Are Staphylococcus normal flora
yes, but they can be opportunistic pathogens
What are the nine groups of Gram positive pathogens we study
- Staphylococcus Aureus
- Streptococcus Pyogenes (A)
- Streptococcus pneumoniae
- Bacillus Anthracis
- Clostridium (perfringins, dificile, tetani, and botulinum)
- Listeria monocytogenes
- Corynebacterium diptheriae
- propionibacterium acnes
- Actinomyces species
Staphylococcus is motile or nonmotile?
non-motile
how does Staphylococcus interact with oxygen (anarobe, aerobe)
facultative aerobe
What does Staphylococcus look like under a microscope
cocci in irregular clusters (grapes)
What is the most common organism found on the skin
Staphylococcus epidermis
Where is Staphylococcus aureus typically carried in 30-50% of the healthy population
nose and perineum
How can you tell between Staphylococcus aureus and Staphylococcus epidermis
Staphylococcus Areus is
coagulase positive, mannitol positive
Staphylococcus Epidermis
coagulase negative, mannitol negative
which is more virulent Staphylococcus Aureus or Staphylococcus epidermis
Staphylococcus Aureus
How many bacteria are required for disease to result from a staph infection
only a few hundred bacteria
what are the three things about Staphylococcus that cause pathogenicity
- It’s ability to evade phagocytosis
- Production of enzymes
- production of toxins
What are the three categories of Staphylococcus diseases
Noninvasive disease
Cutaneous disease
Systemic disease
What is a non-invasive Staphylococcus disease
food poisoning that results from ingested food contaminated with enterotoxin
What are examples of cutaneous Staphylococcus disease
scalded skin syndrome
impetigo
folliculitis
furuncles
How does Staphylococcus defend itself against phagocytosis
Protein A
Bound Coagulase:
how does Protein A help Staphylococcus defend against phagocytosis
Protein A onthe bacterial surface binds antibodies by the Fc end. This inhibits opsonization and complement
how does bound coagulase help Staphylococcus defend against phagocytosis
converts blood protein fibrinogen into fibrin molecules, which make blood clots, the Staphylococcus hides from the phagocytes in the clots
What are the 5 enzymes created by Staphylococcus that attribute to its virulence
Cell-free coagulase hyaluronidase staphylokinase lipases B-lactamase
What does Cell-free coagulase do for Staphylococcus
triggers fibrin formation, which helps the Staphylococcus hide from phagocytes
What does hyaluronidase do for Staphylococcus
breaks down hyaluronic acid, which allows the bacteria to spread between cells
what does staphylokinase do for Staphylococcus
dissolves fibrin threads in blood clots, which allows Staphylococcus aureus to free itself from clots
what do lipases do for Staphylococcus
digests lipids, allows Staphylococcus to grow on the skins surface and in oil glands
what do B-lactamases do for Staphylococcus
Breaks down penicilins, makes them resistant to beta-lactams
What are the 4 toxins produced by Staphylococcus
Cytolytic toxins
exfoliative toxins
Toxic shock syndrome toxins
Enterotoxins
What are the two cytolytic toxins created by Staphylococcus and what do they do
alpha-toxins- pore forming toxins
PVL - beta pore forming toxin that lyses leukocytes
What do the exfoliative toxins of Staphylococcus cause
they cause the patients skin cells to separate from each other and slough off the body
What does the toxic shock syndrome toxin of Staphylococcus cause
it causes toxic shock syndrome, which is caused by the creation of a superantigen
What do enterotoxins of Staphylococcus cause
they stimulate intestinal muscle crampings, naseua, and intense vomiting (staph food poisoning)
Does Staphylococcus aureus cause food poisoning
yes
Does Staphylococcus cause colitis
yes
what is colitis (caused by Staphylococcus )
overgrown Staphylococcus aureus in the bowels (caused by broad-spectrum antibiotic treatment), when they produce enterotoxin B you get damage to intestinal mucosa, cramps, pain, diarrhea, and fever
What are the 4 skin diseases caused by Staphylococcus aureus
impetigo
furuncles (boils) (infected hair follicle)
Carbuncler (many boils)
Scalded skin syndrome
What are the 5 systemic diseases caused by Staphylococcus
Toxic shock syndrome Bacteremia Endocarditis Pneumonia Osteomyelitis
What causes Toxic shock syndrome
the TSS toxin (from Staphylococcus ) being absorbed into the blood, and being used as a superantigen, which causes T-cells to produce far too many cytokines
what are the symptoms of toxic shock syndrome
high fever, rash, vomiting, diarrhea
renal, liver, and blood involvement
What is bacteremia
bacteria in the blood
What is endocarditis
when bacteria attack the lining of the heart
what is pneumonia
inflammation of the lungs in which the alveoli and bronchioles become filled with water
what is osteomyelitis
inflammation of the bone marrow and surrounding bone
What is the drug of choice to treat staph infections
Methicilins
Are any Staphylococcus organisms resistant to methicilins? what are they called
