mastitis (inflammation of breast tissue)
peritonitis (inflammation of lining of abdominal cavity)
streptococcal sore throat
pneumonia
purpural sepsis (disease of the uterus following childbirth)
erysipelas (St. Anthony's Fire) - skin level attack which spreads
to lymph nodes, may become septicemic; high mortality rate
glomerular nephritis
rheumatic fever (Ab against streptococci attach to heart valve)
Organisms in this group are transmitted through the air; starts in the
upper respiratory tract with potential spread to other parts of the body;
many people are symptomless carriers of Group A; these organisms are
sensitive to penicillin and other antibiotics which are normally
effective against Gram + bacteria; resistant strains are rarely seen
Extracellular Products of Group A Streptococci
erythrogenic toxin Scarlet fever rash
streptolysins S & O hemolysins
streptokinase dissolve blood clots
deoxyribonuclease decomposes DNA
ribonuclease decomposes RNA
hyaluronidase breaks down hyaluronic acid
proteinase nonspecific protease
amylase breaks down amylose starch
LANCEFIELD GROUPS
GROUP SPECIES SIGNIFICANCE
A S. pyogenes important human diseases; infection
S. pneumoniae by beta, hemolytic strep initiates
S. scarlatinae acute rheumatic fever; group is
sensitive to penicillin -- all
major and classical diseases
B S. agalactiae bovine mastitis
C S. equi animal infections; mild respiratory
S. zooepidemicus infections in humans; endocarditis
S. equisimitis
S. dysagalactiae
D S. faecalis enterococci; urogenital tract
S. durans infections; endocarditis; wound
S. zymogenes infections in humans; found in
S. liquefaciens dairy products
S. bovis
E disease of swine, found in normal
milk
F found in human respiratory tract
G S. anginosus mild respiratory infections in
humans; canine genital infections
H S. sanguis found in human respiratory tract;
endocarditis; dental caries
K S. salivarius found in human respiratory tract;
endocarditis; dental caries
L canine genital infections
M canine genital infections
N S. lactis lactic acid group; found in
S. cremoris dairy products
S. thermophilus
O S. viridans Viridans group; subacute bacterial
endocarditis; found in upper res-
piratory tract of humans
Anaerobic streptococci - 13 species
Not grouped
S. mitis endocarditis and dental caries
S. mutans
Staphylococcus
parasites of humans and animals, occasionally cause serious infections;
non-motile, non sporulating, Gram + cocci; division occurs in several
planes causing clumped arrangement
relatively resistant to drying; easily dispersed in the air; can grow in
high salt concentration (6.5 - 7.5 %)
Staphylococcus epidermidis - non pigmented, non pathogenic;
found on skin and mucous membranes
Staphylococcus aureus - golden yellow pigment on blood agar
(not all strains are yellow); commonly associated with boils,pimples,
impetigo, pneumonia, osteomyelitis, carditis, meningitis, arthritis
Human disease strains form a number of extracellular toxins and enzymes,
including at least four different hemolysins
coagulase cause fibrin to coagulate
leukocidin destroys white blood cells
fibrinolysin breaks down fibrin clots
lipase nonspecific lipid destroyer
hyaluronidase
ribonuclease
deoxyribonuclease
common habitat is the upper respiratory tract, especially the nasopharyngeal
passages; many people are symptomless carriers
serious staph infections occur when resistance is low due to hormonal
changes, illness, steroid or anti-inflammatory drug treatment; many
antibiotic resistant strains exist
food poisoning is due to an enterotoxin producing strain; symptoms occurs
usually 2-4 hours after ingestion; death wish common; about 95-99 % of all
food poisoning due to staph
Neisseria
Gram - cocci that live in humans; nutritionally highly specialized;
grow well near or at body temperature; extremely sensitive to inhibitory
materials and conditions
Neisseria gonorrhoeae (gonococcus) - "diarrhea of the gonads";
sexually transmitted disease, rarely results in serious
complications or death; mild vaginitis may spread to uterus
where inflammation could lead to sterility; painful infection
in urethral canal of males - in conjunction with Herpes
II virus is implicated in uterine cancer; eye infections in
newborns and adults
fastidious, difficult to culture on initial media - requires
2-10 % carbon dioxide atmosphere; grows only between 30 - 38.5° C
killed rapidly by drying, sunlight, and ultra violet radiation
toxicity is due to ENDOTOXIN, no significant extracellular products
produced; penicillin effective except against PPNG
Incidence of infection remains high because:
1. acquired immunity does not occur; reinfection possible
2. symptoms in female may go undetected; she may serve as a
reservoir of infection
Incidence of gonorrhoeae correlates closely with sexual activity of society;
elimination difficult because it continues to be viewed as a social rather
than a medical problem
Neisseria meningitidis (meningococcus)
parasite of humans only; nasopharynx is natural habitat;
fastidious; sensitive to adverse environmental factors; many
carriers in human population
may invade bloodstream and set up a generalized body infection
by way of the lymphatics; may invade the CNS and become
established in the meninges; symptoms include: severe headache,
muscular spasm, stiff neck, exaggerated reflexes -
leading to convulsions, coma, death
pathogenicity results from ANTIPHAGOCYTIC CAPSULE and production
of a characteristic ENDOTOXIN; sensitive to sulfonamides,
penicillin, and most other antibiotics; sulfonamides
are useful because they can penetrate the meninges
Virtually impossible to control because of inapparent infections; common in
crowded areas such as military barracks; serum of carriers contains Ab
bactericidal to N. meningitidis. This may prevent the spread
of the organisms from the nasopharynx to the bloodstream and CNS.
