reportable disease
in U.S.
• Increase epidemic in 1960’s:
– Social change (sex outside of marriage)
– Non-barrier contraception (birth control pill)
• Concomitant Chlamydia trachomatis
infection common (most reportable disease
in U.S. today)
• Asymptomatic (AS) infections:
– Males = 5%
– Females = 50%
– Serve as carriers to transmit disease
Uncomplicated GC
Infections: Males
• Incubation 1-4 days
• Acute urethritis, profuse
purulent discharge, dysuria.
• Usually restricted to urethra;
symptoms clear in few weeks
• Rare complications – prostitis,
epididymitis
• Oropharyngeal infection mild pharyngitis
• Anorectal infection – common
in homosexual men
Uncomplicated GC Infections:
Females
• Cervix primary site of infection
(endocervical columnar epithelial cells)
• Increased vaginal discharge, burning or
increase frequency of urination, abdominal
pain, menstrual abnormalities
• Symptoms clear in few weeks
• Infected mothers can transmit GC to
babies at birth (ophthalmia neonatorum):
– Lead to blindness
– Erythromycin eye drops given
at birth for prevention
Complicated GC Infections
• Untreated AS infection may spread to the
bloodstream causing disseminated
gonococcal infection (DGI) in both men
(rare) and women (1-3%)
• Infection of skin & joints – fever,
arthritis, maculopapular rash
Complicated GC Infections: Women
• 10-20% present with pelvic
inflammatory disease (PID)
• Ascending infection, spread
• Resulting in:
– Endometritis
– Salpingitis (fallopian tubes)
– Peritonitis
• Symptoms:
– abdominal pain
– abnormal vaginal, cervical
discharge
– uterine tenderness
• Can result in ectopic
pregnancy, infertility
GC: Treatment and
Antimicrobial Susceptibility
• Penicillin no longer drug of choice
• Resistant strains emerging (do lactamase testing
• CDC recommends combination of
antibiotics
– Ceftriaxone (1 dose) treat GC
– Doxycycline (7 days) treat possible C.
trachomatis infection
• Prevention requires:
– Public Health education
– Detection by lab testing
– Follow-up of sexual contacts
Pathogenicity: N. meningitidis
• Capsule (polysaccharide) – host antibodies
against capsule protective; only certain
serotype antigens found during epidemics
(used for vaccine)
• Pili - binding to specific NP receptors
• IgA protease
• Ability to acquire iron from human
transferrin
Pathogenicity: N. meningitidis
• Class 1, 2, 3 antigens function as porins
(~Protein I of GC)
• Class 5 antigens involved in attachment
and antigenic variation (~Protein II of GC)
• LOS – endotoxin, symptoms of toxemia
common in infection
Clinical Significance: N. meningitidis
• Endemic worldwide
• Epidemic in developing countries
• Colonizes nasopharynx of healthy people (3-30%); most
common in children, young adults, low socioeconomic
population
• AS carriers primary source of spread
• By aerosols - people with prolonged contact; family
members, college dorm, military barrack, prison
• Transient infection, clearance after Ab develops
• Invasion of bloodstream in individuals lacking
bactericidal antibodies, or deficient in certain
complement components (C5-C8)
• May result in:
– Septicemia (meningococcemia)
– Meningitis
– Pneumonia
Meningococcemia
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•
•
•
•
High fever
Shaking
Chills
Muscle pain
Petechial rash (hallmark of
MGC infections)
• Disease may be moderate,
chronic or fulminant
MGC: WaterhouseFriderichsen Syndrome
• Fulminant type of
meningococcemia
• Characterized by endotoxin,
disseminated intravascular
coagulation (DIC)
• Hemorrhaging in skin, adrenal
glands, other internal organs
• Rapid death due to acute
generalized toxemia and shock
Meninges and CSF
MGC: Meningitis
• ~300 cases/year in U.S.
• Abrupt symptoms:
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Fever
Headache
Stiffness of back and neck
Vomiting
Petechial rash
• Highly fatal without rigorous antimicrobial
therapy (<10% fatality with antibiotics)
MGC: Treatment and
Antimicrobial Susceptibility
• Drug of choice is I.V. penicillin
• Or chloramphenicol, ceftriaxone
• Use rifampin or cefriaxone for
prophylaxis of close contacts
• Prevention requires:
– Public Health education
– Vaccination at risk groups
MGC Vaccine
• Polyvalent polysaccharide capsular antigens
for virulent types (A, C, Y, W1).
• Administered to children and adults
• Given to those at risk groups:
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Students
Military
Travelers to endemic areas
Patients with C’ deficiency
Clinical Significance: Other
Neisseria, Moraxella
• Other Neisseria species - rare septicemia
and meningitis
• M. catarrhalis – NF, opportunistic
infections:
– Otitis media, maxillary sinusitis in children
– Pneumonia and bronchitis in
immunocompromised individuals
– Occasional meningitis, septicemia, endocarditis
Class Assignment
• Textbook Reading: Chapter 17
Neisseria Species and Moraxella
Catarrhalis
• Key Terms
• Learning Assessment Questions
Case Study: MGC
• A 22-year-old female schoolteacher was brought
to the emergency room after a 2-day history of
headache and fever.
• On the day of admission the patient had failed to
come to school and could not be reached by
telephone.
• When notified of this fact, the patient’s mother
went to her daughter’s apartment, where she
found her daughter in bed, confused and highly
agitated.
• The patient was rushed to the local hospital,
where she was comatose on arrival.
Case Study: MGC
• Purpuric skin lesions were present on her trunk
and arms.
• Analysis of her CSF revealed the presence of 380
cells/mm3 (93% polymorphonuclear leukocytes), a
protein concentration of 220 mg/dl, and a glucose
concentration of 32 mg/dl.
• Gram stain of CSF showed many gram-negative
diplococci, and the same organisms were isolated
from blood and CSF.
• The patient died despite prompt initiation of
therapy with penicillin.
Case Study: MC - Questions
• 1. What is the most likely organism
responsible for the fulminant disease?
What is the most likely source of this
organism?
• 2. Chemoprophylaxis should be
administered to which people? What are
the criteria for administering
chemoprophylaxis?
• 3. What other diseases does this
organism cause?
• 4. What virulence factors have been
associated with other bacterial species in
this genus?