yes, MRSA (methicilin resistant staph. aureus)
What is the drug used for MRSA
vancomycin
how are staph infections prevented
- proper food prep and storage
- hand antisepsis
- proper cleansing of wounds, catheters, and needles
Which type of bacteria is tracked by phage typing
Staphylococcus
What is the arrangement of cocci in streptococcus
cocci arranged in pairs or chains
how does streptococcus interact with oxygen
aerotolerant anaerobes
What is the system of classification often used for streptococcus
lancefield classification
What are the two groups of streptococcus that are common pathogens of humans
Group A and Group B strep
What is used to determine the group of streptococcus organisms
the bacterias C antigens
What is the name for the only organism in Group A strep
streptococcus pyogenes
what does strep pyogenes cause on blood agar plates
it forms white colonies surrounded by beta-hemolysis on blood agar
What does strep pneumoniae cause on blood agar plates
it does alpha hemolysis
do pathogenic strains of streptococcus pyogenes often form capsules
yes
When do Group A strep generally cause disease
- normal microbiota are depleted
- large inoculum enable strep to establish themselves before antibodies are formed against them
- specific immunity is impaired
What does protein M of streptococcus pyogenes do
it interferes with opsonization and lysis of the bacteria, and helps the bacteria attach to keratinocytes of the host
What does a hyaluronic acid capsule do for streptococcus pyogenes
it camoflages the bacteria
What are the enzymes produced by streptococcus pyogenes, and what do they do?
Streptokinases
Deoxynucleases
C5a
They facilitate the spreading of streptococcus through the tissues
What are the toxins released by streptococcus pyogenes and what do they do
they are pyrogenic toxins, and they induce macrophages and T-helper cells to release cytokines
What do streptolysins do
they lyse RBCs, WBCs and platelets
What are the 6 diseases caused by group A strep
- Pharyngitis (strep throat)
- Scarlet fever
- Pyoderma (impetigo)
- Erysipelas
- streptococcal Toxic Shock syndrome
- Necrotizing Fasciitis
Scarlet fever is caused by a toxin of streptococcus pyogenes, what else is caused by that toxin
puerperal sepsis (an infection of the uterus)
What is scarlet fever
a rash that begins on the chest and spreads across the body, it is caused by erythrogenic toxin
What is pyoderma (impetigo)
confined, pus-producing lesions, usually on the face, arms or legs
What is erysipelas
lymph node involvement with pain and inflammation (bright red face-mask shaped inflammation)
What is streptococcal toxic shock syndrome
bacteremia and severe multisystem infections
What is necrotizing fasciitis
Flesh eating strep
strep that spreads in the deep tissues along fascia, it destroys tissues including fat and muscle. 50% mortality
What are two post-streptococcal diseases? (poststreptococcal sequelae) and what cause them
Rheumatic fever and glomerulonephritis
cross reactive antibodies
Which age group is the most common carrier and infected by streptococcus pyogenes
Children 1-15
How is Group A strep transmitted
by respiratory droplets, direct and indirect contact
How is Group A strep diagnosed
hemolysis, bacitracin sensitivity, gram morphology, catalase tests
What is used to treat Group A Strep
penicilliin G
how is group A strep prevented and controlled
isolation, early and complete treatment
What is the other name for the alpha-hemolytic streptococci
the viridans group
Where are the viridans group of streptococci normally found
the mouth, pharynx, GI tract, genital tract, and urinary tract
Which group of strep play a significant role in dental caries, and dental plaque production
Alpha-hemolytic Streptococci (The viridans group)
What can the alpha-hemolytic strep (viridans group) cause when they enter the blood
meningitis, and endocarditis
Which group of Strep mostly forms pairs of cocci
streptococcus pneumoniae
What happens when streptococcus pneumoniae is grown on blood agar? and then on blood agar in anaerobic conditions
it forms alpha-hemolytic colonies, then in anaerobic conditions it produces beta-hemolytic colonies
Where does streptococcus pneumoniae normally colonize
the mouoth and pharynx (pathogenic in the lungs)
What was the leading cause of human death before antibiotics
streptococcus pneumoniae
What percent of bacterial pneumonia is caused by streptococcus pneumoniae
60-70%
Which bacteria causes the majority of otitis media
streptococcus pneumoniae
in streptococcus pneumoniae, pathogenesis is tied to what
a large polysaccharide capsule
how does the polysaccharide capsule of streptococcus pneumoniae’s polysaccharide capsule aid in pathogenicity
it binds factor H which inhibits the alternative complement pathway, and protects the bacteria from phagocytosis
What does the protein adhesin of streptococcus pneumoniae aid in its pathogenicity
it helps the cells bind to epithelial cells of the pharynx
