BACTERIOLOGY PART 2 (Staphylococcus - Listeria)

staphylococcus

grape-like clusters

staphylococcus

members of this species are facultative anaerobes.

staphylococcus

most grow well high osmotic pressure and low moisture, making them normal flora of the skin and other organs

protein A

inactive lgA

coagulase

enzyme for coagulation (only present in staph. aureus)

Hemolysis

staph. aureus has the ability to break down RBC’s

Leukocidin

kills RBCs

penicillinase (Beta lactamase)

enzyme responsible to void the action of penicillin (produced by staphylococcus)

Lipase

responsible for causing boils

protease

break down amino acids

Hyaluronidase

has the ability to spread staph. aureus to the different parts of the body

exfoliative toxin

staphylococcal scalded skin syndrome

exfoliative toxin

• bullous impetigo

• affecting skin

enterotoxin

heat-labile causing food poisoning (vomiting-type)

-Toxic shock syndrome

enterotoxin

responsible for gastroenteritis

gastroenteritis, toxic shock syndrome, scalded skin syndrome

Disease by exotoxin release (staph. aureus)

skin infection, acute bacterial endocarditis, urinary tract infection

Direct organ invasion (staph. aureus)

staphylococcus saphrophyticus

• Non-hemolytic

• coagulase negative

• novobiocin resistant

Staphylococcus saphrophyticus

causes “honeymoon cytitis”

staphylococcus epidermidis

• Novobiocin sensitive

• frequently isolated in infected indwelling catheters:

Prosthetic Heart Valve Endocarditis

staphylococcus epidermidis

has the ability to adhere to artificial materials in the body (e.g. catheters and prosthetic heart valves)

Lactobacillus

some are normal flora of the human body

Lactobacillus

also used commercially in the production fermented foods like sauerkraut, pickles, buttermilk, and yogurt

Streptococcus

Spherical, catalase negative, gram-positive bacteria. Typically appear in chains or in pair

Streptococcus

Responsible for more illnesses and causing a greater variety of diseases than any other group of bacteria

Beta-hemolytic streptococci

produce streptolysin, a hemolysin that forms a clear zones of hemolysis on blood agar

Lancefield Classification

A system of classification that classifies catalase-negative Gram-positive cocci based on the carbohydrate composition of bacterial antigens found on their cell walls

Streptococcus pyogenes

Lancefield Classification Group A

Streptococcus agalactiae

Lancefield Classification Group B

Enterococci, Streptococcus bovis

Lancefield Classification Group D

Hemolysis Test

is used in the empirical identification of microorganisms based on the ability of bacterial colonies grown on agar plates to break down red blood cells in the culture

Streptococcus pyogenes

Known as group A beta-hemolytic streptococcus

• Causes scarlet fever, pharyngitis, erysipelas, impetigo, and rheumatic fever

-has M protein

Streptococcus agalactiae

• known as group Beta-hemolytic streptococcus

• causes neonatal sepsis and pnuemonia

Pharyngitis

is the most common disease caused by streptococcus pyogenes

Erysipelas

is a massive brawny edema and a rapidly advancing margin of infection

brawny edma

swelling that is usually dense ad feels firm due to the presence of increased connective tissue

puerperal fever

is a septicemia originating in the infected wound following childbirth

Scarlet fever

is caused by strains producing one of the two closely related erythrogenic toxins. It can accompany pharyngitis or a streptococcal skin infection

Rheumatic fever

the most serious sequela of hemolytic streptococcal infection because it results in damage to heart muscle and valves

Streptococcus agalactiae

● Known as group B beta-hemolytic streptococcus

● Causes neonatal sepsis and pneumonia

● With Capsule

● Part of normal flora of vagina, mouth, urethral mucous membrane, GIT

S. pneuoniae, S. viridans, S. mutans

Non-beta-hemolytic streptococci

Streptococcus pneumoniae

• Alpha-hemolytic

• Cause pneumococcal pneumonia (1st), otitis media, adult meningitis

Streptococcus viridans

Alpha-hemolytic (virescent), causes subacute bacterial endocarditis

Streptococcus mutans

• Gamma-hemolytic

• primary cause of dental caries

Streptococcus pnuemoniae

A. Quellung reaction:

● Pneumococci + anti-serum and methylene blue = swollen capsule (Viridans = negative)

B. Optochin Test: a derivative of

● Quinine; VROPS (Viridans Resistant [to] Optochin, Pneumoniae Sensitive

Enterococcus

Relatively hardy microorganisms adapted to areas of the body that are rich in nutrients but low in oxygen

• High resistance to most antibiotics

E. faecalis and E. faecium

• Responsible for most infection of surgical wounds and the urinary tract

• Can enter the bloodstream through indwelling catheters

Listeria monocytogenes

• Can contaminate foods, especially dairy products

• Can survive within phagocytic cells

• Capable of growth at refrigeration temperature

• Poses the threat of stillbirth or serious damage to the fetus if it infects a pregnant women

Listeria monocytogenes

Motility: Tumbling end-over-end motion

Causes neonatal meningitis

The only G(+) bacteria with endotoxin