BIOL 250 - Chapter 19: Gram-Positive Bacteria

two main phyla of gram-positive bacteria

firmicutes and acintobacteria

characteristics of *Staphylococcus*

catalase positive, salt tolerant (up to 10% NaCl)

two species commonly associated with staphylococcal disease

*Staphylococcus aureus, Staphylococcus epidermidis*

pathogenicity of *Staphylococcus*

defense: Protein A
enzymes: coagulase, hyaluronidase, staphylokinase, lipase, penicillinase (beta-lactamase)
toxins: cytolytic toxins, exfoliative toxins, TSS toxins, enterotoxin

protein A

a protein that coats S. aureus that interferes with the antibody immune responses by binding to the stems of IgG; inhibits opsonization

coagulase

triggers blood clotting

hyaluronidase

hydrolyzes hyaluronic acid, a major component of the matrix between cells

staphylokinase

dissolves fibrin threads in blood clots, allowing *S. aureus* to free itself from clots

lipase

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

penicillinase (beta-lactamase)

breaks down penicillin to help, allowing bacteria to survive antimicrobial treatment

cytolytic toxins

work by degrading cytoplasmic membrane integrity, causing cell lysis and death

exfoliative toxins

cause skin cells to separate and slough off

TSS toxins

protein that causes TSS

enterotoxins

cause intestinal disturbance

three categories of staphylococcal diseases

noninvasive, cutaneous, systemic

noninvasive disease of *Staphylococcus*

food poisoning

three cutaneous diseases of *Staphylococcus*

scalded skin syndrome, impetigo, folliculitis

scalded skin syndrome

pyogenic lesions whereby epidermal layers peel off--does not contain staph cells, just the toxin

impetigo

staph infection (contains cells)

folliculitis

inflammation of the hair follicle

six systemic diseases of *Staphylococcus*

TSS, bacteremia, endocarditis, pneumonia, empyema, osteomyelitis

toxic shock syndrome (TSS)

potentially fatal condition characterized by fever, vomiting, red rash, low blood pressure, and loss of sheets of skin

bacteremia

presence of bacteria in the blood

endocarditis

inflammation stemming from bacterial invasion of the outer layers of the heart and heart valves

pneumonia

inflammation of the alveoli and bronchioles and the accumulation of fluid

empyema

accumulation of pus in the space between the lung and chest wall

osteomyelitis

inflammation of the bone marrow and bone tissue

characteristics of *Streptococcus*

catalase negative, cocci arranged in chains or pairs

specie differentiation of *Streptococcus*

hemolysis reactions and serological reactions (Lancefield antigens). group A streptococci (ex. *Streptococcus pyogenes*) have large zones of beta-hemolysis, group B streptococci (ex. *Streptococcus agalactiae*) have small zones of beta-hemolysis. viridans group have alpha-hemolysis

pathogenicity of group A *Streptococcus*

defense: M protein, hyaluronic acid capsule
toxins: pyrogenic toxins, streptolysins

M protein

interferes with complement; prevents opsonization; allows strep to adhere to cells

hyaluronic acid capsule

protects/hides from phagocytosis

pyrogenic toxins

stimulate fever

streptolysins

lyse RBC, WBC, and platelets--interfering with the oxygen-carrying capacity of the blood, immunity, and blood clotting

diseases of group A *Streptococcus*

pharyngitis, scarlet fever, pyoderma and erysipelas, toxic-shock-like syndrome, rheumatic fever, glomerulonephritis, necrotizing fasciitis

pharyngitis

inflammation of the pharynx; "strep throat"

scarlet fever

rash and systemic toxemia following pharyngitis

pyoderma and erysipelas

pus-filled lesions on skin (pyoderma); localized swelling and inflammation (erysipelas)