Bacillus
aerobic, sporeforming, Gram + rods; easy to isolate from soil or air;
most common organisms to appear from soil samples
Major human disease to be caused by a Bacillus is anthrax caused by
Bacillus anthracis; some food poisoning has been associated
with Bacillus cereus. Anthrax was the first disease shown
conclusively to be caused by a bacterium.
primarily a disease of farm animals, occasionally transmitted
to humans; organism is large (1-1.5 - 4-8 µ); has a
capsule, resistant to phagocytosis; highly invasive, grows
throughout body - gets into bloodstream and releases an
EXOTOXIN responsible for most symptoms: shock, electrolytic
imbalance, swelling, hemoconcentration, acute renal failure
Human beings become infected when they come into contact with diseased
animals, their hides or products. Susceptible animals include cattle,
sheep, horses, goats, pigs, minks, dogs, deer, birds, frogs, and fish.
Animals usually ingest bacilli or spores from infected carcasses; spores
may persist for several years. Human infection is usually an occupational
hazard in the meat packing and tanning industries.
The organism invades by way of skin cuts and abrasions. A primary lesion
develops at the site as an inflamed pustule or blister - this can spread
and become systemic, in which case it is often fatal. Inhalation of spores
causes "woolsorter's disease" often leading to pneumonia and death.
Initial work was done by Koch and formed the basis for his Postulates.
Immunity is developed through production of Ab to toxins. Pasteur produced
the first attenuated vaccine for sheep (immunity is relatively short-lived,
lasting 9-12 months). There is still no anthrax vaccine considered safe for
humans.
can be treated effectively with penicillin, tetracyclines, or erythromycin
if symptoms are detected before bacteremia develops
Clostridium
Gram +, sporeforming, usually rods; obligate anaerobes (with exceptions);
main habitat is anaerobic pockets in the soil; most produce EXOTOXINS
responsible for the symptoms
Clostridium botulinum - botulism
Clostridium tetani - tetanus
Clostridium perfringens - gas gangrene
Botulism is FOOD POISONING rather than a FOOD INFECTION since the microbes
grow in the food and not the host; toxins are released into the food and are
ingested if not heated to at least 60° C.
Tetanus is generally fatal due to a toxin that acts on the nerves of the
CNS causing spastic paralysis; infects dirty wounds; once toxin combines
with nerves the action cannot be reversed; treat-ment is difficult, control
is through immunization with TOXOID.
Gas gangrene organism also infects wounds; more invasive due to a series
of toxins that cause extensive tissue damage. Gangrene refers to dead tissue
and gangrenous conditions may result from microbial or nonmicrobial causes.
Dead tissue frequently contains gaseous products of the bacterium's activity.
The infected region may become liquid or hollow. Toxins may spread and cause
destruction of heart tissue and internal organs leading to death.
Immunization against all toxins is not possible therefore control is by
antibiotics and surgery (super oxygenation has been effective in some cases).
