Gram Positive Bacteria

  1. What do INVASINS do?
/ They activate the host cell's cytoskeletal machinery enabling bacterial entry into the cell so it can get nutrients and be protected from complement (the host’s way of popping the bacterial cell membrane), antibodies, and other body defenses.
  1. What are ADHESINS?
/ They are surface proteins found in the cell wall of variousbacteria to enable them to bind to specific receptor molecules on the surface of host.
  1. What are Enterotoxins?
/ Enterotoxin: acts on the intestinal wall (causes GI upset)
They tend to be produced by Gram-positive bacteria rather than by Gram-negative bacteria. There are exceptions, such as Vibrio cholerae.
  1. What is an Endotoxin?
/ Endotoxin: Pieces of the bacterium which are toxic to humans
  1. What is a Lipopolysaccharide (LPS)?
/ Lipopolysaccharide (LPS): a protein in the cell wall of many Gram negative organisms. It is detected as foreign (an antigen) and launches an immune response.
  1. What is Lipid A?
/ Lipid A: A portion of the lipopolysaccharide which is also an antigen
  1. What is an Exotoxin?
/ Exotoxin: produced by a bacterium and then released from the cell into the surrounding environment. The damage caused by an exotoxin can only occur upon release.
  1. What does Hemolysin cause?
/ Hemolysins: cause rupture of red blood cells
  1. What do Neurotoxins do?
/ Neurotoxin: disrupts nerve cells.
  1. What does H Ag stand for?
/ The H antigen (H Ag) is a flagella on bacteria
  1. What is K Ag?
/ K Ag: an antigenetic protein on the capsule of bacteria
  1. What is O Ag?
/ O Ag: a string of sugars on the lipopolysaccharide (LPS)in bacterial cell walls.
  1. What do capsules do for bacteria?
/ Capsule: Helps prevent phagocytosis
  1. How does motility help bacteria?
/ Motility: Helps to spread disease within host
  1. Define Angiotropic.
/ Angiotrophic: Means the organism has the ability to cause blood vessels to grow towards it to feed it.
  1. What does β lactamase block?
/ β lactamase: an enzyme produced by some bacteria thatblocks the ability of certain antibiotics (penicillin) to destroy the bacteria
  1. What are MDR plasmids?
/ MDR plasmids (genes that provide tetracycline resistance)
  1. What are facultative intracellular pathogens?
/ Facultative intracellular pathogens: are capable of transient survival even in phagocytes that exert oxidative / non-oxidative mechanisms
  1. What is Ribosylase?
/ Ribosylase: an enzyme produced by some bacteria thatmodifies host’s proteins, causing massive fluid secretion from the lining of the lumen (in intestines causes diarrhea, in trachea causes coughing). Seen in cholera toxin, diphtheria toxin, and pertussis toxin.
  1. What does Coagulase do?
/ Coagulase: enzyme produced by some bacteria thatcauses tiny blood clots so bacteria can hide from WBC’s
  1. What does IgA or IgG protease do?
/ IgA or IgG protease: enzyme produced by some bacteria that preventsagglutination by antibodies
  1. What does PG (prostaglandin cause?
/ PG (prostaglandins):The immune response causes the host to release PG to fight the infection but the side effects are fever (pyrogenic) and inflammation.
  1. What does hyaluronidase do?
/ Hyaluronidase: an enzyme produced by some bacteria thatdissolves fluid between cells so bacteria can spread faster between tissue planes
  1. What does SOD (superoxide dismutase) do?
/ -SOD (superoxide dismutase): an enzyme produced by some bacteria that deactivates contents of lysosomes
  1. What does Staphylokinase do?
/ -Staphylokinase: an enzyme produced by some bacteria thatdigests clots so bacteria can spread
  1. Is Staphylococcusnormal flora?
/ Yes; that means it is part of every human’s microbiota, and can be opportunistic pathogens if the skin is broken
