The Gram-Negative Cocci
Case Study
 A 20-year-old female college student complained of a
low-grade fever and pain, redness, and swelling of
several of her joints
 Aspirates from both ankles and an elbow showed
many PMNs and gram-negative intracellular and
extracellular diplococci
 Cultures on Thayer-Martin and MacConkey agar
failed to produce growth after 5 days of incubation
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Points to Consider
 What special growth requirements should be
available to these organisms to be recovered from
clinical samples?
 What virulence factors do these organisms use to
produce disease?
 What complications may develop from initial forms of
infections?
 How are these organisms identified?
 Other points to consider
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The Pathogenic Neisseria Species and
Moraxella catarrhalis
 General characteristics
 Aerobic, gram-negative diplococci
 Oxidase-and catalase-positive
 Neisseria elongata is an exception (catalase-negative and
rod-shaped)
 Exist as usual flora in the upper respiratory and urogenital
tracts
 Primary pathogens include N. gonorrhoeae and N.
meningitidis
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Neisseria gonorrhoeae
 Virulence factors
 Fimbrae (common pili)enhance the ability of
bacterial cells to adhere
to host cells and to each
other
 Lipopolysaccharide:
resembles that of other
gram-negative organisms
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Neisseria gonorrhoeae:
Virulence factors
 Outer membrane proteins
 Protein I (PI): demonstrated in patients with disseminated
disease; also found in rectal cultures of male homosexuals;
resistant to serum bactericidal effects
 Protein II (PII): sensitive to bactericidal effects; associated with
adherence to mucosal cells
 Protein III (PIII)-major binding site for immunoglobin-G– blocking
antibody
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Neisseria gonorrhoeae:
Clinical Infections
 Disease in the male
 Incubation period: 1 to 7 days
 Transmitted only by intimate sexual contact
 95% show symptoms of acute infection
 Symptoms include dysuria, urethral discharge
 Complications include epididymitis and urethral stricture,
and prostatitis
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Neisseria gonorrhoeae:
Clinical Infections
 Disease in the female
 20% to 80% are asymptomatic
 Symptoms (if symptomatic) include burning or frequency of
urination, vaginal discharge
 Fever and abdominal pain
 Complications include pelvic inflammatory disease (PID)
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Neisseria gonorrhoeae:
Infections in Other Sites
 Disseminated gonococcal disease
 Acute form has the following symptoms: fever, chills, malaise,
intermittent bacteremia, and skin lesions
 If untreated will progress to septic joint form of the disease
 Gonococcal arthritis occur as a result of disseminated
gonococcal bacteremia
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Neisseria gonorrhoeae:
Infections in Other Sites
 Disease in children
 In infancy, an eye infection (ophthalmia neonatorum) may
occur during vaginal delivery
 Infection is preventable with the application of eye drops at
birth
 Extragenital infections
 Pharyngitis
 Anorectal infections
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Laboratory Diagnosis:
Neisseria gonorrhoeae
 Clinical specimens
 Genital sites
 Anal- oral/pharyngeal
 Eye
 Blood/joint fluids
 Transport media:
Transgrow or
JEMBEC
JEMBEC
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Laboratory Diagnosis:
Neisseria gonorrhoeae
 Identification
 Morphology
Gram-negative, kidneybean–shaped diplococci
A direct gram-stained smear
of male urethral discharge
showing intracellular gramnegative diplococci
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Laboratory Diagnosis:
Neisseria gonorrhoeae
 Identification
 Inoculated culture media
must be incubated at 350
C in 3% to 5% CO2
 Colony morphology on
modified Thayer-Martin
(MTM) agar
Small, gray
Translucent, raised
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Laboratory Diagnosis:
Neisseria gonorrhoeae
Candle extinction jar with
inoculated MTM agar plates.
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Laboratory Diagnosis:
Neisseria gonorrhoeae
 Identification
 Oxidase test
Carbohydrate utilization test;
acid produced only in the glucose
tube indicates that the isolate is N.
gonorrheoae
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Neisseria meningitidis
 General characteristics
 Exclusively human parasite
 Exist as harmless member of normal upper respiratory flora
 Identical with Neisseria gonorrhoeae
 Antigenic structures
 Capsular polysaccharide: nine serotypes—
B, C, D, X, Y, Z, W135, 29E.
 Contribute to invasive properties by inhibiting phagocytosis
A,
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Neisseria meningitidis:
Clinical Infections
 Bacterial meningitis
 Transmission is by respiratory droplets and requires both
close contact and lack of specific antibody (susceptibility)
 Symptoms include fever, headache, stiff neck, nausea,
vomiting, and purulent meningitis with increased WBCs
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Neisseria meningitidis:
Clinical Infections
 Bacteremia (meningococcemia)
 Appearance of skin petechiae
Hemorrhage in the adrenal
glands in W-F syndrome
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Laboratory Diagnosis:
Neisseria meningitidis
 Identification
 Examine direct smear
from CSF
Gram-stained smear of CSF
showing the extracellular
and intracellular gramnegative diplococci
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Laboratory Diagnosis:
Neisseria meningitidis
 Identification
 Examine cultures on blood
agar and chocolate agar
plates
 Oxidase-test–positive
 Conventional CTA
carbohydrates for
biochemical identification
or immunologic methods
are available for
serogrouping
Neisseria meningitidis
growing on sheep blood agar
(right) and chocolate agar
(left)
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Other “Related” Species
 Moraxella catarrhalis
 Clinical infections
 Pneumonia
 Normal commensal of the
respiratory tract
 Sinusitis
 Has become an important
 Otitis media
opportunistic pathogen
 Predisposing factors
 Advanced age
 Immunodeficiency
 Neutropenia
 Other debilitating
diseases
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M. catarrhalis
Moraxella catarrhalis
growing on chocolate
agar after 48 hours of
incubation
Direct smear from an otitis
media sample showing
intracellular gram-negative
diplococci; M. catarrhalis
was identified from cultures
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Identification of
Selected Neisseria Species
Species
BAP
Growth
R.T
T/M
Acid production
Gluc Mal Lac Suc
N. gonorrhoeae
=/+
=
+
+
=
=
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N. meningitidis
+
=
+
+
+
=
=
N. lactamica
+
v
+
+
+
+
=
N. sicca
+
+
=
+
+
=
+
M. catarrhalis
+
+
=
=
=
=
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Points to Remember
 Clinically significant Neisseria species
 Other related opportunistic pathogens
 Clinical infections associated with pathogenic species
 Complications that may result from these infections
 Methods of identifying important species
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