What type of protease does streptococcus pneumoniae release
secretory IgA protease (destroys IgA)
What does the streptococcus pneumoniae toxin, pneumolysin do
a toxin released when the bacteria is lysed the lyses epithelial cells and suppresses digestion of the phagocytized bacteria
What are the 6 diseases caused by streptococcus pneumoniae
pneumococcal pneumonia sinusitis otitis media bacteremia endocarditis pneumococcal meningitis
What is pneumococcal pneumonia
bacteria multiply in the alveoli, damaging it, and causing an inflammatory response
What is sinusits
streptococcus pneumoniae bacteria in the sinuses
what is otitis media
streptococcus pneumoniae bacteria in the middle ear
What is pneumococcal meningitis
when streptococcus pneumoniae bacteria spread to the meninges of the CNS
how is streptococcus pneumoniae diagnosed
gram stain of sputum smears, growth, optochin sensitivity, and bile solubility
How is streptococcus pneumoniae treated
penicillin or cephalosporins
how is streptococcus pneumoniae prevented
pneumovax 23 (adults) pneumococcal conjugate vaccine (PCV) 7-valent
What is the structure of enterococcus
short chains or pairs without a capsule
where is enterococcus normally found
the human colon, rarely pathogenic here (pathogenic in the lungs, urinary tract, and blood)
What is enterococcus resistant against
B-lactams, sulfonamides, aminoglycosides, tetracyclines, and erthyromycins (some are even resistant to vancomycin)
What is VRE
Vancomycin resistant enterococcus
what is the structure of Bacillus
Bacilli that can occur singly, in pairs, or in chains
What makes bacillus particularly difficult to get rid of
it forms endospores
What is bacillus anthracis
Anthrax, a strict pathogen of humans and animals
How do humans contract bacillus anthracis
- inhalation of spores
- ingestion of spores
- inoculation of spores into the body via a break in the skin
how long can anthrax spores survive
decades, possibly centuries
What is responsible for the virulence of anthrax
a 3 component toxin and a protein capsule
What are the two plasmids which house the virulence factors of anthrax
pXO1 and pXO2
What are the three forms of anthrax disease in humans
inhalation (pulmonary)
Gastrointestinal
Cutaneus
What is woolsorters disease
a pulmonary anthrax infection, induces capillary thrombosis and cardiovascular shock
How does one get gastrointestinal anthrax
ingestion of spore contaminated meat
What is a sign of cutaneus anthrax infections
Echar lesions (black, necrotic skin lesions)
how fatal are cutaneus anthrax infections
usually not fatal
how is bacilli diagnosed
large, non-motile, bacilli in the lungs or skin
how is bacilli anthracis treated
with ciproflaxin, penicilin, or tetracycline
how is bacilli anthracis prevented
control the disease in animals
vaccination (requires multiple doses and boosters)
besides bacilli anthracis, what are other important bacilli
bacilli cereus - food poisoning in rice, beans, and potatoes
Bacili subtilis - produces bacitracin
what produces bacitracin
bacilli subtilis
are clostridium bacteria aerobic or anaerobic
anaerobic
do clostridium bacteria produce endospores like bacillus
yes
Where are clostridium found
soil, water, and the GI tract of humans
What are the 4 different types of clostridium
clostridium perfringins
clostridium dificile
clostridium tetani
clostridium botulinum
what are the two main diseases caused by clostridium perfringins
food poisoning (enterotoxin) Gas gangrene
how is gas gangrene caused by clostridium perfringins
endospores enter the tissues in a traumatic event, they germinate and cause necrosis,
what are the two toxins of clostridium perfringins that cause gas gangrene
lecithinase and pore-forming toxin
it is when there is necrosis that is accompanied by gas build up in the tissues
how is gas gangrene diagnosed
easily, just by its symptoms
how is gas gangrene treated
removing dead tissue, large doses of penicillin, and hyperbaric chamber
how is gas gangrene prevented
proper cleaning of wounds, but it is difficult to prevent because clostridium perfringins is so common in the environment
Where is clostridium dificile normally found
part of the intestinal microbiota
What leads to an infection of clostridium dificile
when patients are treated with broad spectrum antibiotic drugs
what are the two degrees of infections of clostridium dificile
minor = self-limiting explosive diarrhea major = pseudomembranous colitis
what is pseudomembranous colitis
swollen colon that can perforate, leading to massive internal infection by fecal bacteria and death
how is a clostridium dificile infection treated
discontinuing antimicrobials, and restoring normal bowerl flora (fecal transplants)
What is botulism, and what bacteria is it caused by
botulism is flaccid paralysis, it is caused by clostridium botulinum
how does one contract botulism
by ingesting toxin from clostridium butulinum
why shoudn’t infants younger than one consume honey
because it could contain the botulism toxin
What is the most potent poison known to man