Corynebacterium
aerobic, nonsporulating, nonmotile, Gram + rods; may have swollen ends
with club shaped appearance (koryne is Greek for "club");
widespread, common in soil; some cause plant diseases, others are
pathogenic to humans and animals; Corynebacterium acnes
(now called Propionibacterium acnes) is a common skin
inhabitant and is implicated as a secondary invader in the skin condition -
acne
Corynebacterium diphtheriae
first infectious disease whose symptoms were shown to be
caused by an EXOTOXIN, also first disease to be controlled
by immunization procedures; strictly an inhabitant of the
respiratory tract - cannot invade other parts; transmitted
by respiratory route; inflammatory response of throat tissue
results in pseudomembrane which blocks the throat and leads
to suffocation; death usually from toxemia as toxin spreads
throughout the body
organism is weakly invasive, powerful toxin makes it viru-
lent; production of toxin requires presence of specific
virus within the cell
toxoids result in formation of antitoxin Ab which neutralize the toxin but
fail to prevent the establishment of the organism in the upper respiratory
tract; inapparent infections are common, as are carriers
Schick test is used to determine if a person is immune; non-immune persons
will show swelling and redness at injection site
Mycobacterium
rod-shaped, nonsporulating, aerobic, ACID-FAST, weakly Gram +
Mycobacterium tuberculosis
tuberculosis was first shown by Koch to be caused by a bacterium;
simple nutritional requirements; able to resist
chemical agents like alkali and phenol due to lipid content
of cell walls; both primary and post primary (reinfection)
infections possible
tuberculin - protein fraction used in testing; positive test may be due to
early inapparent infections; Streptomysin, INH (isonicotinic acid hydrazide)
and PAS (para-aminosalicylic acid) are presently the most effective drugs
BCG - live vaccine which may turn negative individuals positive;
TB is serious in cattle, contaminated dairy products; site of infection
becomes the lymph nodes and it localizes in the bones and joints;
pasteurization has eradicated most of this type of TB
Mycobacterium leprae (Hansen's disease - Leprosy)
difficult to culture, grows in intracellular sites in lesions;
intermediate hosts are armadillos in south
cutaneous form - affects skin, causing extensive disfiguration
neural form - infects peripheral nerves, causes loss of sensation
patient may have both types; NOT contagious - requires prolonged and
intimate contact such as crowding, poor sanitation;
DDS (di-aminodiphenylsulfone) is effective but treatment is prolonged
The Enteric Bacteria
Most belong to the family Enterobacteriaceae. As a group they are Gram -,
nonsporulating, stubby to short rods, facultative anaerobic, have
simple nutritional requirement, show varying degrees of motility based
on species.
Quick Comparison of Some of the Enteric Group
Use Produce
Lactose Indole H2S Motile Gas from Glucose
Esherichia + + - var/- +
Shigella - + - - -
Salmonella - - + + var/+
Proteus - var/+ + + +
Enterobacter + - - var/+ +
Escherichia - rarely pathogenic, primarily opportunistic causing
problems when host's resistance is lowered or defenses have
been breached; has been implicated in infant diarrhea in
epidemics in nurseries; may cause urinary tract infections
in older persons (_ and _) or surgical patients; streptomycin,
chloramphenicol, and tetracyclines are all effective
Salmonella and Escherichia are closely related; Salmonella
are usually pathogenic, either to humans or warm blooded animals;
most common diseases in humans are TYPHOID FEVER and GASTROENTERITIS
Salmonella typhi
organism resists digestion after phagocytosis; can live and
reproduce intracellularly in macrophages and other phagocytic
cells; transmitted in food and water contaminated from fecal
sources. Organisms replicate in intestinal tract, enter the
lymphatic vessels that drain the intestine, travel to the
bloodstream and spread throughout the body; organism grows
in the bile duct, spleen and lymph nodes.
Once the organism is established a characteristic FEVER
develops as the result of the release of EXOTOXIN; diarrhea
is NOT a common symptom; ROSE SPOTS appear on the trunk of
the body; the intestinal phase is treated with antibiotics
active against Gram - bacteria; organisms may still be shed
from the bile duct and appear in the feces (carrier state)
intracellular phase is treated with chloramphenicol - antibiotic
therapy must be continued
Controlled by pasteurization, sewage treatment, water purification,
and elimination of chronic carriers as food handlers. A killed bacteria
vaccine is available and used in areas where epidemics are still common.
