Pathogenic Gram-Positive Bacteria

Describe the morphology and arrangement of Staphylococcus

gram-positive, faculatatively anaerobis prokaryotes. spherical cells are typically clustered in grapelike arrangements.

Are Staphylococci species salt sensitive or salt tolerant, and what might this have on their ability to tolerate the salt deposited on human skin by sweat glands?

salt tolerant- they tolerate the salt deposited on human skin by sweat glands

What are the two species of Staphylococcus that are most commonly associated with staphylococcal diseases in humans?

S. aureus and S. epidermidis

Of the two species of Staphylococcus, which is more virulent and which is part of the normal microbiotoa but can be an opportunistic pathogen?

S. aureus is more virulent. S. epidermidis is part of the normal microbiota of human skin, but it can be opportunistic pathogen

With regard to S. aureus, how does protein A interfere with 'normal' antibody binding, and what effect does this have upon opsinization and subsequent phagocytosis?

binds to the Fc regions of class G antibodies. inhibits opsonization (opsonins enhance phagocytosis)

What effect does "bound coagulase" of S. aureus have upon the soluble blood protein "fibrinogen", and what is the end result of this change in protein structure?

converts fibrinogen into long, insoluble fibrin molecules that form blood clots around the bacteria

Name two functions of the loosely organized slime layers produced by both S. aureus and S. epidermidis?

inhibits chemotaxis of and endocytosis by leukocytes and facilitates attachment of Staphylococcus to artificial surfaces

Between S. aureus and S. epidermidis, which produces "cell-free coagulase", and what effect does this enzyme have upon blood clotting?

S. aureus produces cell-free coagulase. triggers blood clotting

What is the substrate of staphylococcal hyaluronidase, and what role does this enzyme play during infection and invaseion?

breaks down hyaluronic acid, which is a major component of the matrix between cells

What effect does "staphylokinase" have upon blood clots?

dissolces fibrin threads in blood clots, allowing S. aureus to free itself from a clot

What "lipases" and what role do they play in staphylococcal growth?

digest lipids, allowing staphylococci to grow on the surface of the skin and in cutaneous oil glands

What is "Beta-lactamase" and what effect does it have on the antibiotic penicillin?

breaks down penicillin

Are the vast majority of S. aureus strains sensitive or resistant to penicillin?

90% break down penicillin. resistant

What specific effect do "cytolytic toxins" have upon host cell cytoplasmic membranes, and how does this ultimately affect the host cell?

cause to lyse. disrupt cytoplasmic membranes

What effect do "exfoliative toxins" have upon host skin cells?

cause skin cells to separate from each other and slough off the body

What are enterotoxins?

stimulate the intestinal muscle contractions, nausea, and intense vomiting

S. aureus causes staphylococcal 'food poisoning', more specifically "food intoxication". What is "food intoxication"?

ingestion of pre-existing toxin

How are commonly affected foods associated with staphylococcal food poisoning most often contaminated?

contaminated with bacteria from human skin, or unrefridgerated

What effect (if any) does warming or reheating of contaminated foods have upon the enterotoxin that cause staphylococcal food poisoning?

no effect

What is the relationship between "exfoliative toxin" (produced by some strains of S. aureus) and "staphylococcal scalded skin syndrome" (SSSS)? Specifically, what effect does staphylococcal exfoliative toxin have upon the epidermis?

causes the affected outer layer of skin to peel off

Between staphylococcal scalded skin syndrome and secondary bacterial infections, which is the more serious?

secondary bacterial infections

Give a brief definition or description of "impetigo".

small, flattened, red patches on the face and limbs

How is impetigo distinguished from staphylococcal scalded skin syndrome?

patches develop into pus-filled vesicles filled with white blood cells

Are the signs and symptoms of "staphylococcal toxic shock syndrome" due to localized infections, toxins that are absorbed into the circulatory system, or a combination of the two?

both

Briefly describe the relationship between super-absorbent, Rely® brand, tampons and staphylococcal toxic shock syndrome.