botulism toxin
how is botulism treated
administration of the polyvalent antitoxin
how is botulism prevented
proper food preparation and storage (botulism toxin is destroyed by heat)
how does botulism cause flaccid paralysis
the toxin enters into a motor nerve terminus, and cleaves the SNARE proteins responsible for fusing the vesicle (containing ACH) with the terminal membrane. (doesn’t allow the muscle to receive the neurotransmitter from the nerve)
What are the 3 forms of butulism
food-borne botulism
infant botulism
wound botulism
how is food borne botulism usually contracted
in home-canned food, or preserved fish
is infant botulism usually fatal
nope
how do the symptoms of wound botulism differ from that of food-borne botulism
they don’t just the means of contraction
How is botulism diagnosed
the symptoms are diagnostic, confirmed by culturing the organism from food, feces or the wound
how is botulism treated
antibodies against the botulism toxin
antimicrobial drugs to kill clostridia in infant botulism
how is botulism prevented
proper canning of food
infants under 1 shouldn’t have honey
how does clostridium tetani interact with air
it is an obligate anaerobe
where can clostridium tetani be found
soil, dust, GI tract of humans
When does tetanus result
when the bacterial endospores germinate and produce toxin
what are the symptoms of tetanus
spasms and contractions, death due to inability to exhale
Which bacteria causes lockjaw (spastic paralysis)
clostridium tetani
how is tetanus treated
cleaning of the wound to remove endospores, administration of antitoxin and antibiotics
how is tetanus prevented
vaccination TDaP, or Td
How does tetanus cause spastic paralysis
the tetanus toxin blocks the release of glycine, making it so the muscles can’t relax
What is the hallmark of an anaerobic infection
foul odor
What is deceiving about the name of the anerobe bacteroides fragilis
it is actually one of the easiest anaerobes to grow
What is the most commonly isolated anaerobic bacterium, especially from the blood
bacteroides fragilis
What are the virulent features of bacteroides fragilis
- attachment pili
- polysaccharide capsule
- modified or absent lipid A
- enzymes
What makes listeria monocytogenes problematic
its ability to live within cells
What are the toxins and enzymes of listeria monocytogenes like
it doesn’t produce any toxins or enzymes
Does listeria monocytogenes produce endospores
nope
how is listeria monocytogenes able to live inside cells, and move from one to another
it’s able to live inside cells by its ability to escape from phagocytic vessicles. Then once inside cells it builds an actin tail (actin polymerization) which helps it propel itself through that cell and into others.
What is the thing that helps listeria monocytogenes escape from vesicles
LLO listeriolysin O - it is pore forming
What about the conditions that listeria monocytogenes can grow in is different from many other bacteria
it can grow at refrigerator temperatures
where do most infections of listeria monocytogenes in humans come from
contaminated milk or meat
What is the problem with a pregnant woman being infected with listeria monocytogenes
it can be transferred to the baby prenatally or postnatally, which can cause meningitis, and still-births
How is listeria monocytogenes treated, and prevented
it is treated with ampicillin, and it is prevented with pasteurization and proper cooking
how is a listeria monocytogenes infection diagnosed
presence of the bacteria in the blood or cerebrospinal fluid (gram staining isn’t effective because so few cells are required to cause disease)
What is the name of the bacteria that causes diptheria
cornyebacterium diptheriae
how is diphtheria transmitted from person to person
respiratory droplets or skin contact
What are the signs and symptoms of diptheria
- pseudomembrane (dead cells and fluid that accumulates) in the respiratory tract, or on the skin (in the case of cutaneous diptheria)
- Bull neck (swelling in cervical lymph nodes)
Which bacteria can often be seen on a micrograph in V-shapes
cornyebacterium diptheriae
besides the respiratory tract, what else can diptheria toxin harm
the heart and CNS
how is diptheria diagnosed
clinical and serological tests
how is diptheria treated
antitoxin, then penicillin or erythromycin
how is diptheria prevented
toxoid vaccination
What is the bacteria that causes most of our acne
propionibacterium acnes
can propionibacterium acnes cause more than just acne
yes, it can also be an opportunistic pathogen
Why is actinomyces an important bacteria to study
because it is a major component of dental plaque and is associated with gingivitis and root caries
how is antinomyces treated
with amoxicillin
What is nocardia
a soil saprophyte that cause nocardiosis
what is nocardiosis
a TB-like pulmonary disease that can progress to form abscesses and can show on the back of the patient
What is streptomyces
a non-pathogenic bacteria that produces most of our antibiotics