  1. Difference between staphylococcus from Streptococcus? Staphylococcus has…..
/ -Catalase present
-Has SOD, which is anti-phagocytic by converting
H2O2 H2O  O2
-That allows them to survive within eukaryotic phagocytic cells (neutrophils/macrophages)
  1. Structure and physiology of staphylococcus
/ - Gram-positive cocci, non-motile, facultative anaerobes
-Cells occur in grapelike clusters because cells division occurs along different planes and the daughter cells remain attached to one another
-Salt-tolerant-allows them to tolerate the salt present on human skin
-Tolerant of desiccation (drying)-allows survival on environmental surfaces (fomites)
  1. Four species of Staphylococcus that cause disease in humans
/ S. aureus
S. haemolyticus (axillae, perineum, and ingunial areas)
S. epidermidis
S. saprophyticus
  1. How else does S. aureusinterfere with white blood cells (WBCs)?
/ Inhibit chemotaxis of WBC’s
Having Protein A on its cell surface inhibits phagocytosis by WBC’s
  1. How does S. aureusinterfere with antibody attacks?
/ Binds the hypervariable region of IgG antibodies
Having Protein A on its cell surface inhibits the complement cascade (part of immune response which pops the bacterial cell membrane)
  1. How does a slime layer provide defense against Phagocytosis?
/ Facilitates attachment of Staphylococcus to artificial surfaces
  1. How does S. aureus interfere with the action of platelets?
/ By producing coagulase, an enzyme that makes tiny blood clots to allow the bacteria to hide from phagocytic cells.
It also produces Fibrinolysis, allowing it to free itself from clots when it wants to spread.
  1. How does S. aureus spread in the body?
/ By producing Hyaluronidase to break down hyaluronic acid, enabling the bacteria to spread between cells. Hyaluronic acid is a fluid between body cells, and is also found in joints.
  1. How does S. aureus survive on the skin surface?
/ By producing the enzyme lipase, which digests lipids, allowing staphylococcus to grow on the skin’s surface and in cutaneous oil glands
  1. What does S. aureus use the enzyme DNasefor?
/ Reduces viscosity in abscesses
  1. What does S. aureus use the enzyme β-lactamase for?
/ Breaks down penicillin and other β -lactam antimicrobial drugs
  1. Which Gram positive bacteria produce more toxins than other species?
/ Staphylococcus aureus
  1. What are Hemolysins?
/ Enzymes produced by some bacteria that breaks down red blood cells so bacteria can ingest the nutrients
  1. What are 3 types of hemolysis?
/ (alpha hemolysis). The red blood cell is only partially destroyed. Shows up as a green color on a blood agar plate
 (Beta hymolysis). The red blood cell is completely destroyed. Shows up as a clear area on blood agar plate. Streptococcus (strep throat) is one organism that does this.
 (gamma hemolysis). RBC is not destroyed. No color change on blood agar plate.
  1. What are enterotoxins?
/ Stimulate the intestinal muscle contractions, nausea, and intense vomiting associated with staphylococcal food poisoning
  1. Staphylococcal Diseases – What are the 3 categories?
/ Noninvasive Disease, Cutaneous Disease, Systemic Disease
  1. What are the characteristics of noninvasive disease?
/ Food poisoning from the ingestion of enterotoxin-contaminated food
  1. What are the symptoms of staph food poisoning?
/ nausea, vomiting, retching, stomach cramping, and diarrhea. In more severe cases, dehydration, headache, muscle cramping, and changes in blood pressure and pulse rate may occur.
