Flashcards in Lecture 4 Deck (46):
- involves the production of immunity following the injection of an antigen
the antigen in a vaccination
The antigen can be a dead (completely inactivated) infectious agent, or a weakened (attenuated) infectious agent. Parts of the infectious agent can also be used for this purpose.
Recombinant DNA technology and genetic
engineering are oftentimes used to
used to produce antigenic parts of infectious agents
involves the injection of a suspension of infectious agent to produce disease. It can also be thought of as the implantation of an organism upon a growth medium to just produce growth of an organism.
science of classification
established by Carolus Linnaeus in 1735. Each organism is assigned two names, a Genus and a species epithet
Bacterial names can be descriptive
For example Staphylococcus aureus (etiologic agent for Toxic Shock Syndrome-fever, vomiting and rash), comes from the Greek words staphyle (bunch of grapes) and
kokkos (berry). The word aureus comes from Latin and means golden.
Bacterial names come from the names of the scientists that either discovered or worked with the organisms.
Pasteurella multocida the organism that causes chicken cholera, was named after Louis Pasteur.
Alexandra Yersin named the genus Yersinia. Yersinia pestis is the etiologic agent that causes
Harold Ricketts lent his name to the genus Rickettsia. Rickettsia rickettsii is the etiologic agent that causes tick-borne Rocky Mountain Spotted Fever. Rickettsia prowazekii is responsible for causing the louse-borne epidemic typhus. Harold Ricketts died of rickettsial infection.
Albert Neisser named the genus Neisseria. These bacteria are Gram negative diplococci. Neisseria gonorrhoeae is the etiologic agent that causes the venereal disease known as gonorrhea. Neisseria meningitidis causes meningococcal meningitis
Erwin Smith, a plant pathologist lent his name to the bacterial organism that causes soft-rot in vegetables. The organism Erwinia carotovora, incorporates the first name of this scientist.
if lower case means small rod
used interchangeably with word rod
are often used. For example instead of Streptococcus pneumoniae, these can be called
Pneumococci. Instead of Neisseria gonorrhoeae, these can be called Gonococci. Neisseria meningitidis
can be referred to as Meningococci
(cocci – plural, coccus – singular) These display the following characteristics
1. Least surface area per unit volume
2. They are more resistant to drying
3. Grow more slowly
4. Most are non-motile
When examining bacterial organisms, we look at both
shape (morphology) and arrangement
Theorganisms must be able to spread out on a slide in a single layer (monolayer) with room between the
characteristic arrangements. Depending upon the species, the organisms may be arranged as singles,
pairs, chains, groups of two or four (tetrads), groups of eight (box cars), irregular clusters, or
- Gram positive diplococci
Gram negative diplococci
- Gram positive cocci that form chains
Growth of Streptococci on Blood Agar
plates can reveal
different patterns of hemolysis
Alpha (partial) hemolytic types
produce a greenish colored clearing
Beta (complete) hemolytic types
produce a complete clearing
most dangerous type
Gamma (no hemolysis) hemolytic types
produce no hemolyis or red blood cell breakdown at all.
Micrococcus luteus and Micrococcus agilis
- Gram positive cocci that form pairs and tetrads
Gram positive cocci that form packets of 8 (box cars)
Gram positive cocci that form irregular (grape-like) clusters
(bacilli – plural, bacillus – singular) These display the following characteristics:
1. More surface area per unit volume
2. They are less resistant to drying
3. Grow more rapidly
4. Many species are motile
vary with the species. Singles, pairs, chains(short ends attached), chains (long ends attached – called palisades layering or picket fence or match stick patterns), chains with branched patterns, chains where the cross walls between cells have broken or failed to form (called filaments)
Many of the Gram negative rod species display a
combination of the above mentioned arrangements.
Also, oftentimes the Gram negative rod cultures consist of very small cells. When observed it can be
difficult to determine their shape (morphology)
Under the microscope they may appear to be cocci due
to their small size. They are however, classified as rods. We sometimes describe them as coccobacilliary
- Gram positive rods that form chains
Gram positive rods that will oftentimes arrange in palisades layers. This organism is the etiologic agent of diphtheria (sore throat, low fever, membrane on tonsils and/pharynx).
Weakly Gram positive, strongly acid fast positive rods that can appear as branched chains. Causes the disease known as tuberculosis.
Gram negative rods and coccobacilliary forms. They appear as singles, pairs and short chains. Filaments are sometimes observed. This is the etiologic agent for Travelers’ diarrhea (watery diarrhea and cramps)
Gram negative rods and coccobacilliary forms. They appear as singles, pairs and short chains. Filaments are sometimes observed. Called the blue-pus organism. Infects burn victims and those that are immunocompromised
Spiral or Helical characteristics
(Spiral is short, Helical if long) These display the following characteristics:
1. Almost all are motile
2. They appear as singles (swim apart)
3. Move through the media in a corkscrew fashion
Spiral or Helical Major groups
(Spirillum – singular) – rigid long axis with polar flagella
no flexibility, common in pond water
flexible long axis. No polar flagella. They possess axial filaments. They coil and then release much like a spring to move
incomplete spirals. They look like commas.
spirochetes, Gram negative etiologic agent for tick-borne Lyme disease
- spirochetes, Gram negative etiologic agent for the venereal disease called syphilis
- vibrios, Gram negative etiologic agent for human cholera.
– more than one shape . Environmental conditions can alter the shape of some bacteria.
Some bacteria are genetically pleomorphic.
Members of the genus Mycoplasma are
pleomorphic. These organisms are considered to be the
smallest of the free-living bacteria. They lack cell walls or have incomplete cell walls. They favor hyper
osmotic fluids such as rich lung exudates. This prevents cell lysis as they lack cell walls
- etiologic agent of Primary Atypical Pneumonia