| Gram-negative cocci, aerobic.
"The family Neisseriaceae comprises the genera
Neisseria, Moraxella, Kingella, and Acinetobacter. The only
significant human pathogens are N gonorrhoeae, the agent of gonorrhea,
and N. meningitidis, an agent of acute bacterial meningitidis. N
gonorrhoeae infections have a high prevalence and low mortality, whereas
N meningitidis infections have a low prevalence and high mortality.
Moraxella is an oxidase-positive bacterium, sometimes mistaken for Neisseria,
that may be isolated from eye infections and respiratory tract infections.
Moraxella catarrhalis causes lower respiratory infection in adults with
chronic lung disease and is a common cause of otitis media, sinusitis, and
conjunctivitis in children. Kingella and Eikenella species are
short bacilli or coccoid bacteria that act as opportunistic pathogens. They are
sometimes secondary invaders of damaged tissues."
Neisseria gonorrhoeae is a fastidious organism
requiring growth factors which are present in hemolyzed blood cells.
Thayer-Martin chocolate agar plates have VCN antibiotics which prevent growth
of most organisms while supporting N gonorrhoeae growth. The gram stain
is considered by many as the single most important characteristic of clinical
bacteria. However the gram stain itself is not used for the identification of
organisms. One rare exception would of course be a gram stain of urethral
discharge which contains gram negative cocci in pairs inside neutrophils. GNID,
gram-negative intracellular diplococci. are widely regarded as pathonomonic for
Neisseria gonorrhoeae infection. On gram-stain they are among the
smallest of bacteria. As a result, it takes a little practice to be able to
quickly recognize their distinctive diplococcoid shape. You may have heard the
term, "kidney bean shaped." But they are so small that you have to have an
imagination to see that. When seen in the pus of a urethral smear their
presence is usually so obvious as to be unmistakable. There will almost always
be wall to wall neutrophils which microbiologists have a habit of calling PMN's
or polymorphonuclear leukocytes since they are gram stained and not stained
with a Wright's stain.. And the tiny diplococci must be seen within the
boundaries of some of the PMN's to qualify as GNID.
In Japan infection with this organism is so uncommon that it
is classified as "rare."
"The only distinguishing structural feature between N
meningitidis and N gonorrhoeae is the presence of a polysaccharide capsule in
the former. The capsule is antiphagocytic and is an important virulence
Here is a GNID image from "Doc" Kaiser's collection.
Urethral Smear GNID, Loyola University website:
SEM x27,200 electron micrograph courtesy of Dennis Kunkel.
Click thumbnail to go to the EM website.
Also the image gallery at
|Neisseria meningitidis in meningococcal
The MMWR lists a cumulative total of 19,870 cases of meningococcal
disease for 1999.
"Before the 1990s, Haemophilus influenzae type b
(Hib) was the leading cause of bacterial meningitis, but new vaccines being
given to all children as part of their routine immunizations have reduced the
occurrence of invasive disease due to H. influenzae. Today, Streptococcus
pneumoniae and Neisseria meningitidis are the leading causes of
"High fever, headache, and stiff neck are common
symptoms of meningitis in anyone over the age of 2 years.""The diagnosis is
usually made by growing bacteria from a sample of spinal fluid. The spinal
fluid is obtained by performing a spinal tap, in which a needle is inserted
into an area in the lower back where fluid in the spinal canal is readily
accessible. Identification of the type of bacteria responsible is important for
selection of correct antibiotics." CDC.
you want to see EM images of N. meningitidis check Dennis Kunkel's EM
Alsohas a gallery in progress at:
Neal Chamberlain's site is
easy to search for Neisseria meningitidis
"Doc" Kaiser's is a
very good site.http://www.cat.cc.md.us/~gkaiser/
|Moraxella catarrhalis "Moraxella is
oxidase-positive, sometimes mistaken for Neisseria, that may be isolated from
eye infections and respiratory tract infections. Moraxella catarrhalis
causes lower respiratory infection in adults with chronic lung disease and is a
common cause of otitis media, sinusitis, and conjunctivitis in children." "M
catarrhalis was formerly placed in the genus Neisseria; however, studies of DNA
base content, fatty acid composition, and genetic transformation showed that
this organism did not belong in that genus. M catarrhalis is a member of the
normal flora in 40-50% of normal school children""M catarrhalis may cause
clinical syndromes indistinguishable from those caused by gonococci, and so it
is important to distinguish these organisms from one another. Many strains
|Gram negative cocci which are anaerobic.
|Veillonella sp. This organism is somewhat
difficult to grow in vitro. It is part of the normal mouth flora.
Veillonella is sometimes mistaken for GC in (oral) gram stain. Most common
species is Veillonella parvula.