  1. What are the characteristics of cutaneous staphylococcal disease?
/ Various skin conditions including scalded skin syndrome, impetigo, folliculitis, and furuncles (boils)
  1. What is Toxic shock syndrome-TSS?
/ toxin is absorbed into the blood and causes shock that is life threatening
  1. What is Bacteremia
/ presence of bacteria in the blood
  1. What is Endocarditis
/ occurs when bacteria attack the lining of the heart
  1. What is Pneumonia
/ inflammation of the lungs in which the alveoli and bronchioles become filled with fluid
  1. What is Osteomyelitis
/ Infection of bone
  1. How do you determine if Staphylococcus species is S. aureus?
/ S. aureus is catalase positive
  1. If a Staphylococcus is catalase negative, how do you determine if the species is epidermidis or saprophyticus?
/ S. epidermidis: Novobiocin-sensitive
S. saprophyticus: Novobiocin-resistant
  1. What are the characteristics of S. epidermidis?
/ -Coagulase-negative
-Produces a biofilm that allows adherence to prosthetic devices. People with artificial joints need prophylactic antibiotics before other surgeries for this reason.
- Quorum-sensing
  1. What is quorum-sensing?
/ Ability to coordinate gene expression according to the density of their local population. They will wait until there are many bacteria nearby, and then they will all start at the same time to express genes for proteins to help with the invasion.This coordinated invasion overwhelms the host defenses.
  1. What drug is used to treat staphylococcal infections?
/ Methicillin
  1. What is Methicillin?
/ Is a semisynthetic form of penicillin and is not inactivated by b-lactamase
  1. What does MRSA stand for?
/ Methicillin resistantStaphylococcus aureus
  1. Where do many MRSA infections occur?
/ in hospitals and healthcare facilities
  1. The type of MRSA with a higher incidence rate in nursing homes or long-term care facilities is known as what?
/ Healthcare acquired MRSA or HA-MRSA
  1. What is becoming increasingly difficult to treat?
/ Serious MRSA infections, especially HA-MRSA infections
  1. How do you prevent infection by S. epidermidis?
/ -Hand antisepsis is the most important measure in preventing nosocomial infections (wash hands after patient contact)
- proper cleansing of wounds and surgical openings
- aseptic use of catheters or indwelling needles
- appropriate use of antiseptics
  1. What is the structure of streptococcus?
/ Gram-positive cocci, arranged in pairs or chains, that are facultative anaerobes
  1. How are streptococci classified?
/ The Lancefield classification
  1. What is the Lancefield classification entail?
/ -Divides the streptococci into serotype groups based on the bacteria’s antigens (M proteins)
-Human streptococcal pathogens are in Lancefield groups A and B
  1. What is the Lancefield Group A pathogen?
/ Streptococcus pyogenes (strep throat)
  1. What is the Lancefield Group B pathogen?
/ Streptococcus agalactiae (normal GI flora in adults, but is the major cause of septicemia in newborns)
  1. Do pathogenic strains of Streptococcus pyogenes form a capsule?
/ YES
  1. What is pharyngitis?
/ Inflammation of the pharynx
  1. Where does scarlet-fever rash begin and where does it spread to?
/ Begins on the chest and spreads to the rest of the body
  1. What is pyoderma?
/ Confined, pus-producing lesion that usually occurs on the face, arms, or legs
  1. What is streptococcal toxic shock syndrome?
/ Bacteremia and severe multisystem infection
  1. What do pyrogenic toxins do?
/ Stimulate macrophages and helper T cells to release cytokines, which call other WBCs to the infection site
  1. What 3 types of cells do streptolysins lyse?
/ 1)White blood cells
2)Red blood cells
3)Platelets
  1. What does Protein M do to help Group A streptococci?
/ Protein Mhelps to camouflage them from WBCs
  1. What is Necrotizing fasciitis?
/ Bacterial infection that destroys muscle and fat tissue and quickly spreads between tissue planes
  1. What are the early signs and symptoms of necrotizing fasciitis?
/ severe pain and swelling. often rapidly increasing, fever, redness at a wound site
  1. What is Rheumatic fever?
/ Streptococcal infection that has entered the bloodstream and can lead to scarring of heart valves