toxic-shock-like syndrome

bacteremia and multi-system inflammation and failure

rheumatic fever

damage to heart valves following pharyngitis

glomerulonephritis

inflammation of the glomeruli and nephrons

necrotizing fasciitis

"flesh-eating" bacteria disease

pathogenicity of group B *Streptococcus*

capsules (not very effective); mainly infect newborns and now the elderly

diseases of group B *Streptococcus*

neonatal bacteremia, meningitis, pneumonia

meningitis

inflammation of the meninges

diseases of viridans streptococci

dental caries

dental caries

cavities

pathogenicity of *Streptococcus pneumoniae*

capsules, adhesins, pneumolysins

pneumolysins

bind cholesterol and make holes in host cells

diseases of *Streptococcus pneumoniae*

sinusitis, otitis media, bacteremia, endocarditis, pneumococcal meningitis

sinusitis

acute infection of the paranasal sinuses

otitis media

acute infection of the ear

characteristics of *Enterococcus*

catalase negative, Lancefield group D (but unencapsulated) and are not hemolytic

two types of *Enterococcus*

*E. faecalis* and *E. faecium* (both found in the human colon)

pathogenicity of *Enterococcus*

bacteriocins

bacteriocins

cytolysins that inhibit growth of Gram-positives

diseases of *Enterococcus*

10% of nosocomial infections, bacteremia, endocarditis and wound infections

characteristics of *Bacillus*

soil dwelling organisms that produce endospores, arranged single, in pairs, or in chains; most notable pathogenic species is *Bacillus anthracis*

pathogenicity of *Bacillus*

anthrax toxins

anthrax toxins

create holes in host cells; stimulate apoptosis

diseases of *Bacillus*

anthrax (GI anthrax, cutaneous anthrax, inhalation anthrax)

anthrax

can be fatal without aggressive treatment; caused by ingestion, inoculation, or inhalation of spores of *Bacillus anthracis*

characteristics of *Clostridium*

ubiquitous in the soil, water and GI tract of animals, produces endospores

four notable species of *Clostridium*

*Clostridium perfringens* (gas gangrene)
*Clostridium difficile* (pseudomembranous colitis)
*Clostridium botulinum* (botulism)
*Clostridium tetani* (tetanus)

pathogenicity of *Clostridium botulinum*

produces 7 distinct botulism toxins, which are very deadly and prevent neurotransmitter release resulting in flaccid paralysis

pathogenicity of *Clostridium tetani*

produces tetanospasmin (tetanus toxin) that causes both muscles in an antagonistic pair to contract

characteristics of *Listeria*

low G + C, Gram-positive, non-endospore-forming, rod-shaped bacterium with end-over-end, tumbling motility outside the body. It is found in soil, water, and animals, including insects. It enters the body through consumption of contaminated drink or food, typically deli meats, hot dogs, soft cheeses, and yogurt

pathogenicity of *Listeria monocytogenes*

enters body through contaminated food/drink and causes listeriosis; rarely pathogenic in health adults, but can infect pregnant women, fetuses, newborns, the elderly, and immunocompromised people resulting in meningitis. Listeria is tolerant of cold temperatures, so it can

signs and symptoms of listeriosis

nonspecific flulike symptoms in healthy, nonpregnant adults. In contrast, infection in pregnant women, fetuses, newborns, the elderly, and immunocompromised patients can be severe, causing bacterial meningitis and possibly death

treatment of listeriosis

ampicillin and other antimicrobials

characteristics of *Corynebacterium*

high G + C, pleomorphic, non-endospore forming, snapping division; all species are pathogenic--*Corynebacterium diptheriae*

pathogenicity of *C. diptheriae*

lysogenic bacteriophage in cell that produces the diptheria toxin; cells lacking bacteriophage are non-pathogenic

diptheria toxin

blocks polypeptide synthesize; formation of pseudomembrane

characteristics of *Mycobacterium*

high G + C, non-endospore-forming pathogen; cell walls with waxlike mycolic acid; two notable disease in humans are *M. tuberculosis* and *M. leprae* (tuberculosis and leprosy)

tuberculosis

a respiratory disease caused by infection with *M. tuberculosis*; its disseminated form can result in wasting away of the body and death

leprosy

disease caused by infection with *M. leprae* that produces either a non-progressive tuberculoid form or a progressive lepromatous form that destroys tissue, including facial features, digits, and other structures

characteristics of *Propionibacterium*

non-endospore forming, found on skin, produce propionic acid as a byproduct of fermentation; causative agent of acne in 85% of adolescents and young adults

characteristics of *Nocardia*

common inhabitor of soils rich in organic matter; mycolic acid in cell wall; acid fast stain

characteristics of *Actinomyces*

hypha-like cells; causes actinomycosis

actinomycosis

characterized by formation of multiple, interconnected abscesses in skin or mucous membrane