Characteristics Of Each Bacterium

Characteristics of each bacterium A. Morphology & identification 1.typical organism 2.Culture 3.antigenic structure 4.classification 5. resistance B. pathogenesis & immunity C. diagnostic laboratory test D. prevention & treatment

The Staphylococci

Coccus • Staphylococcus aureus • Staphylococcus epidermidis • Staphylococcus saprophyticus

Morphology & Identification  Gram positive  Facultative anaerobes  Grape like-clusters  Catalase positive  Major components of normal flora  skin  nose

Pathogenesis & Immunity of Staphylococcus aureus

Antigenic Structure

Toxins & Enzymes • Catalase • Coagulase • Hyaluronidase and Lipase • Hemolysin or sphingomyelinase C • Leukocidin • Exfoliative Toxin • Toxic Shock Syndrome Toxin (superantigen) • Enterotoxins

Pathogenesis

Clinical Findings- Suppurative • A. (Skin) Furuncle; Stye; Impetigo; Mastitis Abscess (deep tissue); B. Systemic : Bactermia (from abscess, wound, burn) , Osteomyelitis (tibia) ,Pneumonia

Clinical Findings- Food poisoning • not a human infection • food contaminated from humans – growth – enterotoxin • onset and recovery both occur within few hours • Vomiting/ nausea/ diarrhea/ abdominal /pain

Staphylococcus epidermidis • major component skin flora • opportunistic infections – less common than S.aureus • nosocomial infections

Staphylococcus saprophyticus • urinary tract infections • coagulase-negative – not differentiated from S. epidermidis

The Streptococcus

Streptococcus

Morphology & Identification • • • •

facultative anaerobe Gram-positive Chains or pairs Catalase negative (staphylococci are catalase positive)

Cell surface structure of S pyogenes and extracellular substances

Virulence factors of Group A streptococcus • Structural components – – – –

Capsule Lipoteichoic acid M protein F protein

• Toxins and enzymes – – – – – –

Pyrogenic exotoxins Streptolysin O Streptolysin S Hyaluronidase Streptodornase streptokinase

• Group A streptococcal infections affect all ages peak incidence at 5-15 years of age

Clinical findings of group A sterptococcus • Pyogenic infection : suppurative inflammation • Toxic disease :scarlet fever • Poststreptococcal allergic diseases:acute glomerulonephritis ; rheumatic fever

S. pyogenes -suppurative • non-invasive – –

pharyngitis skin infection, impetigo

• invasive bacteremia – toxic shock-like syndrome – "flesh eating" bacteria – pyrogenic toxin

Acute glomerulonephritis • immune complex disease of kidney

Prevention and Treatment • Immunity ; 14 capsule types mixed vaccine • Most strains susceptible to penicillin , but resistance is common

NEISSERIA Neisseria gonorrhoeae

Neisseria • • •

Gram negative diplococci (pairs of cocci) oxidase positive

• culture • Thayer Martin. – selective – chocolate agar * heated blood (brown)

N. meningitidis

N. gonorrhoeae

Virulence Factors Similar, but – Differences in utilization

LPS

LPS

Capsule

IgA protease

Hemolysin IgA protease PILI Opacity (OPA) proteins Outer Membrane Proteins

PILI Opacity (OPA) proteins Outer Membrane Proteins

X

NO capsule NO hemolysin

N. gonorrhoeae the "gonococcus" • After 2-14 days •Found only in man • Gonorrhea: second most common venereal disease

N. meningitidis (the "meningococcus")

N. meningitidis • resides in man only • usually sporadic cases – mostly young children • outbreaks – adults – crowded conditions * e.g. army barracks

Neisseria meningitidis upper respiratory tract infection – adhesion pili

bloodstream

brain