  1. What is Mortality of Streptococcal Toxic Shock Syndrome (STSS)
/ 35%
  1. What are the early signs and symptoms of STSS?
/ fever
abrupt onset of generalized or localized severe pain, often in one arm or leg
Dizziness
Influenza-like syndrome
A flat red rash over large areas of the body (only occurs in 10% of cases)
  1. Diagnosis of Streptococcal Toxic Shock Syndrome (STSS)
/ Observation of Gram-positive bacteria in short chains or pairs or immunological tests that identify the presence of group A streptococcal antigens
Streptococci are normally in the pharynx so their presence in a respiratory sample is of little diagnostic value
  1. Treatment of Streptococcal Toxic Shock Syndrome (STSS)
/ Cephalosporin (third generation penicillin) is very effective
  1. Prevention of Streptococcal Toxic Shock Syndrome (STSS)
/ Antibodies against M protein provide long-term protection against future infection of S. pyogenes, but only if it is the same strain
  1. GROUP B STREPTOCOCCUS
/ Gram positive, beta hemolytic bacteria
Common colonizer of human gastrointestinal and genitourinary tracts
Causes serious disease in young infants, pregnant women and older adults
The most common cause of sepsis and meningitis in infants <3 months
  1. What is the leading infectious cause of neonatal sepsis in U.S.?
/ Group B Streptococcus (GBS) Disease
  1. Where dose GBS usually live?
/ In gastrointestinal tract but can spread to the genital tract.
  1. What are the risk factors for early-onset GBS disease?
/ Obstetric risk factors
GBS in the mother’s urine during pregnancy (marker for heavy colonization).
Previous infant with GBS disease
Low maternal levels of anti-GBS antibodies
  1. What are the prevention of early-onset GBS disease?
/ Intrapartum antibiotics (IAP)
  1. Intrapartum antibiotics (IAP)
/ Highly effective at preventing early-onset disease in women at risk of transmitting GBS to their newborns.
Efficacy in clinical trials: 100%.

  1. Alpha-Hemolytic Streptococci
/ Produce a green pigment when grown on blood agar.
Normally inhabit the mouth, pharynx, GI tract, genital tract, and urinary tract.
One of the causes of dental caries and dental plaques.
If enter the blood can cause meningitis and endocarditis.
  1. What organism produces alpha hemolysis?
/ Streptococcus pneumoniae
  1. What organism normally colonizes the mouths and pharynx but can cause disease if travels to the lungs
/ Streptococcus pneumoniae
  1. What is pneumolysin?
/ Enzyme produced by some bacteria which lyses epithelial cells in the lungs
  1. What to diseases are caused by bacteria invading the sinuses or middle ear, often following a viral infection
/ Sinusitis (sinus infection) and otitis media (middle ear infection)
  1. How do you diagnose Streptococcus pneumoniae?
/ Gram strain of sputum smears, then Quelling reaction (anti-capsular antibodies cause the capsule to swell), confirming the presence of bacteria
  1. What would be treatment for Streptococcus pneumoniae?
/ Cephalosporin
  1. How can you prevent Streptococcus pneumoniae?
/ Vaccine made from purified capsular material. Provides long lasting immunity in normal adults but is not as effective in children, the elderly, or AIDS patients
  1. Previously classified as group D streptococci but differed enough to be reclassified as a separate genus
/ Enterococcus
  1. Form short chains and pairs and lack a capsule
/ Enterococcus
  1. Found in the human colon but are rarely pathogenic at this site
/ Enterococcus
  1. Can cause disease if they are introduced into other parts of the body, such as the urinary tract or bloodstream
/ Enterococcus
  1. What types of infections may be caused by Enterococcus?
/ An important cause of nosocomial infections
  1. Why is treatment for Enterococcus difficult?
/ Treatment is difficult because enterococci are often resistant to antimicrobials
  1. Why is prevention for Enterococcus difficult?
/ Prevention is difficult, especially in a health care setting, where patients’ often have weakened immune systems
  1. Describe Bacillus
/ •Gram-positive bacilli, that occurs singly, in pairs, or in chains
•Forms endospores
•Typically motile
  1. What is the rapid-onset emetic syndrome of B. cereus?
/ Rapid-onset emetic syndrome
Causes nausea and vomiting
  1. When does vomiting occur
/ Begins one to five hours after contaminated food is eaten.