Gastroenteritis - often called food poisoning but is not
since the symptoms develop as the result of the multipli-
cation of the microbe in the intestinal tract of the host.
rarely spreads from the intestine and thus is self limiting;
symptoms develop 8-48 hours after ingestion and include
headache, chills, vomiting, diarrhea, followed by fever
Shigella
differs from Escherichia in being UNABLE to utilize lactose or
produce gas during fermentation of sugars; shigellas are non flagellated
and nonmotile
commonly pathogenic to humans causing a severe gastroenteritis called
"bacterial dysentery" - pathogenicity seems related to its ability
to produce a powerful ENDOTOXIN almost exclusively in humans and other
primates
affects communities with poor sanitation, e.g.military troops in combat
zones; does not invade bloodstream, usually self limiting, rarely fatal,
unless patient is debilitated initially, spontaneous cure within a few days
Yersinia pestis - causative agent of bubonic plague;
epidemic in Middle Ages
associated with severe HEMOLYSIS, producing dark skin in dying person -
hence the name "black death"; this symptom is usually not seen
in cases today; still ENDEMIC in parts of Asia, Africa, and U.S.
(sylvatic plague in rodents and ground squirrels of the West -
sylvatic vs. urban plague); carried by flea on surface of rodent, etc.
as a result of the bite of an infected flea, bacteria get into the
lymphatic system, multiply in the lymph nodes and cause the nodes to
enlarge (enlarged nodes are called BUBOES) thus the name
"Bubonic Plague"; in the latter stages the bacteria spread
throughout the body; in untreated cases mortality reaches 100 %;
death results from release of an ENDOTOXIN; invasiveness is determined
at least in part by a capsule; optimum growth temperature is
28° C rather than 37° C; at 28° C virulence factors are not produced;
bacteria can also reproduce in fleas;
can become established in the lungs and is known as PNEUMONIC PLAGUE,
highly contagious by droplet infection
recovery involves formation of OPSONIZING ANTIBODIES that seem to confer
lifelong immunity; control in urban areas is affected by the elimination
of rats; sylvan plague cannot be eliminated because the vectors are wild
animals
Franciscella tularensis - causes tularemia, primarily a
disease of wild animals; microbe is small enough to get through
breaks in the skin; humans acquire organism by handling
infected carcasses; organisms concentrate in lymph glands
and cause headache, body pain, fever, and sometimes death;
symptoms probably due to ENDOTOXIN; Streptomysin useful;
sometimes called rabbit fever
Hemophilus influenzae - mistakenly thought to cause flu;
nonmotile, aerobic, nonsporeforming, Gram - with varying shapes
(pleomorphic); virulence seems related to capsule; six antigenic types;
requires growth factors found in lysed red blood cells (X and V factors);
drug of choice is combination of ampicillin and chloramphenicol
primarily a secondary invader implicated in generalized inflammatory
responses such as meningitis and nasopharyngitis, also in pneumonia;
implicated as cause of meningitis in about 15 % of cases in children
under 4 years of age - Hib vaccine has nearly eliminated this as a problem;
Hemophilus aegypticus implicated in conjunctivitis
Bordetella pertussis - Gram -, nonmotile, coccobacillary shape;
virulent strains form capsule; causative agent of whooping cough; organism
is weakly invasive; growth induces mucus secretion which induces coughing;
ENDOTOXIN and EXOTOXIN released upon death of organism; highly infectious
through droplet transmission; erythromycin, tetracyclines or chloramphenicol
render patient noninfectious; recovery confers immunity; DPT vaccine regularly
used to prevent
Brucella abortus - small Gram - , nonspore forming rods,
pathogenic to humans and animals; enters body through cuts and abrasions;
ingested by fixed macrophages; travels via lymphatics to various lymphatic
organs; grows intracellularly thus making eradication difficult;
streptomycin in combination with tetracycline may be effective, but not
long term; causes infectious abortions in cattle and UNDULANT FEVER;
disease may last for several years and spread by infected dairy products;
symptoms include intermittent fever, chills, and body aches
Vibrio cholerae - Gram -, polar flagellated, comma shaped
rods, waterborne, aerobic; virtually absent from Western world since advent
of water purification; produces two substances that affect intestinal
mucosa - enzyme like hyaluronidase and an EXOTOXIN
(ENTEROTOXIN) that affects the permeability of the intestinal walls and
causes water loss and electrolyte imbalance; "rice-water stools";
may lose 10-15 liters of fluid a day leading to shock, dehydration, death;
streptomycin, tetracyclines, chloramphenicol sometimes effective in early
stages of disease; fluid replacement and electrolyte balance most critical
factors to control; humans are only natural host of organism
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