Actinomycetes: fungus-like bacteria; A. israelii  most commonly associated with actinomycosis

Bacteroides genus: Their pathogenicity is limited, Infection only occurs after severe trauma to the abdominal
region. Infection could lead to abscess formation and possibly fever.

Clostridium:  When the environment becomes stressed,  the bacteria produce spores that tolerate the
extreme conditions that the active bacteria cannot. In their active form, these bacteria secrete powerful
exotoxins that are responsible for such diseases as tetanus, botulism, and gas gangrene.  This non-motile
bacterium is an invasive pathogen that can be contracted from dirt via large cuts are wounds. C. perfringens
cells proliferate after spore germination occurs and they release their exotoxin. The toxin causes necrosis
[death] of the surrounding tissue

(Clostridial myonecrosis destroys muscular tissus). The bacteria themselves produce gas which leads to a
bubbly deformation of the infected tissues.

C. perfringens is capable of necrotizing intestinal tissues and can release an enterotoxin that may lead to
severe diarrhea.  Clostridium difficile is a motile bacterium that can be part of the natural intestinal flora.
Infection can occur through the use of broad-spectrum antibiotics which lower the relative amount of
other normal gut flora. When this situation occurs, C. difficile proliferates and infects the large intestine. The
bacterium then releases two enterotoxins that destroy the intestinal lining and cause diarrhea.

EUBACTERIUM: E. lentum, the most often isolated species, has been linked to endocarditis and some
wound infections

Fusobacterium species, the most common of which is F. nucleatum, are associated with pleuropulminary
infections and disease. They are also capable of causing infection in the oral cavity (the mouth). F.
nucleatum has been cited as one of the causes of gingivitis.

Neisseria genus: N. meningitidis causes meningitis, inflammation of the membranes covering the central
nervous system. The different strains of N. meningitidis are classified by their capsular polysaccharides.
This bacterium is the second leading cause of meningitis in the United States. Early symptoms may include
headache, fever, and vomiting. Death can quickly follow due to endotoxin shock or focal cerebral

PEPTOSTREPTOCOCCUS: P. magnus is  the species that is most often isolated from infected sites.  they
can cause infections of bones, joints and soft tissue. Their increasing resistance to such antibiotics as
penicillin G and clindamycin makes them especially important to clinical work.

Propionibacterium species:  P. acnes, is a usually harmless microbe that has pathogenic potential. It has
been linked to certain cases of endocarditis, wound infections, and abscesses. it can infect acne sites on
the skin but it does not cause them.


Bacillus represents a genus of Gram-positive bacteria with the ability to produce endospores when
environmental conditions are stressful. The only other known spore-producing bacterium is Clostridium.
B. anthracis causes anthrax.

B.cereus cause toxin-mediated food poisoning.  two toxins released by the bacterium lead to vomiting and
diarrhea, symptoms similar to those of Staphylococcus food poisoning. Because toxin production usually
takes place after the infected foods are cooked,

Corynebacterium: C. diphtheriae produces the toxin that causes diphtheria, a disease of the upper
respiratory system in humans. C.diphtheria is unique in its exotoxin formation.

Listeria:  L. monocytogenes has been implicated in several food poisoning epidemics. The bacterium usually
causes septicema and meningitis in patients with supressed immune function. It also causes listeriosis which
is an inflammation of the brain.  Those at high risk include newborns, pregnant women and their fetuses, the
elderly, and persons lacking a healthy immune system.

Gram-positive cocci --- have taken on the invasive traits in the past 15 years

Staphylococcus genus: S. aureus is a leading cause of soft tissue infections, as well as toxic shock
syndrome (TSS) and scalded skin syndrome. pathogenic effects of Staph are mainly asssociated with the
toxins it produces. it is not uncommon for an infected site to contain no viable Staph cells. The S. aureus
enterotoxin causes quick onset food poisoning which can lead to cramps and severe vomiting. microbes
also secrete leukocidin, a toxin which destroys white blood cells and leads to the formation of pus and acne.

S. aureus has been found to be the causative agent in such ailments as pneumonia, meningitis, boils,
arthritis, and osteomyelitis (chronic bone infection).

S. epidermis is an opportunistic pathogen which is a normal resident of human skin. Those susceptible to
infection by the bacterium are IV drug users, newborns, elderly, and those using catheters or other artificial

Streptococcus genus:  S. pyogenes is responsable for about 90% of all cases of pharyngitis. "Strep throat"
which is characterized by inflamation and swelling of the throat, as well as development of pus-filled regions
on the tonsils. infection spreading from the upper respiratory system into the lungs. Once in the lungs, the
infection could give rise to pneumonia. Some cases also develop into rheumatic fever if left untreated. Other
diseases linked to S. pyogenes are skin infections such as impetigo, cellulitis, and erysipelas.

S. agalactiae. For years this bacterium has been the causative agent in mastitis in cows. Currently, it has
been found to be a cause of sexually transmitted urogenital infections in females. Although infection is easily
treated with penicillin, proper diagnosis is necessary for women nearing labor because the infection can
easily spread to the child via the birth canal.

Type D Streptococcus The Enterococci include E. faecalis, a cause of urinary tract infections, and E.
faecium, a bacterium resistant to many common antibiotics. Diseases such as septicemia, endocarrditis, and
appendicitis have also been attributed to group D Strep.

Streptococcus pneumoniae causes pneumonia, meningitis, and otitis media.
S. mutans and S. mitis, are alpha-hemolytic bacteria. These bacteria inhabit the mouth. In fact, a large
percentage of tooth decay can be attributed to S. mutans.