  1. What is the slow-onset diarrheal syndrome of B. cereus?
/ Diarrhea
Abdominal pain occurs 8 to 16 hours after consumption of contaminated food.
  1. What are treatments for symptoms caused by B. cereus?
/ Oral hydration
IV fluid
  1. What are the 3 ways humans can contract Bacillus Anthracis
/
  1. Inhalation of spores
  2. Inoculation of spores into the body through a break in the skin
  3. Ingestion of spores

  1. What disease does Bacillus Anthracis cause?
/ Anthrax
  1. What three clinical manifestations can Anthrax have?
/ Gastrointestinal, cutaneous, and inhalation anthrax
  1. What are the signs and symptoms of GI Anthrax?
/ -Rare in humans
-Stomach pain
-Loss of appetite
-Bloody diarrhea
-Nausea
-Fever
-Vomiting blood
  • Intestinal hemorrhaging and eventually death in 60% of cases

  1. Signs and symptoms of Cutaneous Anthrax
/ Produces a black scabby ulcer called an eschar as well as toxemia (toxins in the blood)
  1. Signs and symptoms of Inhalation Anthrax
/ -Similar to GI Anthrax
-Fever
-Nausea
-Vomiting
-Aches
-Fatigue
  1. Symptoms of advanced Inhalation Anthrax
/ -Labored breathing
-Shock
-Death
  1. How does Inhalation Anthrax infect?
/ Rare in humans
Spores germinate in the lungs and secrete toxins that are absorbed into the bloodstream
Mortality rate of 75%
  1. Diagnosis of anthrax
/ Presence of large, nonmotile, gram- positive bacilli in clinical samples of the lungs or skin
  1. What is the treatment for anthrax?
/ Ciprofloxacin and many other antimicrobials are effective against B. anthracis
  1. What are 2 methods of prevention?
/ Control the disease in animals
Anthrax vaccine – available but requires multiple doses and boosters
  1. What is Clostridium?
/ Gram-positive, anaerobic, endospore-forming bacillus
  1. Where is it found?
/ Ubiquitous in soil, water, and the gastrointestinal tracts of animals and humans
  1. Does the presence of endospores allow for survival in harsh conditions?
/ Yes
  1. Where does Clostridium perfringens grow?
/ Commonly grows in the digestive tracts of animals and humans
  1. What does C. perfringens produce?
/ 11 toxins that have various effects on the body and can result in irreversible damage
  1. What 2 diseases does C. perfringens cause?
/ 1) food poisoning
2)gas gangrene
  1. What is food poisoning characterized by?
/ Abdominal cramps and watery diarrhea
  1. How are C. perfringens endospores introduced into the body in the case of gas gangrene?
/ Through some traumatic event.
  1. What do the endospores cause once they begin to germinate?
/ They cause necrosis that is often accompanied by foul smelling gaseous bacterial waste products.
  1. What indicates the involvement of Clostridium in food poisoning?
/ The presence of more than 10-5 bacteria in a gram of food or 10-6 cells per gram of feces.
-Gas gangrene is usually a diagnostic by itself
  1. What is the treatment for most cases of food poisoning?
/ Ride it out; drink lots of water, eat only grains (toast) or sugars (7-Up), replace electrolytes (Pedialyte)
  1. What is the treatment for gas gangrene?
/ Remove the dead tissue and administer large doses of Cephalosporin.
  1. How does one prevent infection by Clostridium perfringens?
/ Proper cleaning of wounds, otherwise fairly difficult to prevent because it is so common.