Prof. Beata Sobieszczańska

Wrocław Medical University

Dept. of Microbiology

S. epidermidis

S. saprophiticus

Coagulase - negative

Coagulase enzyme

production

Staphylococcus

Coagulase - positive

Staphylococcus

aureus

Staphylococcus aureus

Virulence factors

associated with the cell

wall:

Peptidoglycan+LTA

Coagulase two types (CF)

Glycocalix

A protein

Surface adhesion

proteins e.g. fibronectin,

collagen, fibrinogen binding

components

Staphylococcus aureus

TOXINS:

Cytolytic exotoxins =hemolysins=pore-forming toxins (toxins: alpha, beta, delta, gamma)

Leukocidin Panton-Valentine

Superantigens:

Exfoliatins (ETA, ETB)

Enterotoxins

Toxic shock syndrometoxin -1 (TSST-1)

Superantigen

Superantigens (Type I toxins)

Unusual bacterial toxins that

interact with exceedingly large

numbers of T4 lymphocytes

This results in the secretion of

excessive amounts of cytokine IL-2

and the activation of self-reactive

T-lymphocytes

Superantigens (Type I toxins)

• Toxic shock syndrome toxin-1

(TSST-1) some strains of Staphylococcus aureus

• Staphylococcal enterotoxins (SE)

• Staphylococcal exfoliative toxin (ETA, ETB)

• Pyrogenic exotoxin (Spe) – toxic shock-like syndrome (TSLS) – rare invasive strains and scarlet fever strains of Streptococcus pyogenes (group A)

Staphylococcus aureus

ENZYMES:

Coagulase

Fibrinolysin

Catalase

Hyaluronidase

Staphylococcus aureus

Source of infection = reservoir (the origin from

which a host acquires the infection):

Human carriers, diseased persons

Transmission:

directly (contact with carriers or infected individual)

indirectly (contaminated surfaces or medical

equipment, food)

Staphylococci – resistant to drying (prolonged

survival), disinfectants, antimicrobials

Routes of transmission of microorganisms to humans:

• person-to-person direct contact = direct contact with diseased person or carrier (touching, kissing, sexual intercourse etc.)

• air-borne route = inhalation of microorganisms spread to the air by infected individuals coughing or sneezing

• exposure to contaminated fomites (objects or materials that are likely to carry microorganisms) such as clothes, utensils, and furniture e.g. keyboard, cell-phones, pens, sharp objects – inhalation or puncture wounds

• by food or water = food-borne (undercooked or fresh food of animal origin, food contaminated by carriers, unwashed vegetables, unpasteurized milk etc.)

• vectors (insects) transmitting microorganisms from animals to humans or from human-to-human e.g. fleas, fly, mosquitoes, bugs

Toxin-mediated (toxin-related) disease –

clinical symptoms are caused by toxin

(damage to cells and tissues)

Pyogenic/purulent = pus producing

Pyrogenic = inducing fever

Staphylococcus aureus – types of infections

Skin &

wound

infections

Endocarditis

Pneumonia

Bacteremia

Food

poisoning

SSSS

TSS

Purulent Toxin-mediated

Skin infections:

impetigo

folliculitis

furuncles

carbuncles

Wound infections

postoperative or

posttraumatic

Osteomyelitis

Pneumonia

Bacteremia

Endocarditis

Septic arthritis

Pyogenic/suppurative

infections

Other staphylococci

Staphylococcus epidermidis

Part of normal flora of the skin and anterior nares

Important cause of infections from prosthetic implants (catheters, heart valves)

Virulence factors: slime layer, lipase

Staphylococcus saprophiticus

Part of the normal vaginal flora

A frequent cause of cystitis in women

Virulence factors: urease

Streptococci

Streptococcus

Lancefield classification

(β-hemolytic) A, B, C, D, E, F, G …….

Group A – Str. pyogenes (GAS)

Group B – Str. agalactiae (GBS)

α-hemolytic:

Oral (viridans) streptococci

Str. pneumoniae

non-hemolytic:

Enterococci (α, β, Ɣ)

Streptococcus

Streptococcus pyogenes

Virulence factors:

Cell wall associated:

Hyaluronic acid capsule

M protein (molecular mimicry – auto-antibodies)

Extracellular:

Streptolysin O (hemolysin)

Pyrogenic streptococcal exotoxins PSE: A, B, C

(former name: erythrogenic toxin)

Streptokinase

Hyaluronidase

Fibronectin-binding proteins

No spread

to blood

PSE+ strain

Post-streptococcal rheumatic fever (ARF) = autoimmune disease

Acute rheumatic fever

Post-streptococcal acute glomerulonephritis

= immune complexes

Streptococcus pyogenes

The most common cause of bacterial

pharyngitis or pharyngotonsilitis

Streptococcus pyogenes

Scarlet fever/scarlatina (pyrogenic exotoxin (PSE) in

non-immunized individuals)

Streptococcus pyogenes

• Erysipelas

• Streptococcal toxic shock syndrome (PSE)

• Bacteremia, sepsis, septic shock

• Pneumonia

Other streptococci

Streptococcus agalactiae (GBS)

Meningitis and septicemia in neonates

Infections in adults: endometritis in postpartum women, septicemia, pneumonia in immunosupressed individuals, UTI, soft tissue infections, endocarditis, bone & joints infections

Virulence factors:

Glycocalix & pili - attachment

Glycosyltransferase – invasion of blood-brain barrier

Polysaccharide capsule – anti-phagocytic

Other streptococci

Streptococcus pneumoniae - diplococci

Capsule – anti-phagocytic (>90 serotypes)

Hyaluronidase

IgA protease

Diseases:

Pneumonia

Sinusitis

Otitis media

Meningitis

Other

STREPTOCOCCUS PNEUMONIAE

Purulent:

Otitis media

sinusitis

pneumonia

INVASIVE:

meningitis

bacteremia, sepsis

endocarditis

peritonitis

Serotypes:

2, 3, 5, 8, 14

Mortality:

15-25%

Anti-pneumococcal vaccines

Prevents any type of pneumococcal disease

Two types:

1. Polysaccharide (PPSV23, Pneumovax) – for

people 2 through 64 years old with certain medical

conditions and 19 through 64 years old who

smoke cigarettes – ineffective in children <2 years

old (against 23 different serotypes)

2. Conjugate (PCV13 capsular polysaccharide +

diphtheria toxoid) against 13 different serotypes –

for all children younger than 2 years old and adults

ENTEROCOCCI

Enterococcus faecalis &

E. faecium cause >90% infections in human

normal intestinal flora of humans and animals

resistant to environmental factors and many antimicrobial agents

Source of infections: endogenous

Indirect: contaminated surfaces & medical equipment

ENTEROCOCCI:

virulence factors

proteins binding ECM = colonization

lipoteichoic acid = fibronectin binding,

induction of cytokines

hyaluronidase = invasion into tissue

Most common infections: UTI,

endocarditis, catheter-related blood

infections

Other: intraabdominal and pelvic infections,

bacteremia, postoperative wounds

infections, meningitis – uncommon

(neurosurgical procedures)

Streptococci in oral cavity

Streptococcus: mitis, mutans, salivarius, sanguis, milleri

normal flora: oral cavity, intestines, urethra

endogenous infections: dental carries, endocarditis, mixed infections within oral cavity (e.g. abscesses)

Thank you for your

attentionNext lecture and class:

Clostridium, Bacillus

Murray chapter 30