S. aureus grows exceedingly well in super-absorbant tampons

Broadly speaking, how do physicians diagnose staphylococcal infections?

by detecting Gram-positive bacteria in grapelike arrangements

If staphylococci isolated from an infection are "coagulase-positive", what Staphylococcus species is most likely involved?

coagulase-positive S. aureus

What do the acronyms MRSA and VRSA stand for?

methicillin resistant Staphylococcus aureus

vancomycin resistant S. aureus

Describe the morphology and arrangement of Streptococcus.

facultatively anaerobic, gram-positive cocci arranged in pairs or chains

Briefly describe the principle behind "Lancefield" classification of the streptococci.

divides streptococci into serotype groups based on the bacteria'a antigens

What is "hemolysis", and describe the difference between beta-hemolysis and alpha-hemolysis?

lysis of red blood cells, beta-hemolysis complete lysis of red cells, alpha- hemolysis is partial or incomplete hemolysis

What is "Group A Streptococcus"?

streptococcus pyogenes have a number of structures, enzymes, and toxins that enable them to survive as pathogens in the body

What type of hemolysis is characteristic of Streptococcus pyogenes?

beta-hemolysis

Describe the two main structural features that enable cells of S. pyogenes to evade phagocytosis.

1. M protein- a membrane localized protein that interferes with opsinization

2. hyaluronic acid capsule-essentially camouflages the bacterium from white blood cells

What are "streptokinases"?

break down blood clots

Briefly describe the effect of Group A "pyrogenic toxins" upon host physiology.

stiulate fever, a widespread rash, and shock

What are "streptolysins"?

membrane-bound proteins which lyse red blood celss, white blood cells, and platelets

What is the causative agent of strep throat?

pharyngitis

What is the fundamental difference between bacterial pharyngitis and viral pharyngitis in terms of treatment?

bacterial pharyngitis is treatable with antibacterial drugs which have no effect on viral pharyngitis

"Scarlet fever" develops in only some cases of streptococcal phyryngitis. Explain.

when the infection involves a lysogenized strain of S. pyogenes

What role do streptococcal pyrogenic toxins play in scarlet fever?

trigger a diffuse rash tha spreads across the body

A further complication of untreated streptococcal pharyngitis is "rheumatic fever". What is rheumatic fever, and briefly describe the apparent cause?

inflammation leads to damage of heart valves and muscles

What is the causative agent of, and what is, "erysipelas"?

when a steptococcal infection also involves surrounding lymph nodes and triggers pain and infammation

What is the causative agent of, and what is, "necrotizing fasciitis"?

S. pyogenes

Why is the observation of Gram-positive bacteria in short chains or pairs in cutaneous specimens diagnostic of Streptococcus infection?

because it is not a normal member of the microbiota of the skin

Would the presence of streptococci in the pharynx be diagnostic of streptococcal disease?

no

Describe the characteristic morphology and arrangement of Streptococcus pneumoniae.

gram-positive coccus that forms short chains or pairs

What type of hemolysis is characteristic of Streptococcus pneumoniae?

alpha-hemolysis

How does the polysaccharide capsule of S. pneumonia, together with "phosphorylcholine", enable pneumococci the 'hide' inside body cells?

stimulates host cells to engulf the bacteria

Briefly describe the roles of streptococcal "secretory IgA protease" and "pneumolysin".

destoys IgA and lyses ciliated epithelial cells

What is the most prevalent disease caused by S. pneumoniae?

pneumococcal pneumonia

How does the disease caused by S.pneumoniae result?

when pneumococci are inhaled from the pharynx into lungs damaged either by a previous viral disease of by other conditions

Briefly describe the nature of the vaccine used to prevent pneumococcal diseases.

made from purified capsular material from the 23 most common pathogenic strains

Briefly explain how Bacillus anthracis can survive in dry and lifeless soil for years, if not centuries.

the tough external coat and the internal chemicals of its endospores enable this

What differentiates pathogenic strains of B. anthracis from nonpathogenic ones?

contain copies of plasmid coding for anthrax toxin

Name and briefly describe the three different 'kinds' of anthrax caused by B. anthracis.

gastrointestinal anthrax- vary rare in humans but common in animals

cutaneous anthrax- causes the formation of a nodule which is followed by a crusty ulcer called an eschar

inhalation anthrax- requires the inhalation of airborne endospores

Of the three different kinds of anthrax, which has the highest mortality rate if left untreated?

inhalation anthrax

What is the main preventative measure for anthrax?

vaccination of livestock

Are Clostridium species obligate aerobes or obligate anaerobes?

anaerobes

What is the causative agent of "gas gangrene"?

clostridial toxins

How does one contract gas gangrene?

when endospores are introduced deep in the tissues

What causes the "gas" in gas gangrene?

when endospores are introduced deep in the tissues

What is the main preventative measure with regard to gas gangrene caused by Clostridium perfringens?

properly cleaning wounds

Clostridium difficile is an anaerobic intestinal bacterium. Briefly explain how this microbe appears clinically as an opportunistic pathogen?

endospored of C. difficile germinate to the extent that it's toxins and enzymes produce hemorrhagic necroisis

What is "hemorrhagic necrosis"?

the premature death of cells and living tissue

What is "pseudomembranous colitis"?

when large sections of the colon wall slough off

What is the causative agent of botulism?

its endospores

Describe the relationship between C. botulinum endospores, an anaerobic environment, and neurotoxin production.

endospores survive improper canning of food, germinationg to produce vegetative cells that grow and release a powerful neurotoxin that cause botulism

What role does "acetylcholine" play at the neuromuscular junction?

A nerve impulse from the central nervous system causes vesicles filled with acetylcholine to fuse with the neuron's cytoplasmic membrane releasing acetylcholine into the synaptic cleft. the binding of acetylcholine to receptors on the muscle cell's cytoplasmic membrance stimulates a series of events that result in contraction of the muscle cell

Briefly describe the effect that botulism toxin has upon muscle contraction.

blocks signals from motor neurons to muscles cells

What is "flaccid paralysis"?

muscles do not contract

Briefly describe the conditions under which "infant botulism" develops.

occur when the pathogen grows in the gastrointestinal tract of an infant

What do microbiologists mean when they sat that botulism (with the exception of 'infant botulism') is not an infection, but instead an "intoxication"?

caused by botulism toxin

When fatal, how does death result in victims of botulism?

results from the inability of muscles of respiration to effect inhalation. victims cannot inhale

What is the causative agent of tetanus?

terminal endospore

Briefly describe the conditions under which tetanus develops.

endospores germinate, grow, and produce potent neurotoxin

What is the name of the neurotoxin produced by Clostridium tetani?

tetanospasmin

Briefly describe the effect that tetanospasmin has upon muscle relation.

blocks the inhibitory neurotransmitter

What is "spastic paralysis"?

form of paralysis in which the part of the nervous system that controls coordinated movement of the voluntary muscles is disabled

When fatal, how does death result in victims of tetanus?

patients cant exhale

How does cleaning of wounds (e.g. stepping on a 'rusty nail') help treat tetanus?

removes endospores

What is "passive immunization", and how is it used in the treatment of tetanus?

immunoglobin directed against the toxin, tbe administration of antimicrobials such as penicillin, and active immunization wtih tetanus toxoid

What is "tetanus toxoid", and how is it used in the treatment and prevention of tetanus?

used for an immunization

What is the causative agent of diphtheria?

corynebacterium diptheriae

What specific effect does diphtheria toxin have upon host cells, and what cellular state results?

causes localized cell death

Briefly describe the nature of "pseudomembrane" formation in cases of diphtheria.

accumulation on the tonsils or pharynx made of dead tissue, mucus, white blood cells, and fibrious material

What is an "antitoxin"?

an antibody with the ability to neutralize a specific toxin

What is the main preventative measure with regard to diphtheria?

immunization with DTaP or treatment with penicillin or erythromycin